How can larvae help reduce food waste and at the same time reduce the risks of spreading diseases? In Sweden, researchers and experts in waste management are working together to turn food waste into animal protein feed.
The start of the project
The initial development of this treatment system started in 2010 and came about as a possible solution for waste management in Kampala, the capital of Uganda. One of the PhD candidates in the Environmental Engineering group performed studies on waste management and found that over 90 percent of the material that ended up in landfills was organic waste. The remaining, e.g. metal, plastic, paper were all either collected in town, or at the landfill, upon which it was sold to a middleman for recycling.
The fraction remaining was, more or less, pure biodegradable waste. When looking into why only food waste end up at landfills and dump sites, it was clear that the sorting and collection of the other fractions were value driven. Food waste has no value. At the same time, food waste is the fraction with the highest negative environmental effect at the landfill, contaminating the water recipients, producing greenhouse gases as well as containing disease causing microorganism.
From food waste to protein
The fly larvae metabolize food waste and convert it into proteins and fats that is then used as a source of nutrition for fish and poultry. The fly larvae can help to minimize food waste up to 80 percent and diminish eutrophication (or over-fertilization) and contagion, due to the growing food-waste in cities.
The production of proteins, which happen in a fly larvae compost, is a mean for increasing the monetary value of food waste, as the fertilizer value is not enough for covering the cost of collection and recycling. In fly larvae composting, complex molecules of potential high value, such as amino acids, are harvested from the food waste by being concentrated in the fly larvae biomass. The proteins are then used as an environmentally friendly ingredient in feed production, replacing fish and soy meal protein.
Bringing the project to Sweden
The fly larvae composting work have after the Uganda project been developed with focus on Sweden. The collaboration between the Environmental Engineering group at the Swedish University of Agricultural Sciences (SLU) and Eskilstuna Strängnäs Energi och Miljö (ESEM) began with a mutual interest of reducing the environmental impact of solid waste management. This ended up in a collaboration, in which SLU focuses on research, process development and optimization of the fly larvae composting process, while ESEM focus on the full-scale implementation.
The aim of the Environmental Engineering group at SLU is to produce world class applied environmental research, while ESEM wants to be take the lead globally in sustainable organic waste management. Making solid waste management economically and environmentally sustainable has guided the research and development of the fly larvae waste treatment system. The product value, if converting one ton of food waste into the larvae to be used in feed and the residue as fertiliser, was estimated to approximately €140. Comparable value of the products from anaerobic digestion, when utilising the biogas as vehicle fuel and the digestate as fertiliser, has a value of approximately €130. The major difference is the complexity of the processes, as the fly larvae treatments is less complex and thus the costs can be expected to be considerably lower.