Biogas generation from insects breeding post production wastes

Insect breeding generates waste: insect excrements, often mixed with the remains of the feed. Insect waste is usually sold as a plant fertilizer, however, there is one more method of its use - methane production via the anaerobic digestion. To the best of the authors' knowledge, this topic is very poorly studied. The aim of this work was the evaluation of the suitability of the waste derived from insects breeding (Hermetic illucens, Tenebrio molitor and Gryllus spp.) for methane production. The mesophilic anaerobic digestion process was performed in 500 ml bioreactors. The temperature of the process was 37 degrees C +/- 1 degrees C and initial pH was 7.0 +/- 0.2. The substrate loading comprised 3.5 g of total solids and the inoculum-to-substrate ratio was 2:1. The biomethane potential of investigated wastes was similar to 177 ml g(-1) TS for H. illucens, similar to 212 ml g(-1) TS for Tenebrio molitor to similar to 225 ml g(-1) TS for Gryllus spp.. The obtained biomethane potentials are similar to more commonly used substrates for anaerobic digestion like: cattle manure, mink manure, poultry manure, fruit and vegetables waste, ryegrass, switchgrass, wheat, and sewage sludge, which points to the reasonability of their use. Anaerobic digestion can be a new method for valorization of insect post-production wastes. (C) 2019 The Authors. Published by Elsevier Ltd.