Farmland & Photovoltaics: It Might Not Be What I Expected
Doing research for my blog, I typically read the titles of well over 300 articles each day. There are some I think are really good, as nearly all of those I find at CleanTechnica are. But I often find articles I think are trash, and this includes those decrying the use of photovoltaics on farm fields because such use takes farmland out of production. Maybe some of these articles do include references, but I don’t remember seeing any that do. It also seems they never address such things as agrivoltaics. And bad information about photovoltaics (PV) on farm fields is something I find really annoying.
To settle my mind, I sometimes sit down and work on mathematical puzzles. They are not usually the sorts of puzzles you might find in books or newspapers. Rather, they are problems that can point to answers to real questions. I was sufficiently annoyed by opinions put forth by people about converting fields to solar power that I took on two questions: First, how much land would be needed for enough solar PV to provide the United States with all of its energy, including electricity, heat, transportation, industry, and whatever else we use energy for. And second, if we devoted that much land exclusively to PV, sited entirely on farmland, what would the effect be on the amount of our agricultural land.
I couldn’t easily find a good number for the PV acreage needed to supply all the energy used for the US. Also, there is a lot of variation in estimates of acreage needed to provide our electricity from PV. I had found that NREL had said 10 million acres would be needed to supply all the electricity. (NREL PV FAQs) I started with a back-of-the-envelope calculation using 11 million acres. Knowing that about 37% of the US energy was electricity, I divided that 11 million by 0.37. This gave a figure of about 30 million acres to supply all US energy from PV.
That figure rang bells in my mind. For one thing, I had recently read that the Bureau of Land Management was thinking of offering 31 million acres of public land for renewable development, in an article in POWER Magazine. I had also read in another recent article at MSN that 30 million acres of farmland had gone out of production since the 1980s, and it was being considered for other uses, which presumably includes solar power. While neither of these addressed the question of what would happen to US farm land if we used 30 million acres purely for solar power, they were interesting.
In my research, the number, 30 million acres, keeps coming up. (Karl Jung might be looking over my shoulder.) I looked to find what was comparable. The floodplain of the Mississippi River is about 30 million acres. The state of New York is a bit greater than 30 million acres, with variation depending on whether water is included or not.
As I was doing this, a thought came to me. How many acres are being used for corn for ethanol? This is important because if all our energy comes from solar, that will include transportation, and there will no longer be a need for corn ethanol. It turns out that 30.2 million acres is devoted to corn for ethanol, according to Ethanol Producer Magazine.
That fact is a revelation. It means that if we got all our energy from solar PV set up on 30 million acres of farm land without agrivoltaics or any other consideration for keeping land usable for agriculture, the amount of farm land available for growing food could actually increase.
Just to check my most important figures, I sought a second opinion by running the problem past Stanford University Professor Mark Z. Jacobson, to find out whether my conclusion makes sense. Here are bits from his email in reply:
Yes, your conclusion is correct, but I would argue that agricultural land would increase even more than you calculate.
I calculate 17.1 million acres are needed for all U.S. energy in 2050 after electrification of all energy sectors.
…
[Upon] electrification, electricity requirements decrease substantially due to the efficiency of electricity over combustion (EVs, heat pumps, etc.) and eliminating energy to mine/transport/refine fossils and uranium.
I should point out that I am not proposing getting all our energy by putting solar PV on farm land. The purpose of this exercise was just to understand things better.
I would like to add one thing, which is an opinion of land use: what I want in my back yard. I spent much of my childhood in communities where I could walk to nearby corn fields. I have lived in other rural areas. My first job was working on a farm. Land use is something I don’t take for granted.
Suppose I lived across the street from an abandoned farm field. The farmer comes to me to find out which of three things I would prefer to see the land used for. The choices are a conventional corn field, development for single unit houses on quarter acre lots, or a large solar array. Which should I pick?
Personally, I would ask that the conventional corn field be ruled out. This is because a conventional corn field is covered with enough toxic chemicals that I think of it as a toxic waste dump that goes without environmental protections. If I want to preserve the quiet lifestyle, I would go for solar PV. And really, they are no more boring than corn, but they are a lot nicer to look at than bare soil in the spring and rows of stubble in the fall.
Image: Corn field, by Gaspar Uhas via Unsplash
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