Large scale composting of poultry slaughterhouse processing waste: Microbial removal and agricultural biofertilizer application

•Poultry slaughterhouse was valorized by large scale composting process.•Thermophilic phase of 65 °C for 20 days enhanced a significant reduction of pathogens.•Produced compost showed a suitable agronomic quality with GI of 90%.•Compost amendment of 8 t ha−1 improved all physiological growth parameters of maize. This work investigated the potential of composting treatment for hygienization and material recycling from poultry slaughtering by-products and wastes in the context of management aspects and the agricultural value of the final product. A large scale composting cycle of 300 m3 was performed for 90 days, in which poultry slaughterhouse waste (59.65%) was mixed with sewage sludge (4.83%), agricultural waste, cardboard (4.83%), and wood dust (19.35%) and activated compost (11.29%). During the composting progress, physical chemical parameters, FTIR analysis and biological indicators reflecting stability of the compost were analysed for the assessment of the product quality. The composted mixture showed a high microbial activity with a succession of microbial populations depending on the temperature reached during different degradation phases. The thermophilic phase lasted 20 days with temperature exceeding 65 °C allowing pathogens reduction. Fecal coliforms, Streptococci and Escherichia coli were reduced and remained less than values recommended by international guideline. Whilst Salmonella has disappeared at the end of the process. The Composting poultry slaughterhouse waste allowed obtaining hygienic compost with sufficient agronomic quality characterized by a relatively high organic matter content (49.12%), a C/N ratio (13.92%), an alkaline pH (7.7) and a high level of nutrients. The germination indexes reached 91% in the end of process that proved to be good maturity indicators. The compost application in peat amended at ratios equal to 8 t.ha−1, improved the growth of stem length (63.8%), leaf length (57.9%), fresh biomass (65.1%) and dry biomass (66.6%) of maize plants showing that the final slaughterhouse compost presented high level of maturity and it was not phytotoxic.