Removing VOCs from biogas to upgrade to biomethane

For communities throughout Europe, municipal organic waste collections have become the norm. Even Christmas trees can be collected, put into anaerobic digesters, and used as the source material for biogas. This biogas contains not only methane, which can then be upgraded into valuable biomethane, but also CO2 and contaminants known as Volatile Organic Compounds (VOCs), such as terpenes and siloxanes. These can cause damage to biogas engines or other purification technology. One molecule of terpene, the alpha-pinene, produces that lovely Christmas tree scent that you enjoy in your home during December. However, other terpenes produce less pleasant emissions that can not only damage equipment such as membranes, but also cause a major odour nuisance. DESOTEC's activated carbon filters can remove VOCs at various stages of the biogas upgrading process, depending on the biomethane technology used. Two common methods of producing biomethane are high pressure water scrubbers and amine scrubbers. In both cases, DESOTEC filters can capture VOCs either before or after the scrubbing process, to avoid causing damage to the equipment. A third method is membrane technology. This involves pushing raw biogas through membranes at very high pressure to separate the valuable methane from the CO2 and other components. However, the VOCs that are contained in raw biogas not only cause environmental harm and odour issues but would also block the membrane. This would reduce the efficiency of the membrane, meaning that it would no longer be possible to reach the required biogas quality. The plant's performance would therefore be reduced. Furthermore, blocked membranes deteriorate over time, and are costly to replace. DESOTEC filters are highly effective at clearing VOCs from the raw biogas before it is put through the membrane separation process, making for a more efficient, cost-effective and sustainable process.