UK research defines new standard test to assess compost quality

Stability and maturity are recognised as important parameters when assessing the quality of composted products and a report published by WRAP (the Waste & Resources Action Programme) will assist in refining the existing standards and ensure that composted products can meet end market requirements.



Entitled Assessment of options and requirements for stability and maturity testing of compost (ISBN: 1-84405-057-2), the report details research undertaken recently by ADAS Consulting Ltd on behalf of WRAP. The aim of the research was to review market-ready and emerging test methods for evaluating compost stability and maturity, and identify and develop a suitable laboratory-based method for use in the UK.



Following a literature review of current stability testing methods, the ADAS project team selected one for development which is largely based on the carbon dioxide evolution method of BS ISO 14855:1999 Determination of the Ultimate Aerobic Biodegradability and Disintegration of Plastic Materials Under Controlled Composting Conditions – Method by Analysis of Evolved Carbon Dioxide. Adapted and refined using samples of various composts of different ages, the main advantages of the method are its simplicity, ruggedness and sensitivity across a range of composting stages, respiration rates and levels of stability.



The European CEN Committee TC223, which covers soil improvers and growing media, carries out research to assess the various tests used across Europe and the WRAP method could now be chosen to form the basis of a European standard.



The research also included an extensive growth trial involving different composts using a phytotoxicity testing method for determination of maturity. Statistical analysis of the results indicated there are no significant differences between any of the composts over all the indicator species and led to the conclusion that a growth test should not be looked on as a stand-alone quantitative test of maturity but could be used to support other tests.



The findings of the report, available in Microsoft Word or PDF format on the WRAP website at www.wrap.org.uk, are now under further review by WRAP and its advisors with a view to taking the test forward and developing a set of limit values related to individual end-uses.