Viabilidade econômica de estratégias de tratamento e reciclagem dos dejetos de bovinos leiteiro

Abstract

Given the growing demand for sustainable and economically viable solutions for managing waste generated in animal production, this study evaluated the economic viability of dairy cattle manure treatment and recycling strategies. Composting and anaerobic digestion were studied in different operational configurations, considering the effects of manure fraction separation and substrate hydraulic retention times (HRT). Five scenarios were analyzed: manure composting without fraction separation (I); anaerobic digestion without fraction separation with HRTs of 20 (II) and 30 days (III); and anaerobic digestion combined with composting after fraction separation with HRTs of 20 (IV) and 30 days (V). Considering a herd of 200 animals and previous experimental data, the economic analysis was conducted using projected cash flows for 15 years, including revenues (sale of biofertilizers and energy) and costs (investments, operation, and maintenance). Financial indicators such as Net Present Value (NPV), Internal Rate of Return (IRR), and Discounted Payback were applied, complemented by sensitivity analysis and Monte Carlo Simulation for risk assessment. The results indicated that anaerobic digestion with a 30-day HRT and without fraction separation (Scenario III A.D.30) presented the best economic performance, with an NPV of US$53,407 (IRR of 15.54%), making it the most profitable and attractive alternative for producers with the necessary investment power. Composting without fraction separation (Scenario I C.) was also considered viable (NPV = US$9,832, IRR = 10.07%), as were the other scenarios (II A.D.20+C., IV A.D.20+C., and V A.D.30+C.). It is concluded that anaerobic biodigestion with 30-day TRH and without separation of fractions represented the most advantageous strategy for dairy farms of producers with high investment power, and composting for small producers, because it combines operational simplicity with low costs and moderate financial return.