It is now becoming painfully clear that the previous model is not sustainable: fertiliser produced with fossil energy and mostly imported has become so expensive that many European countries expect drastic harvest losses for the coming year. Yet with the appropriate technologies, fertiliser and even humus could be produced from the fermentation residues of biogas plants: cost-effectively, regionally and in a climate-friendly way. <\/p>\n\n
“BioProfit” is the name of the project to which five institutes – GET, AEE INTEC, LVA, ZFE and IWI – have joined forces. The project group will develop processes to profitably use the fermentation residues of biogas plants, which until now have had to be disposed of at high costs. <\/p>\n\n
The fermentation residues that are produced in biogas plants during the generation of biogas consist of 90 per cent water and contain nutrients that are just as valuable in addition to the valuable water: Nitrogen, phosphorus and potassium, for example. This digestate slurry is usually spread on fields as fertiliser. The problem is that the slurry leads to further overfertilisation of the soil, especially to a local nitrogen surplus. This not only destroys soil life, but also the climate, as soon as the nitrogen has turned into nitrous oxide. What carbon is still present in the manure escapes into the atmosphere as CO2 when digestate is used in this way. To make matters worse, liquid manure may not be spread in the winter months precisely because of its high nutrient content. The result: a raw material that is valuable in itself becomes a problematic substance and is stored unused in large tanks or transported over long distances. <\/p>\n\n
Separating solids and liquid, treating the water, has so far only been profitable for a few biogas plants, mainly because of the nitrogen: Classic methods such as evaporation and ultrafiltration need a lot of energy and chemicals for pre-treatment. The processes are expensive and inefficient and not economically viable for most biogas plants. <\/p>\n\n
BioProfit is changing this by using a novel, cost-effective process: Membrane distillation. The aim of the project is to develop the process, which currently works on a laboratory scale, so that it works in real plants and under the sometimes harsh conditions at biogas plants.” <\/p>\n\n
In membrane distillation, nitrogen in the form of ammonia is evaporated at a low temperature (25-40 \u00b0C) through a hydrophobic membrane and thus separated from the fermentation residues. The ammonia is bound as a high-purity distillate in the so-called permeate as ammonium sulphate and made usable as a basic fertiliser. <\/p>\n\n
The energy supply for membrane distillation can optimally be provided by free low-temperature waste heat. Chemicals for the pre-treatment of fermentation residues are not required. <\/p>\n\n
At the end of the process there are three products: The purified water, which can be fed back into the biogas process (closing the internal water cycle) and ammonium sulphate as a biological regionally produced fertiliser additive.<\/p>\n\n
In the future, the solids separated from the fermentation residues can be used specifically to build up humus in soils. Humus formation is one of the few possibilities that allow CO2 to be removed from the atmosphere on a large scale. This is also referred to as “carbon capture” or “negative emission technology”. In addition, this has a positive effect on soil fertility, increases water storage capacities and thus the resilience of agriculture to the consequences of climate change. <\/p>\n","protected":false},"author":4,"featured_media":2446,"parent":0,"menu_order":0,"template":"","class_list":["post-2447","project","type-project","status-publish","has-post-thumbnail","hentry"],"acf":[],"yoast_head":"\n