Biomethane plant
Recently, biogas plant builder Weltec Biopower completed a biomethane plant for Altho, a French manufacturer of potato chips in St. Gérand, Brittany.

By Ann Börries, Weltec Biopower

Recently, biogas plant builder Weltec Biopower completed a biomethane plant for Altho, a French manufacturer of potato chips in St. Gérand, Brittany. The plant was planned and set up by the German manufacturer in collaboration with its French partner Weltec France. Some 52,800 gallons per hour of biomethane are generated from production waste and sludge from the company’s own wastewater treatment plant. This corresponds to the gas consumption of a town with a population of 5,000.


For more than a year, France has promoted the establishment of biomethane plants. Now, an action package implemented by the government makes sure that the projects can be rolled out speedily and with minimum bureaucracy. The improved framework conditions have started showing up in the order books of experienced biogas specialists like Weltec Biopower. 

The biomethane production is in line with the CSR (corporate social responsibility) policy of Altho, which holds more than a third of the market share with its chips brand, Bret‘s. 

“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,” says Christophe Chrétien, managing director of the biogas plant of Sober.


The chips production yields 22,000 tons 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 1.17 million gallons. 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. 

The process that transforms the biogas into biomethane also stands out with its sustainability: To condition the biogas, Weltec Biopower 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,” says Alain Priser, who is responsible for Weltec‘s business in France. Another major benefit is that thanks to the upstream compression, the methane has exactly the right pressure that it needs in order to be fed into the natural gas grid without any further compression. The separation takes place at ambient temperature and without using any chemicals. 

To condition the biogas into biomethane, Weltec Biopower integrated a membrane technology as a compact container solution.


In this way, 10,500 gallons per hour of raw biogas yield about 52,800 gallons per hour of processed biomethane. “Owing to the durable membranes, the plant availability is high, and the maintenance overhead is low,” says Priser. “In St. Gérand, we ensure uninterrupted gas feed-in with our custom-developed LoMOS PLC.”

With this equipment, Altho is able to focus on its core business and make efficient use of accumulating leftovers. This fills an urgent need, as many French biogas operators struggle with technical problems. A survey conducted by the ATEE (Association Technique Énergie Environnement) has revealed some sobering results: 94 percent of the plant operators had technical problems, and 65 percent did not see their efficiency expectations fulfilled. This was usually because the technology did not meet the requirements. In view of these challenges, the cooperation between Weltec Biopower and Weltec France is just what is needed. 

“Our team has a wealth of experience in handling various substrates, and it custom tailors the technology implemented in each plant. In this way, we ensure stable, economical operation,” explains Priser. “Over the last eighteen years, we have successfully installed and commissioned more than 300 biogas plants in twenty-five countries. The combination of ‘Made in Germany’ with the cooperation with strong local partners ensures security and efficiency for our customers.“ 

This is an optimum basis for the further development of the portfolio of biogas plants in France and around the globe.


The strength of Weltec Biopower lies in custom-tailored design and technically mature solutions for projects up to 10 megawatt capacity. In this context, the high proportion of internally developed components is a key success factor. The company also owes its leading edge to the use of stainless steel. This enables the input of a diverse range of feedstocks, a fast and economic assembly and a consistently high quality standard—regardless of the location. 

After a biogas plant goes live, Weltec Biopower offers additional support through its experienced mechanical and biological service team. 24/7 availability contribute significantly to the efficiency of the plant. 

Nordmethan, a subsidiary company of Weltic Biopower, addresses another business area: The operation of biomethane plants and the provision of heat through energy contracting. In this way, the Weltec Group covers the entire value chain of energy generation with biogas and biomethane—from the plant construction to the plant operation.


Weltec Biopower GmbH is one of the world‘s leading enterprises in the field of stainless-steel biogas plant construction. The company has planned, developed and built anaerobic digestion plants since 2001. Today, the medium-sized company has about eighty employees at the headquarters in Vechta, Germany, and has established more than 300 energy plants in twenty-five countries worldwide. The global distribution and service network spans six continents. The range of customers includes businesses from the agriculture, food, waste, and wastewater industries. For more information,

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