Aquafin ramps up production of green gas to 40 GWh per year

From next spring, green gas from the treatment of household wastewater will be injected into the Fluvius gas grid in Ghent. For Aquafin, after Antwerp, it is one of the next locations where the company will start biomethane production in 2025, alongside Genk and Dendermonde. Deurne will follow in 2026.

Aquafin operates 328 sewage treatment plants (WWTP) across Flanders. Here, the wastewater from over 86% of Flemish households is treated to the quality required to discharge it into surface water. The excess sludge produced in the biological treatment process is partly fermented, forming biogas.

From CHP to biomethane

Until now, Aquafin converted that biogas into electricity and heat in CHP (combined heat and power) plants. "The CHPs are gradually reaching the end of their lifespan," says Maarten Raemdonck, manager Innovation at Aquafin. "In Antwerp South, we replaced a CHP with a biomethane unit for the first time in 2021. In such a unit, the methane and CO2 in the biogasare separated. In several steps, the methane is then purified until it has the same quality as natural gas. In this process, we use the full energy potential and no nitrogen or combustion gases are released. Biomethane production is therefore a much more sustainable alternative, which we will now also roll out at four additional WWTPs."

Sewer heat up fermentation

Environmental consultancy Nuoro from Heist-op-den-Berg is managing the implementation of a biomethane unit in Ghent, supplied by Prodeval, the French market leader in biogas upgrading. Nuoro is also implementing a riothermal project here. This involves extracting heat from the treated wastewater and using a heat pump to bring it to the right temperature for the digester. Maarten Raemdonck: "We used to get that heat from the CHP, but obviously that's no longer possible now. It is the first time we are using riothermal energy to heat the digesters. That makes the whole project even more sustainable and innovative."

Nuoro started the works in the summer of this year. "This water and energy project is a big step for Nuoro," says Michaël Faes, project manager at Nuoro. "We strive to implement sustainable techniques in the water sector on a large scale and, thanks to our partnership with Prodeval, we are bringing cutting-edge technology to Belgium."

Direct injection on natural gas grid

The biomethane plant in Ghent is expected to be operational in spring 2025. Currently, grid company Fluvius is preparing the injection of the biomethane into the natural gas grid. For this purpose, it installed a special gas cabin at Aquafin's site from where the biomethane can be safely injected into the grid. "The composition of the gas is automatically checked with it and the gas is also given the specific gas smell so that it is detectable and unsafe situations are noticed immediately," says Wesley Servaes of Fluvius.

At maximum capacity, the plant at the WWTP in Ghent will be able to inject 300 m³ of biomethane per hour. When the plants in Genk, Dendermonde and Deurne will also be operational, Aquafin will produce biomethane at a total of five locations. Good for 40 GWh per year or the gas consumption of some 2,650 Flemish households (based on an average gas consumption of 15 MWh per average family and home).

Whether the green gas produced by Aquafin reaches your living room is difficult to say. One way in which the generation of green gas pays for itself is by selling green gas certificates to companies that want to buy renewable energy. It is the international VARO Energy that buys and trades the certificates of biomethane produced by Aquafin. Aquafin also uses the green gas itself to run its service vehicles on CNG.

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