Table 4.

Inoculum technical specifications for ASTM D5338:15 and ISO 14855:2012.

Specifications	ASTM D5338:15	ISO 14855-1:2012
Inoculum	Industrial compost soil that has a maturity level of 2–4 months	Stabilized, mature compost derived (four-month old), if possible, from composting the organic fraction of solid municipal waste
Particle size	-	0.5 cm to 1 cm
Room temperature	Incubated in the dark at 58 °C ± 2 °C	Incubated in the dark at 58 °C ± 2 °C
pH	7.0–8.2	7.0–9.0
Total dry solids content	between 50% and 55% of the wet solids	between 50% and 55% of the wet solids
Volatile solids content	To produce more than 50 mg but less than 150 mg of CO2 per gram of volatile solids after 10 days of incubation	No more than about 15% of the wet or 30% of the dry solids
Moisture holding capacity (MHC)	50%	50–60%
Running time	Minimum of 90 days and should not exceed 6 months	Minimum of 90 days and should not exceed 6 months
Reference material	Celullose	TLC (thin-layer chromatography)-grade cellulose with a particle size of less than 20 μm
Validation criteria	If: (a) more than 2 g of volatile fatty acids per kilogram of dry matter in the composting vessel is formed, the test must be regarded as invalid; (b) a minimum of 70% for cellulose within 45 days is not observed with the positive reference, the test must be regarded as invalid and should be repeated, using new inoculum; (c) the deviation of the percentage of biodegradation of the positive reference is greater than or equal to 20% at the end of the test, then the test shall be regarded as invalid.	The test is considered as valid if: (a) the degree of biodegradation of the reference material is more than 70% after 45 days; (b) the difference between the percentage biodegradation of the reference material in the different vessels is less than 20% at the end of the test; (c) the inoculum in the blank has produced more than 50 mg but less than 150 mg of carbon dioxide per gram of volatile solids after 10 days of incubation.