Mono-digestion of stillage to produce power and steam

In the ethanol plant of Biodegviela SIA, about 160,000 m³ of stillage are produced each year as waste product to be recycled.

The stillage is recycled in the AD plant to generate energy from the digestion process. The digestion takes place in a digester with a downstream post-digester. The biogas produced is burned in twocombined heat and power units to generate electrical and thermal energy. Around 17 million kWh of electricity is produced each year. The conversion of exhaust heat from the cogeneration units provides an additional 1.5 t/h of steam for the ethanol plant. The combination of electricity and steam generation makes it possible to reduce the energy requirement of the ethanol plant.

The residues after the digestion are subjected to a solid-liquid separation. The liquid phase is purified to surface water quality in a downstream wastewater treatment plant and fed into a nearbyriver. The solid phase is used as fertilizer.