Composting for valuation of marine fish waste

SUMMARY This trial evaluated the composting for valuation of marine fish waste. The study was carried out in a composting cell (1.10m length, 1.50m width, 1.20m height, and 2.50m headroom), which received a mixture of marine fish waste (skin and fin) and reused wood shavings at a 7:3 proportion. The efficiency of the composting process was evaluated through analysis of biomass temperature, moisture, pH, ash, compost mineralization index, carbon/nitrogen ratio, total organic matter, total organic carbon and total nitrogen. Data were tested by analysis of variance and polynomial regression, and the means compared by Tukey's test at 5%. The results showed that composting is an efficient alternative for the valuation of fish residues. The compost complies with the Brazilian Standards (Normative Instruction 25/2009 of the Brazilian Ministry of Agriculture, Livestock and Food Supply). The C/N ratio lower than 15/1 combined with the high moisture content of the substrates inhibit the increase in the biomass temperature. The wood shavings reused for three consecutive times provide nitrogen. The addition of water to the composting process should be suppressed when using the proportion of 7kg fish waste and 3kg reused wood shavings.