Environmental and Regulatory Assessment of Methanol Propulsion for a Livestock Carrier Under the IMO Net-Zero Framework

Abstract

Livestock carriers contribute to greenhouse gas emissions through the continued use of conventional fossil fuels. This study presents a theoretical, steady-state case study of replacing the Wärtsilä W7X35 diesel engine of the livestock carrier Motor Vessel MV Ganado Express with a Wärtsilä 46F methanol-fueled engine (7500 kW, operated at 81.2% load to deliver the required 6090 kW), using published specific fuel consumption values and emission factors. Fuel consumption and exhaust emissions were estimated with a bottom-up method over a 24 h sailing period, and the annual well-to-wake (WtW) greenhouse gas fuel intensity (GFI) and compliance costs were assessed for 2028–2035 against the two-tier targets of the IMO Net-Zero Framework approved at MEPC 83. Because methanol is a carbon-bearing fuel, tank-to-wake carbon dioxide emissions are nearly unchanged, declining by only 5.4%, whereas nitrogen oxide emissions fall by 73.2% and sulfur oxide emissions are eliminated. The decarbonization benefit arises instead on a well-to-wake basis: with renewable e-methanol, annual lifecycle emissions fall from 29,897 to 2291 tCO2eq. Diesel operation exceeds both targets from 2028, at a compliance cost rising from USD 0.91 to 3.85 million per year, while e-methanol remains in direct compliance throughout the period. E-methanol nevertheless remains the more expensive option, the annual cost gap narrowing from USD 15.1 to 12.2 million by 2035.