Carbon emission accounting for peak-shaving LNG plant and suggestions on emission reduction countermeasures

Objective The "dual carbon" goals have heightened the demands for reducing carbon emissions and enhancing environmental protection within the LNG industry. To devise viable emission reduction solutions, it is crucial to precisely monitor the carbon emission levels throughout the LNG industry supply chain and comprehensively grasp the factors influencing them.

Methods Following the typical natural gas liquefaction process, this study identified and categorized the carbon emission sources at peak-shaving LNG plants, utilizing a three-level classification method consisting of production systems, industrial processes, and emission facilities, and analyzed the input-output relationships within the basic production system. Based on the results, a dynamic carbon emission accounting system was established. This system primarily relies on the carbon balance approach, complemented by the emission factor method to tackle prevalent issues within the current carbon emission accounting system, such as inaccuracies in accounting outcomes and the absence of fugitive carbon emission evaluations. Subsequently, the proposed system was applied to a large peak-shaving LNG plant in China. The annual carbon emissions from the production and operation of this plant in 2022 were meticulously calculated. Furthermore, the carbon emission breakdown and the factors influencing various emission sources were thoroughly scrutinized.

Results In 2022, the total carbon emissions of this plant amounted to 15.43×10⁴ t. The carbon emission intensity stood at 0.51 t CO₂/t LNG for the liquefaction process and 1.37 t CO₂/(10⁴ m³) for the gasification process. Indirect emissions from electricity constituted the largest share, reaching 66.95%, followed by emissions from fuel combustion, processes, and flare combustion, accounting for 18.42%, 12.58%, and 1.79% respectively. Fugitive emissions made up 0.27% of the total emissions.

Conclusion According to the carbon emission composition and intensity characteristics of this plant, suggestions for carbon emission reduction countermeasures are proposed from four aspects: (1) employing cold energy power generation technologies and purchasing green electricity as complementary sources; (2) implementing energy conservation transformations through energy conservation and emission reduction measures; (3) optimizing seal gas sources for the flare system, and utilizing Boil-off Gas (BOG) as an additional gas source for the fuel gas system; (4) deploying carbon capture and recycling facilities. These study outcomes provide logical recommendations and probable pathways for fostering the low-carbon advancement of the LNG industry.