Rice University scientists and their colleagues have found that when growing corn crops for ethanol, more means less.
A new paper in today's online edition of the American Chemical Society's journal Environmental Science and Technology shows how farmers can save money on fertilizer while they improve their production of feedstock for ethanol and alleviate damage to the environment.
The research has implications for an industry that has grown dramatically in recent years to satisfy America's need for energy while trying to cut the nation's reliance on fossil fuels.
The team led by postdoctoral researcher Morgan Gallagher as part of her dissertation at Rice discovered that corn grain, one source of ethanol, and the stalks and leaves, the source of cellulosic ethanol, respond differently to nitrogen fertilization.
The researchers found that liberal use of nitrogen fertilizer to maximize grain yields from corn crops results in only marginally more usable cellulose from leaves and stems. And when the grain is used for food and the cellulose is processed for biofuel, pumping up the rate of nitrogen fertilization actually makes it more difficult to extract ethanol from corn leaves and stems.
This happens, they discovered, because surplus nitrogen fertilizer speeds up the biochemical pathway that produces lignin, a molecule that must be removed before cellulosic ethanol can be produced from corn stems and leaves.
The findings are an important next step in building a sustainable biofuel economy. Plants benefit from some nitrogen from fertilizer to produce the biomolecules they need to grow and function, said Carrie Masiello, an assistant professor of Earth science at Rice and Gallagher's adviser. But for many crops, a little is enough.
"We already know too much fertilizer is bad for the environment. Now we've shown that it's bad for biofuel crop quality too," Masiello said.
While farmers have a clear incentive to maximize grain yields, the research shows a path to even greater benefits when corn residues are harvested for cellulosic ethanol production, she said.
The study, conducted at and in collaboration with the National Science Foundation's W.K. Kellogg Biological Station at Michigan State University (MSU), showed that although feeding the plant more fertilizer increases the grain's cellulose content, grain yield quickly hits a plateau. "The kilograms of grain you get per hectare goes up pretty fast and peaks," Masiello said. At the same time, the researchers found only a modest increase in plant and stem cellulose, the basic component used to produce cellulosic ethanol.
"The implicit assumption has always been that the response of plant cellulose to fertilizer is going to be the same as the grain response, but we've showed this assumption may not always hold, at least for corn," Gallagher said.
Nitrogen fertilization encourages production of lignin within the plant, and without lignin, stalks won't stand. Lignin production comes at the expense of useful cellulose production. The researchers found that lignin yields from plant residue increased at nearly twice the rate as cellulose in response to nitrogen fertilization, and they said this implies "that residue feedstock quality declines as more nitrogen fertilizer is applied."
Lignin breaks down slowly via bacterial enzymes, and it is expensive to remove by chemical or mechanical processes that create a bottleneck in cellulosic ethanol production. "The ideal cellulosic ethanol crop has no lignin -- except you can't have a plant without it, because it would fall over. Plants need some lignin to maintain structure," said co-author Bill Hockaday, a former Rice postdoctoral researcher and now an assistant professor at Baylor University. "What we want is a low lignin-to-cellulose ratio."
Reducing fertilizer to the bare-bones minimum serves that purpose. "Morgan showed that if you look at kilograms of cellulose per hectare, yields don't increase at the same rate for the grain and the leaves and stems. There's really only a small amount of fertilizer needed if you're cropping strictly for cellulose," Masiello said.
Overfertilization also increases the decomposability of corn residue plowed back into the fields. This implies that soil carbon storage becomes less efficient -- another minus for the environment because storing additional carbon in soil can reduce the atmospheric concentration of carbon dioxide and help crops access soil water.
Issues associated with the runoff of nitrogen from fertilizer into streams and leaching into groundwater are common knowledge, Masiello said. She noted the well-established link between nitrogen fertilizer use in the Mississippi Valley and a "dead zone" -- defined as a lack of life-supporting oxygen -- in the Gulf of Mexico. Nitrate runoff and leaching into drinking water supplies has also been linked to a number of health problems, the researchers wrote.
Finally, Gallagher noted that improving the yield of feedstock for cellulosic ethanol leaves more corn for food. "There's a billion people who are malnourished, so it's ethically questionable to use corn grain for fuel rather than food," she said.
The researchers hope their methods can be transferred to other crops grown for ethanol. Gallagher, who recently earned her doctorate at Rice and is starting a joint postdoctoral stint between Masiello's lab and the NSF agricultural research station at Michigan State, plans to quantify the effects of nitrogen fertilization on switchgrass, which is growing in importance as a biofuel feedstock.
Co-authors of the paper include Sieglinde Snapp, an associate professor at MSU and a soils and cropping system ecologist at the W.K. Kellogg Biological Station; Claire McSwiney, a postdoctoral researcher at the Kellogg Biological Station; and Jeffrey Baldock, a researcher at Australia's Commonwealth Scientific and Industrial Research Organization.
The National Science Foundation and its Long-Term Ecological Research Program at the Kellogg Biological Station and MSU's AgBioResearch supported the research.
Read the abstract at http://pubs.acs.org/doi/abs/10.1021/es103252s
See a video of Masiello and Gallagher discussing their research here: http://www.youtube.com/watch?v=32BS7kpSeIs
A high-resolution photo of Masiello and Gallagher is available for download at: http://media.rice.edu/images/media/NewsRels/0217_ETHANOL.jpeg
CAPTION: Carrie Masiello, left, an assistant professor of Earth science at Rice University, and Morgan Gallagher, a postdoctoral researcher at Rice, found overfertilizing corn grown for ethanol is bad for the production of biofuel as well as the environment. (Credit: Jeff Fitlow/Rice University)
Located in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. A Tier One research university known for its "unconventional wisdom," Rice has schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and offers its 3,485 undergraduates and 2,275 graduate students a wide range of majors. Rice has the sixth-largest endowment per student among American private research universities and is rated No. 4 for "best value" among private universities by Kiplinger's Personal Finance. Its undergraduate student-to-faculty ratio is less than 6-to-1. With a residential college system that builds close-knit and diverse communities and collaborative culture, Rice has been ranked No. 1 for best quality of life multiple times by the Princeton Review.
David Ruth | EurekAlert!
Not of Divided Mind
19.01.2017 | Hertie-Institut für klinische Hirnforschung (HIH)
CRISPR meets single-cell sequencing in new screening method
19.01.2017 | CeMM Forschungszentrum für Molekulare Medizin der Österreichischen Akademie der Wissenschaften
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
19.01.2017 | Earth Sciences
19.01.2017 | Life Sciences
19.01.2017 | Physics and Astronomy