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Table 1

Original and refined requirements and validation criteria for BMP measurements

Requirement/validation criterionOriginalaRefinedb
Replicates At least in triplicate Same as original 
Assays besides test substrate Blanks and positive control (unspecified) Blanks and microcrystalline cellulose positive control 
Duration of BMP test Terminate BMP test when daily methane production during three consecutive days is <1% of the accumulated volume of methane Same as original but with clarification that methane production is net (inoculum contribution subtracted) 
Expression of BMP BMP is expressed as the volume of dry methane gas under standard conditions (273.15 K and 101.33 kPa) per mass of volatile solids (VS) added, with the unit NLCH4 kgvs−1 Same as original 
Calculation of BMP BMP is determined by subtracting the mean methane production of the blanks from the gross methane production of the substrate/positive control assays Same as original but calculations now described in detail in Hafner et al. (2020a)  
Calculation of standard deviation of BMP For the calculation of the standard deviation of the BMP of the substrate and the positive control, the standard deviation (SD) of the blanks must be taken into account Same as original but with addition of SD of VS measurement and clarification of calculations (Hafner et al. 2020a) 
Validation criterion 1 Only if the RSD of the blank or the positive control is <5%, BMP results can be validated. It is possible to eliminate a single outlier after applying a statistical test Only if the RSD of cellulose is <6%, BMP results can be validated. Rejection based on too high RSD of blanks is not recommended and elimination of outliers is only allowed if triplicates are still available at the end 
Validation criterion 2 Only if the RSD of a homogeneous or heterogeneous substrate is <5% and <10%, respectively, BMP results can be validated. It is possible to eliminate a single outlier after applying a statistical test No validation criterion recommended for substrate BMP, but RSD has to be provided for each substrate tested 
Validation criterion 3 Only if the BMP of the positive control is between 85 and 100% of the theoretical BMP (e.g. for cellulose: between 352 NLCH4 kgvs−1 and 414 NLCH4 kgvs−1), BMP results can be validated Only if the BMP of microcrystalline cellulose is between 340 NLCH4 kgvs−1 and 395 NLCH4 kgvs−1, BMP results can be validated 
Requirement/validation criterionOriginalaRefinedb
Replicates At least in triplicate Same as original 
Assays besides test substrate Blanks and positive control (unspecified) Blanks and microcrystalline cellulose positive control 
Duration of BMP test Terminate BMP test when daily methane production during three consecutive days is <1% of the accumulated volume of methane Same as original but with clarification that methane production is net (inoculum contribution subtracted) 
Expression of BMP BMP is expressed as the volume of dry methane gas under standard conditions (273.15 K and 101.33 kPa) per mass of volatile solids (VS) added, with the unit NLCH4 kgvs−1 Same as original 
Calculation of BMP BMP is determined by subtracting the mean methane production of the blanks from the gross methane production of the substrate/positive control assays Same as original but calculations now described in detail in Hafner et al. (2020a)  
Calculation of standard deviation of BMP For the calculation of the standard deviation of the BMP of the substrate and the positive control, the standard deviation (SD) of the blanks must be taken into account Same as original but with addition of SD of VS measurement and clarification of calculations (Hafner et al. 2020a) 
Validation criterion 1 Only if the RSD of the blank or the positive control is <5%, BMP results can be validated. It is possible to eliminate a single outlier after applying a statistical test Only if the RSD of cellulose is <6%, BMP results can be validated. Rejection based on too high RSD of blanks is not recommended and elimination of outliers is only allowed if triplicates are still available at the end 
Validation criterion 2 Only if the RSD of a homogeneous or heterogeneous substrate is <5% and <10%, respectively, BMP results can be validated. It is possible to eliminate a single outlier after applying a statistical test No validation criterion recommended for substrate BMP, but RSD has to be provided for each substrate tested 
Validation criterion 3 Only if the BMP of the positive control is between 85 and 100% of the theoretical BMP (e.g. for cellulose: between 352 NLCH4 kgvs−1 and 414 NLCH4 kgvs−1), BMP results can be validated Only if the BMP of microcrystalline cellulose is between 340 NLCH4 kgvs−1 and 395 NLCH4 kgvs−1, BMP results can be validated 

aDefined in Holliger et al. (2016).

bDefined in Hafner et al. (2020b).

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