Evaluation of co-products of the food industry through high-quality compost production

Food industries produce huge quantities of organic byproducts, which have been, until now, rarely valued. A detailled characterization of the different byproducts of food production (biscuits, chocolate, cereals, nutritive bars) plants has been carried out in this research. Some adequate mixtures of ingredients (cocoa shells, biscuit and cereal residues, physico-chemical sludge, and biological sludge) has been defined for composting assays. An experimental setup including six compost piles (approximately one metric ton each pile), which were manually mixed, has been run for a 4 month period. Maximal temperatures varying between 60 and 68 °C have been measured in the different piles during the composting period, whereas average temperature values above 50 °C have been established for 6 to 10 week periods. High quality composts, satisfying the criteria for the AA type compost (Bureau de normalisation du Québec norms), in terms of metal and microbial pollutant contents and microbiological stability, have been produced at the end of the composting period. These tests have also revealed that cocoa shells, an important by-product of chocolate fabrication, are an excellent bulking agent for compost production.