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Natural gas is regarded as a cleaner alternative to coal combustion-based power generation (CPG) for urban use. Because of the insufficient natural gas reserve in China, coal-based synthetic natural gas (SNG) has been under rapid development. However, coal-based SNG production process has problems of environmental pollution and emission transfer. This paper uses life cycle assessment to compare the CPG and SNG energy production and usage routes, in order to find a reasonable way to reduce the environmental pollution and production cost. Results show that the CPG route is superior to the SNG route in terms of the haze pollution emissions, greenhouse gases emissions, coal resource consumption and life cycle cost. However, the water consumption of the CPG route is much higher than that of the SNG route. The SNG route is more suitable to adopt in water-deficient areas. [ABSTRACT FROM AUTHOR]

China's growing capacity of bioethanol production renders the conversion of ethanol-to-jet fuel (ETJ) promising. However, ETJ studies are currently scarce in China. This study employed process simulation to model two novel ETJ processes that combined corn cob gasification, syngas-to-ethanol, and ethanol-to-jet fuel. This paper also discussed the other three ETJs, in which ethanol were obtained via direct-fermentation of corn, cassava, and corn cob, respectively. Life cycle assessment (LCA) was performed to evaluate energy consumption and greenhouse gas (GHG) emissions of ETJs in China. The results showed that the ETJ pathway, which included corn cob gasification plus fermentation, showed the least energy consumption and GHG emission, with 370.05 KJ/MJ jet fuel and 31.66 gCO 2 eq/MJ jet fuel, respectively. Sensitivity analysis was performed to identify parameters that had a significant impact on the results, and uncertainty analysis was implemented to check the reliability of the result. Further analysis revealed that cleaner electricity and heat production could effectively reduce the GHG emissions of the energy-intensive ETJs, with the highest reduction of 21.55%. Given that few life cycle assessments of ETJs in China have reported, this study can assist policy-makers to decide the path in which China's sustainable aviation fuel (SAF) should evolve. [Display omitted] • Life cycle analysis for 5 ethanol-to-jet fuels established toward China situation. • The process based on corn-cob-syngas fermentation showed the best carbon reduction. • Optimizing biomass and ethanol conversion could greatly reduce GHG emissions. • Electricity mixes highly impacted on the process based on corn-cob-syngas catalysis. • Life cycle results were mostly sensitive to the displacement allocation method. [ABSTRACT FROM AUTHOR]

Life cycle environmental performance of lignocellulosic ethanol produced through different production pathways and having different co-products has rarely been reported in the literature, with most studies focusing on a single pre-treatment and single co-product (electricity). The aim of this paper is to understand the life cycle energy use and greenhouse gas (GHG) emissions implications of alternative pre-treatment technologies (dilute acid hydrolysis, ammonia fiber expansion and autohydrolysis) and co-products (electricity, pellet, protein and xylitol) through developing a consistent life cycle framework for ethanol production from corn stover. Results show that the choices of pre-treatment technology and co-product(s) can impact ethanol yield, life cycle energy use and GHG emissions. Dilute acid pathways generally exhibit higher ethanol yields (20-25%) and lower net total energy use (15-25%) than the autohydrolysis and ammonia fiber expansion pathways. Similar GHG emissions are found for the pre-treatment technologies when producing the same co-product. Xylitol co-production diverts xylose from ethanol production and results in the lowest ethanol yield (200 L per dry t of stover). Compared to producing only electricity as a co-product, the co-production of pellets and xylitol decreases life cycle GHG emissions associated with the ethanol, while protein production increases emissions. The life cycle GHG emissions of blended ethanol fuel (85% denatured ethanol by volume) range from -38.5-37.2 g CO2 eq/MJ of fuel produced, reducing emissions by 61-141% relative to gasoline. All ethanol pathways result in major reductions of fossil energy use relative to gasoline, at least by 47%. [ABSTRACT FROM AUTHOR]

Coal direct chemical looping hydrogen generation (CDCLHG) is a promising technology to convert coal into high purity hydrogen. Cradle-to-grave life cycle greenhouse gas (GHG) emissions and primary fossil energy consumption (PFEC) analysis are developed to study the CDCLHG process in this paper. The results show that the total GHG emissions and PFEC of the CDCLHG process are 9.54 kg eq. CO 2 /kg H 2 and 312.02 MJ/kg H 2 , respectively. The CDCLHG stage is the largest GHG emissions stage and the largest PFEC stage. The total GHG emissions of the CDCLHG process is larger than the ash agglomerating fluidized bed (AFB) gasification process, whereas the total PFEC of the CDCLHG process is smaller than the AFB gasification process. In addition, the sensitivity analysis demonstrates that GHG emissions of the CDCLHG stage are sensitive to reducer temperature, reducer pressure and n F e 2 O 3 to n C . • Cradle-to-grave life cycle analysis is carried out to the CDCLHG process. • The total GHG emissions of the CDCLHG process are 9.54 kg eq. CO 2 /kg H 2. • The PFEC of the CDCLHG stage is 283.61 MJ/kg H 2. • The PFEC of the CDCLHG process is smaller than the AFB gasification process. [ABSTRACT FROM AUTHOR]