Case Story Denmark

Production of food grade sustainable CO2 from a large biogas facility

GO’CO2 at The Korskro Biogas Plant, Denmark.

November 2020

From residual CO2 to GO’ CO2

Strandmøllen A/S developed Denmark’s first biogas-based CO2 plant at one of the world’s largest biogas plants, built by Nature Energy in Korskro, outside the city of Esbjerg (Figure 1). Biogas typically consists of 60% biomethane which is used as a renewable fuel, while the remaining 40% is a natural residual product in the form of CO2. Instead of wasting this residual CO2 and emitting to the atmosphere, a specially built unit was designed to recover and recycle all of the CO2 enhancing the sustainability and the circular economy credentials of the facility.

CO2 recovery is part of the circular economy

The biogas plant processes around 1 million tonnes of biomass per year, of which 85% is composed of animal manure and slurries; this is co-digested with animal bedding, industrial waste, food waste and small amounts of energy crops. The biogas plant produces c. 49 million Nm3 of biogas each year. The produced digestate is returned to the farmers, to be applied on their crops as plant biofertilizer while the produced biogas is upgraded to biomethane quality and injected in the gas grid, to be used as a renewable substitute for natural gas and as a means of “greening” the gas grid. The upgrading process removes the CO2 from the biogas.

Instead of release to the atmosphere, CO2 is captured and transferred to the CO2 facility (Figure 2), where it undergoes a complex, seven-step process of purification. The seven step purification process consists of filtering, washing, distillation, compressing, condensation, drying and cooling. These steps remove all unwanted residues and impurities from the CO2, producing a product of quality and purity suitable for use in the food industry. The produced purified CO2 trades as GO’ CO2. It is also used in other industries and sectors beyond the food industry. The residual CO2 from the biogas production which would have been emitted to the atmosphere is now captured, reused and integrated into a circular economy system.