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Resource Efficiency

We turn biowaste into green energy

Bioenergy is indispensable as a climate-friendly substitute for fossil energy. In Germany alone, it saved some 65 million metric tons of CO2 equivalents across all industries over the past year, as calculated by the Capital City Office for Bioenergy.

What we are doing:

Thanks to an innovative membrane technology from Evonik, the biogas released in wastewater treatment or in the anaerobic fermentation of household waste can be easily and efficiently turned into pure biomethane and fed directly into the natural gas grid or used as a biofuel.

Biogas results from the fermentation of biomass – an organic substance consisting of, for example, food scraps, plants, manure or sewage sludge. However, in addition to the energy carrier methane, raw biogas also contains carbon dioxide (CO2) as well as other trace gases. Since CO2 is non-combustible, it reduces the calorific value and must therefore be separated.

Evonik has developed SEPURAN® Green membranes for particularly efficient CO2 separation. The product, which at first glance looks like spaghetti or a brush, in fact comprises highly selective membranes made of multiple cylindrical hollow polymer fibers. The small CO2 molecules dissolve more easily in the polymer and penetrate the membrane relatively quickly. In contrast, the larger methane molecules do not penetrate the membrane at all. They gather on the high-pressure side and can then be fed into the natural gas grid or be used as a biofuel to power compressed natural gas (CNG) vehicles. Even the CO2 can be recycled. A few plant nurseries channel the gas into their greenhouses to promote plant growth, but CO2 also has uses in the food industry.

Since their market launch in 2011, SEPURAN® Green membranes have been installed in more than 250 biogas treatment facilities and produce a total of tens of thousands of standard cubic metres of high-purity biomethane. The carbon dioxide emissions measured over the life cycle are around 60 percent lower than when the same amount of natural gas is produced and processed. This results in an emission reduction of significantly more than one million tons of the greenhouse gas per year.

Membrane-based processing of biogas with technology from Evonik is associated with particularly high system availability, minimal energy consumption and low maintenance costs. In addition, the treatment does not generate any waste or emissions. No auxiliary agents such as water or sorbents are needed.

If biomethane replaces fossil natural gas in the application, significant CO2 savings are achieved once again. Biomethane is not only an alternative fuel, but is also used in industry as a chemical building block or in gas-fired power plants in the form of pipeline gas as a rapidly available energy store.