Cost and Life Cycle Emissions of Ethanol Produced with an Oxyfuel Boiler and Carbon Capture and Storage

Oxyfuel Combustion Makes Carbon Capture More Efficient

Fossil energy carriers cannot be totally replaced, especially if nuclear power stations are stopped and renewable energy is not available. To fulfill emission regulations, however, points such as emission sources should be addressed. Besides desulfurization, carbon capture and utilization have become increasingly important engineering activities. Oxyfuel technologies offer new options to reduce greenhouse gas emissions; however, the use of clean oxygen instead of air can be dangerous in the case of certain existing technologies. To replace the inert effect of nitrogen, carbon dioxide is mixed with oxygen gas in the case of such air combustion processes. In this work, the features of carbon capture in five different flue gases of air combustion and such oxyfuel combustion where additional carbon dioxide is mixed with clean oxygen are studied and compared. The five different flue gases originate from the gas-fired power plant, coal-fired power plant, coal-fired combined heat and power plant, the aluminum production industry, and the cement manufacturing industry. Monoethanolamine, which is an industrially preferred solvent for carbon dioxide capture from gas streams at low pressures, is selected as an absorbent, and the same amount of carbon dioxide is captured; that is, always that amount of carbon dioxide is captured, which is the result of the fossil combustion process. ASPEN Plus is used for mathematical modeling. The results show that the oxyfuel combustion cases need significantly less energy, especially at high carbon dioxide removal rates, e.g., higher than 90%, than that of the air combustion cases. The savings can even be as high as 84%. Moreover, 100% carbon capture was also be completed. This finding can be due to the fact that in the oxyfuel combustion cases, the carbon dioxide concentration is much higher than that of the air combustion cases because of the inert carbon dioxide and that higher carbon dioxide concentration results in a higher driving force for the mass transfer. The oxyfuel combustion processes also show another advantage over the air combustion processes since no nitrogen oxides are produced in the combustion process.

Should Transportation Be Transitioned to Ethanol with Carbon Capture and Pipelines or Electricity? A Case Study

An important issue today is whether gasoline vehicles should be replaced by flex-fuel vehicles (FFVs) that use ethanol-gasoline blends (e.g., E85), where some carbon dioxide (CO2) from ethanol's production is captured and piped, or battery-electric vehicles (BEVs) powered by wind or solar. This paper compares the options in a case study. It evaluates a proposal to capture fermentation CO2 from 34 ethanol refineries in 5 U.S. states and build an elaborate pipeline to transport the CO2 to an underground storage site. This "ethanol plan" is compared with building wind farms at the same cost to provide electricity for BEVs ("wind plan A"). Compared with the ethanol plan, wind plan A may reduce 2.4-4 times the CO2, save drivers in the five states $40-$66 billion (USD 2023) over 30 years even when BEVs initially cost $21,700 more than FFVs, require 1/400,000th the land footprint and 1/10th-1/20th the spacing area, and decrease air pollution. Even building wind to replace coal ("wind plan B") may avoid 1.5-2.5 times the CO2 as the ethanol plan. Thus, ethanol with carbon capture appears to be an opportunity cost that may damage climate and air quality, occupy land, and saddle consumers with high fuel costs for decades.