Bioconversion of Cattle Manure by Hermetia Illucens Larvae: Mineral Content Changes in Manure and Larval Biomass.

Abstract

Bioconversion by Hermetia illucens larvae is a novel technology for organic waste treatment and valorization. However, since the possible uses of products from this process are in agriculture and livestock, the bioconversion must guarantee the mineral quality of both the Hermetia illucens larvae frass and larval biomass. Therefore, this study aimed to assess the mineral content changes for both the larval biomass and larvae frass of Hermetia illucens after the manure bioconversion to determine their suitability as animal feed and organic fertilizer, respectively. Hermetia illucens larvae were put into a plastic box containing fresh cattle manure, and the control treatment with the same conditions without larvae was established. After the first pre-pupae were detected, frass and larvae were collected, and their mineral content was analyzed. At the end of the experiment, the larvae showed increases in some micro and macronutrients, especially calcium and manganese, increasing up to 2.6 and 22.6 times the initial concentration, respectively. The toxic elements concentration was increased in larval biomass, but these levels met the international legislation for animal feed. As a result, the mineral content in larval biomass revealed that Hermetia illucens could be potentially used as animal feed, which could be comparable with fish meal, and is probably better than soybean meal. However, the larvae frass could only be used as organic fertilizer in a Canadian context, with further treatment for decreasing the chromium content being necessary.