Ethanol Industry Provides Critical CO2 Supply

by Steffen Mueller (University of Illinois at Chicago/Ethanol Producer Magazine) Strategically located ethanol sources cannot be economically replaced. -- Carbon dioxide sourced from corn-ethanol plants is not a waste-recovery product but a coproduct that, in many regions, can only be replaced by higher-emitting, less-economical resources. A reduction in U.S. ethanol production (for example, in response to policy changes) would inadvertently pose a significant disruption to the billion-dollar carbon dioxide industry, and the U.S. food industry.

Fermentation from corn-ethanol plants is the largest single-sector CO2 source for the U.S. merchant gas markets. A valuable commodity, it averages $95 per ton with a large number of applications led by food and beverages and dry ice applications. Light industrial users in the merchant market include metal welding, chemicals, pH reduction and CO2 fracking applications in oil and gas.

Ethanol sources have become so popular that major industrial gas companies have added new CO2 sources. Notable additions from Air Products, both completed in 2014, were the 400 ton-per-day (TPD) plant sourcing gas from Southwest Iowa Renewable Energy, Council Bluffs, Iowa, and the 250 TPD plant at Big River Resources in Boyceville, Wisconsin.

Nearly 43 percent of domestic CO2 by-product for refinement and liquefaction is derived from 48 ethanol plants, mostly in the Midwest. While several regions in the U.S. are saturated, more ethanol plants will be tapped for carbon dioxide feedstock in the future as the U.S food industry continues to expand. For example, Continental Carbonic this fall announced a new CO2 plant to be colocated with ethanol producer Pennsylvania Grain Processing in Clearfield. The Pennsylvania project is an example of a strategically located CO2 source that cannot be replaced by other sources in an affordable and clean manner.

Ethanol byproduct cleanup is generally less technology- and equipment-intensive than other sources, and there is significantly more experience in the construction of CO2 plants from ethanol than other sources in recent years. Other CO2 sources include 21 ammonia plants, 18 reformer refineries, 15 natural sources and a handful of others such as flue and natural gas.

Natural geological sources can be the cheapest of all types. When source quality and well-head pressure is ideal, the feedstock is extremely clean, requiring only minor carbon filtration, and the elimination of a feed compressor can save half the power demand. In many cases, however, natural sources also contain hydrocarbons, heavy sulfur and benzene, all of which are expensive or difficult to remove, as in the case of benzene. Natural sources are in specific limited markets and cannot replace the predominately Midwestern-located ethanol sources.

Traditional technologies for ammonia production can yield some of the cleanest raw CO2. Ethanol fermentation raw gas, in comparison, usually contains several constituents not found in ammonia, such as trace sulfur compounds and acetaldehyde. Newer ammonia technologies are said to produce an intermittent raw stream that present new engineering and production challenges, leading to higher costs. Numerous ammonia projects were slated to be constructed (usually with international principals) in recent years, but never progressed beyond the drawing board.

A flue gas CO2 recovery plant costs between $20 million and $30 million, which compares with the $3 million to $5 million cost for a similarly sized ethanol system. Power consumption for the flue gas plant is estimated to be at least double that of traditional plants. READ MORE