ČSN EN ISO 21644 - Tuhá alternativní paliva - Metody stanovení obsahu biomasy

3.14 sample preparation

actions taken to obtain representative laboratory samples (3.7) or test portions from the original sample (3.13) as received

[SOURCE: ISO 21637:2020, 3.66]

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Symbols and abbreviations

For the purposes of this document, the following symbols and abbreviations apply.

C

symbol for element carbon

D

diameter (mm)

14C

carbon isotope with an atomic mass of 14 u

LSC

Liquid Scintillation Counter or Liquid Scintillation Counting

Msort

manual sorting method

RSD

relative standard deviation

SDM

selective dissolution method

SRF

solid recovered fuel

TC

total carbon content

u

atomic mass unit

w

mass fraction expressed as a percentage by mass

wcal

content expressed as a percentage of the energy content

wTC

content expressed as a percentage of the total carbon content

The different references used in this document are indicated by the following indices:

— (ad) for air dried (dried at room temperature 20°C to 25 °C for 24 h)

— (ar) for as received

— (d) for dry

— (daf) for dry and ash free, where appropriate.

EXAMPLE

Principle

The determination of the biomass content is based on selective dissolution, manual sorting or 14C measurement of biomass in solid recovered fuel. The choice for the method to be used is described in Clause 6. The biomass content gives an estimation of the content of the biogenic fraction in solid recovered fuel.

Determination of biomass content

Sampling

Sampling, transport, storage of the solid recovered fuel and sample preparation in the field shall be conducted according to ISO 21645 and ISO 21646.

Sample preparation

Preparation of the test sample for the 14C or SDM shall be conducted according to ISO 21646. For the Msort, no sample preparation is performed.

Since SRF is considered as a heterogeneous material, the minimum sample amount to be used for each test shall be:

— 14C method: a quantity between 0,4 g and 2 g of the material with a nominal top size of 1 mm or less, depending on the device used for combustion (bomb, combustion tube furnace or elemental analyser) or the quantity indicated by the constructor in the case of the use of a laboratory scale combustion apparatus;

— selective dissolution method (SDM): at least 5 g of the material with a nominal top size of 1 mm or less;

— manual sorting method (Msort): at least as big as the minimum sample size according to ISO 21645 (as received), as calculated in ISO 21646.

Applicable methods

For the determination of biomass content three methods are available:

1) the instrumental 14C method shall be according to Annex A. This method is based on the determination of the ratio of 14C to the total carbon content; the 14C is proportional to the biomass content of the SRF. This method is suitable for samples of all types of fuel and shall be according to Annex A. A value of 10 % biogenic carbon can be considered as the lower range of application of 14C method by liquid scintillation counter (LSC);

2) the selective dissolution method (SDM) shall be according to Annex B. The determination of the biomass content by the SDM is based on the property of biomass that it can be dissolved in a sulphuric acid / hydrogen peroxide mixture. This method has limitations that makes it less suitable if the content of natural and/or synthetic rubber in the SRF is more than 10 %, or if the sum of the content of hard coal, coke, brown coal, lignite, degradable plastics of fossil origin, non-degradable plastic of biogenic origin, oil or fat present as a constituent of biomass, wool, viscose, nylon, polyurethane or other polymers containing molecular amino groups and silicon rubber exceeds 5 %. Additional information about these limitations is found in Annex D. The selective dissolution method (SDM) is applicable for the biomass percentage content between 10 % and 90 %;

3) the manual sorting method (Msort) shall be according to Annex C. The determination of the biomass content by the manual sorting method is based on the visual examination of fractions and their separation on the basis of their nature and origin. The method is suitable for samples with a particle size >10 mm.

For the limitations of the three methods see Annex D.

Expression of results

Depending on the use of the results, three different dimensions are used to express the biomass content:

a) biomass in percent by mass wB;

b) biomass in percent by calorific value

c) biomass in percent by carbon content

The expression of results by 14C method shall be according to Annex A.

The expression of results by SDS method shall be according to Annex B.

The expression of results by Msort method shall be according to Annex C.

Performance characteristics

External data for the calculation of the expanded uncertainty of measurements are presented in Annex E where results of round robin and validation studies are summarized. These values should be used in combination with individual laboratory performance characteristics and a desired coverage factor to get the overall uncertainty.

Practical examples of use of the data from Annex E:

EXAMPLE 1  

A laboratory wants to determine the expanded uncertainty of measurement of SDM method (% by mass).

The intra-laboratory reproducibility for the laboratory calculated from internal validations studies and control charts was determined to be 2,5 % (RSD).

The round robin results from the QUOVADIS[3] study (Table E.2) give a RSD value of 3,43 % (at 67,79 % level).

uc,rel = √(2,52+3,432) = 4,24 %

Urel = 2 × uc,rel = 8,48 %

where uc,rel is the combined uncertainty of measurement and Urel  is the expanded uncertainty of measurement using a coverage factor of 2 (~95 % confidence interval).

EXAMPLE 2  

A laboratory measures the biomass content by 14C method – LSC B (% by TC).

The intra-laboratory reproducibility for the laboratory calculated from internal validations studies and control charts was determined to be 2,4 % (RSD).

The round robin results from the QUOVADIS[3] study (Table E.6) give a RSD value of 2,5 % (at 55,5 % level).

uc,rel = √(2,42+2,52) = 3,5 %

Urel = 2 × uc,rel = 7,0 %

where u c,rel is the combined uncertainty of measurement and Urel is the expanded uncertainty of measurement using a coverage factor of 2 (~ 95 % confidence interval).

Test report

The test report shall contain at least the following information:

a) identification of the laboratory performing the test;

b) date of the test;

c) identification of product (sample) tested;

d) sample preparation (e.g. method of size reduction, drying, subdivision);

e) storage conditions;

f) date of receipt of laboratory sample and dates of the test (beginning and end);

g) a reference to this document (ISO 21644:2021) and the method used;

h) in case of 14C-method, the results of the test including the basis on which they are expressed and application of the isotope correction;

i) the biomass content expressed as a percentage by mass, calorific value and/or carbon content, rounded to the nearest 0,1 %;

j) any operation not included in this document, or regarded as optional;

k) any unusual features noted during the test procedure.

(normative) Determination of the biomass content based on the 14C method

General

The two proposed methods for 14C measurement, Proportional Scintillation Method (PSM) or Accelerated Mass Spectrometry (AMS), require specialised personnel and instrumentation. However, the preparation step for instrumental analysis can be completed as normal routine laboratory activity. For the collection from the sample of the 14C fraction, generally accepted methods for the conversion of the carbon present in the sample to CO2 are described.

Principle

The methods for the determination of the biomass content specified in this annex are based on the determination of the 14C content. The amount of biomass carbon in solid recovered fuel is proportional to this 14C content.

The carbon present in the sample is converted to CO2 by combustion. The combustion is carried out in a way to comply with the requirements of the subsequent measurement of the 14C content. This measurement is carried out according to one of the two following methods, Proportional Scintillation Method (PSM) or Accelerated Mass Spectrometry (AMS). These methods are considered equivalent, giving the same results within the scope of this document. The results are expressed as the percentage biomass carbon of the total carbon content. The fraction of biomass content by mass and the fraction of biomass by energy content are calculated from the carbon content of biomass, using the carbon content of biomass and the energy content of the biomass fraction that is present in the sample.

Limitations

For the limitation of this method see Annex D.

Symbols

For the purposes of this annex, the following symbols apply.

C

symbol for element carbon

14C

carbon isotope with an atomic mass of 14

AMS

Accelerator Mass Spectrometry

β

beta particle, electron emitted during radioactive decay

Bq

Bequerel, disintegrations per second

d

on dry base

DPM

disintegrations per minute

CPM

counts per minute

CV

coefficient of variation

GM

Geiger Müller

LCV

Low calorific value

LLD

Lower Limit of Detection

m

mass expressed as a percentage by mass

M

moisture expressed as a percentage by mass

MOP

3-Methoxy 1-propyl amine

NCV

Net Calorific Value

LSC

Liquid Scintillation Counter or Liquid Scintillation Counting

REF

reference value of 100 % biogenic carbon

pmC

percentage modern Carbon

PSM

Proportional Scintillation-counter Method

X

fraction expressed as a percentage by mass

RSD

Relative Standard Deviation

SRF

Solid recovered fuel

TC

Total carbon content

Reagents and materials

CO2 absorber for LSC (methoxypropylamine or equivalent).

Universal LSC cocktail for aqueous and non-aqueous sample.

2 mol·l−1 to 4 mol·l−1 KOH or NaOH absorption liquid (standard glass bottles with plastic screw caps that are resistant to alkaline solutions shall be used).

For the preparation of a carbonate free adsorption liquid, preparation using freshly opened KOH or NaOH pellet containers is sufficient. Dissolve the KOH (NaOH) pellets in a small amount of water (the heat produced during the dissolution process will enhance the dissolution process). When NaOH is used, small amounts of precipitation are an indication of the presence of Na2CO3. By decanting the clear phase, the almost carbonate free solution shall be diluted to the desired volume. As the dissolution of KOH or NaOH is an exothermic process, extra care should be taken as boiling of the concentrated solution during dilution can occur.

For high precision measurements the following procedure shall be used to produce a 0,7 l carbonate free KOH (NaOH) 4 mol·l−1 solution.

— 670 ml demineralised water (water from a system producing ultrapure water for laboratory use);

— 156,8 g KOH pellets (112 g NaOH);

— 30 ml saturated Ba(OH)2 solution. [2,4 g Ba(OH)2 ÷ 2,6 g Ba(OH)2 in 30 ml demineralised water];

— dissolve the KOH (NaOH) pellets in the demineralised water (use magnetic stirrer);

— heat the solution and the saturated Ba(OH)2 solution to 80 °C, and mix the two solutions. Cool down the solution to −8 °C, stop the stirring and leave the solution overnight at −8 °C. After filtration the solution is ready for use. Keep stored in a well-sealed container.

Procedure for the conversion of the carbon present in the sample to CO2 for 14C determination by PSM

General

Three procedures are allowed for the conversion of the sample to a form that can be used for the determination of the 14C content:

1) combustion in a calorimetric bomb,

2) combustion in a tube furnace,

3) combustion in a laboratory scale combustion apparatus.

NOTE The method mentioned under 3) is not validated.

Other apparatus may be used which provide a complete combustion in the reported experimental conditions. As an example, the combustion may be performed by using elemental analyser. The CO2 formed is then absorbed in a suitable solution, which depends on the combustion method and the selected method for the subsequent 14C measurement. Two absorption solutions are available: in case substantial chemical or optical quenching is foreseen (high NOx values, formation of coloured substances) collection of the CO2 shall be done in the NaOH solution. The use of pure oxygen or a mix of oxygen and argon during combustion will reduce the formation of nitrous oxides to an acceptable level.

Combustion of the sample in a calorimetric bomb

Procedure

For the combustion according to the determination of the calorific value of the sample, ISO 21654 shall be used. The test sample is a general analysis sample passing through a sieve with 1 mm aperture and prepared according to ISO 21646. The test sample mass of less than 1 g is pressed in the form of a pellet by using a suitable pressing device (manual or pneumatic). For SRF materials with high content of plastic or rubber showing higher LCV values, the test sample mass should be reduced to a mass in the range from 0,4 g to 0,8 g to be suitable for safe bomb operation. For materials difficult to combust (e.g. material with high ash content >30 % on dry basis) it is recommended to use a combustion aid.

The appropriate mass of the test sample to be combusted depends on the total carbon content in order to have similar amount of absorbed CO2 in the scintillation cocktail for subsequent 14C measurement to reduce the measurement bias due to different quenching conditions: for this purpose, the total carbon content of the sample shall be determined before the combustion step.

After combustion, the combustion gases are collected in a suitable mixture. Alternatively, the gases are collected in a gas bag as described in A.6.2.2. For the determination of the 14C content the CO2 shall be collected in cooled (<10 °C) absorbing solution or a cooled mixture of absorbing solution and scintillation liquid.

As the bomb volume is released to atmospheric pressure, there will be a residual amount leftover in the bomb that is directly related to the pressure in the bomb after the combustion (with a residual pressure of 2,5 MPa 4 % of the combustion gas will be left after release to atmospheric pressure).

To overcome this issue:

a) perform the calibration and the analysis taking account of this residual amount by using the pressure correction factor,

b) use the vacuum pump to remove the residue gases;

c) flush the bomb with Argon or (CO2-free) N2 and collect the CO2 in the rinsing gases as well.

Absorption of the gas sample

If a gas sample bag is used, it shall be connected to a small pump with a connection line into a 20 ml glass vial, filled with 10 ml of absorbing solution or a mixture of 10 ml of the absorbing liquid and 10 ml of the scintillation cocktail, placed in an ice bath or cooling device at <10 °C, to remove the heat of the exothermic carbamate formation reaction. The pumping speed shall be about 50 ml·min−1. The transfer of the gas from the bag takes about 2 h to 3 h. After the sample is collected, it is ready to be counted on a LSC. Blank samples should also be counted at the same time to allow that small day-to-day variations in the background can be accounted for.

In case of direct absorption of combustion gases, the outlet of the combustion device (e.g. oxygen combustion bomb) is connected via transfer line, equipped with a valve, to an empty cooled impinger for water removal and a second cooled impinger with 10 ml absorbing solution or scintillation cocktail. Using the proper safe device, the bomb valve is opened and the gases are collected at a low flux rate (optimal value 50 ml·min−1 to 60 ml·min−1). The transfer takes about 3 h. Blank samples should also be counted at the same time to allow that small day-to-day variations in the background can be accounted for.

Measurements shall be started after leaving the vial to cool down to the measurement temperature and to reduce any chemiluminescence due to manipulation. Absorbing solution are stable at least for 1 week after sampling: alternatively, the CO2 shall be collected in a 4 mol·l−1 KOH (NaOH) solutions for longer period.

NOTE 1 There are strong indications that the NOx formed during the combustion reacts with the absorption mixture resulting in yet unexplained errors after a few days of storage.

NOTE 2 The initial and final mass of the absorbing solution is an estimation of the recovery of CO2 and indicates the possible sources of error in the procedure, such as a leakage in the absorption system.

Combustion of the sample in a tube furnace

A suitable amount of sample (seaved at 1 mm nominal size) is weighed in the boat to be inserted in the combustion tube. The test mass depends on the carbon content of the SRF and the capacity of the absorption solution; generally, up to 2 g are processed in macro instruments and typically 200 mg in microtube furnace. The gas bubbles set is filled with the absorption solution. The temperature of the furnace is raised at the operation value (e.g. 1 100 °C or 1 350 °C): when temperature reaches the set point the oxygen supply is connected and the flow rate is adjusted at the desired value. The sample boat is inserted and combustion is started. At the end of the combustion the impingers are removed and the absorption solutions collected for subsequent analysis. The oxygen flow rate should not exceed the maximum flow rate allowed for the gases to be quantitatively collected in the absorption solution. In case of the use of microtube the representativity of the test sample should be verify according to the grain size.

For the determination of the 14C content the CO2 shall be collected using an impinger filled with a cooled absorbing solution or a mixture of absorbing and scintillation liquid; alternatively, a 4 mol·l−1 KOH (NaOH) solution may be used (see A.6.2.2, NOTE 1 and 2).

As an alternative, the CO2 may be trapped by means of a cryogenic trap. In that case the cryogenic trap shall consist of a water trap (dry ice in ethanol or acetone) followed by a cryogenic trap. Care shall be taken to avoid formation of liquid oxygen, which shall be achieved by heating the trap slightly above the boiling point of oxygen, using liquid argon or by performing the separation at diminished pressure.

Combustion of the sample in a laboratory scale combustion apparatus

The combustion condition and test sample amount depend on the apparatus used and manufacturer instructions.

The CO2 may be trapped using different methods, depending on the laboratory. Some examples are reported below.

The lab-scale combustion apparatus shall be able to combust a suitable SRF-sample at a constant rate, with a complete conversion of the carbon present to CO2. For the determination of the 14C content the CO2 shall be collected using a suitable impinger filled with a cooled mixture of absorbing solution and a suitable scintillation liquid or a 4 mol·l−1 KOH (NaOH) solution (see A.6.2.2, NOTE 1 and 2). As a result of the absorption of the CO2 a large volume reduction of the gas volume will be observed after trapping. Therefore, the gas pump is to be positioned in front of the impinger, and the gas pump used shall be gas tight.

As an alternative, the CO2 may be trapped by means of a cryogenic trap, which consist of a water trap (dry ice in ethanol or acetone) followed by a cryogenic trap. Care shall be taken to avoid formation of liquid oxygen, which shall be achieved by heating the trap slightly above the boiling point of oxygen, using liquid argon or performing the separation at diminished pressure. As an alternative, when AMS is being used, CO2 may be collected by mixing homogenized SRF with cupric oxide (CuO) in a sealed, evacuated quartz or high silica, high temperature glass tube. Water vapour (up to 3 Pa) can be added to the tube prior to introduction of the CO2 to help remove sulphur compounds. The tube is heated to 900 °C for 3 h to 5 h. The CO2 is collected by breaking the tube using a tube-cracker connected to an evacuated glass collection line.

Measurements

If collected samples are sent to specialized laboratories, the samples shall be stored in a way that no CO2 from air can enter the absorption solution. A check on the leak of CO2 from air shall be performed by preparing laboratory blanks during the sampling stage.

For the determination of the 0 % biomass content the combustion of a coal reference material (e.g. BCR 182) shall be used.

For the 100 % biomass content the Oxalic acid primary standard (SRM 4990c) is available: however, this material is difficult to combust due to its low calorific value and the difficulties in the preparation of a suitable pellet. Other reference materials such as Lichen BCR 482 may be used because their biomass content is 100 % by total carbon by definition (the reported organic C content is 42,1 % and total carbon is 44,7 %). A control by using independent 100 material (laboratory internal reference materials such as collected vegetable prepared for other type o chemical analysis are suitable) is recommended.

NOTE Oxalic acid can be difficult to completely combust under the conditions used in this document for the bomb combustion.

Among the materials which may be used the following are included:

— vegetable, with known TC content, assuming 100 % biomass;

— L-ascorbic acid from natural sources, with known purity and TC content from chemical formula;

— material with recent carbon, with reference biomass content from AMS method.

This aspect regarding uncertainty evaluation should be considered:

— 0 and 100 % biomass reference values should be used without uncertainty since they derive from theoretical consideration and not from accepted averages values from round robin test;

— 14C content should be based on reference method determination such as AMS; or on theoretical consideration from actual CO2 average level.

Procedure for the 14C determination by Proportional Scintillation-counter Method (PSM)

General

This procedure describes the determination of the 14C by Proportional Scintillation-counter Method (PSM) in absorbing solutions obtained from the combustion of SRF samples in a calorimetric bomb, a tube furnace or a laboratory scale combustion device as described in A.6.

Principle

PSM (also called Liquid Scintillation Counter method, LSC) determines the isotope abundance of 14C indirectly, through its emission of β particles due to the radioactive decay of the 14C isotope. The β particles are observed through their interaction with scintillation molecules. The CO2 formed by the combustion of SRF is trapped in an absorbing solution. This solution is mixed with the organic solution containing the scintillation molecules and the 14C activity of this mixture is measured in a Proportional (Liquid) Scintillation Counter. In case substantial chemical or optical quenching is foreseen (high NOx values, formation of coloured substances) collection of the CO2 shall be done in the NaOH (KOH) solution. As an alternative the use of pure oxygen or a mix of oxygen and argon during combustion will reduce the formation of nitrous oxides to an acceptable level. In this case either absorption solutions may be used.

Reagents and materials

— scintillation liquid;

— absorbing solution (e.g. 100 % ethanolamine or 5M ethanolamine in 2-methoxyethanol or 3-methoxypropylamine);

— commercial 14C labelled substance in solution with known dpm/ml valid to check instrument performances;

— oxalic acid primary standard (SRM 4990c) or other suitable reference material;

— a 14C-free reference material.

Apparatus

The extremely low natural levels of radiocarbon in the earth's atmosphere (about 1,10−12 %) requires extra precautions for accurate measurement of 14C. Care should be taken to eliminate the influence of cosmic and environmental background radiation, other radioisotopes being present, electronic noise and instability. Any LSC used should meet these specifications.

Key

1

lead shield

8

pulse addition circuit

2

active guard

9

fast coincidence analyser

3

sample

10

pulse height analyser

4

photomultiplier tube

11

circuit

5

photomultiplier tube

12

multi-channel analyser

6

external standard radiation source

13

command analyser

7

high-voltage power supply

 

 

Figure A.1 — LSC

Procedure

An absorption flask is loaded with a known volume of CO2 absorbent, e.g. with an absorbing solution. The absorbing capacity of an absorbing solution of about 4,8 × 10−3 mol/ml shall be taken into account; no more than 80 % of this capacity should be used. The flask shall be cooled in ice or by a cooling device during the absorption process. The sample gas is collected from a flue gas duct or from a gas bag. In either case, the sample has to be dried by passing through dryer or empty cooled impinger and the CO2 concentration of the dried sample has to be known (either by a flue gas monitor or by the analysis of the solid sample that was used to generate the CO2) or by measuring the amount of CO2 absorbed (the absorbing solution absorbs the CO2 quantitatively) If acquired directly from a flue gas duct, the sample volume has to be measured with a gas meter and corrected for the volume of CO2 absorbed by the absorbing solution. After absorption of the CO2, the absorbent is transferred to the measuring vial. An equal volume of the scintillation liquid is added and the mixture is homogenized.

Then the vial containing the mixture is placed in the PSM and measured. Typical counting times are 6 h to 24 h: the total counting time is composed of a suitable number of 30-min counting cycles (for example a total of 24 cycles of 30 min each). The final count (DPM) is the average value from single results from every cycle.

The activity of a sample is compared with the activity of a reference material. The number of 14C registrations (=β counts of 14C decay in radiometric detectors (PSM) is related to the number of registrations of the reference sample under the same conditions.

Standard addition techniques can be used to check for the occurrence of chemical or optical quenching for each sampling or sample type. For that purpose, 14C labelled components shall be used.

Measurement shall be performed together with a measurement of the “background” sample (0 % biomass material, such as coal or equivalent sample) that is counted for the same period of time as the actual sample. The result obtained is the background level for the whole system (apparatus and reagent) given in CPM or DPM. After this the actual sample is counted, which also gives a counting result in CPM or DPM.

The statistical error of counting, background and standard is a result of the decay counting, (Poisson) process; hence the precision of the result depends on the number of counts observed, where the relative error is inversely proportional to the square-root of the number of counts. The total error is then the combination of the analytical errors and the errors of the standard and background determination

The detection limit (LD) is the smallest amount of radioactivity that statistically differs from the background. The LD shall be calculated from the counting time of the sample and the background counting rate assuming the same counting times for background and sample:

where

 

E(Rn,LD)

is the Limit of Detection (LD);

 

k1-α, k1-β

is the confidence level (1,645);

 

E(R0)

is the counting rate of blank [cps] (0,316 7 cps);

 

t0

is the counting time of blank [s] (16 000 s);

 

tb

is the counting time of sample [s] (16 000 s).

where

 

cps

counting rate of blank (0,316 7 cps);

 

dps

disintegrations per second [Bq];

 

η

counting efficiency of the apparatus (0 < η < 1) (0,8).

EXAMPLE The calculation of LD using a counting time of 16 000 s (266,67 min) and 19 CPM (0,316 7 counts per s) background with a counting efficiency of 0,8:

Calculation of the results

From the sample count rate, the background count rate of the counter is subtracted (net count rate). The 14C activity (DPM) is obtained by normalizing the net count rate to the count rate of the reference standard (Oxalic acid SRM) or other suitable reference materials.

Example for PSM measurements

In an absorbing solution obtained from a calorific bomb combustion of pure wood (REF = 114 pmC, TC = 48,0 %) an 14C activity of 7,75 DPM is measured. 13,56 DPM/gC is the value of 100 % biomass.

In the bomb an amount of 1,050 g (sm) of sample was combusted (air dry).

Then the biogenic carbon content (on air dry base) will be calculated by the following formula:

% Biogenic Carbon = [DPM/(13,56 × REF/100)/sm] × 100

% Biogenic Carbon = {[7,75/(13,56 × 114/100)]/1,050} × 100 = 47,8 %

Example for PSM measurements from calibration with reference materials

In an absorbing solution obtained from a calorific bomb combustion of SRF (REF = 107 pmC, TC = 47,5 %) an 14C activity (net value) of 1,36 DPM is measured.

In the bomb an amount of 0,55 gram of sample was combusted (air dry).

In a previous phase, in the same conditions, a reference sample from coal (e.g. BCR 182), after bomb combustion gave an average net activity of 0,22 DPM; similarly, a reference sample from lichen (BCR 482) gave a net average activity of 2,53 DPM. BCR 182 result was used as reference 0 % biomass fraction, while BCR 482 was set as 100 % biomass fraction. As reported in Table A.1, the correction factors were applied:

BCR 182 (0 % biomass) = 100

BCR 482 (100 biomass) = 101

SRF (unknown) = 107

The corrected DPM were: 0,22 (0 % biomass); 2,50 (100 % biomass); 1,27 (unknown).

After combustion, the absorbing solution cocktail was weighted before and after gases collection: from the difference the carbon content was calculated since the recovery can be considered as quantitative. The net DPM/gC were calculated:

0 % = 1,06 DPM/gC

100 % = 10,08 DPM/gC

Unknown = 6,98 DPM/gC

Procedure for the conversion of the carbon present in the sample to CO2 for 14C determination by AMS

General

Three procedures are allowed for the conversion of the sample to a form that can be used for the determination of the 14C content:

1) combustion in a calorimetric bomb,

2) combustion in a tube furnace,

3) combustion in a laboratory scale combustion apparatus.

NOTE The method mentioned under 3) is not validated.

Other apparatus may be used which provide a complete combustion in the reported experimental conditions. As an example, the combustion may be performed by using elemental analyser. The CO2 formed is then absorbed in a suitable solution, which depends on the combustion method.

Combustion of the sample in a calorimetric bomb

Procedure

For the combustion according to the determination of the calorific value of the sample, ISO 21654 shall be used. The test sample is a general analysis sample passing through a sieve with 1 mm aperture and prepared according to ISO 21646. The test sample mass of less than 1 g is pressed in the form of a pellet by using a suitable pressing device (manual or pneumatic). For SRF materials with high content of plastic or rubber showing higher LCV values, the test sample mass should be reduced to a mass in the range from 0,4 g to 0,8 g to be suitable for safe bomb operation. For materials difficult to combust (e.g. material with high ash content >30 % on dry basis) it is recommended to use a combustion aid.

The appropriate mass of the test sample to be combusted depends on the total carbon content for this purpose, the total carbon content of the sample shall be determined before the combustion step.

After combustion, the combustion gases are collected in a suitable mixture. Alternatively, the gases are collected in a gas bag as described in A.6.2.2.

For the determination of the 14C content the CO2 shall be collected in a KOH or NaOH solution. Alternatively, ca. 2 ml of the combustion gas shall be taken from the bag using a glass syringe and the gas shall be transferred to the AMS target preparations system.

As the bomb volume is released to atmospheric pressure, there will be a residual amount leftover in the bomb that is directly related to the pressure in the bomb after the combustion (with a residual pressure of 2,5 MPa 4 % of the combustion gas will be left after release to atmospheric pressure).

To overcome this issue:

a) perform the calibration and the analysis taking account of this residual amount by using the pressure correction factor,

b) use the vacuum pump to remove the residue gases;

c) flush the bomb with Argon or (CO2-free) N2 and collect the CO2 in the rinsing gases as well.

Absorption of the gas sample

If a gas sample bag is used, it shall be connected to a small pump with a connection line into a 20 ml glass vial, filled with 10 ml of absorbing solution or a mixture of 10 ml of the absorbing liquid and 10 ml of the scintillation cocktail, placed in an ice bath or cooling device at <10 °C, to remove the heat of the exothermic carbamate formation reaction. The pumping speed shall be about 50 ml·min−1. The transfer of the gas from the bag takes about 2 h to 3 h. After the sample is collected, it is ready to be counted on a LSC. Blank samples should also be counted at the same time to allow that small day-to-day variations in the background can be accounted for.

In case of direct absorption of combustion gases, the outlet of the combustion device (e.g. oxygen combustion bomb) is connected via transfer line, equipped with a valve, to an empty cooled impinger for water removal and a second cooled impinger with 10 ml absorbing solution. Using the proper safe device, the bomb valve is opened and the gases are collected at a low flux rate (optimal value 50 ml·min−1 to 60 ml·min−1). The transfer takes about 3 h. Blank samples should also be counted at the same time to allow that small day-to-day variations in the background can be accounted for.

Absorbing solution are stable at least for 1 week after sampling: alternatively, the CO2 shall be collected in a 4 mol·l−1 KOH (NaOH) solutions for longer period.

NOTE 1 There are strong indications that the NOx formed during the combustion reacts with the absorption mixture resulting in yet unexplained errors after a few days of storage.

NOTE 2 The initial and final mass of the absorbing solution is an estimation of the recovery of CO2 and indicates the possible sources of error in the procedure, such as a leakage in the absorption system.

Combustion of the sample in a tube furnace

A suitable amount of sample (sieved at 1 mm nominal size) is weighed in the boat to be inserted in the combustion tube. The test mass depends on the carbon content of the SRF and the capacity of the absorption solution; generally, up to 2 g are processed in macro instruments and typically 200 mg in microtube furnace. The gas bubbles set is filled with the absorption solution. The temperature of the furnace is raised at the operation value (e.g. 1 100 °C or 1 350 °C): when temperature reaches the set point the oxygen supply is connected and the flow rate is adjusted at the desired value. The sample boat is inserted and combustion is started. At the end of the combustion the impingers are removed and the absorption solutions collected for subsequent analysis. The oxygen flow rate should not exceed the maximum flow rate allowed for the gases to be quantitatively collected in the absorption solution. In case of the use of microtube the representativity of the test sample should be verify according to the grain size.

For the determination of the 14C content, the CO2 shall be collected using a suitable impinger filled with a 4 mol·l−1 KOH (NaOH) solution.

As an alternative, the CO2 may be trapped by means of a cryogenic trap. In that case the cryogenic trap shall consist of a water trap (dry ice in ethanol or acetone) followed by a cryogenic trap. Care shall be taken to avoid formation of liquid oxygen, which shall be achieved by heating the trap slightly above the boiling point of oxygen, using liquid argon or by performing the separation at diminished pressure.

Combustion of the sample in a laboratory scale combustion apparatus

The combustion condition and test sample amount depend on the apparatus used and manufacturer instructions.

The CO2 may be trapped using different methods, depending on the laboratory. Some examples are reported below.

The lab-scale combustion apparatus shall be able to combust a suitable SRF-sample at a constant rate, with a complete conversion of the carbon present to CO2. For the determination of the 14C content the CO2 shall be collected using a suitable impinger filled with a 4 mol·l−1 KOH (NaOH) solution. As a result of the absorption of the CO2 a large volume reduction of the gas volume will be observed after trapping. Therefore, the gas pump is to be positioned in front of the impinger, and the gas pump used shall be gas tight.

As an alternative, the CO2 may be trapped by means of a cryogenic trap, which consist of a water trap (dry ice in ethanol or acetone) followed by a cryogenic trap. Care shall be taken to avoid formation of liquid oxygen, which shall be achieved by heating the trap slightly above the boiling point of oxygen, using liquid argon or performing the separation at diminished pressure. As an alternative, when AMS is being used, CO2 may be collected by mixing homogenized SRF with cupric oxide (CuO) in a sealed, evacuated quartz or high silica, high temperature glass tube. Water vapour (up to 3 Pa) can be added to the tube prior to introduction of the CO2 to help remove sulphur compounds. The tube is heated to 900 °C for 3 h to 5 h. The CO2 is collected by breaking the tube using a tube-cracker connected to an evacuated glass collection line.

Measurements

If collected samples are sent to specialized laboratories, the samples shall be stored in a way that no CO2 from air can enter the absorption solution. A check on the leak of CO2 from air shall be performed by preparing laboratory blanks during the sampling stage.

For the determination of the 0 % biomass content the combustion of a coal reference material (e.g. BCR 182) shall be used.

For the 100 % biomass content the Oxalic acid primary standard (SRM 4990c) is available: however, this material is difficult to combust due to its low calorific value and the difficulties in the preparation of a suitable pellet. Other reference materials such as Lichen BCR 482 may be used because their biomass content is 100 % by total carbon by definition (the reported organic C content is 42,1 % and total carbon is 44,7%). A control by using independent 100 material (laboratory internal reference materials such as collected vegetable prepared for other type o chemical analysis are suitable) is recommended.

NOTE Oxalic acid can be difficult to completely combust under the conditions used in this document for the bomb combustion, but this does not influence the analytical results in case of use of the AMS apparatus.

Among the materials which may be used the following are included:

— vegetable, with known TC content, assuming 100 % biomass;

— L-ascorbic acid from natural sources, with known purity and TC content from chemical formula;

— material with recent carbon, with reference biomass content.

This aspect regarding uncertainty evaluation should be considered:

— 0 % and 100 % biomass reference values should be used without uncertainty since they derive from theoretical consideration and not from accepted averages values from round robin test.

Procedure for the 14C determination by Accelerator Mass Spectrometry (AMS)

General

This annex describes the procedure for the determination of the 14C determination by AMS in the carbonate solutions obtained from the combustion of SRF samples in a calorimetric bomb, a tube furnace or a laboratory scale combustion device.

Principle

The accelerator mass spectrometry (AMS) method determines the presence of 14C directly. The atoms in the sample are converted into a beam of ions. The formed ions are accelerated in an electric field, deflected in a magnetic field and detected in ion detectors resulting in the determination of the relative isotope abundances of these ions.

AMS is a form of mass spectrometry that uses a high potential electrostatic field, which serves not only to accelerate them but also to specifically form only Cn+ ions (n = from 1 to 4) that are allowed into the spectrometer, excluding all other ionic species. This greatly enhances sensitivity without compromising selectivity. The 14C is determined in graphite (carbon) that is why all the carbon in the samples has to be converted into graphite before analysing.

With AMS the modern fraction in the carbon, present in the sample, is determined. The total carbon content is not determined with this technique and shall be determined separately.

Reagents and materials

— oxalic acid primary standard (SRM 4990b). Although not certified other reference materials may be used (e.g. L-ascorbic acid or lichen BCR 482);

— iron catalyst;

— hydrogen;

— HCl solution (5 M);

— dry ice;

— acetone or ethanol;

— liquid N2.

Apparatus

— sample preparation equipment;

— liquid nitrogen freezing station;

— accelerator mass spectrometer (AMS) (see Figure A.2).

Key

1

59 sample ion source

7

high energy mass spectrometer

2

recombinator

8

12C-cup

3

chopper

9

13C-cup

4

tandem accelerator

10

33° electrostatic deflector

5

stripping canal

11

90° magnet

6

110° magnet

12

ionisation chamber

Figure A.2 — Schematic presentation AMS

Procedures

a) Transfer the carbonate solution to the extraction bottle.

b) Attach the HCl dosing device.

c) Evacuate the bottle and dosing device (degassing, removal of dissolved N2 and O2 from air).

d) Add HCl to the carbonate solution.

e) Remove water vapor using a trap filled with acetone and dry ice.

f) Collect the formed CO2 in a trap that is submersed in liquid N2.

g) Take a small sample for 13C determination at this stage.

h) Transfer the CO2 to the graphitizing rig system (see Figure A.3).

Gaseous sample shall be either let in the system released from a quartz tube or after they are trapped in liquid nitrogen followed by subsequent heating. The gas is then converted to graphite using an iron catalyst, according to the following formulae:

 

CO2+ H2 ←→ H2O

+ CO

 

CO+ H2 ←→ H2O

+ C

The water produced by this reaction is removed to ensure a complete reduction to graphite. This is particularly important to avoid fractionation.

Key

1

sample ampoule as CO2

4

quartz tube

2

pressure sensor

5

graphite oven at 600 °C

3

electronic cooling element at −18 °C to trap H2O

6

Fe powder

Figure A.3 — Graphitization rig

The graphite is pressed into a target and mounted on a wheel before it is loaded into the accelerator mass spectrometer. In the ion source a high current beam of caesium ions (Cs+) is focused on the target. This liberates negatively charged target atoms, producing a 36 keV beam of C-ions. Targets are kept 10 mm away from each other to avoid cross-contamination and moved during sputtering to avoid cratering, which causes fractionation. The negative ion beam is then focused by a lens into a recombinator. Here a series of magnets remove non-carbon ions from the beam and separate the three carbon isotopes (12C, 13C and 14C). The chopper wheel then physically blocks most of the 12C, allowing a much reduced beam of carbon ions to be recombined for simultaneous injection into the accelerator. In the tandem accelerator the C-ions are accelerated to the terminal (at +2,5 MeV) then changed to C3+ ions by collision with Ar atoms in the gas stripper. These positive ions are accelerated to 10 MeV. A charge state of 3+ is chosen because the mass/charge ratio of 14C3+ is truly unique, allowing its accurate separation in the high-energy mass spectrometer. The first element of the high-energy mass spectrometer is a 1100 bending magnet, separating in the accelerated 12C, 13C and 14C ions. The 12C and 13C beams are measured in Faraday cups (typical currents 250 nA). The 14C3+ ions are further purified by a 33° electrostatic deflector a 90° magnet. They are measured in an isobutene-filled ionization chamber, isolated from the accelerator vacuum by a thin metal foil (density 250 µg/cm2). Typically, a sample is counted for one hour.

Calculation of the results

The isotopic ratios of 14C/12C and 13C/12C are determined relative to the appropriate primary reference material. All percent modern carbon (pmC) values obtained from the radiocarbon analyses measurements shall be corrected for isotopic fractionation using stable isotope data (13C/12C ratios) obtained on CO2 derived from combustion of the sample. Do not determine 13C/12C ratios on the raw product material itself, since that approach can lead to erroneous results in some cases.

Calculation of the results

Correction factors

Before the above-ground hydrogen bomb testing (started around 1955 and terminated in 1962), the atmospheric 14C level had been constant to within a few percent, for the past millennium. Hence a sample grown during this time has a well-defined 'modern' activity, and the fossil contribution could be determined in a straightforward way. However, 14C created during the weapons testing increased the atmospheric 14C level to up to 200 pmC in 1962, with a decline to 102 pmC in 2015. The 14C activity of a sample grown since 1962 will be elevated according to the average 14C level over the growing interval.

In addition, the large emission of fossil C during the last decades contributes to the decrease of the atmospheric 14C/12C ratio.

In ASTM D 6866-20[4], the 100 % bio-based C value of 101,5 pmC (for year 2016) is used. This value shall be the base of calculations. Other values are only acceptable if evidence can be given on the pmC value of the biogenic part of the material. From the 101,5 (rounded to 102) pmC value the correction factor of 0,98 (1/1,02) is derived. It is considered that such correction factor is now stable during a period of a few years. For the calculation of the bio-based carbon content, a 14C content of 100/0,98 pmC or 13,56/0,98 dpm per gram C is considered as a 100 % bio-based carbon content for biomass that is grown in year 2015.

NOTE 1 This correction factor of 0,98 is in accordance with the value that is given in ASTM D 6866–20[4]. The fraction of biomass content by dry mass will be calculated using the biomass carbon in the biobased product as for other organic carbon materials. Table 2 lists typical values for such common materials.

NOTE 2 The reference value for 2016 is based on the measurements of CO2 in air in a rural area in the Netherlands (Lutjewad, Groningen), performed by CIO (Centre for Isotope Research, university Groningen)[7]. Measurement performed in year 2018 resulted in a pmC value of 100,7 (101).

The increase of the CO2 concentration in air is caused by the increase of combustion of fossil fuels. That this raise of CO2 concentration (the so-called Suess effect[2]) is caused by the increased emission of fossil fuels is confirmed with 14C measurements in atmospheric CO2. Measurements in international sites (Schauinsland, Black Forest, Groningen) give values of around 102 pmC in the year 2015. Presently the decline is ca. 0,4 pmC to 0,5 pmC per year, mainly due to fossil fuel combustion.

For high precision pmC measurements, the 14C/12C and 13C/12C isotopic ratios shall be determined, as correction for isotopic fractionation should be done. During working up of the sample this fractionation can occur if only a part of the combusted sample is analysed. In biomass, small variations in carbon isotope ratios occur as well, it depends on the type of photosynthesis that formed the biomass. Most biomass (e.g. wood) is of the so-called C3 type photosynthesis, some tropical plants (corn, tropical grasses) are of the C4 type photosynthesis. For SRF applications the maximum error is estimated to be well below 1 % as for 100 % C4 biomass a value of 99 % biomass will be measured if no isotope correction is done.

The fraction of biomass content by mass and the fraction of biomass by energy content shall be calculated using the biogenic carbon in the solid recovered fuel and the carbon and energy content of the biomass fraction.

According to experimental reported data (ASTM D 6866-20[4]), a consensus value of 101 pmC for biomass may be used for 2019, considering an estimate decrease of 0,3 pmC/year, due to 14C dilution from atmospheric emissions; a value of 100 pmC can be extrapolated for 2022 year. After 2022 a further reduction will probably result in a pmC value lower than 100: a more precise extrapolation will be possible in the future and the new value will be included in the next revision of this document. Extrapolated data should be verified in the future.

For solid recovered fuel (SRF) produced mainly from urban waste, pmC values can be different on a regional base and they may be used if general accepted evidence is provided. A general value reported in this document for European waste material is 116 pmC in 2009. The literature[9] report an extrapolated value of 109 for 2009 and a 2006 value of 113 pmC which is significatively higher than of 108 pmC (as reported in ASTM D6866-20[4]). The literature[8] report 2008 values for different type of SRF ranging from 115 (SRF from urban waste) and 121 (SRF from large wastes): a value close to 117 can be estimated for SRF from mixed waste. In ISO 13833:2013 reference is done to pmC value for 2010 of 111 with a decrease to 109 in 2015. These literature values are reported in Figure A.4.

SRF pmC values (2008-2015)

Figure A.4 — pmC values for SRF from literature

Since pmC values differ on regional values and for different SRF types the reported data are scattered. From the extrapolated value for 2015 and considering the 0,3 pmC/year an extrapolated value for 2020 of 108 pmC can be proposed.

For other fuels composed of single materials, pmC values may be used (UNI/TS 11461[5]):

— paper and cardboard: 117 (2008); 112 (2015) 109 (2020, calculated reported value from ECN database).

Figure A.5 — pmC values for paper and cardboard

— wood-based material (with the exception of pure biomass): 121 (2015); 122 (2020).

An increase is expected due to increase of the reuse of more recent materials. A consensus value may be proposed to be 122.

From the previous reported data, it is clear that an accurate selection of pmC reference values for fresh biomass and for SRF is of crucial importance for the application of this standard. 101 pmC for fresh biomass and 107 pmC for SRF shall be used on the basis of available literature data.

When available accurate information about the composition of the SRF and the pmC value of the individual fractions a more accurate pmC value for that type of SRF can be obtained, then that pmC value can be used. This value and the method for its calculation shall be included in the test report (Clause 9).

NOTE  Calculation example is reported in Table A.1.

Table A.1 — Data used for the calculation

Material

Carbon

Net calorific value

pmC

DPM

Correction factor

% (daf)

MJ/kg (daf)

%

%

%

Demolition wood

50

19

114

15,4

88

Cardboard

45

17

110

15,1

91

Used paper

47

17

110

15,4

91

Fresh biomass

48

18

101

14,3

99

SRF value

47,5

18,4

107

15,2

93

If for instance the biomass fraction of SRF only would consist of used paper then for that biomass fraction a pmC value of 110, a DPM value of 15,4, a carbon content of 47 % and a net calorific value of 17 MJ/kg has to be used as a basis of the calculation (see Table A.1). Hence a SRF mix containing 50 % used paper (m/m) and 50 % non-biomass fraction a pmC value 114/2 = 57 (or a DPM value of 15,4 / 2 = 7,7) will be measured, resulting in a biomass energy content of 17/2 = 8,5 MJ/kg.

Example of conversion from biogenic carbon content to biomass content

In a SRF sample with a total energy content of 18,1 MJ/kg, an amount of 20,0 % of biogenic carbon was measured.

The biomass fraction of the SRF sample was estimated to be a paper fraction containing 46,6 % of carbon.

The biomass mass fraction (wB) then will be 20,0 × 100/46,6 = 42,9 %.

Example of conversion from biogenic carbon content to biomass energy content with a mixed biomass fraction

In a SRF sample with a total energy content of 18,1 MJ/kg (ad) and TC = 43 % (ad), an amount of 20 % of biogenic carbon was measured.

The biomass fraction of the SRF sample was estimated to consist of 30 % (m/m) of demolition wood and 70 % (m/m) of paper.

The biomass mass fraction (wB) then will be 30/100 × 20 × 100/50 (from Table A.1) + 70/100 × 20 × 100/47 (from Table A.1) = 41,8 %.

The biomass energy content will be 30/100 × 20 × 19/50 + 70/100 × 20 × 17/47 = 7,34 MJ/kg ad

(normative) Determination of biomass content using the selective dissolution method (SDM)

General

This annex specifies the procedures for the determination of the biomass content expressed in percent by mass, by calorific value and by carbon content using selective dissolution. The selective dissolution method (SDM) is based on the fact that biomass oxidizes significantly more quickly than non-biomass.

Principle

The SDM for the determination of the biomass content expressed in percent by mass involves the treatment with concentrated sulphuric acid topped with hydrogen peroxide. As a general rule, the biomass in the solid recovered fuel will selectively dissolve and the non-biomass will remain in the residue.

For the determination of the biomass content expressed in percent by mass, the sample shall be weighed before and after selective dissolution. The biomass content by mass is corrected for the content of carbonates by measuring the ash content (according to ISO 21656 Method A) before and after dissolution. Figure B.1 shows which steps are performed when determining the biomass content by percent in mass using the SDM.

The determination of the biomass content by calorific value consists of two procedures. The first procedure determines the calorific values of the total sample and non-biomass fraction. The second procedure calculates the biomass content by energy content. Figure B.2 illustrates the principle by which the fraction specific calorific values shall be determined. Depending on the use of the results, the biomass content may be calculated in percent by net calorific value or by gross calorific value. Before this annex is applied, a choice shall be made whether the biomass fraction shall be determined by net calorific value or gross calorific value. All calorific values in the rest of this annex will then be expressed according to that choice.

The determination of the biomass content by carbon content involves the determination of the TC content before and after the selective dissolution of the biomass fraction. The results are used for the calculations of the biomass content expressed in percentage by TC. The maximum relative error for the biomass content by TC is 0,4 % per 1,0 percent by mass of the ash fraction. Therefore, a correction for carbonate present in the ashes is made if the ash content in the original sample (as determined in this annex is larger than 10 % by mass on a dry basis. Figure B.3 shows which steps are performed when determining the biomass content by using the SDM for the determination of the biomass content in percent by TC.

Limitations

The minimum sample amount to be used for each test shall be at least 5 g of the material with a nominal top size of 1 mm or less. Other details on limitations of this method can be found in Annex D.

Symbols

For the purposes of this annex, the following abbreviated terms apply.

ASRF

ash content of SRF sample according to ISO 21656;

Cash

total carbon content of the ash fraction expressed as a percentage by mass;

Cresidue

total carbon content of the non-biomass fraction expressed as a percentage by mass;

Ctot

total carbon content of the total sample expressed as a percentage by mass;

daf

dry and ash free

M

moisture content (percentage by mass)

mresidue-ash

mass of ash of dissolution residue (including filter), burned according to ISO 21656 in g;

mSRF

mass of dry SRF test portion used for dissolution, in g;

mresidue

remaining dry mass (including filter) after the test portion has been dissolved, in g;

qB(daf)

calorific value of the biomass fraction on a dry and ash-free basis, in MJ/kg;

qNB(daf)

calorific value of the non-biomass fraction on a dry and ash-free basis, in MJ/kg;

qresidue(daf)

calorific value of the residue resulting from the dissolution test on a dry basis, in MJ/kg;

qSRF(daf)

calorific value of the SRF on a dry basis sample, in MJ/kg;

TC

total carbon;

biomass content expressed as a percentage by mass;

wNB

non-biomass expressed as a percentage by mass;

biomass content expressed as a percentage by calorific value;

non-biomass content expressed as a percentage by calorific value;

biomass content expressed as a percentage by TC;

amount of dissolution residue, expressed as a percentage by mass.

Reagents and materials

Reagents and materials needed for performing the SDM are:

— 78 % (g/g) H2SO4 (laboratory quality);

— 35 % (g/g) H2O2 (laboratory quality);

— glass fibre filter, ∅ 10 cm or 12,5 cm, GF 6 (this means that it is a filter which is equipped to block particles larger than 1 µm); in case of high biomass content (>80 %) SRF a filter with a smaller diameter (e. g. 5 cm) may be used. Filters shall be resistant to temperatures of 550 °C;

NOTE See Table D.1 for examples of high biomass materials.

— water of at least demineralized quality.

Apparatus

Apparatus needed for performing the SDM are:

— filtration device, for example Büchner funnel;

— conical flask (500 ml);

— desiccator;

— muffle furnace at a temperature over 550 °C (ashing temperature is not important for this document);

— a dish consisting of inert material such as porcelain, silica or platinum;

— cutting grinder or other grinding apparatus that may be used to reduce samples to <1 mm;

— fume cupboard;

— pH measuring device;

— balance, capable of weighing the dish containing the sample to the nearest 0,1 mg.

Procedure for the determination of the biomass content expressed in percent by mass

General

This procedure specifies the determination of the biomass content expressed in percent by mass, using the SDM. Figure B.1 illustrates the principle by which the percentage by mass is determined.

Figure B.1 — SDM for biomass content expressed in percent by mass

Procedure

Sample preparation in the field shall be conducted according to ISO 21645 and to ISO 21646. Preparation of the test sample shall be conducted according to ISO 21646. Perform the following steps for implementing the SDM:

a) take two test portions of 5 g and a nominal top size of 1 mm or less according to ISO 21646. Record the mass of the two test portions;

b) determine the ash content of test portion A, ASRF according to ISO 21656, Method A. When the biomass content expressed in percent by total carbon is to be determined (see B.9), the ash shall be retained;

c) dry and cool the test portion B in a crucible at (105 ± 2) °C to a constant mass according to CEN/TS 15414-1 and cool in a desiccator. In case SRF contains volatile compounds other than water, the Karl-Fischer method is advisable on a different test portion;

WARNING — For some types of solid recovered fuels there can be a risk of self-ignition when drying at 105 °C.

d) weigh the dried test portion B to the nearest 0,1 mg. Record the mass (mSRF);

e) place test portion B in an empty 500 ml flask;

f) make sure the crucible is completely empty after emptying into the flask. If not, the mass before and after emptying shall be determined which enables the recalculation of mSRF;

g) add 150 ml of 78 % (g/g) H2SO4 to the conical flask. Stir carefully, but thoroughly by hand. The sample has to be completely moistened with H2SO4. Place the (full) flask away in a fume cupboard for 16 h ± 2 h (cooling may be required);

h) after 16 h ± 2 h, add 30 ml of 35 % (g/g) H2O2. Add slowly to control the reaction. Stir carefully, but thoroughly by hand. The sample shall be completely moistened with H2O2. Place the conical flask away in a fume cupboard for 5 h ± 1 h (cooling may be required);

i) dry a glass fibre filter and record the mass of the glass fibre filter (mfilter);

j) after 5 h ± 1 h, dilute the sample B with 300 ml of demineralised water and then filter it over a glass fibre filter in a Büchner funnel or similar device;

k) remove the sulphuric acid by rinsing the residue with 6 doses of 50 ml demineralised water. Make sure the entire 50 ml demineralised water is removed before another dose is added or until the last filtrated volume has a pH of at least 3,0;

l) dry the solid residue from test portion B together with the filter at 105 °C until a constant mass has been achieved;

m) weigh the dried residue B together with the filter to the nearest 0,1 mg. Record the mass (mresidue);

n) determine the ash content (mresidue-ash) of the solid residue from test portion B according to ISO 21656, Method A.

Calculation of the results

The results of the dissolution test and the Formulas (B.1) and (B.2) shall be used to calculate the biomass content, the ash content and the non-biomass content on a dry basis expressed as a percentage by mass.

Use Formula (B.1) for the determination of the biomass content on a dry basis expressed as a percentage by mass:

Use Formula (B.2) for the calculation of the non-biomass content on a dry basis.

It should be noted that the result is pure (100 %) biomass, or non-biomass calculated from total dry mass. This means that when calculating e.g. energy content of SRF, calorific values on dry ash-free (daf) shall be used.

EXAMPLE  

— An SRF sample has an ash content of 15,0 % (d).

— A test portion of about 5 g is taken (after drying, the dry mass was noticed to be 5,101 3 g).

— A dissolution is carried out for this material.

— After dissolution, the residue is dried and weighed. The mass is noticed to be 2,502 8 g.

— The residue is then ashed and the remaining mass of residue ash was noticed to be 0,411 0 g.

The calculation now gives [according to Formula (B.1)]:

The non-biomass content on dry basis can now be calculated [according to Formula (B.2)]:

Procedure for the determination of the biomass content by calorific value

General

This procedure specifies the determination of fraction specific calorific values of biomass and non-biomass. These calorific values can be expressed either as net calorific value or as gross calorific value. Determination of the biomass content of solid recovered fuels is based on the SDM.

Procedure

The determination of the biomass content by calorific value consists of two procedures. The first procedure determines the calorific values of the biomass and non-biomass fraction. The second procedure calculates the biomass content by energy content. Figure B.2 illustrates the principle by which the fraction specific calorific values shall be determined.

Figure B.2 — Determination of the biomass content by calorific value

Depending on the use of the results, the biomass content may be calculated in percent by net calorific value or by gross calorific value. Before this annex is applied, a choice shall be made whether the biomass fraction shall be determined by net calorific value or gross calorific value. All calorific values in the rest of this annex will then be expressed according to the choice.

The calorific value and the ash content of both the sample and the residue shall be determined according to ISO 21654 and ISO 21656 Method A respectively. With these values the fraction specific calorific values shall be calculated.

In case of gross calorific values, the formulas in Table B.1 can be used for conversion of data from dry base to as received base or dry ash free base:

Given

Wanted

As analysed (air-dried) (ad)

As receiveda   (ar)

Dry   (d)

Dry, ash free   (daf)

As analysed (air-dried, ad)

As received (ar)

Dry (d)

Dry, ash free (daf)

a   Note that the formulae given for calculating results to the “as received” basis can be used to calculate them to any other moisture bases.

Table B.1 — Formulae for conversion of gross calorific value

In order to determine fraction-specific calorific values the following steps shall be performed:

a) take a sample according to ISO 21645 and prepare the sample according to ISO 21646;

b) determine the calorific value and the ash content of the sample according to ISO 21654 and ISO 21656, Method A;

c) determine the non-biomass content of a test portion according to B.7;

d) take a new test portion and follow steps c) to m) of the instructions in B.7.2. If an estimation of the biomass content indicates that 5 g of a test portion will result in insufficient material to determine the calorific value of the residue, then the volumes shall be scaled up proportionately;

e) determine both the ash content and the calorific value of the residue. When less than 1 g of residue is obtained after selective dissolution or the part of the fines in the residue is high, the residue together with the filter should be crushed for the determination of the calorific value and the contribution of the filter should be deducted in the result.

Calculation of the results

Calculate the dry ash-free fraction-specific calorific value of the non-biomass fraction and the total sample using the values obtained in steps b) to e). To this end, Formulas (B.3) and (B.4) shall be used:

Calculate the ash-free fraction-specific calorific value of the biomass fraction using Formula (B.3):

EXAMPLE In a dry SRF sample, following properties were found: qSRF(daf) = 18,21 MJ/kg; ash content ASRF(d) = 8,0 %. In the Selective dissolution test the amount of residue, xNB (daf) was 40 %, ash content ANB = 10,2 % and qNB = 25,03 MJ/kg. We now have:

The procedure for determining the biomass content in percent by calorific value consists of four steps:

a) determine the biomass content, xB, and non-biomass content, xNB, according to B.7.3;

b) determine the fraction specific calorific values according to B.8;

c) determine the biomass content in percent by calorific value;

d) The biomass content by calorific value is calculated as follows:

Procedure for the determination biomass content by TC

General

This procedure specifies the procedure for the determination of the biomass content in percent by TC by selective dissolution of the solid recovered fuel. The TC content is determined before and after the selective dissolution of the biomass. The results are used for the calculations of the biomass content expressed in percentage by TC. The maximum relative error for the biomass content by TC is 0,4 % per 1,0 % by mass of the ash fraction. Therefore, a correction for carbonate present in the ashes is made if the ash content in the original sample (as determined in this annex) is larger than 10 % by mass on a dry basis.

Figure B.3 shows which steps are performed when determining the biomass content by using the SDM for the determination of the biomass content in percent by TC.

Figure B.3 — SDM for biomass content in percent by TC

The following steps shall be performed for implementing the SDM for the determination of the biomass content in percent by TC:

a) take four test portions A, B, C and D. Test portions A and B shall have a mass of at least 5 g. Test portion C and D shall meet the requirements of ISO 21663; record the mass of all test portions;

b) determine, with test portions A and B, ash (ASRF) and residue fraction (xresidue) by mass according to procedure B.7.1. Store the ash;

c) if the ash content is larger than 10 % by mass go to step d), otherwise, go to step e);

d) determine the TC content of the ash fraction according to ISO 21663 of the ash residue stored in step b). Record this as Cash. Dependent on the TC analyser, greater sample volumes should be used or analyses be repeated;

e) determine the TC content of test portion C according to ISO 21663. Record this as the TC content of the total sample, Ctot;

f) take test portion D with a minimum size according to the content of the residue xresidue;

NOTE In case of micro-methods typical sample mass is 5 mg: if the residue is 40 %, then the minimum size of the test portion is 5/0,4 = 12,5 mg; in case of macro-methods typical sample mass is 500 mg: then the minimum size of test portion is 500/04 = 1 250 mg in case of 40 % residue. When using the micro-methods the representativity should be verified.

g) perform step c) to e) of B.8.2 on test portion D;

h) remove the residue of test portion D from the filter carefully and determine the TC content of the residue according to ISO 21663. The TC content of the residue is equal to the TC content of the non-biomass fraction. Record this as Cresidue. Dependent on the TC analyser, greater sample volumes should be used or analyses be repeated.

Calculation of the results

If the ash content is larger than 10 % by mass, use Formula (B.7) to calculate the biomass content expressed as a percentage by carbon content.

If the ash content is smaller than 10 % by mass, use Formula (B.8) to calculate the biomass content expressed as a percentage by carbon content.

NOTE In the calculations, it is assumed that there is no inorganic carbon in the biomass fraction. Also, it is assumed that in the selective dissolution test all inorganic carbon is lost i.e. there is no inorganic carbon in the dissolution residue.

Depending on the quality of the ash, a deviation of up to 0,4 % per 1,0 % of ash content may be caused by carbonates present in the ash.

(normative) Determination of biomass content using the manual sorting method (Msort)

General

In the Msort, a sample of the solid recovered fuel is sorted by hand into sub-fractions, such as plastics, paper/cardboard, wood, vegetable, fruit, garden waste and inert matter.

Principle

The Msort for the determination of the biomass content in percent by mass involves the separation of the components into a number of fractions which are either (mostly) biomass or (mostly) non-biomass.

Limitations

This method is not applicable for solid recovered fuels with a particle size smaller than 10 mm and/or SRF that is pelletized. Other details on limitations of this method can be found in Annex D.

Symbols

For the purposes of this annex, the following symbols apply.

wB

biomass content on a dry basis, expressed as a percentage by mass;

biomass content in the sorted non-biomass fraction on a dry and ash-free basis, expressed as a percentage by mass;

content of component i in the biomass category on a dry basis, expressed as a percentage by mass;

content of component i in the ash matter category on a dry basis, expressed as a percentage by mass;

content of component i in the non-biomass category on a dry basis, expressed as a percentage by mass;

inert content on a dry basis, expressed as a percentage by mass;

inert content in the sorted biomass fraction on a dry basis, expressed as a percentage by mass;

inert content in the sorted non-biomass fraction on a dry and ash-free basis, expressed as a percentage by mass;

non-biomass content on a dry basis, expressed as a percentage by mass;

non-biomass content of the sorted biomass fraction on a dry basis, expressed as a percentage by mass;

biomass content of the sorted inert fraction on a dry basis, expressed as a percentage by mass;

non-biomass content of the sorted inert fraction on a dry basis, expressed as a percentage by mass;

inert content of sorted inert fraction expressed as a percentage by mass.

Apparatus

Apparatus needed for performing the Msort are:

— screen sieve of 10 mm;

— balance with accuracy of 0,1 g;

— containers for the sorted fractions (14);

— desiccator.

Procedure

General

The procedure consists of the following two steps:

a) manual sorting;

b) calculation of the results.

Manual sorting

The instructions for implementing the Msort comprise the following steps:

a) take a sample according to ISO 21645. Prepare the sample according to ISO 21646. The test portion for the Msort shall be at least as big as the minimum sample size according to ISO 21645.

b) sort all particles larger than 10 mm of the sample into the fractions mentioned in Table C.1;

NOTE The sample is sieved with a 10 mm sieve to remove all particles below 10 mm which are classified as “fines” fraction.

c) dry all fractions at 105 °C to a constant mass;

WARNING — For some types of solid recovered fuels there can be a risk of self-ignition when drying at 105 °C.

d) allow the dried fractions to cool down in a desiccator (with samples over 100 g it is not feasible to use the desiccator and the samples shall be weighed directly);

e) weigh the dried fractions with four significant digits. Record the mass for each fraction;

f) cluster the masses of the categories according to Table C.1 into biomass, non-biomass and inert fractions and determine the mass per fraction by summing.

NOTE Examples of components/subfractions are given in Table C.2.

For determining the biomass content, the selected sub-fractions concerned shall be clustered into the categories biomass, non-biomass and inert matter. This classification will never be exact, due to e.g. the presence of composite materials. For example, drink cartons contain not only paper (biomass) but also small quantities of plastic (non-biomass) and aluminium (inert).

Table C.1 presents the subfractions of solid recovered fuels in which the sample shall be sub-divided. In Table C.2 examples are given of the components/sub-fractions as mentioned in Table C.1.

Table C.1 — Categorization of components for manual sorting

Fraction

The fraction is characterized as a

For the determination of biomass, non-biomass or inert content, expressed as a percentage by mass, the fraction shall be assigned to the category

Biological waste

biomass fraction

Biomass

Paper/cardboard

biomass fraction

Biomass

Wood

biomass fraction

Biomass

Tissue

biomass fraction

Biomass

Fabric

mixed fraction containing mostly biomass

to be determined by one of the other methods specified in the present standard

Leather

fraction containing mostly biomass

biomass

Natural rubber

 

to be determined by one of the other methods specified in the present standard

Glass

inert fraction containing mostly contaminations of biomass

Inert

Stone

inert fraction containing mostly contaminations of biomass

Inert

Fines

fraction with a nominal top size less than 10 mm.

to be determined by one of the other methods specified in the present standard

Plastic

non-biomass fraction

to be determined by one of the other methods specified in the present standard

Rugs/carpets/mats

mixed fraction containing mostly non-biomass

non-biomass

Iron

inert fraction containing mostly contaminations of non-biomass

Inert

Non ferrous metals

inert fraction containing mostly contaminations of non-biomass

Inert

Table C.2 — Examples of components/sub-fractions

Examples of components/sub-fractions

Biological waste

— leaves, grass

— biodegradable food residues (bread, rice, vegetables, …)

Paper/cardboard

— packaging paper

— cardboard

— magazines, newspaper

— milk cartons

— drink cartons (80 % biomass)

Wood

— waste wood

— sawdust

— waste wood from gardens

— mats

Tissue

— diaper

— tissues

— tampons, napkins

— toilet paper

Fabric

— any (remains of) cloths other than leather and/or metal

Leather

— leather and similar materials

Rubber

— any kind of rubber including used tyres

Glass

— bottles

— glasses

— shards

Stone

— stones

— pottery (remains)

Fines

— any material smaller than 10 mm

Plastic

— soft plastic

— plastic bags

— plastic packaging material

— plastic cups

— PE, PP, Polystyrene

— Rigid plastic

— PET(-bottles)

— PVC(-tubes)

— polyester

Rugs/Carpet

— rugs

— carpets

Iron

— any particle (mostly) made of iron or steel

Non-ferrous metals

— copper/zinc/ lead tubing

— aluminium cans

— (electrical) wires

— strip (of medicines or candy)

NOTE   Some plastic can be made by degradable product (e.g. plastic bags).

Calculation of the biomass content

Use Formula (C.1) for the determination of the biomass content in percent by mass:

Use Formula (C.2) for the calculation of the non-biomass content expressed as percentage by mass:

Use Formula (C.3) for the calculation of inert content expressed as a percentage by mass:

NOTE 1 Biomass and non-biomass content of the mixed fraction are determined as described in Table C.1 and the values are included in the respective calculation by using the previous formulae.

NOTE 2 In the Msort method ash of each sorted fraction is considered to belong to this fraction. Thus, when calculating e.g. energy contents of different fractions calorific values on dry (d) ash free basis will be used.

(informative) Limitations of the determination methods

General

A method that determines a certain property by separating two or more fractions, uses the differences of one or more properties between those fractions. However, separation methods never achieve a perfect separation because they tend to model the most common chemical and/or physical features instead of performing a perfect separation. This applies for virtually all determination and separation methods. Any method has its own situations in which its precision decreases, because of interfering components and properties.

Biomass is no intrinsic property of substance, but it is a classification of origin. The number of different materials that is present in waste is vast and many materials are transformed or modified chemically and/or physically numerous times. Traces of their origin may vanish and therefore exceptions in the classification of origin occur always. Only when the total (organic) carbon content of biomass is determined by the 14C method no exceptions occur.

The methods described in this standard are developed to determine the biomass content in mixture of biomass and non-biomass substances. Problems with the reliability of the SDM and the Msort can occur specially for biomass concentrations below 5 % and above 95 %. The influence of non-regular substances might modify the results significantly in these regions. Verification with the 14C method will solve these problems.

This annex intends to give some information on how and when care should be taken when using this document. D.2 and D.3 are describing the limitations of the SDM and D.4 gives some limitations in the use of the 14C method.

Influence of solubility of various materials with the SDM

The basic assumption of the SDM is a complete degradation of biomass materials and no degradation at-all of non-biomass materials. Most biomass materials have degradability of almost 100 % under the condition of this standard and the performance of the selective dissolution test is likewise. Some materials show larger deviations. Some of these materials are completely biomass but dissolve only partly during selective dissolution. This mostly coincides with biomass materials which show a high resistance against degradation as well.

Most non-biomass materials are not dissolvable and the performance of the selective dissolution test is quite well, revealing almost 0 % dissolution. Some non-biomass materials are chemically modified for their dissolvable properties and are therefore completely dissolvable. Other non-biomass materials such as polyamide and polyurethane also dissolve during selective dissolution. Besides dissolving, these non-biomass materials are more dissolvable than most common non-biomass materials.

Tables D.1 and D.2 show the performance of the SDM on a large number of respectively biomass and non-biomass materials.

Table D.1 — Performance of SDM on biomass materials

Biomass/ non-biomass

Material

Biomass content according to the dissolution test

Maximum difference observed

biomass

Tropical hard wood (Bankirai)

100 %

0,0 %

biomass

Pine

100 %

0,0 %

biomass

Fir

100 %

0,3 %

biomass

Oak

100 %

0,1 %

biomass

Duck feathers

100 %

n.a.

biomass

Linen

99 %

0,0 %

biomass

MDF residues

99 %

0,0 %

biomass

Cotton

99 %

0,0 %

biomass

BIOPAC® (based on starch)

99 %

0,1 %

biomass

Copy paper

99 %

0,5 %

biomass

Shea nut residues

99 %

0,9 %

biomass

Pulverized cacao shell residues

98 %

0,9 %

biomass

Coconut residues

98 %

0,7 %

biomass

Waste wood pellets

98 %

1,6 %

biomass

Willow

98 %

0,4 %

biomass

Olive pit residues

98 %

8,4 %

biomass

Pelletized cacao shell residues

97 %

0,8 %

biomass

Newspaper

97 %

0,2 %

biomass

Seeds of grass

97 %

n.a.

biomass

Palm pit residues

97 %

n.a.

biomass

Glossy paper

97 %

0,2 %

biomass

Cherry pits

94 %

5,2 %

biomass

Leather

93 %

0,1 %

biomass

NR (natural rubber)

84 %

3,3 %

biomass

Viscose (based on cellulose)

83 %

0,2 %

biomass

Wool

82 %

36,2 %

biomass

Frying fat

41 %

2,5 %

biomass

Charcoal

2 %

n.a.

biomass

ECOPLA® (based on corn)

0 %

0,2 %

Table D.2 — Performance of SDM on non-biomass materials

Biomass/ non-biomass

Material

Biomass content according to the dissolution test

Maximum difference observed

non-biomass

PS foam (Polystyrene)

-2 %

1,5 %

non-biomass

PC (Polycarbonate)

−1 %

0,1 %

non-biomass

IIR (Butyl Rubber)

0 %

13,7 %

non-biomass

PS dense (Polystyrene) PS non-expanded (Polystyrene)

0 %

0,1 %

non-biomass

LDPE (Low density polyethylene)

0 %

0,7 %

non-biomass

PP (Polypropylene)

0 %

0,3 %

non-biomass

PET (Polyethyleneterephtalate)

0 %

0,9 %

non-biomass

HDPE (High density polyethylene)

1 %

1,4 %

non-biomass

PVC (Polyvinylchloride)

2 %

0,9 %

non-biomass

CR (Chloroprene rubber)

10 %

1,1 %

non-biomass

SBR (Styrene-butadiene rubber)

14 %

3,6 %

non-biomass

Hard coal

43,5 %

10,6 %

non-biomass

Silicon rubber

86 %

6,1 %

non-biomass

Lignite

93 %

1,5 %

non-biomass

PUR non-expanded (Polyurethane)

95 %

0,4 %

non-biomass

Polyamide 6.6

97 %

3,1 %

non-biomass

PUR foam (Polyurethane)

98 %

0,1 %

The results show that most common materials present in mixed waste streams are handled adequately with the SDM. For those samples with significant amounts of deviant substances, a correction should be made. Unfortunately, this is impossible due to the complexity and diversity of substances present in many types of solid recovered fuel. In general, for solid recovered fuels comprising of a mix of biomass and non-biomass materials, the SDM is rather reliable, but outside the concentration range 10 % to 90 % the relative reliability decreases for some materials. Some suggestions are given in Tables D.1 and D.2.

Influence of physical shape and composition of materials/particles in Msort method

The influence of the physical shape and composition of materials/particles affects the Msort, because it is based on differences in the physical appearance and properties of biomass or non-biomass materials.

Three sources of error exist that affect the performance of the Msort. These sources of error are:

1) the potential presence of mixed materials that are not feasible to separate manually. These mixed materials are particles which are made of both biomass and non-biomass indistinguishably connected together;

2) minimum particle size, below which effective manual separation is impossible without using a microscope;

3) the presence of materials which mimic the physical appearance or properties of the complementary material class, such as degradable plastics.

The quantitative implications of these sources of error are difficult to predict and therefore the SDM prevails on the sorting method.

Limitations to the 14C-method

1) Conversion of the sample to CO2 can be done at every well-equipped analytical lab, however the 14C measurements requires highly specialized instruments and personnel.

2) 14C releases in the 1950’s (hydrogen bomb experiments) has decreased the accuracy of the 14C method. Moreover the fossil fuel consumption contributed in lowering the accuracy in the estimation of 14C level in atmosphere.

The quantitative implications of these limitations are difficult to predict and should be considered when using this method.

(informative) Performance data

Performance data for the SDM

An inter-laboratory study, named Quovadis[3] was carried out by laboratories in Austria, Finland, France, Germany, Italy, Poland, Sweden, The Netherlands and the United Kingdom.

For the description of sample type see Table E.1.

The performance data according to ISO 5725-2[1] are presented in Tables E.1, E.2, E.3 and E.4.

Table E.1 — description of sample types

nr

Sample

Matrix

2

QV-B

SRF produced from demolition wood

4

QV-D

SRF produced from Municipal waste

5

QV-E

SRF produced from Municipal waste (paper and plastic rich)

Table E.2 — Performance data for biomass content with SDM by mass content

Sample

l

n

xm

CV,R

CV,r

2

54

9

95,93

0,97

0,93

4

57

9

67,79

3,43

2,34

5

54

9

54,17

7,04

2,37

Table E.3 — Performance data for biomass content with SDM by calorific value content

Sample

l

n

xm

CV,R

CV,r

2

7

3

99,03

NA

NA

4

19

4

77,53

6,26

6,26

5

19

4

69,92

14,3

14,3

Table E.4 — Performance data for biomass content with SDM by carbon content

Sample

l

n

x m

CV,R

CV,r

2

16

3

99,47

0,51

0,51

4

24

4

71,94

6,45

5,85

5

24

4

54,31

12,6

12,6

where

 

l

is the number of outlier-free individual analytical values per level;

 

n

is the number of laboratories after outlier elimination;

 

o

is the percentage of outlying values from the replicate determinations;

 

xm

is the overall mean, expressed in %;

 

CV,R

is the coefficient of the variation of the reproducibility;

 

CV,r

is the coefficient of the variation of the repeatability.

Performance data for the 14C-method

This inter-laboratory study was carried out by laboratories in Austria, Germany, United Kingdom and The Netherlands.

For the description of sample type see Table E.5.

The performance data according to ISO 5725-2[1] are presented in Table E.6.

Table E.5 — Description of sample types

Sample

Matrix

Nr-1

SRF from industrial waste

Nr-2

SRF from household waste

Nr-3

Reconstructed SRF [15 % paper/cardboard, 44 % wood, 18 % hard plastics, 12 % soft plastics (foils), 4 % carpets, 4 % fabrics, 3 % tissue]

Nr-4

Synthetic SRF [20 % paper/cardboard, 20 % wood, 20 % hard plastics (PET), 20 % soft plastics (foils), 20 % tissue (Zellstoff)]

Table E.6 — Some performance data for 14C methods

 

AMS F

 

AMS B

 

AMS L

 

LSC B

 

LSC L

 

 

xm

s

xm

s

xm

s

xm

s

xm

s

Nr-1

12,6

1,3

15,6

1,0

18,9

1,4

—

—

—

—

Nr-2

61,0

0,02

60,4

1,0

—

—

55,5

1,4

—

—

Nr-3

56,6

1,6

56,5

1,8

—

—

—

—

—

—

Nr-4

64,0

2,9

50,5

1,7

—

—

46,2

—

—

—

AMS F = Furnace combustion and AMS measurement

AMS B = Calorimetric bomb combustion and AMS measurement

AMS L = Lab scale combustion and AMS measurement

LSC B = Calorimetric bomb combustion and LSC measurement

LSC L = Lab scale combustion and LSC measurement

xm = mean value

s = standard deviation

A performance study in one laboratory (Italy) using n. 4 SRF type and LSC B technique resulted in a relative expanded uncertainty (k = 2) value of 8,1 % at 46,0 % level (S = 3,7). This Figure includes analysis sample preparation, combustion and instrumental measurement, but not sampling and preparation of laboratory sample.

Table E.7 — Some performance data for 14C methods for AMS method (ISO 13833[6])

 

Biogenic to total CO2 ratio

Coefficient of variation (CV, %)

Biomass material

0,506

0,6

Biomass material

0,531

0,4

Table E.8 — Some performance data for 14C methods for LSC method (ISO 13833[6])

 

Biogenic to total CO2 ratio

Coefficient of variation (CV, %)

Biomass material

0,579

4,3

Biomass material

1,000

4

Bibliography

[1] ISO 5725‑2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method

[2] Suess H.E. Science. 1955, 122 pp. 415–417

[3] QUOVADIS Deliverable 7.4–2007, Report on the validation of the sampling procedures including recommendations to TC 343 for the eventual revision of the TS before its upgrade to a International standard (EN). EU-Project number EIE 2003 031 — Grant Agreement EIE/031/S07.38597, 2007

[4] ASTM D6866-20:2020 “Standard Test Methods for Determining the Biobased Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis”

[5] UNI/TS 11461, Co-combustion, incineration and co-incineration plants — Determination of the renewable energy fraction produced by plant with 14C method

[6] ISO 13833, Stationary source emissions — Determination of the ratio of biomass (biogenic) and fossil-derived carbon dioxide — Radiocarbon sampling and determination

[7] New reference values for 2016 and later will be available on the CIO internet site: https://www.rug.nl/research/centre-for-isotope-research/customers/tools/reference-radiocarbon-values-palstra-and-meijer?lang=en

[8] Mohn J., Szidat S., Fellner J., Rechberger H., Quartier R., Buchmann B., Emmenegger L., 2008. Determination of biogenic and fossil CO2 emitted by waste incineration based on 14CO2 and mass balances. Bioresource Technology 99, 6471–6479

[9] Mohn J., Fellner J., Rechberger H., Abundance of 14C in biomass fractions of wastes and solid recovered fuels, Waste Management (2009), doi:10.1016/j.wasman.2008.11

[10] ISO 21660-3 , Solid recovered fuels — Determination of moisture content using the oven dry method — Part 3: Moisture in general analysis sample

� Under preparation. Stage at the time of publication ISO/FDIS 21645.

� Under preparation. Stage at the time of publication ISO/DIS 21646.

� Under preparation. Stage at the time of publication ISO/FDIS 21654.

� Under preparation. Stage at the time of publication ISO/FDIS 21656.

� Under preparation. Stage at the time of publication ISO/FDIS 21660-3.