From Waste to Feed: Waste products as a source of protein-rich feedstuff

Facing increasing human population, expansion of large cities and a rising throw-away-society economy, effective waste management has become a major challenge. The recycling and processing of biodegradable material, be it organic waste, wastewater or a renewable resource, is an excellent option for avoiding negative impacts on the environment and climate. Currently, biodegradable wastes can be incinerated in disposed on landfills, anaerobically digested or directly treated at composting plants. However, from a thermodynamic point of view, organic wastes which contain valuable bio-molecules should be used at an energetically higher level: Suppose we were asked to imagine the best possible way to use these sludges. The process should require no energy, no chemicals, not even water. It should be self-contained and not emit a drop of effluent, and aside from some CO2 it should not produce greenhouse gases or offensive odours. The process should operate with the simplicity of a garbage bin, have no moving parts, and require little maintenance. This bioconversion process should be powered by a well established creature. It must have the ability to thrive in the presence of salts, alcohols, ammonia and a variety of food toxins. Upon reaching maturity, this creature should be rigidly regimented by evolution to migrate into a collection vessel for self- harvesting, and the bundle of nutrients it contains should rival the finest fish meal. Is the bioconversion process nothing but a fanciful leap of imagination? Surprisingly the process does, indeed, exist, and it may once become the fastest, cleanest, most efficient, and most economical way to recycle many types of organic agricultural waste. This process is driven by the larvae of the black soldier fly (BSF), Hermetia illucens. The aims of this project are: Characterisation and comparison of different organic waste resources Adaptation of process conditions to BSF life history Qualitative and quantitative chemical-physical analysis of the gained larvae and their suitability to serve as animal feed Identification of the larval digestive tract microbiota Hygiene screening and monitoring of pathogens

Facing increasing human population, expansion of large cities and a widespread throw- away-mentality, effective waste management has become a major challenge. The up- /recycling and valorization of biodegradable material, be it organic waste, wastewater or other renewable resources, is an excellent option for avoiding negative impacts on the environment and climate. Currently, biodegradable wastes can be incinerated or disposed on landfills, anaerobically digested or directly treated at composting plants. However, from a thermodynamic point of view, organic wastes which contain valuable bio-molecules should be used at an energetically higher level. In this FWF project we investigated the potential of the Black Soldier Fly (Hermetia illucens; BSF) and its larvae, and assessed their biodegradation potential for various organic waste resources. We set up a steady and stable BSF laboratory population at our institute and optimized breeding and oviposition conditions for BSF in small-scale artificial habitats. Results of this optimization process are published open access in Heussler et al. (2018). In feeding experiments, we investigated the impact of different diets (e.g. chickenfeed, grass cuttings, fruits and vegetables) on the microbial community composition in the gut of developing larvae. It was shown that the type of diet plays a lesser role in guts of BSF larvae than previously assumed. An autochthonous collection of bacteria, mainly dominated by Actinomyces spp., Dysgonomonas spp., and Enterococcus spp., supports the ability to effectively degrade a variety of organic substrates. In a hygiene-screening, numbers of E. coli, coliform bacteria and Salmonella sp. were determined to evaluate pathogenic bacteria associated to BSF larvae. Minor counts of E.coli and no Salmonella sp. colonies were detected in treatments of grass cuttings and fruit/vegetables. Additionally, the frass - consisting of undigested waste material, larval shavings and feces - was characterized and its potential as soil fertilizer was evaluated in greenhouse plant growth tests with ryegrass. The frass fractions of the different treatments revealed significantly similar physicochemical properties and plant biomass among each other and in comparison to artificial control soils. Results of this project underline the potential of BSF in terms of contributing to a circular economy by addressing two environmental concerns waste management and protein supplementation at the same time.