Formation of chloromethoxybenzaldehyde during composting of organic household waste

Standardized household waste was mixed with different litter amendments, straw, leaves, hardwood shavings, soft-wood shavings, paper. and sphagnum peat, resulting in six compost mixtures. In addition non-amended household waste was composted. Composting was done in small rotatable bins and compost samples were taken on a regular basis until day 590. Extraction and analysis of wet compost samples showed no evidence for the presence of chloroorganic compounds. Drying and re-wetting of compost samples, however, revealed that chloromethoxybenzaldehyde (CMBA) was formed in all composts at concentrations varying between 5.6 and 73.4 mug kg(-1) dry matter. CMBA was not present in the original materials. During composting, there was a clear positive relation between formation of CMBA and microbial activity, as indicated by C losses and temperature. Formation took place during the most intensive phase of composting when C losses were highest. Under anaerobic conditions, however, which prevailed initially in the non-amended compost. no CMBA was formed. Calculation of total amounts of CMBA in composts revealed that there was a small decrease during storage in the hardwood, peat, and softwood composts. However, all composts contained CMBA after 590 days. The mean concentration was 33.4 mug kg(-1) dry matter (s.d. = 21.9). Possible biocidal effects of composts when used in cultivation may be explainable by the presence of natural toxic compounds formed during composting. (C) 2004 Elsevier Ltd. All rights reserved.