Integrating anaerobic digestion of sugarcane vinasse vinasse with microalgal cultivation

• Grant number: 24/10992-5
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: July 01, 2025
• End date: February 28, 2027
• Field of knowledge: Engineering - Sanitary Engineering - Environmental Sanitation
• Principal Investigator: Marcelo Zaiat
• Grantee: Juliano Curi de Siqueira
• 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

Sugarcane vinasse is a byproduct of ethanol production commonly used in the fertigation of sugarcane fields. However, in the long term, its direct application to the soil can result in negative environmental impacts. Anaerobic digestion has established itself as a technique that, in addition to reducing the pollutant potential and maintaining the nutritional content of vinasse, allows for energy recovery through biogas generation. Nonetheless, the high alkalinity requirement to adapt vinasse to high-rate anaerobic treatment still represents a financial obstacle to the full-scale application of this technology. An operationally simple and low-cost solution is the co-digestion of vinasse with organic substrates with alkalizing potential, such as algal biomass. As an alternative to cultivation in synthetic medium, studies report microalgae growth in digested vinasse, suggesting the possibility of combining different biotechnological processes in a single treatment plant. Based on this context, this research project aims to answer the following question: is it technically feasible to integrate the anaerobic digestion of sugarcane vinasse with the production of algal biomass and its subsequent use as an alkalizing agent? In this regard, the proposed methodology will involve conducting laboratory experiments to evaluate the co-digestion of vinasse and algal biomass heterotrophically cultivated in digested vinasse as a strategy to minimize the addition of conventional alkalizing agents in the wastewater pre-treatment. Thus, the results derived from this project may provide a basis for planning anaerobic biorefineries that include algal cultivation systems and, subsequently, their implementation on an expanded scale in the sugar and alcohol industries. (AU)