Engineering interface between bioenergy recovery and biogas desulfurization: Sustainability interplays of biochar application

Abstract

The sustainability of anaerobic digestion (AD) is often challenged by the low energy efficiency of sulfur-contaminated waste and subsequent high carbon emission in biogas desulfurization. Recent advances in the direct interspecies electron transfer (DIET) mechanism present a unique biotechnological means to cope with relevant fundamental constraints of microbial competition. This study aims to provide a systematic investigation regarding how and to what extent can DIET-conductive materials (especially biochar) mitigate relevant AD away from the environmental burdens of hydrogen sulfide generation. Through the experimental validation of biochar applications in bioreactor trials, the profiles of intermediates pathways and electron diversion were first examined together with microbiological analysis. Instead of suppressing the notorious growth of sulfate-reducing bacteria, the results revealed an interesting phenomenon of enriched coexistence but a reduced hydrogen sulfide generation with DIET application. In a stoichiometric relationship, around 26.6% of the total electrons were migrated from hydrogen sulfide production back to methane generation. Sensitivity analysis of life cycle assessment (LCA) was applied to better understand the environmental significance of electron diversion by biochar application in the systematic context of bioenergy recovery and biogas desulfurization. The LCA results characterized the benefits and limitations of DIET-driven desulfurization for the environmental performance of each impact category, while the potential improvement through better resource circularity in the desulfurization unit was also highlighted. Overall, built on experimental validation, this study frames relevant evaluations to achieve insights into the pivotal roles of biochar application as well as the quantitative interdependencies between DIET-driven desulfurization and AD sustainability.