Biowaste means biodegradable garden and park waste, food and kitchen waste from households, offices, restaurants, wholesale, canteens, caterers and retail premises and comparable waste from food processing plants. Biodegradable waste is even wider group of material inclunding all subdtrated degrding biologically. In municipalities, that can also include e.g. wastewater sludge, by-products from industries and farms.
From 2016 landfilling biological waste has been prohibited. This has increased utilization levels significantly. Now, biowaste is used to produce compost and biogas.
In Finland biowaste and wastewater sludges from the municipalities and industry are processed in the biological treatment plants. In 2020, 186 composting plants were operational in Finland, most of which were windrow composting plants. Windrow composting is mainly used as a post-composting method of wastewater sludge. There has been a strong shift from composting to anaerobic digestion of biodegradable waste. Composting is becoming a post-treatment of already digested waste. Most of the new biological treatment plants under design or in construction are biogas plants. Composting and biogas plants are owned by municipalities, governmental companies, or private companies (including biogas plants in farms).
In 2021, there are 78 biogas plants in Finland. Biogas plants can be divided into co-treatment plants. farm plants and wastewater sludge treatment plants. Co-treatment plants treat a variety of biowastes with agricultural manure and wastewater sludges. Farm plants deal with manure as well as other organic waste and by-products of agriculture.
In addition to the widely used wet digestion plant, dry digestion plants are becoming more common. Dry digestion differs from the traditional wet digestion plants as the process uses solid materials, which usually have a dry matter content of about 30%. In this case, the amount of wastewater from the plant requiring treatment is also lower.
In Finland, ethanol is made from biowaste to be used e.g. as transport fuel. There are several plants manufacturing biowaste ethanol in Finland. Plants use municipal biowaste or waste from the food industry to manufacture ethanol.
Ever tightening emission reduction targets have increased the interest of the industry, agriculture and transport sectors in biogas and biomethane, as well as boosting nutrient recycling. Both biogas production and demand have grown steadily in Finland and Europe. The biogas industry has potential in terms of raw material exploitation and biogas production. New carbon neutrality targets, need for improving the national self-sufficiency of energy and nutrients, advancing the vitality of the regions and emission reduction targets for transport and agriculture create opportunities for the biogas.
Biogas sector should make a clear shift from waste management towards the production of energy and recycled nutrients. The low profitability of biogas production is challenging, as the end-product markets (energy and nutrient) are still developing. The low price of fossil fuels is also slowing down the development of the biogas industry It is estimated that in 2030 biogas production could be even up to 4-7 TWh. Production would be based specially on the utilization of by-products from the agriculture, but also new technologies and feeds would have an important role (e.g. gasification). In 2035, biogas production could be 6-15 TWh.
Biogas production happens in four sectors: wastewater treatment plants, farms, composting plant and landfills:
In the end of 2017 Finland had 16 wastewater treatment plants which used biogas reactors. Sludge from industrial wastewater was treated in four plants by anaerobic method. 15 farms produced biogas locally and biological communal waste was treated in 18 biogas plants. In addition, biogas is collected from 38 landfills making the total biogas production 72,3 million cubic meters per year.
172,2 million cubic meters of biogas in 2017
+10% icrease in biogas production
Industrial complexes of wastewater treatment producing biowaste
Combined digestion plants, their type and year of opening
In a combined digestion plant, several different biowaste types are processed together
There is a new patented dry digestion plant being built in Jepua Biogas using Hardferm technology by company Doranova. The plant will be able to produce biogas from less clean waste fractions and process up to 25 000 tons (wet mass) difficult waste per year.
520,2 GWh of heat and 178,4 GWh of electricity was produced from biogas in 2017. In the same year, 30,2 ± 0,8 GWh of biogas was used as a fuel for transport. That is 41% more than in the previous year 2016. The biggest reason is the increase of biogas use in buses and waste transport machines.
Source: Finnish national biogas statistics. Data year 2017.