Use of biodigested vinasse as a source of alkalinity and nutrients in biogas biodesulfurization in microalgae-bacteria systems

• Grant number: 25/05365-4
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: December 01, 2025
• End date: November 30, 2028
• Field of knowledge: Engineering - Sanitary Engineering - Water Supply and Wastewater Treatment
• Principal Investigator: Marcelo Zaiat
• Grantee: André do Vale Borges
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 22/10615-1 - Consolidation of the biorefinery concept applied to the biological treatment of wastewater and solid wastes, AP.TEM

Abstract

In recent years, two-stage anaerobic digestion of sugarcane vinasse has been investigated to reduce sulfate in the fermentative phase (acidogenesis) and eliminate microbial competition in the methanogenic phase. However, the high sulfate content in raw vinasse results in the formation of acidogenic biogas rich in hydrogen sulfide (H2S) (3-9% v/v) and carbon dioxide (CO2) (70% v/v), contributing to harmful atmospheric emissions. Although the complete removal of H2S (5% v/v) in high-rate biotrickling filters has been recently reported, operational challenges related to oxygen limitations and bed clogging due to elemental sulfur accumulation highlight the need for more cost-effective and sustainable solutions. A recent unpublished study demonstrated the simultaneous removal of H2S (100%) and CO2 (98%) in a combined microalgae-bacteria (MB) system fed with acidogenic biogas rich in sulfide (5,000 ppmv). However, the intensive use of chemical alkalinizers for buffering these systems presents significant economic and environmental challenges, limiting their large-scale applicability. This project proposes, for the first time, the use of digested vinasse from different biological processes as an alternative source of nutrients and alkalinity in an MB system for the biodesulfurization of methanogenic and acidogenic biogas from sugarcane vinasse processing. The originality of this approach lies in integrating an abundant agro-industrial residue into an innovative circular bioeconomy strategy, enhancing process sustainability and enabling scalability in the sugar-energy sector. To support the development of this technology, metagenomic, transcriptomic, and metabolomic analyses will be conducted to characterize the specific microbial interactions involved in H2S and CO2 removal, allowing the optimization of sustainable strategies for gas emission mitigation and vinasse valorization in Brazilian biorefineries. (AU)