|Photo by Irene Miles|
On its millions of acres of farmland, Illinois grows enough corn and soybeans to produce more ethanol than any other state in the US. If Illinois farmers decided to grow perennial grasses for biofuel rather than corn and soybeans, though, how might the way Illinois uses water and fertilizer change? That’s what Andy VanLoocke and Carl Bernacchi wanted to know, and they won an IWRC Annual Small Grant to fund their search for an answer. At the end of their project, Andy and Carl told us about their findings, what the research could mean for Illinois water resources, and what Andy is doing with his new PhD.
A cellulosic biofuel feedstock is a crop that is grown primarily to convert the cellulose, most of a plant’s structural material, into a fuel like ethanol. This is in contrast to the “grain or oil” being used to produce ethanol or biodiesel, because with cellulosic feedstocks the energy source isn’t limited to the seed of the crop, like with corn or soybean.
Would you please give us a quick overview of the whole project, not just the IWRC-funded piece?
The overall goal of this project was to come up with a quantitative way to assess large-scale land use shifts across the Midwest that are associated with biofuel production. We also looked at the impacts this could have on the critical aspects of our agro-ecosystems, such as the cycling of carbon, water, and nutrients. Within the context of the IWRC funding, we were particularly focused on ecosystem water use, such as determining how producing cellulosic bioenergy crops would alter stream flows and water quality of our rivers.
Would you talk about the models you used a little bit: what is IBIS, how do you determine model inputs, and how accurate are the results?
Because we are asking questions on such a large scale, and with numerous hypothetical scenarios, we had to use computer models to answer our research questions. To model the production of the crops we chose an ecosystem model called Agro-IBIS, which stands for the Integrated BIoSphere model – Agricultural version. We ran this model in conjunction with a stream flow and nutrient transport model called Terrestrial Hydrology Model with Biogeochemistry (THMB).
To conduct this research, we fed the ecosystem model (Agro-IBIS) climate data including temperature and precipitation. The model then simulated the uptake of carbon through photosynthesis, the loss of water through transpiration and evaporation, and a range of other outputs. We also input management information into Agro-IBIS, such as crop type and fertilization rates that are used with the climate data to determine how much carbon, nitrogen, and water are entering and leaving a given location (typically the size of a county). The results of Agro-IBIS are then given as inputs into THMB, which simulates the movement of water and nitrogen runoff from each location, through the various rivers and streams of the Mississippi River Basin, and eventually out to the Gulf of Mexico.
We compare the model results to any available observations we can find to insure the model is accurate. For the new cellulosic biofuel crops, information is limited, but we have been able to compare the model predictions for key components of the carbon, water, and nitrogen cycles for a few locations in Central Illinois. So far the models do a pretty good job simulating what we have seen in the field. Given the limited data, there are uncertainties when scaling from the well-measured areas to the whole region. We can increase the confidence in the model over larger spatial scales by modeling existing crops (corn, soy, and wheat), which we have much more information on, and determine how well the modeled data and measured data agree.
What were your major findings?
The primary question we were trying to address is: What impact would large-scale production of cellulosic feedstock in the Midwest have on water quality and quantity in the Mississippi River Basin? We know from observations that Miscanthus and Switchgrass, the two major leading candidate cellulosic feedstocks and our study focus, use more water than corn and soybean, but require less fertilizer to achieve high yields. When we expanded the study with the computer models we found that, as long as we kept production less than the current fraction levels (i.e. ~40% of corn grain goes to ethanol each year), there was a minimal impact on streamflow for most of the Mississippi River Basin. At the same time we saw that we could significantly improve water quality if we followed these production scenarios.
Did any of those findings surprise you?
We had a pretty good idea of what to expect, given that we knew the model was based on measurements, so we were not totally surprised by our findings. The extent that the cellulosic feedstock production has a small effect on stream flow yet a large effect on improving water quality, however, was unexpected.
What kind of implications do you see for agriculture in the Midwest based on your work?
We are aware that economics truly drive this, and any other, industry. Cellulosic feedstock production is not increasing rapidly, as was initially predicted, but our research will provide evidence for ecosystem services should this industry begin to expand.
What about implications for Illinois water resources? Considering the number of droughts Illinois has experienced recently, what kind of changes do you think would happen to water usage in Illinois agriculture if every farmer switched from corn to miscanthus or switchgrass?
We never really considered a scenario where all farmers make this transition, as this would not be practical. There is tremendous uncertainty on how land-cover changes could affect the climate, so there are very interesting questions that can be addressed with coupled ecosystem-climate models. Observational data from a variety of sites are currently being analyzed over the recent drought years by the Bernacchi Lab, and we will soon have a pretty good estimate of how these specific species responded to the drought, but the interactions with the climate would require much more research and improved model coupling.
What kind of response have you received as you’ve shared the results of your research? And where have you shared your results? Does being at a Land Grant school change your outreach strategy at all?
These results have been presented at a wide range of meetings, including the Tropical Maize/Energy Crop Field Day, the Illinois State Water Survey, the Illinois Water 2012 Conference, the Pan American Congress on Plants and Bioenergy, and at the American Geophysical Union annual meeting. The data has been published in a peer-reviewed journal Agricultural and Forest Meteorology and another manuscript is in preparation to be submitted to the Proceedings of the National Academies of Science. The research is generally well received, and most people are excited to see a study conducted at such a large scale and with direct implications to national policy. Being at a land grant university has made outreach a bit easier, given the excellent resource of U of I Extension.
Andy, how did you become interested in the role of biofuel crops in the hydrologic cycle?
This one is pretty simple, I was visiting a field site when I was an intern at the Illinois State Water Survey, during a tour of the SoyFACE research site at the University of Illinois. I had recently learned about techniques to measure plant water use in a course I took as an undergrad at Ohio State University, and when I saw how large Miscanthus grew in Illinois, my very first question to Carl (my future PhD supervisor) was “Wow, that’s big, but how much water does it use?” The rest is history.
We know you’ve defended your PhD and moved on to a post-doc over the last 13 months. Could you tell us a little about your plans for the future and how the IWRC-fellowship has helped you?
In the year or so since I graduated, I’ve been working as a postdoctoral research associate in the USDA Agricultural Research Service – Global Change and Photosynthesis Unit. On January 1st, 2014 I started as an Assistant Professor in the Department of Agronomy at Iowa State University. The experience of writing the proposal for the IWRC fellowship and the opportunities to present my research that the fellowship facilitated were really vital to advancing as a scientist. In addition, securing the fellowship illustrated my ability to get external funding, and I’m sure this was a key factor in the decision for the hiring committee at Iowa State.