July 25, 2023

Farming for cars

My dad, an inveterate driver, has made car trips across the width of the United States half a dozen times. At the end of the first day of their first trip, having started out from Boston, he called me and told me, with awe in his voice, that after driving all day they hadn't made it farther than Buffalo. 

Well, it's a big country.

Photo by Don Graham under CC-BY-SA-2.0

The middle of the country is given to mostly one crop: corn. (That's maize to European readers). My mom, who liked to see interesting things on the way, was astounded by just how much land was dedicated to the growing of corn. She was also bored to tears. So on the next trip, she insisted that they go farther south. They never crossed the country as far south as Texas, but all up and down the midwest, they saw a lot of corn.

The US Midwest is blessed with the best farmland in the world, but humans' relationship with it is not that great: that land is regarded as a commodity, and is used for growing commodity crops. Like corn.

Here is a stat that blew my mind when I first heard about it: of the 80 million acres of corn planted in the United States, a lot goes into processed foods, more goes into cattle feed, but the single largest chunk of it, 45 percent, doesn't get eaten at all but goes to the making of corn ethanol. That ethanol is used as an additive to the gasoline you pour into your car's tank.

I am not making this up: it is the United States Department of Agriculture that says 45 percent of the country's corn crop goes into cars' tanks.

Such is the tyranny of the car that not only do people give up huge portions of the public space in cities to it, but also in the United States alone we sacrifice 36 million acres of prime farmland to feed it, or at least the version of the car that needs to burn stuff to move forward.

Which is a crying shame: because internal combustion engines are so incredibly inefficient that two thirds of that corn ethanol just gets wasted as heat. And where I come from there is a word for that kind of wanton waste: it's called a sin.

Think about it: two thirds of that good farm land is wasted. Two thirds of the water to irrigate the corn, thrown away. Two thirds of the fertiliser and the attendant runoff: for nothing. Two thirds of the fossil fuels burned for energy to work the land and process the ethanol: wasted. Speaking of energy: ethanol from corn yields only 1.5 units of ethanol energy for each energy unit used to grow it. Throw away two thirds of that, and you end up with half a unit of ethanol energy, that is, less energy than you put into the process. The word "insane" comes to mind.

The waste of farm land at this scale is the more unwise as extreme weather from human-made climate change makes it that much harder to farm food for people. India has suspended rice exports following catastrophic monsoon rains, even as Indian farmers grow huge amounts of sugarcane for car ethanol.

It doesn't have to be that way.

Imagine that, instead of planting corn, you install solar panels on that land, and used the electricity to power electric cars. An increasing number of people have imagined this, and some have actually done the math to do a miles-per-acre comparison.

The bottom line: An acre of land, if planted with PV solar, could yield 70 times more EV miles than corn ethanol from that same acre powering a combustion engine car. The number varies depending on who is doing the estimating and what assumptions go into their estimate, but a factor 70 is about the median value.

In Brazil and India where they plant sugarcane for car ethanol, the math works out about the same: 70 times more miles per acre if you use the same land for solar energy powering EVs.

This is awesome!

That is, this is awesome from an environmental and climate point of view. But does it make sense for farmers?

A group at UC Davis asked this question, then crunched the numbers. The answer is: Right now, the farmer can make a lot more profit with PV solar on their land, even when you include the installation costs. Farther down the timeline, it's complicated. Whether or not the farmer makes more profit from the solar than the corn depends on the wholesale electricity price, the initial costs to purchase, install, and connect the PV panels, and so on. A price on carbon would tilt the balance away from growing corn for fossil fueled cars. And of course, once everyone drives an EV the demand for corn ethanol would evaporate and its price would go down.

But an early adapter switching from corn to PV solar could really come out ahead. Sweeter yet, they could get into agrivoltaics, where you install PV solar on your land AND plant a crop in between the solar panels. It's like getting two crops from the same land, simultaneously. There is a symbiotic relationship: the presence of the crop cools the surroundings, boosting the PV yield, and the PV array gives partial shade which is beneficial for cooler-climate crops, and conserves water. Some solar panels are raised, and some can be tilted to vertical so that a tractor can access the area in between the panels.

Agrivoltaic vineyard in Laterza, Taranto, Italy. Photo by Emilio Roggero under CC-BY-4.0

Best of all, even when all the EVs in the country are powered off solar PV where ethanol corn used to grow, there will still be plenty of land left. A farmer could choose to diversify their crops, as a hedge against extreme weather events. They could decide to re-wild some of their land and be paid for the carbon capture and ecological services. 

And driving through the Midwest won't be boring any more.

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