Influence of C/N ratio and nutritional conditions of anaerobic co-digestion of swine manure and coffee industry residues

• Grant number: 21/10685-7
• Support type: Scholarships in Brazil - Doctorate
• Effective date (Start): April 01, 2022
• Effective date (End): February 29, 2024
• Field of knowledge: Engineering - Sanitary Engineering - Environmental Sanitation
• Principal researcher: Maria Bernadete Amâncio Varesche
• Grantee: Vitor Alves Lourenço
• Home Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 15/06246-7 - Biorefinery concept applied to biological wastewater treatment plants: environmental pollution control coupled with material and energy recovery, AP.TEM

Abstract

Intensive swine farming can cause soil and water pollution through the disposal of waste generated, thus requiring alternative technologies to remove organic and nitrogen compounds. In the composition of such wastes, ammonium concentrations are observed, which can inhibit anaerobic digestion. For that, an alternative is the application of co-digestion with solid residues and/or agricultural effluents with the availability of organic material. From this, there are the solid and liquid residues of coffee growing. For example, the existence of pig farms that have coffee crops on their land contributes to the possibility of applying co-digestion on a large scale in situ and the transition to a circular economy. Thus, this project intends to investigate the production of biogas, organic acids, and alcohols from the co-digestion of swine manure and residues from the coffee sector in batch and continuous reactors. The batch tests for optimization of co-digestion via rotational central composite design will be carried out with variation of the C/N ratio (26 - 54) and the concentration of organic matter (6 - 34 gCOD L-1) at pH 7, 37 °C and 130 RPM The variation in the C/N ratio will occur as a function of different proportions of swine manure and coffee wastewater. After validation, the optimized condition will be used to operate a continuous leached bed reactor with varying hydraulic detention time (24 - 72 hours). Throughout the execution of the project, periodic monitoring will be carried out regarding the composition of biogas, pH, alkalinity, COD, total solids, total volatile solids, suspended solids, volatile suspended solids, carbohydrates, phenols, total nitrogen kjeldahl, total ammonia nitrogen, acids volatile organics and alcohols. The impacts on the microbial community of batch reactors under optimized conditions and of the continuous reactor for different detention times will also be evaluated, through large-scale sequencing of the 16S rRNA gene using the Illumina plataform. Considering that there is no report in the scientific literature involving the proposed co-digestion, either in batch or continuous reactors, it is expected to establish the best conditions for the production of compounds of biotechnological interest (biogas, volatile organic acids, and alcohols). (AU)