Comparative Life Cycle Assessment of remanufactured liquefied natural gas and diesel engines in China

Life cycle assessment (LCA) is a useful analysis tool to estimate the energy consumption and environmental emissions resulting from economic activities. This study provides a comparative LCA of remanufactured liquefied natural gas (LNG) and diesel engines. Furthermore, the paper identifies the processes that contribute most to energy consumption and environmental impacts during the life cycles of the two engines. Six environmental impacts were considered in this study: global warming potential (GWP); acidification potential (AP); eutrophication potential (EP); photochemical ozone creation potential (POCP); ozone depletion potential (ODP); and primary energy demand (PED). The results show that remanufacturing LNG engines reduces energy consumption by 41.91% compared with remanufacturing diesel engines. The greatest benefit related to the environmental impacts is EP, which is reduced by 73.69%, followed by AP, GWP and POCP, which are reduced by 71.49%, 47.14% and 43.90%, respectively. In addition, the cost benefit of the entire life cycle is also significant for LNG engines. In the life cycle of the two types of remanufactured engines, engine usage causes larger environmental impacts, especially with regard to PED and POCP, and component remanufacturing contributes most to ODP. However, it should be noted that in the remanufacturing stage, because more materials and energy are consumed for the LNG engine, the environmental impacts and costs are higher than those for the diesel engine. Nevertheless, the advantages of remanufacturing end-of-life diesel engines into LNG engines are obvious because of the significant benefits during LNG engine use.