Biogas plant builder Weltec Biopower has completed a biomethane plant for French crisps manufacturer Altho.

The production of crisps at Altho’s site in St. Gérand, Brittany yields 22,000 tonnes of leftovers and sludge a year, which thanks to the new plant can be turned into 200 standard m3/h of biomethane.

This corresponds to the gas consumption of a town with a population of 5,000.

pic 1 WELTEC Altho

Source: Weltec Biopower

Weltec Biopower explained the process:

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 fertiliser.

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.

pic 2 WELTEC Altho

Source: Weltec Biopower

“In the container, the raw gas passes through special membranes that separate it from carbon dioxide, steam and other components,” said Alain Priser, who is responsible for Weltec‘s business in France.

“The three-stage separation, which has already been successfully employed in other Weltec plants, reduces the methane slip to less than 0.5%.”