The future of ethanol production in the US is from cellulosic- and algae-based feedstock facilities. By-product CO2 (crude feed) from these plants will be a target of sequestration projects, used as feedstock for liquid merchant CO2 plants, and used in industrial processes such as enhanced oil recovery (EOR) and coal bed methane (CBM) projects.
In the US, the ethanol production is rapidly evolving away from the grain-based, or first generation, feedstock facilities, to second generation biofuels derived from crop byproducts or biomass, and third generation fuels derived from algae (see “Trash to Treasure,” CGI February 2010, p. 30).
The corn-based production of ethanol, a commodity in increased demand as an oxygenate in gasoline blending, has been in rapid development in the US for many years. However, beginning in 2007, numerous factors — including the collapse of financial capital markets, changing farming practices, uneven commodity prices for corn in the US, and politics — brought corn-based ethanol plant developments practically to a standstill. To a large extent, what changed the appetite for financing grain-based ethanol projects is the so-called “food versus fuel” argument and the US ethanol industry, like much of the world, is moving to non-grain (food) feedstocks for ethanol plants.
Second generation biofuels, often referred to as cellulosic, include a wide variety of feedstocks ranging from biomass to wood to grasses to MSW (municipal solid waste), and are made from a variety of processes like acid–hydrolysis and enzyme-based production. Sourcing CO2 from an ethanol plant that is MSW-based can raise concerns. While CO2 supply to strictly industrial service, such as EOR, uranium leaching, or CBM projects, would not be a problem, CO2 sourced from a waste-based plant would be unacceptable to food and beverage service, despite the ability to conceivably purify it to meet beverage standards.
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