Can greenhouse gas emissions be reduced by inclusion of waste-fed larvae in livestock feed?

Attention for insects as food for humans and feed for livestock is increasing. The livestock sector requires for alternative protein sources, because of the expected increase in demand for animal products. Insects have a high protein content and, therefore, can contribute to this goal. Moreover, use of insects may reduce the environmental impact of livestock production as insects have the potential to turn organic waste streams, such as manure or food waste, into high quality insect-based feed products. Such insect-based feed products may replace conventional feed ingredients with a high environmental impact, like fishmeal, fish oil and soybean meal. To our knowledge no studies explored the potential to reduce the environmental impact of livestock production by including insects in livestock feed. The aim of this study was to explore the potential reduction in greenhouse gas emissions from inclusion of larvae of the common housefly fed on food waste in diets for piglets. We, therefore, compared the greenhouse gas emissions of piglet diets with and without larvae. Data were based on a business model to produce 20 ton dried larvae meal per day. The model, based on experimental studies, is developed by four companies in the Netherlands: an animal nutrition company, two waste processing companies and an insect rearing company. The larvae are fed on a substrate of poultry manure and food waste. After harvesting the larvae, the remaining substrate is used for anaerobic digestion, thus replacing fossil fuels and artificial fertiliser. Larvae meal is included in a diet of piglets and mostly replacing fishmeal and soybean meal. Furthermore, we accounted for the current use -anaerobic digestion- of food waste. The reduction in biogas and digestate was replaced by fossil fuels and artificial fertiliser. Preliminary results showed that the piglet feed with larvae has a GWP between 0.63 kg CO2-eq and 0.85 kg CO2-eq per kg of feed. The piglet feed without larvae has a GWP of 0.67 kg CO2-eq per kg. The uncertainty in the GWP estimate of the larvae originates from lacking knowledge around three important aspects. We have limited insight in the potential of the remaining substrate as fertiliser; the use of energy for larvae production; and greenhouse gas emissions from the substrate (i.e. a mix of manure and food waste) during larvae cultivation. To conclude, inclusion of waste fed larvae in diets of piglets has the potential to reduce greenhouse gas emissions with 6%. Further research about the environmental impact is needed to supply lacking knowledge required for an accurate estimate of the reduction potential and potential improvement options of the current process.