Biogas turns into biomethane

At the Antwerpen-Zuid waste water treatment plant, Aquafin converts the biogas produced by the fermentation of sewage sludge into biomethane. We inject that green gas into the natural gas grid.

Christel Van Moer

Sludge is a by-product of the water treatment process. By fermenting it, some of the organic matter in the sludge is converted into biogas. We now use this biogas to produce green electricity and green heat. To make the most of the biogas, we will upgrade it to valuable biomethane in future. This can be done by separating the methane and the CO2 using a membrane system.

At our Antwerpen-Zuid WWTP, we have a prefabricated unit that converts biogas into green gas. The clean-up takes place in several steps. In the first phase the biogas is cooled and dewatered. This is followed by purification with activated carbon filters. The gas is then compressed to 12-16 bar, after which it passes through a membrane system. Finally, the methane and the CO2 are split. This leaves only high-grade biomethane that can be used in the same way as natural gas.

Aquafin’s biomethane plant is the first in Belgium to purify green gas from biogas originating from waste water flows.

Biomethane is a very eco-friendly solution. It's sustainable, renewable and has very low CO2 emissions. Another crucial argument for Aquafin to invest in this technology.

Christel Van Moer, project manager Innovation

60 cubic meters gas per hour into the grid

Grid operator Fluvius has put in place the necessary infrastructure to inject the biomethane into the natural gas grid. The injection of biomethane generated from water treatment sludge is a first for Flanders. In Antwerp, 60 m³ of green gas is fed into the gas pipes every hour on average. “The experience with this first plant will be a good guide for possibly expanding the technology to other Aquafin sites in future,” says Christel Van Moer, project manager Innovation at Aquafin.

Green gas certificates

The production of biomethane leads to green gas certificates. We sell some of them to interested purchasers. The market for this is still quite new. Mainly companies that are committed to use 100% renewable energy show an interest. But suppliers of fuel for the transport sector are also potential purchasers because the EU imposes a green quota on them and because it tends to fit their sustainable company vision. We use some of the certificates ourselves to run our 185 CNG cars on the eco-friendly fuel.