From the standpoint of producing carbon-free energy, using ethanol to supplement gasoline might seem like a no-brainer. Ethanol comes from crops like corn, which collect carbon from the atmosphere as they grow. When the ethanol is burned, it does releases carbon into the atmosphere–but then carbon can again be collected in the next corn crop. But of course, nothing is that simple. Corn needs to be grown, typically using machinery and fertilizer, and then processed into ethanol, all of which require energy inputs. If growing additional corn for ethanol requires cultivation of additional land, plowing and preparing that land will release substantial amounts of carbon dioxide. Moreover, the use of corn for ethanol drives up demand for corn and keeps the price of corn higher than it would otherwise be, which is a political selling point for US farmers, but can put stress on the diets of the poor–especially in developing economies.

These issues have bubbled up again with the disruption of agricultural markets due to Russia’s invasion of Ukraine, combined with the ongoing global supply chain disruptions, but the topic isn’t new. Back in 2011, I amused myself for a few months at this blog by posting examples about of international organizations that had come out against subsidizing biofuels like ethanol. For example, in a June 2011 post, ”Everyone Hates Biofuels,” I pointed out a report in which 10 international agencies made an unambiguous proposal that high-income countries drop their subsidies for biofuels. I followed up with ”The Committee on World Food Security Hates Biofuels” in August 2011 and ”More on Hating Biofuels: The National Research Council” in October 2011. For a couple of additional whacks at the pinata, see “Biofuels and Hunger in Low-Income Countries” in January 2013 and “Against Biofuel Subsidies” in June 2015.

For an update, Dan Charles focuses on the environmental issues in a readable essay “How green are biofuels? Scientists are at loggerheads” (Knowable Magazine, October 6, 2022). Here’s a figure showing the rise in US ethanol production, which was launched to higher level starting in 2005 with a mixture of government requirements and subsidies.

Charles emphasizes some useful points about where the argument over biofuels currently stands. One key issue dividing supporters and opponents is the extent to which corn grown for ethanol affects land use. On one side, there is a detailed and comprehensive model of land use called the Global Trade Analysis Project at Purdue University, or GTAP-BIO, which broadly suggests that the rise of ethanol hasn’t cause much additional land to come under cultivation but instead has been enabled by higher crop productivity on existing land.

On the other side, the crops for ethanol have to come from somewhere. Charles writes:

 Ethanol factories now consume about 130 million metric tons of corn every year. It’s about a third of the country’s total corn harvest, and growing that corn requires more than 100,000 square kilometers of land. In addition, more than 4 million metric tons of soybean oil is turned into diesel fuel annually, and that number is growing fast.

Charles notes that the amount of US farmland under cultivation had been gradually declining from the 1980s up until the passage of the Renewable Fuel Standard in 2007. At this point, the decline in cropland stopped–because of the rise in corn and soybean production for biofuels. “Without the ethanol boom, the pre-2007 trend in land use would have continued. More land — 5 million acres — would have remained in grass between 2008 and 2016, rather than being converted to grow crops.” Thus, it can simultaneously be true that crops for ethanol have not dramatically expanded land under cultivation, and also that without crops for ethanol, there would be substantially less land under cultivation.

If we work from the political assumption that US corn and soybean farmers are a potent and focused special interest, and that their Congressional representatives will be able to block the withdrawal of ethanol requirements and subsidies for the indefinite future, what are the possible next steps here? There seem to be two answers on which supporters and opponents of ethanol can more-or-less agree.

One approach “is figuring out ways to measure those environmental benefits and pay landowners for them, just as they get paid for growing corn. To some extent, the US Department of Agriculture does this already, with programs that pay farmers to preserve areas of grassland or forest. Such initiatives are set to expand; the Inflation Reduction Act, which Congress passed in August, gives them an extra $18 billion in funding.”

The other approach is technological. For some years now, there has been discussion of “cellulosic biomass,” which involves getting ethanol from prairie grasses. This transmutation is possible in a laboratory, at high cost, but it seems far from being a commercial proposition. But if the process was commercially viable: “The grass could be harvested, leaving the roots to grow undisturbed, building up carbon-rich organic matter in the soil and avoiding most of the environmental damage that results from converting land into cornfields.”

Ultimately, the idea of using corn and soybeans as a primary energy source doesn’t seem like sensible policy, whether the goals are environmental or to ensure affordable global food supplies. Charles writes:

[T]he world’s croplands, which have claimed vast ecosystems, cover less than half an acre per person on the planet. Producing enough biofuel to power one typical passenger car, meanwhile, requires more than 1.2 acres. (Photovoltaic solar arrays produce many times more usable energy per acre of land than biofuels, and can also be located in dry areas that can’t grow food.)