Probiotic bacteria impact on greenhouse gas and odor emissions during dairy manure digestion by black soldier fly (Hermetia illucens, Diptera: Stratiomyidae) larvae at an industrial scale

Unprocessed animal manure is a source of greenhouse gases (GHGs) and malodorous volatile organic compounds (VOCs), which reduce air quality. Hermetia illucens, (L.) (Diptera: Stratiomyidae), commonly known as the black soldier fly (BSF), has gained attention for the ability of its larvae to reduce these compounds emitted from several types of animal manure. Microbial amendment of manure can accelerate digestion of these lignocellulose-rich substrates, increasing nutrient availability for BSF larvae (BSFL). In a study consisting of two trials, we tested whether amending dairy manure with the probiotic bacteria Paenibacillus polymyxa, Rhodococcus rhodochrous 21198, or their combination, influences the ability of BSFL to reduce the emission of GHGs and malodorous VOCs at an industrial scale. Emissions of carbon dioxide and methane varied significantly across the two trials, while sampling day only affected methane production. Bacterial treatments tended to release higher levels of carbon dioxide and methane compared to non-amended dairy manure; however, these differences were not significant. Trial and sampling day significantly affected the blends of VOCs emitted. Among the VOCs tentatively identified, several are known to be malodorous and a few are related to BSFL digestion of organic waste. A few VOCs were emitted in higher abundances from bacterial treatments (especially P. polymyxa and combination) compared to control manure. Further studies are required to characterize the contributions of the initial microbial communities of dairy manure and their interactions with probiotic amendments during BSFL digestion and the resulting impacts on GHG and malodorous VOC emissions.