Evonik is responding to the challenges of today's security of energy supply: Using the group's innovative SEPURAN^® Green membrane technology, pure biomethane can be extracted from biogas released during, for instance, wastewater treatment or organic waste processing, and used as a renewable industrial component to make other chemically based materials.

Renewable power plays a key role in clean energy transitions and it is one of the main enablers of limiting and reusing waste, and achieving energy security. The rise of renewables is steadily growing – according to the International Energy Agency, they accounted for 28.7%, almost two-thirds, of all global electricity generation in 2021. Still, there’s much more development needed in this field to achieve a viable renewable energy mix that includes wind, biogas, solar and hydropower.

Biogas is a byproduct of decaying matter like animal manure, organic waste, specific high-energy crops, sewage and sludge, and even landfills. Consisting primarily of methane, the other main component of biogas is carbon-dioxide. Both are considered greenhouse gases, and as such, would harm the environment if released directly into the atmosphere. Luckily, it is possible to capture and upgrade these gases into usable biomethane, which can be used as a renewable feedstock that is further processed into other materials within the chemical industry.

Evonik’s SEPURAN^® Green membranes are the key elements of processing of biogas. These membranes are housed in canisters and when pressurized biogas is fed through the assembly, a chemical reaction causes the carbon dioxide to separate from the methane. Through a patent protected 3-membrane-stage process, Evonik’s SEPURAN^® Green membranes are able to separate methane and carbon dioxide with purity levels of 99% from crude biogas.

The resulting biomethane can then be further processed for use as a substrate for producing other key chemicals, acids and polymers, which are needed to create many daily consumer and industrial products, including hoses, seals and detergents. Because the bio-methane is so pure, it is an ideal foundation for further chemical engineering.

One example is the use of biomethane to produce hydrogen, carbon monoxide or even syngas, which is a combination of the two, used as a chemical feedstock to produce ammonia, which could be used further in the production of fertilizer, or methanol, which could be used as a building block for creating acetates. Additionally, some of the bio-carbon-dioxide separated using SEPURAN^® Green membranes could be used in the process to boost the production of these chemical feedstocks.

The renewable aspect of using Evonik’s SEPURAN^® Green membranes to produce biomethane also contributes towards establishing a circular economy, and contributes towards the Net Zero Emissions by 2050 Scenario, set out by the International Energy Agency.

Evonik's SEPURAN^® Green membrane has been especially developed for the efficient upgrading of biogas into high purity biomethane. In fact, the market entry of Evonik into the biogas upgrading industry in 2011 revolutionized the market and set new technology standards. The introduction of a highly selective SEPURAN^® Green membrane in combination with a patent protected 3-membrane-stage process allowed for high methane yields and high product purities with an optimized energy consumption.

Various technologies are available for separating CO₂ from raw biogas and upgrading it into biomethane. In addition to well-known technologies such as pressurized water scrubbing, amine scrubbing or pressure swing absorption, membrane technology has become increasingly established in recent years. Thanks to highly efficient and highly selective membranes, it is possible to separate CO₂ almost completely from methane in a compact, three-stage process.

Polyimide-based membranes are the most widely used membrane treatment systems. The advantage of membrane upgrading plants over conventional technologies lies, among other things, in the simplicity of the process and the low maintenance requirements. Of course, the spread of biogas upgrading plants is also influenced by local conditions and regulations as well as national incentives.