Black Soldier Fly Diet Impacts Soil Greenhouse Gas Emissions From Frass Applied as Fertilizer

Increased global production of animal-based protein results in high greenhouse gas (GHG) emissions and other adverse consequences for human planetary health. Recently, commercial insect rearing has been claimed a more sustainable source animal protein. However, this system also leaves residues called frass, which—depending on the diet—is rich carbon (C) nitrogen (N), could thus be used as fertilizer agriculture. The impact kind soil GHG is yet unknown. Therefore, we investigated effect black soldier fly ( Hermetia illucens L.) frass derived from carbohydrate (Carb-) or (Prot-) based diet applied at two different application rates to an arable C N fluxes microbial properties 40-day incubation experiment. CO 2 , O, NO, CH 4 water extractable organic (WEOC), inorganic were continuously measured quantitatively. At end incubation, biomass (MB), stoichiometry, community composition, abundance functional genes assessed. Along with strong increase WEOC Carb-frass caused initial O associated availability. In contrast, Prot-frass showed lower release, although nitrate levels higher. MB was significantly increased, which pronounced following compared application, higher amendment rates. Fungal increased most both types even stronger response rates, whereas bacterial rose Prot-application. Abundance related ammonia-oxidizing bacteria archaea enhanced by but did not clearly differ between types. use efficiency microorganisms, revealed metabolic quotient, strongly reduced rate. Overall, influenced available affected mineralization dynamics, emissions, growth. very undermining potential environmental benefit calling detailed analyses before widely