ASTM Committee E48 has jurisdiction over bioenergy and indus- trial chemicals. In that capacity, some standards have been issued by this committee. Most of these are similar to techniques based on chemical or physical test methods used in ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants or ASTM Committee D05 on Coal and Coke. A list of the standards issued by ASTM Committee E48 related to bioenergy from biomass is given in Table 7.1.
Standard terminology used in the context of this chapter is listed in Table 7.2. The terminology is excerpted from ASTM Standard E1705. All these definitions were under ASTM E1126, Terminology Relating to Biomass Fuels, which was withdrawn in 2003.
ASTM E870, Standard Test Methods for Analysis of Wood Fuels
These test methods cover the proximate and ultimate analysis of wood fuels and the determination of gross caloric value of wood fuels sampled and prepared by prescribed test methods and ana- lyzed according to ASTM established procedures. Test methods as
herein described may be used to establish the rank of fuels, to show the ratio of combustible to incombustible constituents, to provide the basis for buying and selling, and to evaluate for beneficiation or for other purposes.
Proximate analysis is considered as an assay of the moisture, ash, volatile matter, and fixed carbon as determined by prescribed test methods. Other constituents such as sulfur and phosphorus are not included.
Ultimate analysis is considered as the determination of car- bon and hydrogen in the material, as found in the gaseous products of its complete combustion; the determination of sulfur, nitrogen, and ash in the material as a whole; and the calculation of oxygen by difference.
Test methods used for these analyses are listed in Table 7.3. The precision and bias of these test methods described herein are con- tained in these individual test methods. These test methods are described here.
Two other parameters that are included in proximate and ultimate analyses are fixed carbon and oxygen. Both of these parameters are obtained by calculations.
TablE 7.1 Bioenergy Standards Issued by ASTM Committee E48
Committee E48 Standard Subject Similar Committee D02 Standard Similar Committee D05 Standard
ASTM E870 Analysis of Wood Fuels
ASTM E871 Moisture in Particulate Wood Fuels ASTM D2961; ASTM D3173; ASTM D3302
ASTM E872 Volatile Matter in Particulate Wood Fuels ASTM D3175
ASTM E873 Bulk Density of Densified Particulate Biomass Fuels ASTM D6347
ASTM E1358 Moisture in Particulate Wood Fuels ASTM D2961; ASTM D3173; ASTM D3302
ASTM E1534 Ash in Particulate Wood Fuels ASTM D482 ASTM D3174
ASTM E1690 Ethanol Extractives in Biomass ASTM E1721 Acid-Insoluble Residue in Biomass
ASTM E1755 Ash in Biomass ASTM D482 ASTM D3174
ASTM E1756 Total Solids in Biomass
ASTM E1757 Preparation of Biomass for Compositional Analysis ASTM E1758 Carbohydrates in Biomass by High Performance Liquid
Chromatography (HPLC)
ASTM E1821 Carbohydrates in Biomass by Gas Chromatography (GC) DOI: 10.1520/MNL772015001107
TablE 7.2 Terminology Related to Biotechnology Used in This Chapter
Term Definition
Bagasse Residue remaining after extraction of a sugar-containing juice from plants such as sugarcane.
Bioconversion A general term describing the use of biological systems to transform one compound into another. Examples are digestion of organic wastes or sewage by microorganisms to produce methane.
Biofuel Biomass-derived fuel.
Biomass Any material, excluding fossil fuels, which is or was a living organism that can be used as a fuel directly or after a conversion process.
Peat is not a biomass.
Biomass fuel Fuel derived from biomass.
Corn stover Stalks of the maize plant.
Denatured fuel ethanol Fuel ethanol to which chemicals (denaturants) have been added to make the ethanol unfit for human consumption in accordance with the regulations of the Bureau of Alcohol, Tobacco, Firearms, and Explosives of the U.S. Department of Justice.
Densified particulate
biomass fuels A fuel made by mechanical compression of biomass to increase the bulk density and to press the fuel into specific shapes, such as pellets and briquettes. The fuel can have a maximum volume of 16.39 cm3 such that the largest dimension is 7.62 cm.
Distillate The overhead product of distillation, such as ethanol liquid from the top of a beer still (ASTM E1344).
Ethanol extractives Residue remaining after evaporation of the ethanol solvent. These are materials that are removed from the biomass by extraction with 190 proof ethanol. (ASTM E1690)
Fermentation Decomposition of organic compounds by microorganisms to fuels and chemicals such as alcohols, acids, and energy-rich gases.
Fermentation fuel A fuel produced by the fermentation of biomass.
Fuel alcohol Ethyl, methyl, or higher alcohols with impurities (including water but excluding denaturants) produced for use as a fuel alone or as an addition to other fuels, such as gasoline.
Fuel ethanol Ethanol with impurities (including water but excluding denaturant).
Municipal solid
waste (MSW) The refuse material collected from urban areas in the form of organic matter, glass, plastics, waste paper, and so on, not including human wastes.
Particulate wood fuel Any wood fuel with a maximum particle volume of 16.39 cm3 such that the largest dimension is 7.62 cm.
Refuse derived fuel (RDF) Fuel processed from industrial waste, municipal waste, garbage, or sewage sludge.
Refuse derived fuel 3 (RDF 3) As defined by ASTM Committee E-38 on Resource Recovery, RDF-3 is a shredded fuel derived from municipal solid waste (MSW) that has been processed to remove metal, glass, and other inorganics. The material has a particle size such that 95 % weight passes through a 2-in. square mesh screen.
Renewable energy resources Sources of energy that are regenerative or virtually inexhaustible, such as solar, wind, ocean, biomass, municipal wastes, and hydropower energy. Geothermal energy is sometimes also included in the definition of this term.
Stover Dried stalks and leaves of a crop remaining after the grain has been harvested.
Syngas Synthetic gas resulting from incomplete combustion or pyrolysis of organic material to primarily carbon monoxide and hydrogen.
Wood fuel Fuel derived from biomass composed of woody trees or shrubs.
• The fixed carbon is a calculated value as the resultant of the summation of the percentage of moisture, ash, and volatile matter subtracted from 100. All percentages shall be on the same moisture reference base.
• The oxygen is calculated as the resultant of the summation of the percentages of carbon, hydrogen, sulfur, nitrogen, and ash subtracted from 100. All percentages shall be on the same mois- ture reference base.
ASTM E871, Moisture Analysis of Particulate Wood Fuels
Significance
This test method covers the determination of total weight basis in the analysis sample of particulate wood fuel, which may be sander dust, sawdust, pellets, green tree chips, hogged fuel, or other type of particulate wood fuel having a maximum particle volume of 16.39 cm3. It is used for calculating other analytical results on a dry basis. Moisture, when determined as herein described, may be used to indicate yield on processes, to provide the basis for purchasing and selling, or to establish burning characteristics.
TablE 7.3 Test methods used in proximate and ultimate analysis of wood fuels
aSTM Standard Test Method analysis
ASTM E871 Moisture
ASTM D1102; ASTM E1534 Ash
ASTM E872 Volatile Matter
ASTM E777 Carbon and Hydrogen
ASTM E775 Sulfur
ASTM E778 Nitrogen
ASTM E711 Gross Calorific Value
analySiS
Collect increments regularly, systematically, and with such fre- quency that the entire quantity of wood sampled will be repre- sented proportionally in the gross sample. The quantity of the sample shall be large enough to be representative but not less than 10 kg. The samples collected from the surface of the pile are, in general, unreliable because of the exposure to the environment.
A minimum of 50 g of sample in a container is dried in the oven for 16 h at 103 ± 1°C. After weighing the sample, the heating procedure is repeated for 2 h. The weighing and reheating is con- tinued until the total weight change among weight values varies less than 0.2 %.
PreciSion
Repeatability: 0.5 %; reproducibility: 1 %.
ASTM E1358, Moisture Content of Particulate Wood Fuels Using A Microwave Oven
Significance
This test method provides a rapid determination of moisture in particulate wood fuels in several minutes. It is an alternative to ASTM E871, which requires a minimum of 18 h. This method is applicable to situations such as the spot check of the moisture delivered by truck where a quick indication of the moisture of wood delivered is desirable.
analySiS
Determine the weight of three sheets of standard paper towels placed on top of each other. Place a 50-g sample of wood on top of the paper towels. Place the sample in the microwave oven and heat on full power using the prescribed schedule. Remove the sample and towels from the oven after each heating interval, weigh, and stir. When the mass change among successive weighing is less than 0.5 g, record this mass.
PreciSion
Repeatability: 1 %; reproducibility: 1.5 %.
ASTM E872, Volatile Matter of Particulate Wood Fuels
Significance
This test method determines the percentage of gaseous products, exclusive of moisture vapor, in the analysis sample of particulate wood fuel that is released under the specific conditions of this test.
The particulate wood fuel may be sander dust, sawdust, pellets, green tree chips, hogged fuel, or other type of particulate wood fuel having a maximum particle volume of 16.39 cm3. The volatile mat- ter, when determined as herein described, may be used to indicate yields on processes to provide the basis for purchasing and selling or to establish burning characteristics.
analySiS
Collect increments regularly, systematically, and with such fre- quency that the entire quantity of wood sampled will be repre- sented proportionally in the gross sample. The quantity of the sample shall be large enough to be representative but not less than 10 kg. The samples collected from the surface of the pile are, in general, unreliable because of the exposure to the environment.
Volatile matter is determined by establishing the loss in weight resulting from heating wood under rigidly controlled con- ditions. The measured weight loss, corrected for moisture as deter- mined by ASTM E871, establishes the volatile matter content.
Approximately 1 g of sample is taken for analysis. The sample is heated in a crucible to 950 ± 20°C in a muffle furnace for a period of exactly 7 min. After removing from the furnace and cooling to room temperature in a desiccator, the sample is reweighed.
PreciSion
Repeatability: 0.3 %; reproducibility: 1.0 %.
ASTM E873, Bulk Density of
Densified Partic ulate Biomass Fuels
Significance
The test procedure described in this test method can be used to determine the bulk density (or bulk-specific weight) of any densi- fied particulate biomass fuel meeting the particle volume of 16.39 cm2 requirements specified in this test method.
analySiS
Collect increments regularly, systematically, and with such fre- quency that the entire quantity of pellets sampled will be repre- sented proportionally in the gross sample. The quantity of the sample shall be large enough to be representative but not less than 45.45 kg. The samples collected from the surface of the pile are, in general, unreliable because of the exposure to the environment.
A box of specified size is filled to a specified height with the sample, the box is dropped five times to settle its contents, and then the box is weighed.
There are no precision or bias estimates available.
ASTM E1534, Ash Content of Particulate Wood Fuels
Significance
The ash content determines the weight of the noncombustible part of a particulate wood fuel that oxidizes during a combustion pro- cess but releases no energy.
analySiS
Ash content is determined by establishing the weight loss of the sample when heated under rigidly controlled conditions of tem- perature, time, sample weight, and equipment specifications. In this test method, a 2-g sample of the wood is placed in a silica or porcelain crucible and slowly heated in a muffle furnace to a
temperature of 580 to 600°C. The crucible is removed from the furnace, cooled, and weighed. Repeat the heating for 30-min periods until the weight of the ash and crucible after cooling is constant to within 0.2 mg.
PreciSion
Repeatability 0.5 %; reproducibility 1.0 %.
ASTM E1755, Ash in Biomass
Significance
The ash content is an approximate measure of the mineral con- tent and other inorganic matter in biomass. The ash content is used in conjunction with other assays to determine the total composition of biomass samples. This test method covers the determination of ash, expressed as the mass percent of residue remaining after dry oxidation at 575 ± 25°C, of hard and soft woods, herbaceous materials (such as switchgrass and sericea), agricultural residues (such as corn stover, wheat straw, and bagasse), wastepaper (such as office waste, boxboard, and news- print), acid- and alkaline-pretreated biomass, and the solid frac- tion of fermentation residues. All results are reported relative to the 105°C oven-dried mass of the sample.
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All samples should be ground or milled to reduce the size of the large pieces to less than 1 mm in diameter. The sample is then redried at 105°C prior to testing. Prepared biomass can be used in place of 105°C dried material, but the mass of the material must be corrected for its moisture content by using ASTM E1756 prior to calculating the ash content.
In this procedure, approximately 0.5 to 1.0 g of a test specimen is weighed into a tared pan or a crucible. It is heated in a muffle furnace at 575 ± 25°C for a minimum of 3 h or until all the carbon is eliminated. After cooling, the crucible with the residue is weighed. The ashing is repeated for 1-h periods until the mass after cooling is constant to within 0.3 mg, and the ash content is calculated.
PreciSion
From an interlaboratory study based on analysis of samples of hybrid poplar in five different laboratories, the following precision was obtained.
• Repeatability: 2.67 % of the average
• Reproducibility: 8.93 % of the average
ASTM E1690, Ethanol Extractives in Biomass
Significance
Ethanol extractives are any materials found in biomass that are soluble in ethanol. They are not considered to be part of the struc- tural components of biomass and should be removed prior to any chemical analysis of the sample. The prolonged extraction removes
nonstructural material that can include waxes, fats, resins, tan- nins, sugars, starches, and pigments. Removing hydrophobic materials from the biomass makes it easier to wet the material for the analysis of structural components. This test method yields results comparable to ASTM D1107.
This test method covers the determination of ethanol-soluble extractives, expressed as a percentage of the oven-dried biomass, of hard and soft woods, herbaceous materials (such as switchgrass and sericea), agricultural residues (such as corn stover, wheat straw, and bagasse), and wastepaper (such as office waste, boxboard, and newsprint). All results are reported to the oven-dried weight of the sample. This test method may not be suitable for hard and soft wood samples that include bark or those with more than 10 % extractable materials.
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A quantity of biomass is filled in a Soxhlet thimble, placed in a Soxhlet apparatus, and is refluxed using at least 160 mL of 190 proof ethanol. The material is heated at reflux for at least 24 h.
When the extraction time is complete, the sample is transferred to a Buchner funnel. Any residual solvent is removed by vacuum fil- tration, and the sample is washed thoroughly with 190 proof etha- nol, collecting all of the filtrate.
The biomass is allowed to dry in the Buchner funnel while it is still attached to the vacuum system. The filtrates are combined, and the solvent is removed using a rotary evaporator with 75 to 100 torr vacuum and a water bath temperature of 45 ± 5°C to heat the flask during evaporation. The flask is placed in a vacuum oven at 40 ± 1°C for 24 ± 1 h after all visible solvent is removed by the rotary evaporator. After cooling the flask in a desiccator, it is weighed to determine the weight of the residue.
Prolonged heating of the extractive residue may result in a low bias for the reported results because of the evaporation of semivolatile constituents. Insufficient heating or using inade- quate vacuum can bias the results high because of incomplete removal of ethanol solvent.
PreciSion
Based on a single laboratory analysis, the following repeatability was observed.
ASTM E1721, Acid-Insoluble Residue in Biomass
Significance
Biomass is composed largely of the following: cellulose, a poly- mer of glucose; hemicellulose, a complex polymer, the main chain of which consists of xylans or glucomannans; and lignin, a complex phenolic polymer. The lignin is mostly insoluble in mineral acids, unlike the other cell wall components of
Material Standard Deviation Coefficient of Variation
Hybrid poplar 0.15 % 0.76 %
NIST 8494 wheat straw 0.20 % 1.6 %
NIST 8493 Pinus radiata 0.20 % 8.0 %
biomass. For this reason, lignin can be analyzed gravimetrically after hydrolyzing the cellulose and hemicellulose fractions with sulfuric acid. This test method covers determination of the acid-insoluble residue of hard and soft woods, her baceous materials (such as switchgrass and sericea), agricultural resi- dues (such as corn stover, wheat straw, and bagasse), wastepaper (such as office waste, boxboard, and newsprint), acid- and alkaline-pretreated biomass, and the solid fraction of fermenta- tion residues.
The residue collected contains the acid-insoluble lignin and any condensed proteins from the original sample. An independent nitrogen analysis would be required to determine the acid-insolu- ble lignin content separate from the condensed protein fraction and is outside the scope of this test method.
A portion of the lignin in some biomass samples will remain soluble during this procedure. The total lignin in a biomass sample includes both acid-insoluble lignin and lignin in the acid-insoluble residue.
All results are reported relative to the 105°C oven-dried weight of the sample. The result of acid-insoluble residue analysis is used in conjunction with other assays to determine the total com- position of a biomass sample.
DefinitionS
• Acid-Insoluble Residue—The solid residue, corrected for acid-insoluble ash, retained on a medium-porosity filter cruci- ble after the primary 72 % and secondary 4 % sulfuric acid hydrolysis described in this test method. The material is pri- marily acid-insoluble lignin and any condensed proteins.
• Prepared Biomass—Material that has been treated in accor- dance with ASTM E1757 in order to raise the total solids content above 85 % based on an oven-dried solids weight.
analySiS
A 0.3-g sample is placed in a test tube and treated with 3 mL of sulfuric acid and thoroughly mixed. The test tube is placed in a water bath controlled to 30°C and hydrolyzed for 2 h. At the end of this time, the sample with added water is placed in an auto- clave for 1 h at 121°C. After cooling, the hydrolysis solution is vacuum filtered through a filtering crucible. The residue is washed, dried, and weighed. It is ignited at 575°C in a muffle furnace for a minimum of 3 h. The residue is cooled and weighed.
The results of acid-insoluble residue analysis are affected by the incomplete hydrolysis of biomass. The results will be biased high unless the sample is hydrolyzed completely. The results are affected by the timing of the acid digestion steps. The insoluble residue will dissolve slowly into solution in an irreproducible manner. The timing within this test method must be followed closely.
PreciSion
Repeatability is 0.41 % standard deviation and 1.59 % coefficient of variation. Reproducibility is 2.37 % standard deviation and 9.92 % coefficient of variation.
ASTM E1756, Total Solids in Biomass
Significance
The total solids content is used to adjust the mass of the biomass so that all analytical results may be reported on a moisture-free basis. Moisture is a ubiquitous and variable component of any biomass sample. Moisture is not considered a structural compo- nent of biomass and can change with storage and handling of biomass samples. The determination of the total solids content allows for the correction of biomass samples to an oven-dried solid mass that is constant for a particular sample. Total solids content may be determined by overnight drying at 105°C in a convection oven or with a loss-on-drying moisture analyzer.
Materials suitable for this procedure include samples prepared in accordance with ASTM E1757 and extractive-free material prepared in accordance with ASTM E1690. This procedure is not suitable for biomass samples that visibly change on heating to 105°C—for example, unwashed acid-pretreated biomass still containing free acid. Some materials that contain large amounts of free sugars or proteins will caramelize or brown under direct infrared heating elements used in Test Method B. Total solids in these materials should be determined by Test Method A. For particulate wood fuels, ASTM E871 should be used.
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There are two procedures that can be used for this determination.
• Procedure A—This test method is suitable for either prepared biomass samples or extractive-free material and involves dry- ing the samples at 105 ± 3°C in a drying oven for at least 3 h but not longer than 72 h.
• Procedure B—This test method is suitable for either prepared biomass samples or extractive-free material and uses an auto- mated moisture analyzer. This procedure is not suitable for materials with bulk densities less than 0.1 g/cm3. In this proce- dure, the analyzer is also programmed to heat the sample to 105°C.
PreciSion
Based on analysis of samples in duplicate by the same operator, the following precision estimates were observed.
• Test Method A: 0.55 % for hybrid poplar samples
1.35 % for washed, lyophilized fermentation residues
• Test Method B: 0.56 % for hybrid poplar samples 0.89 % for switchgrass samples
ASTM E1757, Preparation of Biomass for Compositional Analysis
Significance
This practice covers a reproducible way to convert hardwoods, softwoods, herbaceous materials (such as switchgrass and seri- cea), agricultural residues (such as corn stover, wheat straw, and bagasse), wastepaper (such as office waste, boxboard, and