A Comparison of Different Bulking Agents for the Composting of Fish Offal

An experiment comparing the effectiveness of three different bulking agents in the composting of fish processing wastes was carried out using small-scale composters operated at ambient temperatures. Fish offal was mixed with each of peat moss, sawdust and wood shavings in a 5:1 ratio by weight. The mixed materials were left undisturbed in the composters for an initial 55 days. They were then mixed and reloaded into their respective composters for a further 95 days of composting. Temperatures were monitored throughout the experiment, while serial physical and chemical analyses of the compost materials were initiated after the mixing. Headspace-gas chromatography was also used to determine the levels of phytotoxic organic acids and phenol. All the compost piles reached thermophilic temperature levels (40–70°C). Due to insufficient pile mass, temperatures over 55°C were not sustained for a sufficient length of time to satisfy the EPA requirements for pathogen reduction. The temperature profiles suggest that ...