The Long Road to Cellulosic Ethanol
Mar 23, 2017
When most non-farmers think about ethanol, they often think about all the corn that goes into producing it, and many non-farmers complain that it could be put to better use by feeding people. This concept was the genesis of the ‘food versus fuel’ debate that roiled policy discussions around the world in the wake of the 2007-08 global food price spike.
Early reaction to the crisis often focused on the increase in biofuel production around the world in recent years and how that had spurred the price increases. Later, more thoughtful analyses acknowledged that biofuels production was one factor out of many that combined to push crop demand above supply, which was exacerbated in many cases by countries’ decisions to protect their markets by imposing trade barriers.
Unfortunately, this framing of ‘food versus fuel’ persisted in many circles, and in many countries, critics of biofuels policy seized upon this argument to justify efforts to roll back or even terminate support for these programs. Among advocates of biofuel policy, especially in the United States, the short term response has been to point out that producing ethanol from corn utilizes only the starch component of the kernel, leaving the rest of the kernel (protein, oil, and bran) available to be incorporated into livestock feed or in the case of the corn oil, refined for human consumption.
The long term answer, that ultimately ethanol will primarily be produced from inedible components of plants, such as corn stover, wheat straw, or even wood waste or dedicated energy crops, has not yet been achieved in commercially meaningful amounts in the United States, or any other country. This product, generally known as cellulosic ethanol, was first produced under laboratory conditions nearly two centuries ago, in 1819, by converting (‘hydrologizing’) cellulose into sugar by treating it with sulfuric acid. Small-scale commercial ethanol production using this process was first established in Germany in 1898, and then in the United States early in the First World War. During World War II, the focus of this technology shifted toward trying to produce synthetic rubber, to help in the war effort.
Breakthroughs in the use of industrial enzymes spurred renewed interest in using this technology to break down cellulose to produce ethanol, as it was recognized by the late 1990’s that it would not be feasible to replace a significant share of gasoline in the U.S. vehicle fuel supply relying solely on corn as a feedstock.
In this recent phase, Initial research on developing cost effective methods to convert cellulose into sugar to produce ethanol were promising, which encouraged Congress to set concrete goals to incorporate such ethanol into the U.S. fuel supply by adding it to the revised Renewable Fuel Standard (RFS) in the Energy Independence and Security Act of 2007. Under that provision, no more than 15 billion gallons of corn-based ethanol would be allowed to count under the RFS rules, and the remainder of the RFS would have to be met by biofuels produced from other feedstocks, such as sugar, vegetable oil (for biodiesel) and cellulosic material.
Unfortunately, the improved technology needed to enable economically feasible conversion of cellulose have not occurred as quickly as originally predicted. Part of the delay is due to the fact that scientific breakthroughs don’t always follow a set schedule, but part of the slowed pace is due to the global financial recession of 2008-09, which caused many private sector investors to pull back on their stakes in this area.
Consequently, EPA has been forced to reduce the target for such fuel as part of the RFS--for 2016, the official goal is 230 million gallons for cellulosic fuel, down 95 percent from the level envisioned in the original 2007 legislation. The 2017 goal has not yet been established.
Although 230 million gallons falls well short of where the United States planned to be in producing cellulosic ethanol by this time, it is a signal that commercialization is finally underway. One example is a new ethanol facility built by DuPont in Nevada, Iowa. This plant is designed to produce 30 million gallons of ethanol a year from corn stover--corn stalks, cobs, and leaves-- collected from corn farmers in central Iowa. That amount of fuel will require 190,000 tons of corn stover from corn acres grown within 30 miles of the facility. The plant’s proximity to ongoing biofuels research at Iowa State University will help both the company and the Iowa State research scientists. The plant opened in October 2015.