Recently, biogas plant builder Weltec Biopower completed a biomethane plant for Altho, a French potato chip manufacturer located in St. Gérand, Brittany.
Courtesy of Weltec
The plant was planned and set up by the German manufacturer in collaboration with its French partner Weltec France. Some 200 standard m³/h of biomethane are generated from production waste and sludge from the company's own wastewater treatment plant. This approximately corresponds to the gas consumption of a town with a population of 5,000.
"Via the Altho subsidiary Sober, which operates the biogas plant, we actively participate in recycling, producing a green energy source from waste. Additionally, we contribute to the reduction of greenhouse emissions and the energy dependence of the region," said Christophe Chrétien, Managing Director of the Sober biogas plant.
The chips production yields 22,000t of leftovers and sludge a year. Potato and starch leftovers as well as other production waste account for about half of the substrate; the rest is made up of the sludge from the washing process. First, the solid and liquid substrates are mashed and shredded in the sturdy MULTIMix input system. After this pre-processing, the mixture is fed into the stainless-steel digester, which has a capacity of 4,436 m³. A post-digester with the same capacity is the last step in the material cycle. Subsequently, the digestate is sold to local farmers, who use it as high-quality fertilizer.
To condition the biogas, Weltec has integrated the membrane technology in a compact container solution.
"In the container, the raw gas passes through special membranes that separate it from carbon dioxide, steam and other components. The three-stage separation, which has already been successfully employed in other Weltec plants, reduces the methane slip to less than 0.5 percent," explained Alain Priser, who is responsible for Weltec's business in France.
Another benefit of the upstream compression is the methane has exactly the right pressure it needs in order to be fed into the natural gas grid. The separation takes place at ambient temperature and without using any chemicals.
In this way, 400 standard m³/h of raw biogas yield about 200 standard m³/h of processed biomethane.
"Over the last 18 years, we have successfully installed and commissioned more than 300 biogas plants in 25 countries. The combination of 'Made in Germany' with the cooperation of strong local partners ensures security and efficiency for our customers," concluded Priser.