BioFlock - organic and sustainable flocculants for digestate treatment

Due to the permissible nutrient loads on agricultural land per hectare and year, biogas plants increasingly rely on digestate treatment to reduce the volume and concentrate most important nutrients. As with sewage sludge, the flocculant polyacrylamide is generally used to separate the fine particles of the fermentation residue. Since polyacrylamide is synthetically produced and is not biodegradable or even difficult to break down, its use, especially in Germany at present, leads to great discussions regarding its effects on humans and the environment. Biogas plant operators strive to produce a high-quality, marketable fertiliser by processing fermentation residues. Therefore, many plant operators want to avoid or minimize the use of polyacrylamide as flocculant in general and fall back on alternative, natural flocculants such as starch or chitosan. Due to the influences on humans and the environment, the present project proposal aims at the substitution of synthetic (polyacrylamide) by natural biodegradable polymers (starch, chitosan) and the general optimization of "flocculation" to reduce polymer consumption.