Biomethane : Biomethane: On the road away from fossil fuels

As horrible as it sounds, the Russian war of aggression in Ukraine has served as a wakeup call to governments worldwide to accelerate the elimination of dependence on fossil fuels – especially of course on Russian gas – and therefore also tackle the climate crisis. In its recently published REPowerEU Action Plan, the European Commission proposes a detailed outline to make Europe independent from Russian fossil fuels well before 2030. The goal is more affordable, secure and sustainable energy.

“It is time we tackle our vulnerabilities and rapidly become more independent in our energy choices. Let’s dash into renewable energy at lightning speed. Renewables are a cheap, clean and potentially endless source of energy and instead of funding the fossil fuel industry elsewhere, they create jobs here. Putin’s war in Ukraine demonstrates the urgency of accelerating our clean energy transition,” said Frans Timmermans, Executive Vice-President for the European Green Deal.

The European Commission plans to diversify gas supplies via higher liquid natural gas (LNG) imports and pipeline imports from non-Russian suppliers and higher levels of biomethane and hydrogen. According to the Biomethane Action Plan, the production of biomethane within the EU should increase to 35 billion cubic metres (bcm) by 2030. This should be made possible through different tools such as biomethane industrial partnership and financial incentives to increase production, including through the Common Agricultural Policy.

The European Biogas Association (EBA) welcomes the steps taken. The EBA is already in discussions with policymakers, Member States, and the whole biogas and biomethane value chain that they represent to work out the most urgent burdens that need to be lifted in order to reach the ambitious target. Harmen Dekker, CEO of European Biogas Association, said: “The EU shows leadership by further speeding up the energy transition and contributing to a more resilient system. The Commission recognises that biomethane will play an important role in this. We are eager to work with the EU Executive and other stakeholders to set up the Industrial Biomethane Alliance announced in the REPowerEU plan.” And EBA Secretary General Giulia Cancian added: “Facilitating the permitting process is essential to accelerate biomethane deployment. Additionally, the 35 bcm target should be accompanied by long-term perspective and clarity on the sustainability requirements included in the Renewable Energy Directive.”

According to the EBA, the 2030 goal of 35 bcm biomethane production must be cemented in EU legislation by including a mandatory EU-wide target in the revised Renewable Energy Directive II (RED) and the Gas Regulation. Furthermore, the rural development funding referred to in the Cap
Strategic Plans should support the conversion of existing biogas capacity to biomethane production, mobilisation of residues and necessary infrastructure adjustment, the EBA states. “The upcoming revision of the Waste Framework and Urban Waste Water Treatment Directives provides an opportunity for the inclusion of regulatory drivers to maximise energy production potential in the waste and waste water sectors,” it reads in a recently published brochure. The Association sees the need for €83 billion worth of investment in biomethane production capacity.

Today there are over 20,000 biogas and biomethane plants in Europe. The EBA’s idea would be to develop 5,000 plants over eight years (many years ago, Germany built 6,000 plants in nine years). So the goal seems feasible.

According to the EBA, France is the country with the most significant growth in the biomethane sector. The Netherlands and the Nordic countries are also rapidly expanding production. Spain also has a lot of potential in terms of feedstock, but this still needs to be unlocked. With regard to biogas (some of the current biogas plants could be converted to biomethane), Germany is the biggest producer, but production is stagnating. Other big producers include the UK and Italy.

“In Germany there has been no project for years because the government cancelled the subsidies,” says Stefan Laumann of upgrading technology producer EnviTec. “In France and Denmark the gas upgrading sector has been booming for years. China and the USA have also built a lot of plants.”

Christoph Spurk, managing partner of German biogas plant manufacturer and planner Ökobit, can also confirm that the effects of the Russian war of aggression in Ukraine and the associated attempts to become independent of Russian gas are being felt in the biomethane market. “Not only is demand increasing. Due to the price development, biomethane is becoming increasingly competitive.” So there is a noticeable search for alternatives to fossil fuels.

Spurk, who is also Vice President of the German Biogas Association, sees two big advantages of biomethane: first, it is a sustainable, CO2-neutral energy source. “Biomethane is the only really green gas,” he says. Second, since it has the same specifications as natural gas, it can be fed directly into existing grids without further adaptation. The existing infrastructure and site technology can simply be reused. So, there are no additional costs here. Unlike biogas, biomethane can replace all uses of natural gas, be it power, heating or transport.

Biomethane is the upgraded form of biogas. Raw biogas produced from digestion is not high quality enough to be used as a fuel gas for machinery. It typically has from 40 to 60% methane (CH4) and 40 to 60% carbon dioxide (CO2). In a biogas upgrader, the methane in the biogas is concentrated to the standards of natural gas (CNG), typically 98 to 99%. Carbon dioxide (CO2), hydrogen sulphide (H2S), water and contaminants such as dust, oil and aerosols are removed. “The separated CO2 can be used as a second product gas for greenhouses, dry ice, technical CO2 or food grade usages,” says Stefan Laumann.

In the past, the natural gas industry expressed concerns that biomethane might introduce microorganisms into the grid, resulting in problems in the infrastructure as well as health hazards. But various studies have showed that pathogenic germs are not present in treated biomethane.

Upgrading technologies can be used for biogas (from anaerobic digestion), sewage gas (from wastewater treatment plants) and landfill gas. “The upgrading technology is now about 25 years old and well established,” the expert says. The technologies are reliable, efficient and safe.

Biogas upgrading methods can be categorised as follows:

• Membrane separation
• Pressure swing adsorption (PSA)
• Amine scrubbing
• Water wash (or water scrubbing)

The aim of all these technologies is to achieve a high level of methane purity and low methane losses with low energy consumption. The methods can be used as standalones or – depending on the needs of the specific project – can also be combined. To ensure long-term project success as well as optimum life cycle cost, each project must be evaluated individually.

The pole charge and size of CO2 and CH4 molecules are key to getting them to separate in a mixed gas stream. PSA is the oldest technology and best used for larger amounts of gas. Membrane systems can also be used with small amounts of gas. These two methods are somewhat similar as both are what can be called dry upgrading systems that involve physical separation of the CH4 and CO2 molecules based on the molecule’s size, ionic charge and driving pressure.

Membrane separation

Membrane separation methods are based on the principle that gases diffuse through the membranes at different speeds. This means that smaller molecules such as CO2 will pass through the membrane while larger molecules such as CH4 will not. The goal is to achieve maximum permeability with high selectivity.

Pressure swing adsorption (PSA)

This method is based on the principle that different gas components are adsorbed differently to specific surfaces. These upgrading processes mainly use pressure differences to carry out separation.

Several vessels are running in parallel under pressure. An adsorptive medium, similar to activated carbon, separates gas molecules based on their molecular weight and size.

The amine scrubbing and water wash technologies are both ‘wet’ upgrading systems and involve separating the CH4 from the CO2 by solubilising the CO2 in a liquid solution while allowing the CH4 to pass

Amine scrubbing

In this two-step method, the amine portion of the scrubbing solvent molecule chemically reacts with the CO2
in the biogas to retain it in solution. Meanwhile, the methane part of the biogas passes through the packed tower reactor untouched by the scrubbing chemical.

Water wash

Just like amine scrubbing, this is a two-step upgrading process. In a tank, chilled water flows downward and biogas flows upward under high pressure. Soluble gases like CO2 dissolve in the water. The second tower serves as a depressurisation tower where pressure is released from the solution.

According to the EBA, the most commonly used method today is membrane separation, as it is highly efficient with low costs, little energy and no chemicals or water needed in the process, although this varies a little between Member States. “The modular design of a membrane system makes it flexible and simple. The biomethane quality is very constant at very low methane slip to the exhaust gas. The separated CO2 comes at very high CO2 content, so it can be used for liquefaction directly,” says Stefan Laumann.

Another promising method is biological methanation, Spurk says. The upgrading process developed by the Research Facilities Department at the testing and research institute PFI Germany (Prüf- und Forschungsinstitut Pirmasens) does not remove CO2 from the biogas, but adds hydrogen and converts it to methane with the help of archaea (primordial bacteria). In the next step the gas is desulphurised via activated carbon and dried via an adsorption dryer. The nutrient medium and water are recovered via a sophisticated recycling system. “It is possible to convert the biogas quantity one-to-one into biomethane,” says Spurk.

The pilot plant in the energy park of the city of Pirmasens has been feeding biomethane into the city’s natural gas grid since the end of 2016. However, the system still needs to be optimised for broad market entry.

Christoph Spurk sees a bright future for the biomethane industry, which can generate energy locally: “It’s a green, climate-saving technology and it does not depend on politically unstable regimes,” he says, with a critical allusion to contracts being signed with regimes in the Middle East.

Currently, even with the sometimes unstable supply chains, it takes about 18 months from the start of construction of a biomethane plant to feeding energy into the grid. “We have no downtime on our construction sites,” says Spurk. The focus is on the European market. “Especially in Eastern Europe, with its strong agriculture, we see a future. But there is considerable interest worldwide. However, there are often administrative barriers and problems with network access.”

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But not all the biomethane produced has to end up in the gas grid. Biomethane can also be liquefied and bottled, serving as an alternative to bottled LNG, which is used for cooking in many countries. And of course it can also be used on-site. Small-scale plants with an output of about 50 cm per day could produce the fuel for the vehicles on a farm. Spurk is convinced that: “We absolutely need sustainable waste management as well as crop management. A farm can grow wheat to sell to produce bread and then put the straw in a digester to produce energy.”

Energy independence is also an important topic for developing and emerging countries. Some companies are already building mini-biogas plants, including Ökobit with its HoMethan. This is designed for small farms, farming households, cooperatives, etc. and is distributed through NGOs.

Energy from waste seems to be a logical step on the road away from fossil fuels. Biomethane, with its well-established technologies and a potentially infinite source of substrate, along with its ability to replace natural gas without having to adapt the infrastructure, seems like a natural choice.

This article was first published in June 2022