Life-cycle Analysis of Methanol Production from Coke Oven Gas in China

The growing demand for transportation fuels and the global emphasis on reducing greenhouse gas (GHG) emissions have led to increased interest in analyzing transport GHG emissions from the life-cycle perspective. Methanol, a potentially carbon-neutral fuel synthesized from CO₂ and H₂, has emerged as a promising candidate. This paper conducts a comprehensive life-cycle analysis (LCA) of the GHG emissions associated with the methanol production process, utilizing data inventory from China in 2019. To simulate the synthesis and distillation process of methanol, Aspen Plus is employed, using parameters obtained from actual plants. GHG emissions are then calculated using the GREET model, incorporating updated industry statistics and research findings. The CO₂ necessary for methanol production is captured from factory flue gas. Two different sources of H₂ are considered: one from Coke Oven Gas (COG) and the hydrogen-rich gas byproduct resulting from COG methanation (Case 1), and the other via water electrolysis (Case 2). The GHG emissions of methanol production for Case 1 and Case 2 are found to be -0.08 and 6.36 kg CO₂-eq/kg methanol, respectively. However, if wind power is the sole source of electricity, the GHG emissions for both cases are reduced to -0.68 and -0.65 kg CO₂-eq/kg methanol, respectively. The adoption of CO₂ capture technology is the main reason for both systems to achieve negative emissions. The lower GHG emissions in Case 1 are attributed to the energy and emission allocation of byproducts. To achieve net zero GHG emissions in Case 2, the GHG emissions of electricity generation need to be reduced by 88% of the current level. This reduction is expected to be achieved by 2050, based on projected power generation mixes and efficiency improvements in water electrolysis in China.