What is Biogas?
Biogas is a mixture of methane and carbon dioxide produced by fermenting organic material – such as sugar beet – in the absence of oxygen. The volume of gas generated and the operating reliability of the production plant are significantly influenced by the type, quality and quantity of the substrate (feedstock) used. The substrate costs make up around 40% of the total expenditure for biogas production, so the choice is also an important factor in plant profitability.
Sugar Beet for Biogas
The ultimate aim is to achieve the highest possible biogas or methane yield per unit area. Sugar beet for biogas provides higher comparable yields and energy levels than energy maize and contains other valuable characteristics for biogas production, these can be seen below:
- Higher energy levels than maize
- Stable yields across seasons
- Good fit in crop rotation
- High dry matter yield
- Excellent fermentation characteristics
- Rapid fermentation
- Faster plant restart
Sugar beet has excellent substrate and fermentation characteristics, which stabilise the microbial conversion and improve the technical processes in the fermenters.
Sugar beet dry matter primarily consists of directly fermentable carbohydrates (sucrose) which are quickly converted into energy. Sugar beet is often completely decomposed in less than 15 days (compared with maize which takes approximately 90 days). It therefore has a shorter fermentation time than other field crops and, in good agricultural regions, sugar beet achieves a methane yield per hectare which, in favourable conditions, is 20% or higher than the yield from silo maize (45 t/ha for maize compared with 80 t/ha for sugar beet).
Sugar Beet’s Stable yields
Due to its stable yields, sugar beet provides consistent energy yields over long periods of time. It also offers high yield security, even under difficult weather conditions, and it compensates for long dry periods without problems. Additionally, sugar beet eases the burden of close crop rotation of maize and so can provide a valuable contribution in widening the biodiversity in our agricultural landscape.
Practical experience has shown that biogas plants that use beet as a proportion of their feedstock can be restarted much faster after disruptions. This is linked to the speed of decomposition of the substrate. Furthermore, a decline in acid production can be observed, which has a stabilising effect on the entire conversion process. If using beet is abruptly stopped, the biogas plant requires some time to be brought back up to full capacity.
The amount of sugar beet being cultivated specifically for biogas production continues to grow, as ever more plant operators discover the advantages of beets as a substrate.
