We go beyond to push renewable energies

Biomethane and natural carbon dioxide ensure greater sustainability in numerous areas of application. SEPURAN® Green enables these gases to be extracted from biogas in high purity. Over 1,000 biogas plants around the world are already operating with this innovative membrane technology for gas separation. Because the number is steadily increasing, Evonik is expanding capacity at its production sites in Upper Austria.

There’s a lot of potential in waste, liquid manure, and sewage sludge. When used as starting materials for the production of biogas, they make it possible to obtain sustainable raw materials for industry and environmentally friendly fuels. To harness their potential, Evonik has developed SEPURAN® Green, a hollow fiber membrane for efficient gas separation. With the membrane’s help, methane and carbon dioxide can be separated from raw biogas with a high degree of purity. Both substances replace natural gas and CO₂ of fossil origin in numerous applications, thus helping to reduce greenhouse gas emissions and drive the energy transition forward.

SEPURAN® Green was launched on the market in 2011. Since then, Evonik has continuously enhanced the technology and worked with partners to establish it as the quality standard for biogas processing. The high-performance membranes were originally intended only for small quantities, but they have also been used on a large scale in biogas plants for a long time. “There are now more than 1,000 plants worldwide that use our technology to produce biomethane and bio-CO₂,” says Götz Baumgarten, the head of the innovation growth field Membranes at Evonik. “One reason for this success is our superior technology. Moreover, SEPURAN® Green requires little investment from biogas plant operators, and it’s quick to install and easy to operate,” he adds.

NUMEROUS AREAS OF APPLICATION FOR BIOMETHANE AND NATURAL CO₂

The biogas required for the separation process can be produced from all types of biomass. In addition to liquid manure, residual and waste materials, and sewage sludge, “energy crops,” which are not intended for food production, are also suitable. The big advantage of millet, sugar beets, corn, and similar crops is that they enable a particularly high gas yield.

The areas of application for the substances obtained with SEPURAN® Green are just as diverse as the starting materials. Biomethane can be used as a renewable source of electricity and heat or in industry as an initial product for the technical synthesis of hydrogen, methanol or ammonia. Compressed as CNG (compressed natural gas) or liquefied as LNG (liquefied natural gas), it is also used as an environmentally friendly fuel for cars and trucks. Bio-CO₂, in turn, is a valuable raw material for the chemical industry. In addition, beverage manufacturers use it as carbonic acid. In greenhouses, bio-CO₂ is used as a gaseous fertilizer. “The great variety of applications shows that SEPURAN® Green opens up ideal marketing opportunities for biogas plant operators,” says Baumgarten.

SEPURAN® GREEN'S MAIN ELEMENT: HOLLOW FIBERS MADE OF POLYIMIDE

In addition to SEPURAN® Green, Evonik offers other innovative membrane technologies for efficient gas separation in areas such as nitrogen production, natural gas processing, and hydrogen extraction. The membrane’s main element consists of fine hollow fibers made of the high-performance polymer polyimide, which resemble macaroni in their shape and color. Evonik’s Schörfling facility in Upper Austria produces the fibers and installs thousands of them in tubular stainless steel modules. The Schörfling facility obtains the pressure- and temperature-resistant polyimide from the Evonik plant in nearby Lenzing.

The way SEPURAN® membranes work is comparatively simple. To separate biogas into its main components methane and carbon dioxide, for example, it is first forced into one end of a module. Because of the different sizes of the molecules, carbon dioxide and water vapor escape sideways through the membrane, whereas the methane comes out the other end of the module. Evonik has also developed a method of biogas processing that optimally utilizes the separation properties of SEPURAN® Green: Thanks to the clever interconnection of the membranes, the raw gas can be purified to produce methane of up to 99 percent purity. All that’s needed is a compressor.

SEPURAN® MEMBRANE CAPACITY AND EFFICIENCY HAVE BEEN STEADILY INCREASED

Evonik has continuously improved the production of hollow fiber membranes in recent years. Polymers have been spun into fibers in Schörfling for almost 100 years—using viscose in the past and polyimide today. “It’s especially challenging to shape the liquid polymer into the desired form,” says Peter Aigner, a chemical process engineer and shift supervisor at Evonik’s Schörfling plant. “But we have perfected the process to the point where we can reliably supply our customers with our products.” Evonik has also continuously increased the capacity and efficiency of the membranes over the years.

As the demand for SEPURAN® membranes continues to grow, Evonik is expanding the capacities in Schörfling and Lenzing. Following the commissioning of a new hollow fiber spinning plant at the beginning of 2023, another plant will now be added. Evonik is also expanding the infrastructure for module production in Schörfling. Polyimide production in Lenzing is being increased accordingly.

100 PERCENT RENEWABLE ENERGIES IN SEPURAN® PRODUCTION

But the production of SEPURAN® membranes is not the only way that Evonik is making a valuable contribution to the energy transition in Upper Austria. The Schörfling facility is already supplied entirely with green electricity from wind, hydropower, and biomass. Since the beginning of 2022, the plant has also been covering 100% of its gas requirements with biomethane from regional production. The environmental benefit: By switching to an environmentally friendly energy supply, Evonik has been able to reduce its direct CO₂ emissions in Upper Austria by around 5,000 tons per year.