A coupling strategy for comprehensive utilization of distillers’ grains towards energy recovery and carbon sequestration

Abstract

This study investigated a coupling strategy for comprehensive utilization of distillers' grains (DGs), which integrated anaerobic digestion (AD) and chemical looping gasification (CLG) towards energy recovery and carbon sequestration. The AD and subsequent CLG performance on DGs were investigated, and the mass-energy flows and potential mechanisms in the coupling process were assessed. In the AD stage, all the fluctuations of solid, liquid and gas phases were concentrated in the first 6–8 days due to the limitation of the biodegradation of DGs. During the CLG stage, the volume fraction of syngas, gas yield and gasification efficiency were altered due to the consumption of the chemical components of DGs at different digestion days. Considering the overall assessment, the coupling strategy of 6-day AD and CLG was optimal, which could obtain 16.80 MJ/kg TS of energy recovery, 47.73 % of mass conversion, 55.06 % of carbon efficiency and 39.72 % of CO2 emissions. Correlation analysis showed that AD was more conducive to energy recover than CLG, and the biodegradable threshold of DGs was expected to be obtained in the AD stage for the coupling strategy. The normalization analysis showed that the variation of cellulose content can be used to determine the optimal AD time (6 Days), which could directly reflect the biodegradation of DGs with the strongest correlation (−0.9901). These findings provide a new strategy of green efficient energy and carbon recovery for the comprehensive utilization of biomass.