Environmental project contractor En-Bio has built a small-scale biogas plant for a dairy farmer in Amel (Belgium). The installation is fed with animal manure from several neighbouring farms to produce electricity, heat, dry pellets and supplements for straw. “Biomass energy is very versatile,” says En-Bio CEO Francies Van Gijzeghem. “But the challenge is to get a firm grip on processing inputs and outputs.”
Dairy farming is the main economic activity in Amel, a village in the south of the High Fens between Malmédy and Sankt-Vith. For economic reasons, several farms in the neighbourhood have been merged into larger conglomerates in recent years. Cattle farmer Dries, for instance, has taken over activities of other farms, thereby expanding his livestock from 140 to 200 animals. However, this has also meant increasing total manure production by more than 40% without being able to spread the surplus on land.
For this reason, Dries contacted Ghent-based En-Bio, which has a solid expertise in treating natural waste such as animal manure. They recommended Dries investing in a small-scale biogas or co-digestion plant. “That in itself was an obvious choice,” says Francies Van Gijzeghem. “Manure is an ideal source of biomass energy, especially when combined with additional feedstock. In a controlled process, we are able to produce electricity, heat and pellets from it. So it delivers a diversity of energy types, either to be consumed onsite, fed into the grid or sold on the market. The applications of biomass are manifold; no other renewable energy source is as versatile as this.”
Neighbouring farmers joined the project in a kind of exchange trade
The challenge, however, is to design and organize a process that is both practical and economical. This involves more than optimizing a plant’s technical parameters. “It’s essential to have a firm grip on both inputs and outputs,” explains Van Gijzeghem. “In this case we had to make sure we had enough manure to feed the digester continuously. That’s why Dries persuaded nearby farmers to join him in a kind of exchange trade. The farmers deliver their manure and receive supplements for straw, pellets, and liquid digestate-fertiliser in return. This digestate is sanitized at 70°C for one hour to make it suitable for any application. Additionally, arrangements have been made with bakeries, chocolate factories, breweries and paper mills to deliver additional waste streams. This is necessary to enhance the digester efficiency and increase the biogas yield.”
A biogas plant is built around a digester unit, where the controlled anaerobic fermentation process of natural waste takes place. The digester produces gas plus a digestate containing a solid fraction. The gas is used in a cogeneration process to produce electricity and heat, in other words energy ready for consumption in whatever application. In some cases, some of the gas is upgraded to be used as a supplement to natural gas, although this technique is currently too expensive for economic exploitation. The digestate is separated into liquid and solids. The liquid part is usually spread on land or can be further purified. The solid fraction is converted into pellets for storage and later use as fertilizer or fuel.
Biomass energy is very environment-friendly as it reduces the organic waste stream without creating additional greenhouse gas emissions. The power generated from biogas is not subject to price fluctuations and – unlike wind power and solar energy – can be obtained regardless of climate and weather conditions.
The co-digestion plant in Amel is designed to process 15,000 tonnes of biomass per year, producing 600 kWe of electricity, with an option to double the capacity in the future.
TCS was in charge of designing and constructing the building of the Amel plant. “It wasn’t easy to find a contractor who would take care of the whole project,” says Van Gijzeghem. “There were, after all, a few challenges. The underground, for instance, is built of schist with a lamellar structure, requiring special care in laying the foundations. They also had to deal with the harsh climate in this area of Belgium. And country planning required that the façade be erected in wood - not the easiest choice. Many contractors were willing to take on part of the job, but TCS was the only one unafraid to assume full responsibility.”
