Using thermodynamic models for bioenergy recovery and generation assessment: a case study with açaí and macaúba by-products

Abstract

Bioenergy recovery from biomass is essential to address an eco-friendly disposal route for industrial by-products. This study focuses on the energy recovery from agro-industrial by-products in a combined heat and power unit (CHP) operating with a gas turbine fed with biogas. A rigorous thermodynamic model was presented and used for the energy generation assessment. The biogas was produced from anaerobic digestion (AD) of macaúba and açaí by-products with and without subcritical water pretreatment. The proposed methodology is easily applied and may provide answers to subside the conceptual design of an industrial plant operating with a CHP with a gas turbine for energy recovery. Simulation results showed electric and thermal energy potentials of, respectively, 3.4 and 11.2 MW when pretreatment is applied before the AD of macaúba shells. The thermal energy surplus was 58% higher than that obtained with direct AD of macaúba shells. On the other hand, applying subcritical water pretreatment of açaí seeds followed by AD to obtain biogas was not energetically profitable. However, feeding biogas from the direct AD of açaí seeds into the CHP would produce 3.4 and 7 MW, respectively, of electric and thermal energy. Moreover, considering the electricity replacement of 3.4 MW, 3699 tCO2-eq year−1 of greenhouse gas emissions could be avoided. Finally, using process simulation of first principle models for energy assessment was evinced to be a powerful tool to evaluate the viability of CHP operating with a gas turbine for bioenergy recovery in the food industry.