October 30, 2015 – Power-to-gas technology increases biogas production and makes wastewater treatment plants greener

October 30, 2015

An innovative power-to-gas technology has the potential of increasing the current biogas production in Europe enormously by enabling cost-effective methods to convert CO2 from biogas production and excess electricity from wind and solar into natural gas. The large-scale ForskEL demonstration project, BioCat, is located at BIOFOS, who operates three of the largest wastewater treatment plants in Denmark.


As Europe and other developed countries are shifting towards renewable energy systems, the need for a technology that enables storage of wind and solar energy is rising. The BioCat project has developed a power-to-gas technology that upgrades biogas to biomethane by combining CO2 from current biogas production, a unique archaea-bacteria and excess solar and wind electricity; a combination that has the potential to solve the key challenges of today’s sustainable energy problems.


Biogas, which is produced from organic materials and waste, is not suitable for direct injecting into the natural gas grid. In order for it to be stored and utilised in the natural gas grid, it has to be upgraded into biomethane – a process that has until now been extremely costly and thus not economically viable.


The power-to-gas technology enables wastewater treatment plants to recycle two by-products produced in the power-to-gas process, resulting in improved biogas production processes.


The biomethane produced through the power-to-gas technology can be stored indefinitely and injected into the natural gas grid and thus be saved for days that are less windy or sunny – enabling the possibility of adjusting our energy consumption in accordance with the electricity prices on the energy market.


Until now, the cost of energy required to upgrade biogas has been one of the major barriers for increased use of biogas in the natural gas grid. In order to upgrade the biogas, you have to remove the Carbon dioxide from the biogas, so only methane remains in the gas. By the end of 2016, it is the goal of the BioCat project to document and demonstrate that the power-to-gas technology can upgrade biogas to contain 97,8% of methane, which is the requirement for injecting it into the natural gas grid.


Making major energy consumers greener

One of the partners, BIOFOS, sees tremendous potential in the ForskEL-funded project and is looking forward to facilitating the large-scale demonstration project at the BIOFOS Wastewater Treatment Plant in Avedøre, Denmark. Participating in the BioCat project goes hand in hand with BIOFOS’ ambition of becoming CO2 neutral by 2020.


Participating in the BioCat project is a reflection of our green ambitions. Moreover, we see great potential in participating in a project that both reduces BIOFOS’ carbon footprint and energy consumption at the same time as it enables us to produce even more biogas, says Dines Thornberg Head of Development at BIOFOS and continues: If we imagine that the Power-to-gas facility runs 3000 hours a year, it will contribute to 7% of the goal we have for CO2 reduction, which are very good prospects.


BIOFOS has more than 24.000 m3 of digester volume and produces 3 mio. cubic metres of biogas each year, and the plant is therefore perfect as a collaboration partner for Electrochaea, who is in charge of the BioCat project. The project will increase the amount of biogas as well as utilise the fact that BIOFOS – due to its location – makes it possible to connect with the natural gas grid.


Converting green electricity to green gas

During the next couple of months, the containers, the electrolysis unit, the reactor and other elements that constitute the BioCat facility will be installed at the BIOFOS wastewater treatment plant. The container environment, where the unique archaea bacteria will “live”, will then be connected with pipes to the biogas and natural gas systems. The demonstration project will deliver 3000 hours of data and is expected to finish by the end of fall 2016.


The electrolysis system, which produces hydrogen, is used for converting electricity from the renewable energy sources into the sustainable natural gas. When electricity from wind and solar starts the electrolysis system, the water is split into hydrogen and oxygen. The archaea-organism eats the hydrogen from the electrolysis as well as the Carbon dioxide (CO2) from the added biogas, which BIOFOS already produces. Hereafter, the organism releases methane, which is what natural gas consists of, and it can thereby be stored and transported in accordance with the demand in the electricity grid.


The large scale demonstration project is determined to show that the power-to-gas technology reduces production costs as well as increases production of biogas and reduces the energy consumption of the wastewater treatment plants that facilitate the power-to-gas process.


Producing greater amounts of biogas

Wastewater treatment plants are big energy consumers, as they need a lot of electricity to pump water around the plant and to pump air through the sludge treatment basins. Turning the sludge that remains at the end of the clean-up process into biogas is one way of recovering some of this energy. Instead of just removing the CO2 (into the air), the BioCat project upgrades the CO2 from the biogas by converting it into methane. That way, the power-to-gas technology reduces the net energy consumption of wastewater treatment plants as well as increases the value of the biogas production.


If the project succeeds in upgrading the biogas, it is predicted that we would be able to produce 58 times more biogas in Denmark. That is if the power-to-gas technology is implemented in all biogas-producing facilities in Denmark, explains Dines Thornberg, who then continues to explain the potential of the biogas production even further;


If we then look at Germany, where the biogas production is 1400 times bigger than the one in the wastewater treatment plant in Avedøre. Well, then it is pretty clear that the potential for this novel upgrading technology is huge. 


The key markets for the power-to-gas technology are countries or regions with a high share of wind and solar energy as the intermittent nature of wind and solar will lead to more frequent and prolonged periods of excess electricity supply, creating the need for energy storage. As Europe and other developed countries are shifting towards renewable energy systems, there are many markets that will benefit from the power-to-gas technology. Power-to-gas’ technical features makes it particularly suitable for storing large amounts of wind and solar energy produced during periods of low demand, such as on a sunny summer weekend or during a windy night. Power-to-gas thereby complements other energy storage technologies focused primarily on short-term storage applications such as peak shaving and voltage control.


Recycling by-products

The power-to-gas technology is particularly interesting to implement at wastewater treatment plants because of the by-products. The first by-product is heat, which is generated by the electrolysis. This heat can be used to heat up the large digesters in the wastewater treatment plants, which has to be at 37 degrees in order for bacteria to strive – a heating process that results in high heating bills. Furthermore, the heat generated by the electrolysis can be used to heat buildings and be exported into the nearby district heating structures.


Consequently, the by-product ‘heat’ will be included in the heating accounts of BIOFOS and not just be wasted. By installing district heating pipes on the grounds of the demonstration project, BIOFOS will be able to lead the excess heat from the power-to-gas facilities to the places where there is need for heating.


The second by-product, oxygen, can be used to replace air in the activated sludge treatment process, thereby reducing the energy consumption of aerating the sludge, which saves BIOFOS electricity.


Until now, the cost of energy required to upgrade biogas has been one of the major barriers for increased use of biogas in the natural gas grid. Thus, being able to recycle by-products makes the biogas production more valuable at the same time as it increases the amount of biogas production, Dines Thornberg concludes.