Comparative Study on Carbon Emission Intensity of Underground Coal Gasification Power Generation

As the sector with the largest greenhouse gas emissions both in China and globally, thermal power generation urgently needs to transition toward the "low-carbon utilization of high-carbon resources" under the "dual-carbon" goals. This study explores the carbon reduction potential of the emerging underground coal gasification (UCG) industry for power generation. Considering the geological setting and coal seam conditions of a site in Guizhou Province, this study developed a shaftless UCG-based distributed power generation route coupled with carbon capture, utilization, and storage (CCUS) technology. This route integrates CO₂ capture, compression, reinjection, and reduction reactions. Theoretical calculations and sensitivity analyses were conducted to evaluate the full-life-cycle carbon emission intensities of various resource extraction and power generation models, including (i) shaftless UCG-gas turbine power generation, (ii) shaftless UCG-solid oxide fuel cell (SOFC) power generation, (iii) underground coal mining-road/rail transport-coal-fired power generation, (iv) natural gas extraction-pipeline transport-gas power generation, and (v) shale gas extraction-pipeline/LNG ship transport-gas power generation. The impact of syngas composition ratios on the carbon emission intensity of UCG-based power generation was also analyzed. The results indicate that natural gas and shale gas power generation models have the lowest carbon emission intensities, followed by the UCG-SOFC model. In contrast, the UCG-gas turbine and coal-fired power generation models exhibit similarly high carbon emission intensities. For both the shaftless UCG-gas turbine and shaftless UCG-SOFC models, syngas is converted into electricity on-site, thereby eliminating transportation-related carbon emissions and resulting in lower pre-power-generation carbon intensities. When CO₂ in the syngas is emitted directly without reinjection or utilization, the carbon emission intensities are 1.058 t CO₂/(MW·h) and 0.705 t CO₂/(MW·h), respectively. Under CO₂ reinjection and utilization scenarios, the full-life-cycle carbon emission intensities drop to 0.870 t CO₂/(MW·h) and 0.580 t CO₂/(MW·h), respectively. By adopting CO₂ reinjection and increasing the proportion of effective components in the syngas to over 85% (with H₂ accounting for more than 44%), the carbon emission intensity of UCG-based power generation can be significantly reduced, achieving a reduction of up to 35.27%. This study highlights the significant potential for further reducing the carbon emission intensity of UCG power generation by analyzing changes in key syngas composition factors. These findings provide a comprehensive demonstration of the competitiveness of the integrated UCG-CCUS power generation model. Given China's current energy endowment and the role of coal and thermal power as regional pillar industries, this research offers valuable references for energy sector transformation in high-carbon-resource regions.