Analysis reveals solar farms produce 100 times more energy per acre than corn ethanol

Image of corn harvest and solar farm

When you drive past mile after mile of Wisconsin corn fields, you may not realize that a quarter of all that corn—about a million acres—is used to produce ethanol. But a new analysis from Clean Wisconsin reveals that when it comes to land use, the state could reap far more energy from solar. “Purely from an energy production perspective, we found that it’s much more efficient to use that land for solar panels to generate energy,” says Clean Wisconsin Science Program Director Paul Mathewson.

The analysis takes into account not just gross energy production, but the energy “inputs” needed for solar and ethanol.

“Corn needs to be grown, harvested and processed into ethanol, all of which require energetic inputs. Likewise, solar panels need to be manufactured and installed,” he explains. “When accounting for inputs, the net energy production of solar is over 100 times that of corn ethanol.”

Wisconsin has about 3,500 acres of solar, just 0.35% of the land currently devoted to corn for ethanol. Based on data from Wisconsin’s Roadmap to Net Zero report, our state needs roughly 280,000 acres of solar farms to meet carbon free goals by 2050. That amounts to less than 1/3 of the current land area already being used to grow corn for ethanol.

“There is a concern that we’re going to take too much farmland out of production to put on solar panels. But we’re already using a lot of land to primarily harvest energy in the form of corn made into ethanol. This analysis demonstrates how, with solar, we can harvest more energy using far less land,” Mathewson says.

He notes that byproducts of ethanol production are often used as animal feed, but the study found that even when that use is factored in, ethanol’s energy potential still falls far short of solar.

“Even if you look at the total energy that corn itself can produce, assuming 100% of it is ultimately used for feed or ethanol—which it is not—solar is still 20 times more efficient,” he says.

“To build a healthier future for our kids in rural and urban communities alike, we urgently need more solar projects in Wisconsin,” says Chelsea Chandler, Clean Wisconsin Climate, Energy and Air Program Director. “This study demonstrates that we could use a fraction of the land currently used to grow corn for ethanol and instead build solar farms that create abundant clean, homegrown energy.”

Mathewson adds that energy produced by growing corn for ethanol comes at a high price for Wisconsin’s waterways.

“Corn is notorious for needing chemical inputs—pesticides and nitrogen fertilizer. Nitrate is the most widespread groundwater contaminant in Wisconsin. Agriculture contributes about 90% of that contamination and corn is a major user of nitrogen fertilizer. So you have water quality issues,” he says. “Working that land continually disrupts the soil, which can lead to erosion, sedimentation and nutrient loss. This all negatively affects waterbody health and drinking water quality.”

Corn is the number one crop in Wisconsin, covering some 4 million acres of land in our state.

“While some conservation improvements, like reduced tillage or cover crops, can help ease corn’s impact on water quality, corn is difficult to grow to in some parts of Wisconsin without causing water pollution issues,” Mathewson says.

Chandler says leasing land for solar projects instead of planting acre after acre of corn for ethanol would be a win-win for Wisconsin farmers.

“Farmers grow a variety of crops important to families in Wisconsin,” she says. “When it comes to growing crops for energy, ‘growing solar’ is a better bet for farmers, families, our water, and our climate than corn for ethanol.”

Read the full analysis here.