Power Pocket visiting two innovative monodigesters on onion residues and on pig slurry

In Flanders, residual flows such as manure and vegetable residues (leek residues, onion peels, etc..) are usually stored and then carried out on the land without further processing. Small-scale anaerobic digestion of these flows can offer opportunities to extract energy from them. To date, small-scale anaerobic digestion in Flanders mainly takes place on cattle slurry. Two pioneers, on the one hand an onion peeling company (Ongena) and on the other a pig company (Akivar), worked out an innovative concept of pocket digestion. Inagro and Biogas-E went along with a group of interested parties at the beginning of April as part of the Pocket Power and Transbio projects.

 

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The onion peeling company Ongena is a family company led by Joeri Ongena that manages the entire process from sowing to cutting and packaging onions. 

The company recently invested in a pocket digester (with CHP of 30kWel), in which the onion skins are anaerobically digested. The thermophilically operated digester is fed daily with 10-15 m3 onion peels and 1.5 m3 waste water from the onion peeling process. The onion skins are sent from the building with the processing lines to the outside with a conveyor belt, where a cutter reduces them. The shells then end up in the premix pit. There they are mixed with the waste water to make the whole pumpable and then reduced for a second time. Nothing else is fed to the digester. One pump serves four different purposes: it pumps the industrial waste water to the premix well, it also takes care of feeding the digester from the premix well, it pumps the digestate to the storage and can also pump digestate back to the premix well. The electricity produced is fully utilized at the company. The heat is used to keep the reactor at the right temperature and for the production of hot cleaning water. 

On the pig farm Akivar of Bart Vanackere and Mieke Baeckelandt recently a stable was built that allows to supply fresh, thicker manure to the recently built pocket digester. The heat that is produced in the near future will be used for the fermentation of vegetables on the farm as a feed for the pigs. Up to now, pocket digesters in Flanders have mainly been found on the farmyard of diary farms and not on pig farms, which is partly due to the composition of the manure. The Pocket Power project investigates, among other things, the possibilities for digesting pig manure as a one-sided flow. To enable the production of biogas from fresh pig manure, the new stable in Ardooie works with a sloping floor in combination with manure scrapers that remove the solid fraction through a central channel. The manure is pumped to an intermediate storage of 10 m3 where a centrifugal pump ensures mixing to make manure more uniform and to allow air to escape. The manure is digested in the mesophilically operated biogas plant. There are currently problems with foam, but the electricity yield was good said Bart during our visit.

Do you want to know more about this? Contact Inagro: Anke De Dobbelaere - anke.dedobbelaere@inagro.be

Both operators apply for innovation support for their investment from the European Agricultural Fund for Rural Development through the Flemish Agricultural Investment Fund (VLIF).

Both projects were realized with various partners, including Biotechnics, Innolab and Pocket Power (Inagro and Ghent University). Pocket Power is financed by the Agency for Innovation & Entrepreneurship (www.vlaio.be), with support from: Boerenbond, ABS, Bioelectric, Continental Energy Systems, Innolab, Vermeulen Construct, United Experts, Biogas-E, Inverde and VLACO.

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Bioenergy processes