Techno-Economic Potential of a Polygeneration System Integrated with Conventional or Hybrid Solar Dual Fluidized Bed Gasification Technology in an Australian Sugar Mill

A techno-economic assessment of a biorefinery plant has been conducted, considering the colocation of solar and biogenic resources. The investigation explored the opportunities for integrating a 50 MWth hybrid concentrated solar thermal dual fluidized bed (SDFB) gasifier into a sugar mill located in Harwood, Australia. Various end-product routes were considered, including utility generation with the additional synthesis of liquid fuels or power. Impacts of process configurations, concentrated solar thermal (CST) plant designs, and direct normal irradiance on energy efficiency, solar share, and economic feasibility were studied. Technical assessments indicate that integrating the SDFB gasifier into the mill enhances overall energetic efficiency (60–73%) and reduces net CO2 emissions, surpassing the cogeneration benchmark. Economic assessments reveal the necessity for further cost optimization for competitive positioning in the current market, as breakeven analyses indicate that economic viability in suitable mill locations necessitates a liquid fuel price range of 2.3–5.1 A$/L (1.5–3.4 US$/L) and electricity price of 250–580 A$/MWh (165–383 US$/MWh), provided the assessed uncertainty variation. Considering the potential revenue stream from selling biochar, a solar multiple (SM) of 3 enables solar-operating benefits to offset investment costs, allowing the SDFB gasifier's competitiveness with its nonsolar counterpart. For this SM, the annual input solar share ranges from 11 to 14% across assessed scenarios, with a 17% reduction in annual CO2 emissions relative to the nonsolar configuration. The competitiveness of the assessed biorefinery would be further improved by increased cost-effectiveness of the main chemical components, by the higher value of biochar, and by access to cheaper biomass during the off-season.