Preliminary biogas production assessment on insect frass and leachates of the organic wastes fed to larvae: A Johannesburg-based factory case study

The biomethane potential of insect frass and leachates from waste (larvae feedstock) stockpile was evaluated. Frass was derived from a black soldier fly larvae (BSFL) operation that uses a fruit and vegetable waste diet. The two waste streams were characterized and the results of their compositional, proximate, and ultimate analysis were used in estimating methane yields from these materials. The estimated biomethane potential (BMP) of the frass ranged 149–275 L/kgVS depending on the calculation method used. This result compares well with that of empirical studies for cow manure whose BMP ranges 110–275 L/kgVS. Cow manure is the most popular biogas feedstock globally. Leachates reported an estimated BMP of 150 L/kgCOD. We conclude that it may be technically feasible to produce biogas from BSFL frass and from fruit and vegetable waste leachates. However, standard BMP experiments and semicontinuous pilot studies are still necessary before commercialization of these findings. These extra tests are executed to validate these findings and ascertain the life cycle attribute and long-term process stability and hence determine the economics of using these potential substrates for biogas production as a strategy to implementing circularity in the fruit and vegetable industry.