Black soldier fly (BSF) larvae (Hermetia illucens), feeding on leachate from decaying vegetable and food scrap waste, increase ammonia (NH4+) concentration five-to sixfold relative to leachate unprocessed by larvae. NH4+ in larva-processed leachate reached levels as high as similar to 100 mM. Most of this NH4+ appears to have come from organic nitrogen within the frass produced by the larvae as they fed on leachate. In nitrate-enriched solutions, BSF larvae also facilitate dissimilatory nitrate reduction to ammonia. The markedly higher concentration of NH4+ recovered in leachates processed with BSF larvae and concomitant diversion of nutrients into insect biomass (itself a valuable feedstock) indicate that the use of BSF larvae in processing leachate of decaying organic waste could be advantageous in offsetting capital and environmental costs incurred in composting.