Life Cycle Assessment of Methanol from Fossil, Biomass, and Waste Sources, and Its Use as a Marine Fuel in Dual-Fuel Engines

Methanol is gaining interest in the
marine sector from
energy security
and reducing emissions perspective. This study provides a comparative
life cycle assessment of methanol as a marine fuel, across GHG and
criteria air pollutant emission metrics, when it is used in a dual-fuel
engine. Twelve methanol pathways from four different feedstock categories
were considered, including (1) cellulosic biomassforest residues
and clean pine mix, corn stover, switchgrass, and miscanthus; (2)
organic wastesrenewable natural gas from wastewater sludge,
swine manure, food waste, and landfill gas; (3) fossil resourcescoal
and natural gas (NG); and (4) e-methanol using captured carbon dioxide.
When used in a dual-fuel engine with pilot fuel, life cycle GHG emissions
for woody biomass-based methanol were approximately 19 gCO2e MJ–1, while emissions from waste-based sources
ranged between −154 and 31 gCO2e MJ–1. Methanol from renewable sources showed a GHG reduction potential
between 58 and 226% compared to conventional NG-based methanol (122
gCO2e MJ–1), primarily due to the avoided
emissions from conventional waste management. When carbon from process
emissions were captured, the reduction could be up to 327%. All pathways
exhibited lower NOX, and particulate matter emissions compared
to the baseline marine fuel (MGO 0.1% sulfur), while woody biomass
and coal pathways had higher SOX emissions.