Anaerobic digestion of the liquid phase from the thermochemical conversion of agro industrial residues

Abstract

The modern society face important challenges among them two can be highlighted: the adequate residues management and the energy obtaining. For the integration of solutions a new paradigm was proposed by researches of the University of Illinois. The process, called Environment-Enhancing Energy (E2-Energy), integrates infrastructure for waste treatment and bioenergy production, simultaneously reducing carbon emissions, and cleaning wastewater. In the E2-Energy process, the biosolids fraction of municipal, industrial, and agricultural wastes are concentrated and converted into bioenergy products such as crude oil through thermochemical conversion. The bioenergy conversion process retains most nutrients in a post-conversion wastewater, which can then be used to grow algae and other microorganisms. The microorganisms clean the wastewater as they assimilate nutrients and can also be harvested and converted into more biofuel. The conversion process again releases most of the nutrients for another cycle of biomass growth. The process is under optimization and one of the most important problems is the limited recycle rate of the effluent from the thermochemical process, which has high organic matter concentrations and presence of recalcitrant compounds. The objective of the present project is to study the utilization of the anaerobic digestion in order to enhance the biogas production and to mitigate the existing negative impacts in the multi-cycle nutrient reuse. The project will includes biomass carefully adaptation, utilization of immobilized biomass in activated carbon and polyurethane matrices and the study of ozonization as anaerobic digestion pre-treatment. This study will be conducted in eight tasks as follows: i) conduction of the thermochemical process; ii) liquid phase physicochemical characterization; iii) liquid phase toxicity determination; iv) ozonization conditions determination; v) determination of the liquid phase anaerobic biodegradability; vi) biomass adaptation and rising toxic loading rates essays; vii) kinetic parameters inference and viii) biomass characterization. The thermochemical process will be conducted with feedstock composed by algae and suine manure. The liquid phase from the thermochemical process will be characterized through physical-chemical, chromatographic and mass spectrometry analyses. The ozonizaton process will be conducted in closed flasks equipped with gas circulation apparatus with 500L.h-1 flux with O3 concentrations of 30 g.m-3. Anaerobic biodegradability of the untreated and treated effluents (ozonizated) will be studied in batch assays. The biomass adaptation will be conducted in chemiostats under magnetic agitation and strict anaerobic conditions. After adaptation, the biomass, suspended and immobilized in activated carbon and polyurethane foam, will be submitted to rising toxic loading rates. The biomass will be characterized through microscopic and molecular biology analyses (PCR/DGGE). Kinetic parameters will be inferred and will be basis for the operation of continuous reactors, which study will be the next phase of the present project, to be conducted in partnership with the colleagues from the University of Illinois and developed partially at FZEA/USP. (AU)