A Comparative Evaluation of Maturity Parameters for Food Waste Composting

Abstract

Four parameters, cation exchange capacity, volatile solids, humification index, and Corg/Norg ratio, were evaluated for three kinds of compost products. An appropriate index of compost maturity for three kinds of food waste compost was cation exchange capacity (ash-free basis). Cation exchange capacity based on ash-free organic matter increased up to 75 ~ 85 meq/100g organic matter during the composting period and finally showed an almost constant value. Volatile solids and humification index (HI) decreased rapidly while temperature increased at the beginning of composting period. Volatile solids decreased rapidly during the composting of ten days and then after little changed. There was a difficulty in evaluating food waste compost maturity using volatile solids content. Humification index may be a good candidate of compost maturity, but more research needs to be done before using it as a maturity index. The Corg/Norg ratio in water extracts was between five and six at the end of the composting periods regardless of initial raw waste composition. This parameter was a useful index of quality, but not compost maturity. Carbon/nitrogen (C/N) ratio and ammonium were undesirable parameters as a compost maturity index. Parameters such as VS, water soluble Corg/Norg, CEC (ash-free basis) and HI were highly correlated.