SilphieSil

Process engineering studies to optimize the silaging of continuous silphia to avoid faulty fermentation while achieving optimum fiber quality for papermaking - Silphie-Sil"

Topic

In order to increase the value added in rural areas, the Baden-Württemberg bio-economy initiative is looking for new or optimized ways of using agriculture. The use of energy crops such as the silphie plant for energy production is already established in Baden-Württemberg. Cultivation of the growing cup plant is particularly interesting because the perennial plant promises significant ecological advantages over corn. However, due to its high fiber content and the resulting low specific methane yield (approx. 250 L CH4/kg oTS), its fermentation is not economically competitive compared to corn (approx. 340 L CH4/kg oTS (KTBL,2013)). One reason is that the fibers cannot be degraded to methane in the biogas plant. With the help of thermal haydrolysis, a physical-thermal pre-treatment, these natural fibers can be separated and used as a high-quality product for paper production. The resulting liquid (pulp), along with the other cell components, is also highly fermentable.

Goals

It has been shown that the ensiling of cup plants as a chipping material is not without problems. The lactic acid content of the silage is very low compared to other energy crops, and butyric acid is formed as a result of faulty fermentation, causing both the silage and the fiber produced from it to have an unpleasant odor, which reduces the marketability of the fiber.

Project tasks of the State Institute

In the Silphie-Sil project, the harvesting and ensiling process of Silphium Perfoliatum is being optimized in the laboratory with the addition of bacterial cultures and other additives to achieve a rapid pH drop, low ensiling losses, and a low-odor fiber product. The overall goal is to increase lactic acid formation in the silage to reduce butyric acid formation, improve silage storage stability, reduce odor emissions, and increase biogas yield from the remaining pulp. For this purpose, three harvest dates of the cup plant and the composition of the fermentation acids during the entire ensiling phase are studied. Fibers are then separated by thermal pressure haydrolysis and evaluated for potential use in papermaking (fiber quality, tensile strength, odor). The pulp is analyzed for methane potential and toxic substances (phenols, furfurals).