Micro-plastics in biogas process – pre-study (WR 48) Source separated food waste is a clean substrate that is suitable for treatment in biogas plants, however there are risks that incorrect sorted plastics can enter the digester, - and then in the form of micro-plastics end up on arable land as a result of spreading the bio-fertilizer. Pretreatment of collected food waste is used to remove plastic bags as well as any other unsorted plastics. Despite this, plastic pollutions are found in the slurry and enter the digester. If plastics are present in the substrate into the facility there is a risk that very small plastic fragments (less than 2 mm), so-called micro-plastics can be formed. Supply of micro-plastics to agricultural land through bio-fertilizer can lead to a gradual increase in the amount in the field as plastics break down slowly. To increase knowledge about micro-plastics in bio-fertilizers and examine the risks for the formation of these fragments in various stages of pretreatment, SP- Technical Research institute of Sweden and JTI Institute of Agricultural and Environmental Engineering performed interviews with industry associations, government agencies, operators of biogas plants and suppliers of pre-treatment equipment. We have also studied literature and Swedish rules and laws for plastics and bio-fertilizer. No analyzes of plastics in the digestate has been implemented. In this pre-study it was not possible to estimate to what extent micro-plastics occur, but these fragments can be theoretically generated during pretreatment with crushing and grinding of the substrate. Such created micro-plastics then stay throughout the process. "Sanitation and anaerobic digestion probably entails no appreciable effect on the degradation of plastic in the digester", says plastic expert Jonas Enebro at SP Chemistry and Materials. To predict what happens to micro-plastics and their effects on the environment, studies are needed to show which plastics are found in bio-fertilizers and in what quantity. "We simply know too little about the potential risks and long-term effects", says project leader Lotta Levén at JTI. What a digestate may contain is currently only regulated by the certification system for bio-fertilizers where limits on plastics larger than 2 mm are included, but not microplastics. At present the Swedish Waste Management work with the issue of socalled visible plastic pollution in certified bio-fertilizers in order to improve the certification method. Furthermore, the efficiency of various pretreatment techniques to separate plastics from the substrate will be studied further and reported on in 2014. www.wasterefinery.se