Techno-economic assessment of a biomass gasification-based polygeneration system for greenhouses

Decentralized biorefineries are an attractive solution to reduce the carbon footprint of agricultural greenhouses, by converting the abundant local residual biomass into value-added products such as biofuels. While the thermodynamic performance of many biomass system configurations has been investigated in the literature, techno-economic assessments are needed to validate the potential of such facilities. This approach is applied to a small-scale polygeneration system for the use -case of a southern Quebec greenhouse. The polygeneration system can produce heat, electricity, methanol, hydrogen, and a CO2-rich stream. A TRNSYS model is used to simulate the heat demand of a 20 000 m2 greenhouse. The work presented here compares the polygeneration system with a conventional solution based on biomass combustion. Nine configurations between 1120 and 5600 kW of thermal output power are investigated for both system types. Twenty-seven market scenarios are generated from the combination of three pricing scenarios for electricity, methanol, and hydrogen: pessimistic, baseline, and optimistic. Fixed capital investment (FCI), operation expenses (OPEX), and NPV are presented. In the most pessimistic market scenario, the best polygeneration system would have an NPV of -8.2 M CAD. In the baseline and optimistic scenarios, the same polygeneration system would have an NPV of 17.6 M CAD and 40.2 M CAD, respectively. By comparison, the best combustion -based solution would have the highest NPV at -5.0 M CAD. Those results highlight that small decentralized polygeneration systems are promising. However, their profitability is heavily dependent on future energy market developments.