EPA: Cellulosic ethanol from corn residue is carbon negative
There has been a lot of talk about the final rule on the Renewable Fuel Standard (RFS2) released recently by the U.S. EPA (funny how 3,000 pages will do that). Most of that talk has centered on what the rules mean for the existing corn ethanol, which the EPA determined meets the threshold of emitting at least 20 percent fewer greenhouse gas emissions than gasoline.
But what hasn't generated nearly as much discussion is what the document had to say about cellulosic ethanol. The cellulosic biofuel requirement in RFS2 is 16 billion gallons by 2022. The law had called for 100 million gallons this year, but the EPA reduced it to 6.5 million due to a projected production shortfall.
In their analysis of cellulosic ethanol made from crop residues such as corn stover using a biochemical process like we're employing for Project LIBERTY, the greenhouse gas (GHG) reduction is 130 percent in comparison to gasoline. In other words, driving your car with POET's cellulosic ethanol actually takes carbon out of the atmosphere.
For this reason and because of the availability of agricultural residue, the EPA expects it, and especially corn stover, to be the feedstock that contributes the most cellulosic ethanol toward meeting the 36 billion gallon target. On page 184 of the preamble, they state:
Agricultural residues are expected to play an important role early on in the development of the cellulosic ethanol industry due to the fact that they are already being grown...The most common residues are corn stover (the stalks, leaves, and/or cobs) and straw from wheat, rice, barley, and oats. These U.S. crops and others produce more than 500 million tons of residues each year, although only a fraction can be used for fuel and/or energy production due to sustainability and conservation constraints. Crop residues can be found all over the United States, but are primarily concentrated in the Midwest since corn stover accounts for half of all available agricultural residues.
The EPA sites one recent study showing that "under current rotation and tillage practices, about 30 percent of corn stover produced in the U.S. could be collected, taking into consideration erosion, soil moisture concerns and nutrient replacement costs." The ultimate amount removable by the farmer will of course vary by geographic location, soil quality and tillage practice, the EPA noted.
The EPA goes on to say: "Our agricultural modeling suggests that corn stover will make up the majority of agricultural residues used by 2022 to meet the EISA cellulosic biofuel standard (4.9 ethanol-equivalent Bgal)." Although we're only producing small amounts of cellulosic ethanol now, POET would like to be a big part of that big goal.
