Techno-Economic Assessment of a Small-Scale Biogas-Based Trigeneration System with Thermoelectric Waste Heat Recovery: Impact of Digestate Valorization and Carbon Financing on Economic Performance

Abstract

A techno-economic assessment of a small-scale biogas-based trigeneration system (CCHP) with thermoelectric generator (TEGs) waste-heat recovery for a decentralized dairy farm application was conducted. In the economic analysis, all the revenue streams, such as electricity, thermal energy, digestate fertilizer, and carbon credits, have been considered. In this study, economic calculation models are built in MATLAB with a 15% discount rate and a 20-year project duration. The net present value, internal rate of return, payback period, and levelized cost of electricity are all used to show economic performance in a sort of clear way. The work looks at three scenarios: Energy Only, Energy plus Fertilizer, and Energy plus Fertilizer plus Carbon. The result demonstrated that the system needs a capital investment of 37,000 USD and achieves a positive net present value (NPV) of 18,892 USD, an IRR of more than 27%, a payback period of less than 3.6 years, and LCOE is 0.038 USD/kWh in scenario 3. In comparison to the energy-only scenario, digestate valorization and carbon credits increase net present value (NPV) by 167% and shorten the payback period by 1.3 years. According to break-even calculations, the system needs to run for only 5,800 hours a year to recoup the expenditure, which is less than the base-case estimate of 7,000 hours. The results show that the economic viability of small-scale biogas CCHP systems for decentralized dairy farm applications can be significantly improved by incorporating TEGs to recover waste heat and monetizing digestate fertilizer and carbon credits.