Sugar beet for biogas is an exciting new market and a potential new source of profits for sugar beet growers. The requirements of a sugar beet variety for biogas though are rather different from those required for the sugar industry. The high juice purity required for the production of sugar is less important for biogas and sugar beet breeders such as Strube UK are working towards a different set of goals for biogas production. These include:
Producing an improvement in the ease of lifting, as well as a lower soil adhesion by means of beets with a smoother exterior, is being taken into consideration in the selection in our proprietary breeding programme. Our first biogas sugar beet varieties for the UK, Barents and Artus, show this and many other of the key biogas characteristics.
Energy sugar beet must have a high biomass yield and a high dry matter content. But it is clear from the experiments at the Institute for Sugar Beet Research in Göttingen (IfZ) that the sugar beet varieties that are the most suitable for sugar production are currently also the best for the fermenters.
Biogas beet is cultivated in broadly the same way as beet for sugar production. However, higher nitrogen fertiliser applications can be used to increase yield. Also, when harvesting, the tops can be cut higher or be defoliated, instead of crowning the beet. Defoliation leads to an increase in yield of up to 10 % in comparison with cutting the tops flat.
Complete removal of stones and sand particles are essential as they can damage or degrade the processing plant. Stones caught up in the process can cause severe mechanical damage. Sand particles wear plant components and build up as a sediment in the fermenter, reducing efficiency and requiring more frequent cleaning.
Fine components of soil, such as clay and silt, remain in suspension and are delivered with the digestate. They may even be beneficial for the process, since the fine soil particles constitute additional area for colonisation by the microorganisms that are involved.
Specialist cleaners such as the “Waschbär” from Doppstadt have been developed which can process up to 100 tonnes of beet per hour.
Sugar beet can be successfully harvested fresh for more than 6 months of the year and the best place to store the beet is generally in the ground.
The preferred form of the beet for storage appears to be as a pulp, either in elevated containers or in lagoons. In that way, the beet is available as a substrate throughout the year. High-powered shredders from the municipal or forestry sectors, such as the Doppstadt AK 235 can also process large volumes of beet like those required for filling a lagoon. The beet pulp has a consistency similar to coarse apple sauce and remains stable for a long period when stored. A further advantage is that it can be pumped, which enables the substrate supply to the fermenter to be largely automated.
Other techniques are selected in plants where beets are only wanted as a feedstock for a small part of the year, such as storing the beets in a storage clamp from which they can then be removed in portions, shredded and added to the substrate mix. Again, stone and sand removal is an important requirement.
If you would like to know more about sugar beet for biogas or Barents, then please do not hesitate to contact the Strube UK team. Alternatively you can contact us by calling Mark at our Newmarket office on 07850 369773 or email him here.
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