Economic Analysis of Internal Circulation Biodigesters and Vinasse Concentrators for the Generation of Electricity, Fertilizers, and Carbon Credits in Various Brazilian Economic Scenarios

Abstract

Vinasse is one of the byproducts of ethanol production, where it is considered to have a high polluting capacity. However, this same byproduct can be used to produce electricity, fertilizers, and biogas from anaerobic biodigesters and vinasse concentrators. Based on the foregoing, a study on the use of vinasse is justified, guided by the following question: what is the economic feasibility of the use of the internal circulation (IC) biodigester, vinasse concentrator, and the conjugate of both in three Brazilian economic scenarios (I, fertilizers, electricity and carbon credits with minimum attractiveness rate (MAR) of 10.5% per year (p.a); II, electricity and carbon credits with MAR of 10.5% p.a; and III, electricity and carbon credits with MAR of 5% p.a and tax exemption)? The general objective is to analyze the economic feasibility of the separate use of vinasse concentrators, IC biodigesters, and the use of both together. The methodology used for the economic feasibility analysis was to calculate the net present value (NPV), internal rate of return (IRR), payback and discounted payback, which were calculated for a production range of ethanol ranging from 500 to 4000 m3/day. As a result, it can be seen that fertilizer prices are important in terms of economic feasibility. Scenarios without tax exemptions and a high MAR are feasible only with sale of fertilizer. Electricity alone will only be feasible in a scenario with a low MAR and tax exemptions. The following measures are thus necessary to enable the use of vinasse to generate electricity: a reduction in interest rates, tax exemption policies for renewable energy, legal impediments to the disposal of vinasse in the soil, and the implementation of policies to encourage the use of biogas.