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What type of inputs for a biogas unit?

Do you have any idea where the first biogas unit created in France can be found?
In Obernai, Alsace, at the company managed by the lycée agricole (agricultural secondary school).

The agricultural school in Obernai is the sole manufacturer of French organic hops, owns a herd of bulls and cultivates 60 hectares of land—bringing in a total turnover of €400,000. In the recent past, the company decided to branch out to a new source of income: energy.

Although it began in 2003, the low-load biogas project has been going strong now for the last three full years. The numbers are impressive: €2.3 million invested, 6,000 tons of digested inputs and a production of 240 kW. The company is targeting a 98% cogeneration rate with downtime under 2%.

What type of inputs? They come from a radius of no more than 15 km from the school and are alternately made up of agricultural waste, rye silage, grape marc, manure and industrial fats. The method adopted in France contains the largest variety of inputs, unlike other countries such as Germany and the United States. Research on the stability of the mix, and therefore the energy production, is infinite. The slightest change in climate will disturb the fragile balance of the bacteria. For example, rainfall on potatoes reduces their rate of dry matter, whereas long dry storage increases it. As a consequence, the entire fermentation process is altered.Obernai2

On the technical side—The semi-subterranean digester contains two 18 kW agitators that mix the digestate at a constant 39° C temperature. It produces 50 m3 of methane per hour. Once out of the digester, the biogas is cooled and the water condenses. A motor then directs the gas into the appropriate circuits. Let’s have a closer look at these.

Efficient, synergistic energy—The agricultural team no longer buys either fertiliser or nitrogen, and instead spreads its digestate on its crops. The energy produced helps heat the school in winter. During the hotter months, it is converted into electricity and sold to a local business. This localised thermal repurposing helped the project get adopted and weighs in heavily on the integration of the unit within the region.

‘The biogas unit needs to be taken care of like a cow. A huge cow’, jokes Freddy Merckling, the company’s GM. Just like bulls, it needs human monitoring 24/7. That means permanent on-call duty for the three team members, who carefully note in a spreadsheet the difficulties they meet and the solutions they set up to help out in the future. As reasonable professionals, the three farmers mentor interns and enthusiastic students, frugally monitoring the biogas unit’s footprint so as not to use too much agricultural soil (ILUC impacts).Obernai5

What do the neighbours think about the biogas? There are flats right next to the school, but its residents have yet to complain about any odours. It’s very closely monitored.

My tour of the biogas unit at the lycée agricole in Obernai, organized as part of the ExpoBioGaz tradeshow, gave me the chance to discover many technical aspects. I am passionate about translating for the renewable energies sector. My inspiration thrives through intelligence assessment, tradeshow visits and exploring remarkable places where I can meet dedicated and fervent individuals who love to share their know-how. And that’s how I go about my in-service training.

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