ETW Energietechnik builds biomethane plant in Rittershoffen, Alsace

ETW Energietechnik (ETW), which is headquartered in the German city of Moers, has built a biomethane plant in Rittershoffen, in Alsace. The plant was built in cooperation with construction company Rytec, based in Baden-Baden, Germany.
The plant went into operation in February this year, and possesses a processing capacity of about 700 normal cubic metres of raw biogas per hour.
This means that up to 350 normal cubic metres of biomethane are fed into the natural gas grid every hour, roughly equivalent to the average fuel consumption of 20,000 passenger cars, according to ETW.
Use of substrates from the region
The project was initiated by three young farmers from Alsace, who are committed to environmental protection and renewable energies, and who want to promote sustainable agricultural use in the region, added the company.
Only agricultural residues from the immediate surroundings are used as substrates.
The biomethane plant is state-of-the-art for its size, due to its low power consumption (137.6 kilowatts). This significantly reduces the risk of future hikes in electricity prices, said ETW.
Even with a downstream high-pressure compression plant, which compresses the processed biomethane to 67.7 barg (bar gauge) and feeds it into the natural gas grid, the power consumption of the entire plant is less than 202 kilowatts, which the organisation stated is significantly lower than comparable products.
"This means that the entire plant consumes less than 7% of the energy provided by the biomethane," noted ETW.
Interface reduction ensured rapid construction progress
The initial steps to realise this project were made as early as 2016, and design and planning work began in 2019.
The approval, application for funding, construction financing and earthworks were all carried out by Rytec, from a single source.
The maximally reduced interfaces allowed the construction work to progress quickly and effectively, ETW commented, and three jobs will be created in the region.
The company went on to say that the residents of the neighbouring village of Rittershoffen had initially expressed concerns. In response, the developers "invested a lot of work and money to ensure that the plant was well-integrated into the landscape."
Focus on highest quality
When designing the plant technology for the fermentation of the diverse residual materials, a lot of emphasis was placed on the highest quality, said ETW.
The ETW SmartCycle® biomethane plant is correspondingly high-quality, reliable and low-maintenance, it added, as it utilises oil-free screw compressors and an intelligent plant control system. ETW said the plant "has the lowest energy consumption on the market".
Prefabricated parts from Drössler Umwelttechnik with factory-concreted installation parts, such as FF pieces and agitator frames, were used for the concrete, and all built-in parts have additional sealing flanges.
The sandwich construction of the tank walls is optimally thermally insulated and already fitted in the factory with integrated heating pipes protected by the concrete, the firm stated.
The stirring and separation technology was carried out by the Paulmichl company. The agitators are equipped with powerful external drive technology.
The fementer agitator Mammut has a strong agitating performance at a high dry matter content, according to ETW.
"Thanks to the infinitely variable hydraulic adjustment of the agitators, optimal adaptation to the fermenter substrate can be achieved," said the organisation.
The panorama sight glasses were developed by Paulmichl, and provide the operators with visual insight and monitoring of the plant operation.
The reliable separation operation at the Rittershoffen plant is carried out by a separator of the PM260 model series, which is specially adapted to the fermentation residue, said ETW.
By means of pressure control of the separator, the feed pump is controlled in its flow rate, so that operation can take place without a feed tank and overflow pipe, it went on to say.
The gas storage tanks from SATTLER, who have almost 45 years of experience in this field, have an enormously high tensile strength and extremely low permeability, continued ETW.
With the BioG solids dosing system, more demanding residues such as straw and manure can be introduced in liquid form. The system in Rittershoffen consists of a 190 cubic metre BioFeeder. The subsequent BioMerge mixing system (market launch 2022) mixes fermenter liquid with the shredded material and pumps it through an eccentric screw pump as a homogeneous mass into the fermenter. Stones as well as other foreign bodies are successfully separated in the overall system. This helps to reduce the wear and tear on the pumps as well as on the downstream technology, said ETW.
Gate valves and measuring technology are each double-protected, so that the plant is equipped with the highest safety standards of the Rytec company.
With the low-energy gas processing plant from ETW Energietechnik, the frequency converters from Rytec and the future CO2 liquefaction, the bottom line is that a negative CO2 footprint is generated, concluded the company.