Where to Listen:
Many farmers are choosing to integrate solar panels into their fields. Now a new analysis shows that decision can impact a lot more than energy costs and the climate. Putting solar panels on conventional farmland can actually change the environment where those panels are located–for the better.
Host:
Amy Barrilleaux
Guest:
Dr. Paul Mathewson, Clean WIsconsin
Resouces for You:
Integrating solar into conventional farmland can restore soil health, provide habitat for native pollinators and improve water quality by reducing sediment and fertilizer runoff into nearby waterways.
According to Clean Wisconsin’s Solar Farm Impact Analysis:
- Solar farms that replace conventional row crops like corn and soybeans reduce sediment and phosphorus pollution runoff into nearby lakes, rivers and streams by 75-95%.
- When deep-rooted, perennial vegetation is planted among the panels, solar farms can increase soil carbon sequestration by 65%, and improve overall soil health.
- Planting perennial vegetation among the panels also improves wildlife habitat compared to existing cropland, including a 300% improvement in habitat quality for pollinators, which are in steep decline.
- Solar farms produce 100 times more net energy per acre than corn grown for ethanol and are a far more efficient use of land. To meet net-zero carbon emissions, Wisconsin only needs about 200,000 acres of land for solar, or about 15% of the 1.5 million acres of land currently devoted to ethanol production in our state.
More to Explore:
Analysis: Solar farms produce 100 times more energy than corn grown for ethanol
Transcript:
Amy Welcome to the Defender Podcast. I’m Amy Barrilleaux. The Defender is powered by Clean Wisconsin, protecting our state’s air, water, and land since 1970. You may have heard the eye-opening number. Wisconsin spends $14 billion a year importing our energy. So the coal, gas, and oil we use gets here from underground pipelines, trains, tanker trucks, because we don’t produce those things here. We import them from other states or countries, and it’s expensive. There’s good news though. The clean energy that we do make here is getting cheaper and cheaper. These days, large solar farms are one of the cheapest ways to produce electricity in Wisconsin, second only to wind. But solar needs more than just sunshine to work. It needs space, a place to put all of those solar panels. And in Wisconsin that usually means farmland. Many farmers are choosing to farm the sun by integrating solar panels into their fields. Now a new analysis shows that decision can impact a lot more than energy costs or the climate. Putting panels on conventional farmland can actually change the environment where those panels are located for the better, if certain practices are followed. A look at the surprising environmental impacts of solar that’s right now on The Defender. When you think solar, you probably think about the climate, about reducing greenhouse gas emissions that come from other energy sources like coal and natural gas. But it turns out that in Wisconsin, solar farms can bring benefits to the land and water where they are located. Joining me to explain how is Clean Wisconsin science program director Dr. Paul Mathewson, who’s out with new research measuring the local environmental impacts of solar farms. Paul, thanks for being here.
Paul Happy to be here.
Paul So before we dig into your research, there are all kinds of sciences out there, things that you could be working on, topics you could looking at. What drew you to science that’s related to our environment? When did you decide to do this day in and day out? Because I think it’s not always the most happy topic.
Paul Yeah, so I grew up in rural New Hampshire, and so my formative years were spent outside, playing in the mountains, the lakes, the rivers, ocean. And so I have a real deep appreciation for the environment and the natural world, and humans have such a profound impact on that. I wanted to get into an area, a field, where I felt as though I could help minimize that impact and do some good for the world.
Amy And have you felt like that over the years?
Paul I have. Very fortunate to have a place like Clean Wisconsin to do this sort of work.
Amy So you’ve looked at all kinds of things. We’re here today to talk about the local environmental impacts of solar, but you’ve looked at, you know, nitrate contamination, PFAS, air pollution, so many topics. If you had to pick one, you know, analysis or research that you’ve done that was maybe the most surprising or most interesting, what kind of pops out for you?
Paul I don’t know if there’s one topic, but I would say what has become very interesting to me is the connection between environmental health and public health. I got into this area mostly from the wildlife aspect, you know, protecting wildlife habitat because I’ve always enjoyed wildlife. But as I’ve done more and more environmental science, just seeing how everything ultimately comes back, everything in environmental science pretty much ultimately comes to human health. And how it impacts us and impacts our family, I found just super interesting.
Amy Today we’re gonna be talking about some of your research that I think on the surface doesn’t seem related to health but in many ways it actually is. And that is the environmental impact of solar farms. Basically, you looked at what happens to the environment when solar panels are integrated into conventionally farmed agricultural land. First though, why would we wanna put solar panels on farm land? Why not, you know, someplace else?
Paul So we’re starting here the premise of, yes, we want to address climate change. That’s worth addressing. Large scale solar farms are an important part of that solution. So where do we put those to make the most sense to have the smallest environmental impact? And as we’ll get to where we can actually have a benefit from having that larger footprint. And so when you take a step back and say, where can we put these? Cause you do need a pretty large footprint to have solar farms. You need about five to seven acres per megawatt capacity. So if you talk a typical solar farm that’s being built right now, about 300 megawatts capacity, you’re talking about 2,000 acres. And so that’s one farm. Based on existing estimates, we need about 20 to 30 gigawatts of capacity of solar by 2050 to reach our carbon-free electricity production goals. And so we’re talking somewhere between 150,000 and 200,000 acres that we’ll need of land, which sounds like a lot. Yeah. But when you consider in Wisconsin, we have over 10 million acres of agricultural land, 150,00 acres is a very small fraction of that. But before we get to ag, just so we step back, you can put it on undeveloped land, Like forests.
Amy Our really nice land!
Paul Or grassland. But then that has clear environmental impacts with habitat destruction, habitat loss, habitat fragmentation. So that’s not great. And if you put it in a forest, there’s huge carbon benefits to keeping trees in place. So those are not great people talk about brownfield sites, contaminated sites that you can’t build on, you can farm on. Why don’t we use those? A couple of issues with that one. They’re relatively smaller sites all scattered throughout. So practically speaking, you have to connect each one of those individual sites to the grid. You know, just technically that’s hard. And even if you sum up all the brownfield sites, the US EPA, they have a mapping application called Repower, where they map out the renewable energy potential on brownfield sites throughout the country. And so even if we were to use all the potential solar brownfields sites in Wisconsin, you’re only talking six gigawatts. So that’s not enough to get where we’re going. So the other land that we have in abundance is agricultural land. It’s flat, it’s already cleared of trees, so it’s perfect for solar.
Amy So when solar farms get put onto land that has been used for conventional crop production, for example, corn, in our state we grow a million acres of corn for ethanol. It’s our most dominant crop. You found that in many cases, putting solar panels on that land has a benefit, a positive impact. And I think we don’t always realize that conventional agriculture can be hard on our land and our waterways. What are some of the environmental issues we see related to intensive agricultural practices in Wisconsin?
Paul Yeah. And so just to start, this isn’t meant to demonize agriculture at all. It’s, you know, it’s incredibly important, economic, socially, culturally important. There are negative environmental issues associated with our current dominant agricultural system of intensive annual row cropping, which means you’re just you’re farming one crop intensively to maximize production on land. And so to do that, you need a lot of inputs, a lot chemical inputs in terms of fertilizers, nitrogen fertilizers. You need pesticide inputs. And those have important environmental issues in the state. You know, when you’re talking nitrogen fertilizer, only half of what we put on the fields actually gets taken up by crops. That means half of we’re putting down or even more than half in a lot cases. Is lost in the environment. So that gets into our waterways, that gets in to the air. And so nitrate groundwater contamination is our largest, most widespread groundwater contaminant in the state. And so nitrogen contamination is associated with, the standard, the health standard is put in place to protect against blue baby syndrome. Nitrate ingestion by infants can impact their blood’s ability to carry oxygen, hence blue baby syndrome. But that’s what our health standards based on that was established back in the 1950s, 1960s. But since then there is increasing evidence linking nitrate drinking water contamination to other health impacts like certain cancers like colorectal cancers and birth defects like neural tube defects. And so there are serious health concerns about nitrate contamination and agriculture is the largest source of nitrate. Largest source of nitrate pollution in the state. The most common estimates of about 90% of our nitrate contamination is coming from agriculture. And then there’s also the issues of pesticide use that’s getting into our drinking water. In certain parts of the state, over half the private wells have multiple detections of different pesticides in their water. So, clear health impacts there as well.
Amy Okay, so the picture you’re painting is yes, I mean, farming is the economic engine in Wisconsin, but some farming practices have degraded water quality in certain places. And I think also soil health, if I’m not mistaken, you know, that same kind of practice of planting the same row crop year after year, we think about, we know that our soil is valuable. It’s our, you It’s just in our hearts that we value our land and our soil, but it’s kind of washing away and having issues. What kind of issues are happening?
Paul Yeah, so when you have the annual row cropping system, so you put the seeds in the ground in the spring, you harvest it in the fall, which means you have a lot of soil disturbance. So it’s not kept in place by rooted vegetation all year round. And so that leads to a lot erosion runoff. Obviously there are practices, people are more and more doing cover cropping, in between the harvesting of the main cash crop, they’ll have some cover over the winter. But regardless, in this dominant system, you do have a lot of soil erosion due to that constant cycle of soil disturbance from the harvesting, from the tilling, from all that. And so we’ve lost a lot topsoil due to agriculture, I don’t have specific numbers on it, but it’s a lot that we’ve lost historically. And then just the intensity with which we are farming really takes all the nutrients out of the soil. And so to have a chance for soil to rest, to recuperate is another important benefit of putting solar on land currently used for row crop agriculture.
Amy So I think, you know, you’re kind of painting a picture of some environmental challenges because of intensive agriculture. And I think there’s also, though, because we don’t wanna just kind of like lay the blame on the shoulders of farmers, there’s the issue of family farms kind of disappearing in Wisconsin. So, you now, it’s hard to, live by commodity prices and there’s so much pressure I think to get the most out of those crops that are put in the soil. And so then we look at solar and I think a lot of farmers are thinking, well this helps my income, it’s a stable source of income that’s not tied to a commodity market. So you have all that going on and so you’ve taken a look at really quantifying what solar means particularly when it comes to the health of our environment. So for farmers who are choosing, yes, I need this stable source of income to keep me on my family farm. I’m going to integrate solar into my farming system. They may not be thinking about the water quality or the soil health, but that’s what you’ve looked into. So what happens when maybe conventional corn or or corn grown for ethanol or soybeans are. Some of those acres are then used for solar farms.
Paul Yeah, and before we do that, one thing I forgot to mention and another environmental pollutant not necessarily related to health, but you know, another important environmental pollutant coming off of our current intensive agricultural system is phosphorus pollution. And so phosphorus is another nutrient that is added in fertilizer important for plant growth, but excess phosphorus binds to soil. And so when soil gets run off in stormwater. That ends up in our surface waters, our lakes, rivers, streams. And so phosphorous contamination, excess phosphorous is the primary reason for a lot of our impaired waterways in the state. And so, again, that’s another important environmental pollution that solar can help address that we’ll talk about.
Amy Is that why we have the green lakes in the summer? Is that phosphorus or is that a whole mixture of things?
Paul Mostly phosphorus and increasingly people understand that nitrogen is also involved in that but nitrogen phosphorus are the reasons for the the algal blooms
Amy And that includes the blue-green algae.
Paul Yes, yeah.
Amy The infamous blue-green algae that we see.
Paul Yeah, the harmful algal blooms. And again, the toxicity of that is thought to be driven by nitrogen availability. So both the phosphorus and nitrogen are implicated in these algal bloom that we see on our lakes and streams. Okay.
Amy I think, so we have a, we are seeing the connection between some of these agricultural practices and some degraded water quality in certain places. So what happens then when you take some of those fields out of production and put solar on?
Paul Yeah, and so when you put on a solar field and we’re talking a solar farm, we’re envisioning a well-designed, well-maintained solar farm which I’ll get into here. And so when we’re taking a well designed, well maintained solar farm that’s a farm that has established vegetation under and around the solar panels that is deep rooted native grassland. Vegetation, native grasses. They’ve also been a lot of the projects they put in pollinator habitat around on the outskirts as well, putting in flowering plants to provide habitat and food resources for insect pollinators which are in serious decline and is useful and helpful. But when you have a solar farm, when you establish that native, that perennial native deep rooted grasses. Those aren’t gonna be plowed up every year. So you have a continuous living cover on that ground and those deep roots will hold that soil in place so you don’t have the soil erosion. So the phosphorus is not gonna be running off like you did before, you know, attached to those soil particles. We’ve done some analyzes, that’s a couple different solar farm proposals, project proposals and found that when you put on… A solar farm that can reduce your phosphorus runoff by 75 to over 95%. So a big reduction in soil sediment and subsequent phosphorus run off from these. In addition, you don’t need to have the annual application of pesticides and nitrogen fertilizer. So you’re having fewer chemical inputs on this land that’s been converted into a solar Finally, those extensive root networks for the deep-rooted native grasses helps with soil carbon sequestration. There’s a lot of evidence that the conversion from grassland, prairie, to agriculture in Wisconsin, and everywhere basically, has resulted in a loss of a ton of soil carbon. And so this is helping to reverse that process. And so increasing that soil carbon, holding that soil in place to let the microbial and all the little bugs in the ground do their thing, helps rebuild that soil health for the 30, 40 years that this will be in place, so that when it is decommissioned, you’ve got healthier, well-rested soil that can be reconverted back into agricultural land if that’s what the landowner wants to do.
Amy Um, how often are these solar farms really putting in the kind of habitat that we need because I think there’s a difference between a solar farm going up and like, you know, just having some grass or whatever in between the panels and one that really has this kind of deep rooted vegetation.
Paul Yeah, I would say in the last couple years, pretty much all the applications that we see for a permit to construct these include putting in native deep-rooted vegetation and pollinator habitat because I think developers are recognizing that these are good things, these are add-ons that are good to include in these proposals. And so, you know, earlier on, you know, when we first started getting involved in these back in 2019, you know it wasn’t as common to see this and so we were always pushing to see, you know, could we put in better vegetation under and around these panels and so it’s been good to see that now we don’t need to be pushing for that anymore. It seems like it’s becoming the practice, at least with respect to these large ones that require PSC approval. I can’t speak to smaller ones that don’t need to go through that process.
Amy So PSC is the Public Service Commission and they approve the big, as we call them, utility scale solar farms in the state.
Paul Yeah, anything 100 megawatts or greater capacity.
Amy Now you’ve submitted testimony in support of some of these projects talking about, hey, if you follow this vegetation management plan and really plant this perennial vegetation, then there is going to be this net benefit to the local environment around the solar When you first started doing that, was it kind of like unusual to have to be in there saying, hey where’s your pollinator habitat or let’s do this?
Paul Yeah, so one of the findings of the PSC that needs to make in order to approve these is that there’s not going to be an undue adverse environmental impact to the project. And so what we wanted to do is to get in there to speak to that point specifically, you know, that’s what we have expertise and be able to speak too. And you know, just to be able lay out what we just talked about. And so the PSC members and others can just understand how when you do it right, you can not only does it not have an adverse negative, you know adverse impact. It can actually provide important local benefits in an area. So yeah, that’s what we’ve been doing.
Amy I know I’ve, sometimes when I’m scrolling on social media, I see some posts that are kind of like, well, let’s just go ahead and cover every parking lot and parking garage and rooftop and brownfield with solar and we won’t need to worry about this at all, this, you know, notion of putting solar farms into agriculture spaces. What’s your reaction to that?
Paul Yeah, so rooftop solar is another piece of the puzzle. We need that. The issue with that is that, yes, we have technical potential. You know, if we put panels on every single rooftop that can handle it in the state, sure, we could maybe get it that way. You know the PSC, they had a technical potential study a few years back that found that we have the technical potential of about 40 gigawatts of solar. Rooftop solar that’s technical potential. That’s basically any structure that can handle it can get it The issue with that is that is a lot of different rooftops, and so it’s very inefficient and it’s hard, you know, very difficult to reach that type of potential. In fact in that study, they said okay, we have the technical potential But if we model if we do our best estimate on the actual build out of rooftop solar by 2034, that’s as far as they went out, they were only estimating 600 megawatts of capacity, which is just two solar farms. And so that having to put solar on multiple, thousands and thousands of individual roofs is a lot bigger undertaking than when you can have these economies of scale on a solar farm. It is much more expensive to do it that way. It’s about twice as expensive per unit electricity generated. To do a rooftop solar versus a large scale solar farm, again, due to economies of scale. And it’s also a lot less efficient. It’s about 50% less efficient in terms of capturing sunlight and converting it into electricity because a roof is fixed in its orientation. You can’t adjust that. And so it may not be optimal for a given roof to be able to capture sunlight. Whereas with the solar farm… They can be engineered design to have the optimal orientation of all their panels to capture as much sunlight as possible. And then they can also do their tilting and following, you know, tracking with the sun as it moves across the sky. So that you can be a lot more efficient in generating electricity with a solar farm. And the efficiencies are important because, you know we’re rapidly approaching 2050, faster than any of us want. And the speed and scale at which we need to be. Converting to carbon-free, emissions-free electricity generation requires, from our perspective, solar farms to be part of that solution. Because we can’t do it fast enough with just rooftops.
Amy When you talk to people about, okay, yes, there are certainly climate benefits, right, to solar farms, but then there are also these kind of environmental benefits to the area around, in and around the solar farm, are they surprised to hear that? Because I think, you know, again, people think, okay replacing this natural thing, which is corn, even if it is grown for ethanol, with solar panels, are they surprised at the solar panels would have a better localized environmental impact?
Paul Yeah, I think that gets back to a lot, you know, the negative aspects of a corn field or, you now, a real crop field, agricultural field are not visible. You don’t see the pesticides in your drinking water or in the air you’re breathing. You don’ see the nitrate in your water. And so, the solar panels, you do see. And so it is part of what we wanted to do is just to raise greater awareness of this so we can get people thinking along those lines.
Amy And I’ve been talking a lot about ethanol because I think back to a study that you did, I guess, last year or the year before that, which is, first of all, I had no idea. We devote a million acres of land in Wisconsin to growing corn that is turned into ethanol. Um, and second of all, you found that, acre for acre, solar is a hundred times more…
Paul Efficient at generating energy.
Amy More better at generating electricity than corn grown for ethanol. So we’re already, I guess, what people may not know is we’re all ready to voting acreage to energy production in Wisconsin.
Paul Yeah, and so one of the pushbacks we often hear about utility-scale solar is we don’t want to take land out of food production, you know, we’re feeding the world. And so what we want to point out, as you mentioned, is we’re already using over a million acres of farmland in Wisconsin to generate energy, for energy production in the form of growing corn that is converted into ethanol that we put into our our gas tanks in our cars. And so that’s not generating food. And so of that million acres, we only need a fraction of that for the utility-scale solar that we need. So like I said earlier, we need somewhere around 200,000 acres to reach our goals. And, you know, with technological improvements, maybe that can even go down as you can get solar farms to be more efficient. So assuming we need 200,000 acres, that’s less than a quarter of what we’re already using to grow corn for ethanol, another use of agricultural land for energy production. And like you mentioned, if you look at the efficiency of an acre of corn grown for ethanol the amount of energy you get out of that, subtracting out the energy you need to put in to generate that, and compared to the amount energy you can get from a solar farm, It’s like you mentioned, it’s a hundred times more net efficient. A hundred times greater net efficiency in terms of producing energy on an acre of land. So it’s a lot more efficient than what we’re currently using for agricultural land energy production.
Amy Is Wisconsin lucky compared to other states that we have this land that we’re already devoting, you know, a whole lot of land to energy production, and that we have this kind of space that’s already been cleared? We don’t have to make a tough decision about how are we going to get clean energy compared to other States that I think aren’t agricultural states.
Paul Yeah, I think you have a lot more wildlife impacts, wildlife concerns in places like the Southeast or the Southwest where you’re having, you know, you’re putting solar farms on endangered, in some cases endangered species habitat or you’re clearing out trees and clearing out land. So yeah, to have this resource and this ability to put solar on land and have a net benefit is I think a good thing, good choice to have.
Amy Yeah, it sounds like it. Well, Paul, thank you so much for all your research into this. You can find that study on our website. It’s very detailed, took a lot of work. So I appreciate your coming in to explain all that.
Paul I was happy to do it.
Amy And thank you for listening to the Defender podcast. You can find a link to the study in our show notes or by logging on to cleanwisconsin.org. I’ve also linked to the solar versus ethanol study. So check that out as well. And remember to leave a rating or review on your favorite podcast platform. It helps other people find the show. So until next time, I’m Amy Berio.
