Climate change is an urgent threat to societies around the world, driven by carbon dioxide emissions from fossil fuels such as oil. One of the most effective ways to curb emissions is to replace these energy sources with others that are carbon neutral or even carbon negative – that is, technologies that remove more carbon dioxide from the atmosphere than they put in.
Bioenergy, or energy derived from organic matter, usually plants, is an attractive option. The U.S. already derives 5 percent of transportation fuel from bioenergy, mostly corn. Even jet fuel could be produced from specially engineered crops, potentially balancing out 3 percent of the world’s human-made emissions.
Because the world population and its demand for food continues to rise, there might not be enough conventional farmland to grow crops for both food and bioenergy. One solution is to grow bioenergy crops on marginal land, which isn’t good enough to grow food. The logical conundrum: If this soil isn’t good, how can we grow anything on it that is reasonably productive?
Claire Benjamin/University of Illinois, CC BY-SA
Miscanthus, the candidate bioenergy crop
That is where Miscanthus x giganteus comes in. This species, also known as elephant grass, is incredibly productive – 59 percent more productive than corn in the midwestern U.S. It grows well on marginal soils with minimal fertilization. M. x giganteus is a perennial, meaning it stores nutrients in underground stems called rhizomes and uses them to regrow from one year to the next. These rhizomes, along with the plant’s roots, store atmospheric carbon dioxide underground and keep soil in place, preventing carbon dioxide loss from erosion. M. x giganteus may be able to sustain significant bioenergy production to replace fossil fuels, while being grown on marginal lands that do not compete with food crops.
M. x giganteus is a naturally occurring hybrid: Despite performing well in experimental trials, it was never designed to be a bioenergy crop. It is produced by crossing the Asian grasses Miscanthus sacchariflorus and Miscanthus sinensis, popular ornamental plants whose flowers form beautiful feathery plumes. M. x giganteus is sterile, and can propagate only clonally – that is, instead of seeds, a rhizome from a M. x giganteus plant can grow into a new, genetically identical plant. A single clone of this hybrid, now called “Illinois,” has been the focus of most trials of Miscanthus as a bioenergy crop in Europe and the U.S.
The incredible productivity and resilience of the “Illinois” clone, especially since the first U.S. agronomic trials at the University of Illinois in 2000, propelled M. x giganteus to prominence as a leading-candidate bioenergy crop. Yet the “Illinois” clone was produced by accident. What if parent species M. sacchariflorus and M. sinensis, growing in the wild in Asia, had even greater resilience, that could be used by plant scientists to breed M. x giganteus hybrids that perform even better than “Illinois”?
Miscanthus, mosquitoes and more cold tolerance
I am a plant physiologist at the University of Illinois at Urbana-Champaign. My job involves understanding how plants work in order to develop improved crops that can mitigate climate change, in this case by developing improved hybrids of M. x giganteus for bioenergy production. I teamed up with Professor Erik Sacks to study some of the plants he had recently collected during a trip to the eastern reaches of Siberia.
In the summer of 2016, Sacks’s team of fearless plant scientists, guided by two adventure ecotourism guides turned amateur botanists, braved the flooding and mosquitoes of eastern Siberia to gather one of the world’s largest collections of M. sacchariflorus plants. The team was interested in collecting plants that could withstand cold better than M. x giganteus “Illinois,” which struggles to photosynthesize, a process where plants use sunlight to capture carbon dioxide from the air and turn it into biomass, when temperatures drop below 50 degrees Fahrenheit.
Eastern Siberia is the coldest part of the world where Miscanthus grows. One species, M. sacchariflorus, was found growing in areas with a minimum October temperature as low as 26°F, compared to 41°F in central Illinois. Most of the region where plants were collected had a continental climate, with severe winters and big temperature swings in the spring and autumn, suggesting these plants can thrive under a wide range of temperatures.