Volume 21: Sustainable Energy Solutions for a Post-COVID Recovery towards a Better Future: Part IV

Lignite as additive in anaerobic digestion of liquid dairy manure without an external inoculum: Impact on BMP tests and fertilizer properties Anna Leithäuser, Mandy Gerber, Roland Span

Abstract

This study simultaneously investigated the effects of lignite as an additive in biogas applications and the suitability of the obtained digestate to produce organic nitrogen fertilizer. Lignite was added to the anaerobic digestion of liquid dairy manure without an external inoculum at a rate of 3.75 w.-% and a particle size of (1250-2500) μm. Maximum methane production rate, methane potential, and lag phase time were determined using the modified Gompertz model, respectively. Subsequently, the digestate was separated into liquid and solid phases, and nitrogen distribution and loadings were examined. Lignite addition increased the max. methane production rate by +34.7% and decreased the lag phase time by -15.17%. The absolute amount of nitrogen attached to the solid phase, which can be obtained from 1 t digestate after centrifugation, increased by 95.36% from 0.767 kgN/tD (DM) to 1.499 kgN/tD (DM + L) for lignite addition.

Keywords Anaerobic digestion, Renewable Energy, Lignite, Biogas, Nutrient recovery