Scandinavian Biogas has recently commissioned a new biogas upgrading system at the Henriksdal wastewater treatment plant (WWTP) in Stockholm, Sweden. Michael Olausson, Director of Business Development at Scandinavian Biogas spoke to Anders Haaker about the new facility and future plans for biomethane production.
The Henriksdal wastewater treatment plant (WWTP) in Stockholm, Sweden has undergone major refurbishment as part of a larger project for Stockholm Vatten, a municipality-owned company charged with supplying potable water and wastewater treatment services to the city of Stockholm.
The plan for Stockholm Vatten is to close its Åkeshov WWTP in Bromma, west Stockholm and instead pipe the wastewater to the Henriksdal facility. The new sewer system from Bromma to Henriksdal is scheduled for completion by 2024 and the entire project has a budget of about SEK 5 billion (≈ EUR 540 million). To be able to handle the increased volume of wastewater a new treatment process has been installed at Henriksdal.
New upgrading plant
This also means that larger volumes of biogas can be produced and, as part of the overall project, Stockholm Vatten has invested around SEK 93 million (≈ EUR 10 million) in a new biogas upgrading facility. The biogas to biomethane unit was built and is operated by Stockholm-based biogas plant designers and operators Scandinavian Biogas and was officially inaugurated at the end of April this year.
– We have also increased the biogas production capacity at Henriksdal. The raw gas from the digester has a methane content of 62-63 percent and we want as pure methane as possible. There is already an upgrading plant at Henriksdal with a capacity of 75 GWh per annum. The new upgrading plant has an annual capacity of 125 GWh, which means Henriksdalnow has an annual upgrading capacity of approximately 200 GWh. This will be sufficient even after the wastewater from Bromma has been led on to Henriksdal. The capacity should also be sufficient for a projected increase in population in Stockholm for at least 20 years, Michael Olausson, Business Development Manager for Scandinavian Biogas, explained.
In the meantime, to make use of the available biogas production capacity while waiting for the new sewer system from Åkershov WWTP to be connected, the company has installed three reception tanks for external substrates. This is for feedstock such as residual fats, oils and grease (FOG) from the food industry and glycerol, a byproduct of biodiesel production.
– We receive the substrates by tanker truck and then dose them into the biogas digesters. We expect to reach an output of between 110-120 GWh in 2016 and 140-150 GWh in 2017, said Olausson.
– The new upgrading plant is of extremely high quality. We have had over 99 percent availability on Carbotechs equipment, said Michael Olausson and described the process. A row of six white tubes each of which contains activated carbon is used to separate carbon dioxide (CO2) from the raw biogas. However it is not a continuous process but a sequential one. A tube is filled with the raw biogas and put under pressure. The CO2 is absorbed into the activated carbon. Once a certain pressure is reached, the biogas is released and moved over to the next tube while the absorbed CO2 remains in the activated carbon. A vacuum is then induced in the tube so the activated carbon releases the CO2 and it is removed from the tube. This process is repeated along the row of tubes.
– We completed all the groundwork, the equipment arrived in complete modules on a truck and a crane lifted everything in place. It was a very smooth process. Everything had been set up at the factory in Germany and test run before it was shipped to Stockholm, said Michael Olausson.
Production, distribution and marketing
An estimated 240 GWh of biomethane will be produced from food waste and WWTPs in Stockholm during 2016. Scandinavian Biogas expects to produce 200-210 GWh at Henriksdals, Åkeshov and Gladö Kvarn whereas the Käppalaverket Lidingö WWTP makes about 30 GWh. The demand for biomethane exceeds production and several operators are transporting compressed biomethane (CBG) to Stockholm from biogas plants outside Stockholm.
Scandinavian Biogas sells its biomethane either directly to some customers such as Stockholm Public Transport (SL) and fuel distributors. In Stockholm, the proportion of biomethane in vehicle fuel is around 75 percent, which is higher than the average in Sweden. The remaining 25 percent is fossil gas that is brought into Stockholm as liquefied natural gas (LNG) and fed into the vehicle gas grid. The fossil gas is either Russian that has been liquefied in Finland or Norwegian liquefied at source.
Cooperation with Stockholm Vatten
Stockholm Vatten built the first biogas upgrading plant in Henriksdal around 2000. In 2010 Stockholm Vatten decided to divest the upgrading facility to a private contractor in an effort to focus on its core business while increasing availability and biogas production the amount of biogas. Scandinavian Biogas bought the plant in competition with other players.
– One of the reasons that we won the bid to buy was that we could present a development plan, and a plan to build the part that we have built. We were able to show that we are focused on increasing production. Already in 2010 we began to sketch out an expansion, remarked Olausson.
Later the city of Stockholm bought back the property and the facility after coming to the conclusion that it would be easier to implement the entire project, Åkershov WWTP relocation and Henriksdal WWTP refurbishment, if Stockholm Vatten owned the entire property and plant. Therefore Stockholm Vatten bought back the existing biogas upgrading plant at Henriksdal and signed a 25-year lease agreement with Scandinavian Biogas.
– We undertook to buy the raw biogas and to manage the operation of the plant, explained Olausson.
1 TWh by 2020
– With the facilities in Gladö Kvarn, Åkershov and Henriksdal we have a biomethane capacity in Sweden today of approximately 300 GWh. We are building a facility in Norway with liquid biomethane (LBG) that will provide approximately 125 GWh. It will be completed by the summer of 2017. In South Korea, we produce approximately 70 GWh. The plan is that we have start another two to three plants and reach a capacity of 1 TWh by 2020, ended Michael Olausson.