Biogas Digestate Treatment

AlgEn is focusing on using biogas digestate for growing microalgae.

Microalgae enhance the removal of nutrients, organic contaminants, heavy metals and furnish an interesting raw material for the production of high-value biochemicals (algae metabolites) or biogas. Nutrients are cycled by algal biomass to biogas plant and thus closing material loops and providing energy. This can contribute to solving pollution problems and reducing energy consumption. Biogas production from the anaerobic digestion of algal biomass allows substantial economic savings.

Why microalgae?

Microalgae enhance the removal of nutrients, organic contaminants, heavy metals and are an interesting raw material for the production of high-value biochemicals (algae metabolites) or biogas. Nutrients are cycled by algal biomass to biogas plant and thus closing material loops and providing energy. This can contribute to solving pollution problems and reducing energy consumption. Biogas production from the anaerobic digestion of algal biomass allows substantial economic savings.

Why treating biogas digestate?

Due to raising number of biogas plants in Europe there is not only increased production of biogas and electricity, but also heat and biogas digestate. In some regions a high number of biogas plants can be found, and therefore the oversupply of the digestate. It is mostly applied to the nearby fields as a fertilizer, but some agriculture areas are too small for proper use of the digestate and it has to be transported to other areas with nutrient deficits. Another option is that biogas digestate is treated mechanically, chemically and/or biologically through the conventional biological wastewater treatment plant, but these options lead to higher costs and lower profitability of biogas plants. Excessive untreated digestate application to the fields, due to its smell and black color also negatively influences the quality of life to nearby residents and can cause environmental problems.

Digestate composition is variable and depends on the input material for biogas production. Vast majority of biogas digestates contain high concentration of organic matter, high concentrations of mineral matter as nitrogen, potassium, phosphorus, salt, trace elements and also heavy metals. It contains a lot of biological contaminants, which includes high number of bacteria, some of them, like Salmonella, are pathogens and can cause health problems. Therefore the biogas digestate has to be treated properly at site.