Determining Compost Maturity: Evaluation Of Analytical Properties

Abstract

Maturity of compost in terms of biochemical activity is assayed by self-heating experiments using Dewar-vessels (TMECC 2001, LAGA M10, 1995). The method is well standardized and resulting temperature readings lead to a value classified on a five level scale. The microbial decomposition of organic matter yields autothermic effects on temperature, which feed back to the activity pattern. Characteristic curves of temperature activity functions of the biological processes were evaluated quantitatively by means of an empirical algorithm. Systematic errors occurred, when assays were performed in Dewars of different size or at several packing densities and humidities of the compost. The vessels were described as heat conduction calorimeters that show characteristic functions of heat transfer. Modeling the process confirmed experimental results and demonstrated a transition to disproportional temperature activity relations of the system, which depended on the size of the Dewar vessel. Combining the algorithms of the biological process and the reactor yielded an instrument that allowed thorough ascertainments of sensitivity towards experimental conditions.