Estudo de viabilidade técnica e econômica de plantas de biogás: avaliação do bagaço in natura versus bagaço pré-tratado e comparação de cenários de suprimento energético

Abstract

The production of biogas from sugar-energy residues, such as vinasse, filter cake and sugarcane bagasse, is a relevant alternative for diversifying the energy matrix and reducing biomass burning in boilers. In this context, this study aimed to technically and economically assess five scenarios for biomethane production in a plant integrated with a sugar‑ethanol mill, comparing co‑digestion with raw bagasse and alkaline‑pretreated bagasse, as well as different routes for biogas energy use. The process was modeled in a spreadsheet using mass and energy balances, biodigester sizing, CAPEX and OPEX structuring, revenues and economic indicators, based on internal technical and economic data from the partner company. The comparison between raw‑material scenarios showed that the use of pretreated bagasse allows operation with a shorter hydraulic retention time, higher organic loading and higher biogas and biomethane production, increasing the IRR from approximately 7.20% to 14.50%. In the scenarios that vary the type of energy supply, all based on pretreated bagasse, cogeneration with a gas engine, gas heating with electricity purchased from the grid and electric‑resistance heating also with grid electricity were evaluated, with central IRR values of about 15.60% for cogeneration with the gas engine, 18.90% for the gas‑heating scenario and 18.92% for the electric‑resistance heating route. Electric heating shows the highest IRR, but only marginally, just 0.02 percentage points above gas heating, making it the most economically attractive alternative, albeit with a very small advantage.