Compost & Waste Stability Testing

Examples of approaches, equipment and costs

TYPE OF STABILITY TEST	Basis of test	Strength / Weakness	Equipment Cost/ OE‡
Dewar Self Heating	1.5 liter compost placed in Dewar Flask, heat rise recorded in 10°C increments	(S) Simplicity of protocol; (W) long read time & equipment quality control	$300 per flask; $45/test
Solvita® Maturity Index (CO2 & NH3)	100 cc compost in incubation jar; gaseous output trapped and measured as colorimetric change of chemistry gel	(S) Low cost, quick reading; (W) Semi-quantitative	No Equipment; $15/test
Oxitop® Respiration	20-40g compost in sealed respiration jar; pressure drop from CO2 absorption recorded electronically and converted to CO2 units	(S) Semi-automatic nature (W) Moderately high cost of apparatus; high maintenance	$4,000/6 units; $80/test
Sapromat (Voith®) Oxygen Uptake	Sealed glass jars with oxygen consumption measured indirectly from electrolysis of copper sulfate	(S) Automatic performance & maintains constant O2 level (W) High cost of equipment; laboratory skill required	$20,000/12 flasks; $100/test
SOUR Std Oxygen Uptake Rate	1-5g Compost dissolved in water and read as in a BOD test over 1 to 4 days	(S) ease of use; low cost (W) small-sample size	$2,000/O2 Unit; $45/test
DRI – Dynamic Respiration Index	40 - 140 liters compost placed in adiabatic reactor and flushed with constant air-flow;	(S) Quasi standard in EU (W) apparatus set-up; large sample size; very high cost	~ $10,000 set up; $500/test
CO2 respiration – Flask Traping Method	20-40 g compost in sealed vessel; HCl titration of absorbed CO2 w/BaCl2	(S) low-cost, accuracy (W) complex equipment set up; chemistry required Most reliable method for over 30 years	Std lab equip; $45/test

‡ operating expense; assumed to include labor, replacement supplies and 10% overhead