Application of biochar in anaerobic digestion of hydrothermal effluent from coffee spends

• Grant number: 19/15663-1
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): March 01, 2020
• Effective date (End): December 31, 2020
• Field of knowledge: Engineering - Sanitary Engineering - Water Supply and Wastewater Treatment
• Principal researcher: Giovana Tommaso
• Grantee: Gabriel Zenatte Frugoli
• Home Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil

Abstract

The growing world energy demand brings to light the need to develop new technologies to obtain this important resource. The advance in food production is the solution to the problem of food security of the population; however, an increasing amount of waste is generated and must be treated. Technologies that integrate waste treatment and energy production are therefore very welcome, since they diversify the energy matrix and prevent negative impacts on the environment. Hydrothermal liquefaction is a biomass conversion process that can be applied to wet wastes for the generation of crude oil still lacking in refining as to coffee spends, one of the most produced food waste in the world. The hydrothermal liquefaction of biomass generates in addition to the crude oil an aqueous phase with high organic matter concentration, and a solid by-product, the biochar. The aqueous phase resulting from the conversion of the coffee spends, besides having a high concentration of organic matter, also has toxic phenolic compounds in its composition, requiring treatment for its disposal or reuse. Anaerobic digestion can be applied to the treatment of the aqueous phase, however toxic components present in the effluent can inhibit the process. The objective of the present project is to study the application of the biochar produced in the hydrothermal liquefaction of coffee spends as a coadjuvant adsorbent in the treatment of the aqueous phase produced in the process. The hydrothermal liquefaction will be carried out in a stirred reactor with a temperature of 275º C for 10 minutes. The adsorbent will be characterized physicochemically with respect to its porosity, density and solids content. Tests to verify the release of organic matter and phenolic compounds will also be performed. Scanning electron microscopy analysis of the material will also be conducted. Subsequently, the dosage of the adsorbent will be determined, as well as the reaction time to equilibrium. Assays for maximum adsorptive capacity determination will also be conducted. The material will then be applied to anaerobic reactors conditioned at 37º C under agitation with increasing concentration of organic matter (three operating conditions). Comparative tests with granular activated charcoal and in the absence of adsorbents will also be performed. To the accumulated methanogenic production the modified Gompertz model will be adjusted and its kinetic parameters will serve as a comparison between the biological processes. As expected results it is intended to contribute to the improvement of the anaerobic treatment of the aqueous phase of hydrothermal liquefaction of the coffee grounds using a by-product of the process itself. (AU)