Maintenance of methane production in sugar-ethanol industries, by replacing vinasse with glycerol in sugarcane off-season

Author(s)

Paula Yumi Takeda

• Document type: Master's Dissertation
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2021-07-02

Examining board members

Marcia Helena Rissato Zamariolli Damianovic; Simone Damasceno Gomes; Rogers Ribeiro

• Advisor: Marcia Helena Rissato Zamariolli Damianovic

Abstract

Wastewater treatment systems using anaerobic processes are promising for removing the organic polluting load from vinasse, associated with the production of bioenergy. Scientific interest points to the improvement of the degradation process of this effluent, through the interpretation of the associated metabolic pathways, allowing the implementation and maintenance of the processes involved with high efficiency and methane production for energy recovery. The interruption in the operation of anaerobic reactors in the off-season of sugarcane is certainly a major challenge to be faced in the anaerobic treatment of wastewater from the sugar-ethanol industries, since the restart-up period is slower than desired, negatively compromising the energy balance in sugar-ethanol industry. Another waste with high organic content that deserves mention is glycerol, a by-product of the biodiesel production chain, produced in expressive volumes and difficult to dispose of, since the market is saturated about its applications. Given the above, the potential use of glycerol by anaerobic digestion for the generation of methane and maintenance of the active microbial population in an anaerobic structured bed reactor (AnSTBR), was evaluated treating vinasse during the off-season period.The co-digestion of both wastes was also evaluated in order to verify improvements in operational conditions and enhance energy recovery. The experimental study was carried out in five continuous phases of substrate replacement in a proportion of organic load of 100% vinasse (I); 50% vinasse and 50% glycerol (IIA, IIB); 100% glycerol (III); 50% vinasse and 50% glycerol (IV); and 100% vinasse (V), respectively, applying an organic load rate of 5.0 kgCOD m-3 d-1. Exceptionally, phase II was subdivided into two stages, in which the operationmof the reactor was interrupted for a period of 150 days between the stages. The operation of the AnSTBR reactor showed promising results regarding the removal of organic matter, with efficiencies of 81.1 ± 1.5%; 84.7 ± 1.1%; 83.7 ± 0.9%; 93.1 ± 0.6%; 91.0 ± 0.9%; 82.3 ± 0.6% in terms of total COD; and the methane production, with yields of 250.6 ± 13.2; 268.8 ± 12.5; 246.5 ± 8.0; 232.2 ± 17.2; 227.7 ± 15.3; 235.2 ± 9.9 mLCH4 g-1CODremoved, respectively. Vinasse and glycerol codigestion increased methane production about 12% compared to vinasse mono-digestion, prior to the interruption of the reactor and use of glycerol as the sole carbon source. The operational strategy of gradual substrates exchange demonstrated stability throughout the operation, maintaining the biomass active, with an alkali supplementation of 0.15 gNaHCO3 g-1COD and pH adjustment at 7.0. The results indicated the potential of the strategy of using glycerol to replace vinasse in the sugarcane off season, as well as the codigestion of both residues from the agro-industry, promoting the maintenance of methane production. (AU)

• FAPESP's process: 19/13847-8 - Use of glycerol in substitution of sugarcane vinasse in off-season period to maintain the methane production in anaerobic reactor
• Grantee: Paula Yumi Takeda
• Support Opportunities: Scholarships in Brazil - Master