Economic feasibility of implementing an infrastructure for collecting rainwater from the roof of free-stall sheds

his study aimed to analyze the economic feasibility of implementing and using the necessary infrastructure to collect rainwater from the roof of free-stall sheds in a dairy production system in southern Minas Gerais, Brazil. Specifically, the total cost (TC), total operating cost (TOC), and actual operating cost (AOC) of a cubic meter of rainwater and the break-even point in cubic meters were estimated. The research was conducted from January to December 2017 on a property located in the south of Minas Gerais. The following MOP scenarios were analyzed: most likely (Scenario 1), optimistic (scenario 2), and pessimistic (scenario 3). The grant value of the Das Velhas River basin was considered for the most likely scenario, as it has the most similar value with that of the basin surrounding the Furnas reservoir, in which the property is inserted. The grant value for water collection and consumption from the Paraíba River basin was considered in Scenario 2, as this Federal basin has the lowest grant value. The grant value for water collection and consumption from the Piracicaba, Jundiaí, and Capivari river basins was considered in Scenario 3, as these basins have the highest prices for the cubic meter of the collected and consumed water. The implementation of the infrastructure for collecting rainwater from the roof of free-stall sheds under the studied conditions was economically unfeasible for all scenarios, with negative net present values (NPV). Simple and discounted paybacks were longer than the proposed horizon. The internal rate of return (IRR) could not be estimated due to the negative values of the net cash flow. The benefit-cost ratios (BCR) were unsatisfactory (lower than 1). The TC values for rainwater collection from the roof of free-stall sheds were R$ 23,206.59 and R$ 20,489.25 for scenarios with interest rates of 8.50 and 6.99%, respectively, while the TOC value was R$ 7,850.30 for all analyzed scenarios. The unit values for TOC and AOC were R$ 9.9024/m3 and R$ 1.3060/m3 of collected water, respectively. The break-even point could not be estimated in the studied scenarios, as the variable cost per cubic meter of water collected from the roof of the free-stall shed was higher than the grant value charged by the water management committees of the different studied basins.