Methanol and wet ethanol as interchangeable fuels for internal combustion engines: LCA, TEA, and experimental comparison

Abstract

The future of the transportation sector is currently in flux as the world moves to reduce fossil fuel usage. Alternative fuels can have a faster technological ramp rate than alternative powertrains and therefore can help reduce fossil fuel usage rapidly, stretching out the carbon budget to allow more time for other technologies to mature. One set of renewable fuels that show great potential for internal combustion engines are the alcohol fuels. Separately, methanol can be produced as a low carbon intensity electro-fuel and ethanol can be produced as a low carbon intensity biofuel; however, the two fuels can be produced together synergistically. In a fully renewable scenario, conventional ethanol production can be combined with gas fermentation and CO2-to-hydrocarbon catalysis to co-produce ethanol and methanol with competitive pricing compared to the current cost of gasoline. In this work, a detailed lifecycle and technoeconomic analysis showed that by combining corn wet ethanol 80 (80% ethanol, 20% water, by mass) with corn stover gas fermentation wet ethanol 80 and fermentation CO2-to-methanol, a 113% increase in alcohol fuel energy production per hectare of crop can be achieved compared to corn ethanol. This process would co-produce wet ethanol 80 and methanol with a 77%/23% energy split. The total carbon intensity and cost is 14 gCO2e/MJ and $2.63/gallon of gasoline equivalent, respectively.The similar liquid and chemical properties of ethanol and methanol result in their similar behavior and performance in internal combustion engines. This work experimentally demonstrates the interchangeability between these two high cooling potential alcohol fuels in compression ignition. The results show that in compression ignition, a hybrid injection strategy including premixed, partially-premixed, and mixing-controlled injections produced the lowest engine-out NOx and the highest fuel conversion efficiencies compared to a conventional mixing-controlled injection strategy. The diluent effect of the water in wet ethanol 80 resulted in slightly lower engine-out NOx levels and fuel conversion efficiency compared to methanol.