Energy recovery and economic viability of animal-derived waste air gasification for syngas production

Abstract

Animal-derived waste poses significant disposal and environmental challenges, yet its organic and mineral-rich composition offers opportunities for energy recovery through thermochemical valorization. Chicken bone waste (CBW), a byproduct of the poultry industry, was selected as a feedstock for conversion into energy. In this study, CBW was first processed via pyrolysis to produce a carbon-rich char, which was subsequently gasified with air at 700 °C in a lab-scale fixed-bed batch reactor to generate synthesis gas (syngas). The resulting syngas was rich in carbon monoxide (~43.5 % CO), carbon dioxide (~39.2 % CO₂), and moderate hydrogen fraction (~14.0% H₂). It exhibited a higher heating value (HHV) of approximately 25.87 MJ/kg, and the gasification achieved a cold-gas efficiency of ~54.6%, suggesting that over half of the feedstock’s energy content was recovered in gaseous form. Based on these results, a conceptual pilot-scale system was analyzed, comprising a 100 kg/h gasifier and a 15.36 kW_e syngas turbine for power generation. Under the stated assumptions, the techno-economic analysis demonstrated economic viability for syngas utilization as an energy source, with net present value (NPV) ≈ 28554 € and internal rate of return (IRR) ≈ 15.3%. Sensitivity analyses were performed to capture the impact of technical and market variability. Increasing the syngas LHV (8.98–11.67 MJ/Nm³) enhanced NPV linearly. Improving electric turbine efficiency (30-40 %) produced the strongest effect, increasing NPV to ≈ 58700 € and IRR to ≈ 21 %, while reducing discounted payback period (DPP) to ≈ 6 years. Electricity price variation (0.09–0.15 €/kWh) identified a break-even tariff of ≈ 0.106 €/kWh, above which profitability rapidly improved. Overall, air gasification of CBW-derived biochar was shown to efficiently produce high-quality syngas for power generation. This waste-to-energy pathway is energy-efficient and economically viable, illustrating a practical approach to circular economic goals through the valorization of animal-derived waste.