Field report biogas plant: concrete coating protects against biogenic sulfuric acid and cracks caused by thermal stresses

Poing near Munich, May 24, 2022. REMA TIP TOP has developed a special coating for concrete surfaces in biogas plants, which was used for the first time in the plant of Marc Hohmeier based in Espelkamp in North Rhine-Westphalia, Germany in 2020.

Background: Biogas plants are used to produce biogas by fermenting biomass. In agricultural biogas plants, mostly animal excrements such as manure and energy crops are used as substrate. These are fermented in so-called fermenters at around 40 to 45 degrees Celsius in the absence of oxygen. This process releases methane gas, which can be used to generate energy.

20 percent of renewable energy in Germany is covered by biogas.

The problem: In addition to methane gas, biogenic sulfuric acid is produced during fermentation, which corrodes the steel reinforcement of the exposed concrete in the fermenter. This subsequently leads to spalling and leakage of the concrete surface. In addition, differences between the inside and outside temperatures can cause considerable stresses in the concrete shell of the fermenter, which also lead to the concrete cracking and thus leaking.

"Many of the plants in Germany, with a total of more than 30,000 tanks, are now twenty or more years old and are tested for leaks every two years. The challenge for plant operators is to find a long-lasting solution against leakage of the concrete surfaces due to biogenic sulfuric acid and thermal stresses," explains Peter Jansen, head of surface technology at REMA TIP TOP West in Kamen.

In response to the stresses caused by biogenic sulfuric acid and thermal tension, the specialists for polyurea coatings at REMA TIP TOP have developed a spray coating for concrete sealing specifically for slurry, manure and leachate. In contrast to standard epoxy resin-based sealing systems, where the entire coating has to be replaced in a costly and time-consuming process, the „REMAPUR-BIO" coating from REMA TIP TOP can be implemented very quickly and cost-effectively.

When it comes to surface treatment inside a fermenter, every day it cannot be used costs the operator a lot of money. That's why fast and durable processing is so important. "Thanks to the new concrete coating from REMA TIP TOP, our fermenter could be refilled after just five days, allowing us to resume operation relatively quickly," explains Marc Hohmeier, an operator from Espelkamp in North Rhine-Westphalia, who assisted with the development and in whose biogas plant "REMAPUR-BIO" was used for the first time in 2020.

For more information on concrete repair in biogas plants, operators and anyone interested can watch the REMA TIP TOP video at