Vinasse digestion on high-rate hybrid anaerobic reactor (HAnR) for biogas generation and energy production increase in sugar and alcohol industry

Abstract

The content of energy remaining in vinasse generated in the sugarcane industry, unexplored technology, could be used by the anaerobic digestion to produce methane and generate electricity, thermal or mechanical. Anaerobic reactors at various scales have been used for vinasse degradation; however, the number of reactors installed in the sugar industry for energy generation is inexpressive due to design deficiencies and the difficulties of maintaining the high rate anaerobic process for vinasse degradation. Recent results obtained with up flow anaerobic sludge blanket reactors (UASB) in pilot scale (LPB-EESC-USP), feed with concentrated vinasse (20 g COD L-1) under different operational parameters, showed high productivity of methane. The results highlighted the energy production potential from this substrate using the startup protocol adopted (postdoctoral project senior-CNPq-158721/2012-8 and project FAPESP- 2013/17591-1). However, the complexity of the vinasse anaerobic digestion requires additional technology studies to ensure the permanence of the biomass in the reactor. Moreover, the knowledge of the vinasse anaerobic degradation, with variable characteristics along the crop, must be studied. The hybrid anaerobic reactor (HAnR), developed by Bio Proj Environmental Technology Ltda., Is a technological alternative to address the weaknesses identified in the UASB reactors for vinasse degradation. Characterized for having a support material layer for adhesion of biomass (Biobob®) above the sludge blanket, the HAnR reactor has a high capacity of solids retention, leading to higher biomass concentration in the reaction area due to Biobob®. This new technology improves reactor performance and can result in more compact units. Although the HAnR reactor has presented excellent results to increase the cellular retention time and maximize the efficiency at treatment of sewage (low concentration) and brewery effluent (medium concentration), specific studies should be conducted with liquid effluents with high organic matter concentration and high biogas production. The main objective of this research project is to adequate the configuration, the startup and the continuous operation of a pilot scale HAnR reactor installed in a sugar and alcohol industry, aiming to establish the anaerobic process for vinasse degradation along the crop and to maximize the methane production. The reactor will be constructed of glass fiber with cylindrical geometry, 1.00 m in diameter and 6.00 m height and total volume of 4.71 m³. The reaction zone is divided into a sludge blanket layer with volume of 2.35 m³ and a support material layer with a volume of 1.57 m³. Will be performed increments of organic loads (from 0.05 to 30 kg COD m -3 d -1) associated with the increments of the flow rate of vinasse (1.6 to 167 L h-1) and up flow velocity (0.01 to 1.27 m h-1), altering the recirculation ratio of 1: 3 to 1: 5, in order to define the best arrangement for reactor startup and operation. The company sees the development of this project bring to the market high-performance compact systems for methane production from vinasse anaerobic degradation, with national capital and technology. The impact of the success of this project will help to maintain the sugar industry to the fore position in the biofuels area, greatly increasing its potential for renewable energy generation. (AU)