Techno-economic and performance evaluation of energy production by anaerobic digestion in Brazil: bovine, swine and poultry slaughterhouse effluents

Abstract

This work describes anaerobic treatment system modeling, using up-flow anaerobic sludge blanket reactors (UASB) reactors, aiming at biogas energy use, under hydraulic retention times (HRT) of 12, 24, 48, 120 and 240 h, from bovine (slaughter capacity: less than 20, 20 to 40, 40 to 80 and more than 80 heads.h−1), swine (less than 80, 80 to 200, 200 to 400, 400 to 800 and more than 800 heads.d−1) and poultry (less than 600, 600 to 1500, 1500 to 3000 and more than 3000 heads.h−1) slaughterhouse effluents. To techno-economic potential evaluate, four scenarios were designed using the combination of maximum and minimum values for the installation of the treatment system (reactors) and the generator system. The scenarios were applied for all classes of slaughterhouses throughout HRTs established under two project concepts: i) full implementation of the treatment and generator systems and; ii) partial implementation, only the generator system. Economic viability analyzes were performed using Net Present Value (NPV), Internal Rate of Return (IRR) and Minimum Attractive Rate of Return (MARR) criteria. In scenario 1, using minimum unit values for the treatment system (USD 43.23.m−³) and the generator set (USD 287.80.KW−1) and HRT of up to 48 h, all bovine, swine and poultry slaughterhouse classes presented potential and economic viability for energy generation, with gains of up to USD 831.462.78 to bovine slaughterhouse, USD 91.977.88 to swine slaughterhouse and USD 179.150.63 to poultry slaughterhouse. The scenarios 2 and 4 result in unviability for al simulations. The scenario 3 result in viability under specific conditions of implementation (total and/or partial); HRT (12, 24, 48 h and sporadically 120); In 24-h HRT show negatives IRRs; and attractive ratio criteria (use of IRR as MARR). In simulated conditions of scenario 1 the techno-economic analysis is HRT of 24 h and HRT of 12 h in scenario 3, both with the need for post-treatment systems. HRTs of 120 and 240 h were found to be infeasible due to system size and costs involved, as well as a non-significant increase in energy generation when compared to lower HRTs.