Poet's removal of crop residue from farmland in Iowa for use at its planned 25 million-gallon/year cellulosic ethanol plant causes no significant soil nutrient loss, Iowa State University, USDA researchers find
June 1, 2011
– Non-traditional stover baling keeps good cover on Emmetsburg, Iowa soil
POET's contracted biomass removal rates with area farmers are conservative and consistent with good soil management, updated site data gathered by Iowa State University and USDA researchers indicate.
Iowa State University has completed analysis on data from the third year of an ongoing study for POET near Emmetsburg, Iowa to monitor how soil health is affected when crop residue is removed. POET's planned 25 million-gallon-per-year cellulosic ethanol plant, dubbed "Project LIBERTY" will use corn cobs, leaves, husks and some stalk to produce renewable fuel.
The newest data confirms previous assertions that removing about 1 bone-dry ton per acre (which is about 25 percent of the area's above-ground crop residue) will not cause significant nutrient loss. In fact, corn yields continued to show no yield loss or moderate increases in fields with this rate of biomass removal.
"Based on this study, we conclude that 1½ to 2 tons/acre of corn stover can safely be harvested" from fields similar to those used in the study, according to the research summary prepared by Dr. Douglas L. Karlen with USDA-Agricultural Research Service and Dr. Stuart Birrell with Iowa State University. Appropriate removal rates will vary depending on how productive the soil is in a specific area.
The data also showed no significant difference in soil carbon after three years. That research will continue as well, including an analysis of deep core samples.
POET is committed to a conservative approach to biomass harvesting, Project LIBERTY Director Jim Sturdevant said.
"The data is our guide, as it should be for everyone looking at this new feedstock," he said. "We're contracting for fewer tons per acre to ensure good soil management even in years when yields are lower. Also, our farmers have moved away from traditional methods of stover removal: of chopping, raking, baling and leaving the field black."
Farmers harvesting for POET typically turn off the chopper on their combines and leave windrows behind during grain harvest. Farmers do not rake the biomass before the baler gathers it. Last fall, 85 farmers harvested 56,000 tons of biomass, and they are almost finished delivering it to Project LIBERTY's 22-acre stackyard. Those farmers are also developing conservation plans with the help of Natural Resources Conservation Service (NRCS).
Once operational, the plant will use approximately 300,000 tons of biomass annually. Construction is planned to begin later this year.
Dr. Karlen and Dr. Birrell will continue their work again this year. They stressed that farmers "know your land," and said routine soil testing and plant analysis are good practices for monitoring nutrients as part of good farm management.
"We're committed to working with researchers and farmers to make sure this is done correctly, and it looks like that is the case right now," POET CEO Jeff Broin said. "There is no model to follow in putting together a system to produce cellulosic ethanol, but we're committed to creating that model for the long-term benefit of the country."
"Renewable fuel requires healthy soil," Broin said. "We're glad to be working with quality research partners to ensure the soil around Emmetsburg remains that way."
Based on the three years of data gathered at the site, the researchers recommend farmers replace about 15 additional pounds of potassium per acre to fields where biomass harvesting has occurred at a rate similar to what POET contracts. No significant increase for nitrogen or phosphorus replacement compared to grain-only harvest is needed.
Removal of biomass also demonstrated no grain yield losses and often moderate grain yield improvements over the control plots. One theory to explain that phenomenon is that removing a small amount of cover helps the soil warm earlier in the spring, causing earlier corn plant emergence.
"We'll continue to monitor the soil through our on-going partnership with Iowa State and USDA, and we'll share that data with farmers," Sturdevant said. "We've learned a lot from the first three years of data and from the feedback from farmers. Results have been positive, but we're trying to be conservative as we keep learning."
"This is exciting," he said. "We're bringing a new way to produce ethanol to America."
A research summary provided by Dr. Karlen and Dr. Birrell is available at POET's website [link]. Photos of fields after biomass harvesting are also available at the site.
POET, the largest ethanol producer in the world, is a leader in biorefining through its efficient, vertically integrated approach to production. The 23-year-old company produces more than 1.7 billion gallons of ethanol and 10 billion pounds of high-protein animal feed annually from 27 production facilities nationwide. POET also operates a pilot-scale cellulosic ethanol plant, which uses corn cobs, leaves, husks and some stalk as feedstock, and will commercialize the process in Emmetsburg, Iowa. For more information, visit http://www.poet.com.