Aki Heinonen
Quality and Environmental Engineer
Suomen Biovoima Oy
Finland
Background
The Baltic Sea encompassed by the Baltic countries and Scandinavia is practically a closed inland sea. Baltic sea conditions have been going into worse for a long period of time. One of the greatest issues for the Baltic Sea has been the incoming nutrition flow from the surrounding countries. Overflow of nitrogen and phosphorous from agricultural farming and manure management have been identified as one of the greatest causes of nutrient leakage and consequently eutrophication of the Baltic Sea.
Surrounding countries have published and initiated several cooperation projects to prevent nutrients from entering the Baltic Sea. Examples of those projects are Sustainable manure and nutrient management (SUMANU-projects) for reduction of nutrient loss in Baltic Sea Region. There are also lots of collaboration companies and communities, like Baltic Sea Action Group, whose target is to improve the condition of the Baltic Sea by bringing businesses and communities together to find ways to reduce the nutrition leakage into the sea.
Sustainable nutrition management in Baltic Sea countries
Like in all areas of Europe in the Baltic and Scandinavian countries, because of farming and meat production, there are areas that produce lots of nutrients. Many agricultural areas are short of phosphorus and therefore need to use artificial fertilizers to fulfill the need to grow the crops.
In Sweden, manure is viewed as a valuable resource, because biogas process reduces its amount while retaining all the nutrients. In Denmark, the legislation has driven the farmers to build biogas plants as for manure treatment before fertilizer utilization as well. This is based on the limitation for animals per hectare and restrictions on nitrogen application to crops.
In Finland, there are different limits for amounts of phosphorus and nitrogen per hectare for different crops. Biggest difference from Denmark is that for example in 2021, Denmark produced 1,724 M kg of pork meat when Finland produced 176 M kg. The area of agricultural land is similar in Denmark and Finland; 2,6 M hectares Denmark and 2,2 in Finland. Because of those numbers, in Finland there has not been so much interest towards manure digestion until 2023. In Finland, the biogas production has concentrated to use source separated food waste and WWTP sludge as feedstocks and origin on biofertilizers.
In Baltic Countries (Estonia, Lithuania and Latvia), there are lots of big farms. Some of them are using biogas plants to produce biofertilizers from the manure, but for source separated food waste, there are so far only very few plants. This is a pity, because food waste is very nutritious and its biogas i.e. energy yield is high, but at the same time, the tide seems to be turning.
Case Maardu Biogasplant
Maardu Biogas plant is a build biogas operated and owned by EKT Ecobio and build by BioWoima Finland. Production started in 2023. It uses source-separated food waste from households and grocery stores as its feedstock (24,000 tons per year) and produces annually 30 GWh of biomethane. Plant is powered by a hybrid digestion process, where the pretreated and hygiene biowaste is first pump to semi dry plug-flow digester and then to traditional wet-digestion to provide a better gas production. Produced biomethane is used as a traffic fuel for Tallin buses to replace the natural gas.
EKT plant is the first biogas plant in Estonia that uses food waste as feedstock and produces organic fertilizers from it for agricultural purposes. To fulfill the EU fertilizer legislations, all plastic, metals and other non-organic materials are removed in a two-step process. Pretreatment before digestion removes the bags, other bigger non-organic particles and heavy fractions like stones, whereas two-step post-separation by screw presses removes the small particles what are left after the pretreatment.
According to regular inspections by a third party, there have so far been no visible non-organic fractions at the solid digestate. This proves that it is possible to produce organic fertilizers from biowaste streams. Separated liquid material is also used as fertilizer as well.
By using biogas process to treat source separated food waste and other high-nutrient organic waste streams, it is possible to capture and reuse the nutrients in farming in a sustainable way. The biogas process also transforms most of the nitrogen into a more soluble ammonium form, which the plants and crops can absorb faster and more efficiently. This decreases the nutritional leakage from farming into the Baltic Sea, in addition to replacing traditional composting processes (where leakages also occur) by fully closed anaerobic biogas process. In the end of the day, all win: the waste producers, the management sector, and the environment.
The Baltic Sea encompassed by the Baltic countries and Scandinavia is practically a closed inland sea. Baltic sea conditions have been going into worse for a long period of time. One of the greatest issues for the Baltic Sea has been the incoming nutrition flow from the surrounding countries. Overflow of nitrogen and phosphorous from agricultural farming and manure management have been identified as one of the greatest causes of nutrient leakage and consequently eutrophication of the Baltic Sea.
Surrounding countries have published and initiated several cooperation projects to prevent nutrients from entering the Baltic Sea. Examples of those projects are Sustainable manure and nutrient management (SUMANU-projects) for reduction of nutrient loss in Baltic Sea Region. There are also lots of collaboration companies and communities, like Baltic Sea Action Group, whose target is to improve the condition of the Baltic Sea by bringing businesses and communities together to find ways to reduce the nutrition leakage into the sea.
Sustainable nutrition management in Baltic Sea countries
Like in all areas of Europe in the Baltic and Scandinavian countries, because of farming and meat production, there are areas that produce lots of nutrients. Many agricultural areas are short of phosphorus and therefore need to use artificial fertilizers to fulfill the need to grow the crops.
In Sweden, manure is viewed as a valuable resource, because biogas process reduces its amount while retaining all the nutrients. In Denmark, the legislation has driven the farmers to build biogas plants as for manure treatment before fertilizer utilization as well. This is based on the limitation for animals per hectare and restrictions on nitrogen application to crops.
In Finland, there are different limits for amounts of phosphorus and nitrogen per hectare for different crops. Biggest difference from Denmark is that for example in 2021, Denmark produced 1,724 M kg of pork meat when Finland produced 176 M kg. The area of agricultural land is similar in Denmark and Finland; 2,6 M hectares Denmark and 2,2 in Finland. Because of those numbers, in Finland there has not been so much interest towards manure digestion until 2023. In Finland, the biogas production has concentrated to use source separated food waste and WWTP sludge as feedstocks and origin on biofertilizers.
In Baltic Countries (Estonia, Lithuania and Latvia), there are lots of big farms. Some of them are using biogas plants to produce biofertilizers from the manure, but for source separated food waste, there are so far only very few plants. This is a pity, because food waste is very nutritious and its biogas i.e. energy yield is high, but at the same time, the tide seems to be turning.
Case Maardu Biogasplant
Maardu Biogas plant is a build biogas operated and owned by EKT Ecobio and build by BioWoima Finland. Production started in 2023. It uses source-separated food waste from households and grocery stores as its feedstock (24,000 tons per year) and produces annually 30 GWh of biomethane. Plant is powered by a hybrid digestion process, where the pretreated and hygiene biowaste is first pump to semi dry plug-flow digester and then to traditional wet-digestion to provide a better gas production. Produced biomethane is used as a traffic fuel for Tallin buses to replace the natural gas.
EKT plant is the first biogas plant in Estonia that uses food waste as feedstock and produces organic fertilizers from it for agricultural purposes. To fulfill the EU fertilizer legislations, all plastic, metals and other non-organic materials are removed in a two-step process. Pretreatment before digestion removes the bags, other bigger non-organic particles and heavy fractions like stones, whereas two-step post-separation by screw presses removes the small particles what are left after the pretreatment.
According to regular inspections by a third party, there have so far been no visible non-organic fractions at the solid digestate. This proves that it is possible to produce organic fertilizers from biowaste streams. Separated liquid material is also used as fertilizer as well.
By using biogas process to treat source separated food waste and other high-nutrient organic waste streams, it is possible to capture and reuse the nutrients in farming in a sustainable way. The biogas process also transforms most of the nitrogen into a more soluble ammonium form, which the plants and crops can absorb faster and more efficiently. This decreases the nutritional leakage from farming into the Baltic Sea, in addition to replacing traditional composting processes (where leakages also occur) by fully closed anaerobic biogas process. In the end of the day, all win: the waste producers, the management sector, and the environment.