Carbon footprint of the hydrogen production process utilizing subbituminous coal and lignite gasification

An analysis was carried out of the carbon footprint (CF) of technology for hydrogen production by subbituminous coal and lignite gasification. The analysis covered entrained flow gasification technology: GE Energy/Texaco and Shell. For calculations, the configuration of the synthesis gas generation system was adopted based on technological solutions available on a commercial scale. Gasification of subbituminous coal using Shell technology gives a yield of 5.1 kg H2 GJ−1 of energy contained in coal. Using the GE/Texaco technology for gasification of subbituminous coal and Shell technology for lignite gasification, hydrogen yields were lower by 8 and 10%, respectively. The scope of the analysis included: mining, mechanical processing, and transport of coal to the gasification plant, as well as gasification and capture of CO2 and its sequestration. The process of sequestration decreased the CF by 69% for the GE/Texaco technology and 78% for the Shell technology. The CFs of producing 1 kg H2 with sequestration of carbon dioxide were as follows: 4.1 and 5.2 kg of CO2 for subbituminous coal gasification using the technology by Shell and Texaco, and 7.1 kg of CO2 for lignite gasification using Shell technology. The CF per 1 GJ of hydrogen produced in the gasification of subbituminous coal with sequestration of captured CO2 amounted to 34.5 and 43.4 kg of CO2 equivalent using the Shell and GE/Texaco technology. This was approximately 2.5 times lower than the CF of 1 GJ of coal. For 1 GJ of hydrogen produced from lignite gasified using Shell technology with sequestration of CO2, the CF was 59.5 kg of CO2, about 65% smaller than the CF of 1 GJ of energy in lignite. When the analyzed variations of hydrogen production did not include the sequestration of captured CO2, the CF of 1 GJ of hydrogen was from 76 to 124% higher compared with the corresponding indicator for coal.