Methods for testing the quality of compost function well

14.6.2013

<p>Compost intended for consumer use is tested in the laboratory inorder to determine its quality and safety. Together with Proftest SYKE, the Finnish Environment Institute, the Finnish Food Safety Authority Evira organised an international proficiency test for laboratories on tests that determine, for example, compost phytotoxicity. The results showed that in principle, laboratories manage these analyses well.</p>

The cress test is a standardised test for determining compost maturity level. In the proficiency test, two samples were used for analysing germination and root growth of cress, carbon dioxide production or oxygen uptake, dry weight, and organic matter content. The sample materials were soil improver and a mixture of soil improver and peat.

Proficiency test was successful with the assigned values
91 per cent of laboratory results were acceptable when target deviations between 4 and 80 per cent of the assigned values were accepted. The fact that the criteria applied in assessing the proficiency of certain analyses were not strict must be taken into account when assessing the results. The results indicate that laboratories participating in the test mainly managed the analyses well. Eight of the 11 participating laboratories achieved acceptable results in all performed analysis.

Room for improvement
Some laboratories need more experience with biological analyses in particular. For instance, in carbon dioxide production and cress germination tests, methods need to be harmonised further. In future rounds of proficiency tests, laboratories' sample pre-treatment practices will also be taken into account. Moistening of samples, storage conditions and time, and the sieving process have a major impact on sample properties and homogeneity.

The laboratories used new EU standard methods for performing analyses of sample characteristics.

Read more in the final report on the Proficiency Test on soil improver maturity tests

Read more about fertiliser production at biogas plants

Further information:
Senior Researcher, D.Ph. Liisa Maunuksela, Plant Analysis Laboratory Unit,
tel. +358 (0)400 256 097

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