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Elephant Grass and Prairie Switchgrass: Second Generation Biofuels to Power American Cars

Climate
Elephant Grass and Prairie Switchgrass: Second Generation Biofuels to Power American Cars

In tomorrow’s world, it won’t be just the corn on the great American plains that is as high as an elephant’s eye. It will be the elephant grass as well.

To deliver on U.S. promises to reduce fossil fuel use, American motorists in future will drive on miscanthus—as elephant grass is also known—and prairie switchgrass.

Elephant grass has a high biomass yield and grows rapidly to over three metres tall.

Photo credit: Tony Atkin / Wikimedia Commons

Researchers led by Evan DeLucia, professor of biology at the University of Illinois, report in a new journal, Nature Energy, that to exploit biofuels—which recycle carbon already in the atmosphere, and are therefore technically “carbon-neutral”—Americans will have to think again about how they manage the change away from fossil fuels.

Right now, the U.S. Environmental Protection Agency’s Renewable Fuel Standards foresee that by 2022 American motorists will start up their cars with 15 billion gallons (57 billion liters) of ethanol from corn. But this could be augmented by 16 billion gallons (60 billion litres) of biofuel derived from perennial grasses.

Energy Source

The switch to the prairie’s native switchgrass (Panicum virgatum) and Eurasian elephant grass (Miscanthus giganteus) will be necessary because there are problems with corn as a source of energy.

One is that, in an increasingly hungry world, it reduces the overall levels of food available. The second is that corn requires annual planting, fertilising and harvesting. Perennial grasses simply grow, and can be mown once a year.

So by turning over surplus land to swift-growing grasses, and at the same time reducing the levels of carbon dioxide released from cultivation, the U.S. could meet its target of a 7 percent reduction in its annual transportation emissions by 2022. If farmers went on gradually to switch from corn to the grasses, the reduction could get as high as 12 percent.

Professor DeLucia said: “Greenhouse gas savings from bioenergy have come under varying levels of attack, and this paper goes a long way to showing that, contrary to what some are saying, these savings can be potentially large if cellulosic biofuels from dedicated energy crops meet a large share of the mandate.

“This is a viable path forward to energy security, reducing greenhouse gases and providing a diversified crop portfolio for farmers in the U.S.”

The researchers used a climate model to test what would happen if land now being used to grow corn (Zea mays) for ethanol—currently, 40 percent of the corn harvest is used for biofuel—was switched to the two candidate grasses.

Store More Carbon

“Our results were staggering,” Professor DeLucia said. “Since both of those plants are perennial, you don’t till every year. The grasses also require less fertilizer, which is a source of nitrous oxide, and they store more carbon in the ground than corn.”

The switch could turn the U.S. Midwest from a net source of greenhouse gas emissions to a “sink” absorbing them. The study assumed that, rather than the most productive soil, the low-yielding land would be converted to grasses for biofuel.

It also factored in some of the other consequences: if the extra billions of gallons of fuel led to a fall in fuel prices, would Americans drive more, and eliminate the carbon savings? Even if that did happen, such a change has the potential to reduce U.S. emissions overall.

But growers have to be sure that energy policies will be consistent, according to the paper’s co-author, Madhu Khanna, professor in the Department of Agricultural and Consumer Economics at the University of Illinois.

“The moral of this whole story is that we need to find a way to expand the production of second generation biofuel crops and maybe even displace corn ethanol,” she said.

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A net-casting ogre-faced spider. CBG Photography Group, Centre for Biodiversity Genomics / CC BY-SA 3.0

Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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