Full Scale Process Design for Energy Recovery from Swine Manure

Abstract

The aim of this study is to investigate biogas reactor designs to recover energy from swine manure and utilize that energy for a small scale pig farm in Norway. Continuous stirred tank reactor (CSTR) and upflow anaerobic sludge blanket (UASB) reactor were the design alternatives investigated. Simulations were based on the anaerobic digestion model no.1(ADM1) implemented in Aquasim software.

The model was calibrated based on a series of laboratory batch reactors. The batch reactor with the highest biogas yield was first simulated to obtain the organic matter concentration in the feed manure. The resulting calibrated model was used to simulate CSTR and UASB reactors for a manure feed flow rate of 2m³/day. Different CSTR volumes in the range of 10- 60 m³ and UASB volumes in the range of 2-20 m³ were assessed using simulations. At low reactor volumes overloaded conditions were observed. Maximum energy production of 128 kWh/day at a biogas production rate of ~20 m³/day (68-71 % methane content in the biogas) was simulated for the reactor volumes for CSTR and UASB of 30m³ and 2.5m³, respectively. An efficient biogas production (e.g. to cover farm energy needs) can be obtained from a UASB reactor that can be constructed and installed at a reasonable cost.