The Biofuel Future: Scientists Seek Ways to Make Green Energy Pay Off
Ehrenberg, Rachel, Science News
Biofuels are liquid energy Version 2.0. Unlike their fossil fuel counterparts--the cadaverous remains of plants that died hundreds of millions of years ago--biofuels come from vegetation grown in the here and now. So they should offer a carbon-neutral energy source: Plants that become biofuels ideally consume more carbon dioxide during photosynthesis than they emit when processed and burned for power. Biofuels make fossil fuels seem so last century, so quaintly carboniferous.
And these new liquid fuels promise more than just carbon correctness. They offer a renewable home-grown energy source, reducing the need for foreign oil. They present ways to heal an agricultural landscape hobbled by intensive fertilizer use. Biofuels could even help clean waterways, reduce air pollution, enhance wildlife habitats and increase biodiversity.
Yet in many respects, biofuels are in their beta version. For any of a number of promising feedstocks--the raw materials from which biofuels are made--there are logistics to be worked out, such as how to best shred the original material and ship the finished product. There is also lab work--for example, refining the processes for busting apart plant cell walls to release the useful sugars inside. And there is math. A lot of math.
The only way that biofuels wilt add up is if they produce more energy than it takes to make them. Yet, depending on the crops and the logistics of production, some analyses suggest that it may take more energy to make these fuels than they will provide. And if growing biofuels creates the same environmental problems that plague much of large-scale agriculture, then air and water quality might not really improve. Prized ecosystems such as rain forests, wetlands and savannas could be destroyed to grow crops. Biofuels done badly, scientists say, could go very, very wrong.
"Business as usual writ larger is not an environmentally welcome outcome." states a biofuels policy paper authored by more than 20 scientists and published in Science last October.
Many scientists have expressed concern that political support for the biofuels industry has outpaced rigorous analyses of the fuels' potential impacts. Others see this notion as manure. Research needed to resolve that disagreement is now underway, as scientists in industry, national labs and universities across the country are assessing every aspect of these fuels, from field to tailpipe.
Researchers are growing crops, evaluating yields and comparing harvesting techniques. Computer models are providing stats on each crop's effect on environmental factors such as soil nutrients and erosion. The plant cell wall is under attack from several angles. And chemists and microbiologists are cajoling an expanding menagerie of microorganisms into producing higher fuel yields.
Ideally, high biofuel yields come with minimal environmental baggage and maximum efficiency at every step. The raw materials for these fuels run the gamut from corn to municipal waste to algae, and each has its own benefits and headaches. To make fuels, researchers must first process the raw material to create fermentable sugars or a crude oil-like liquid. Further refinement yields fuels such as ethanol, butanol, jet fuel or biodiesel.
In some cases, such as algae-based biodiesel, the technologies are far from mature. Squeezing ethanol from crops such as corn, on the other hand, uses a technology as old as whiskey. An infrastructure already exists for growing and moving grain, and distillation and fermentation techniques work at large scales.
But grain-based fuels raise several environmental issues, such as emissions of the potent greenhouse gas nitrous oxide from heavy fertilizer use. So, many scientists see corn ethanol as a bridging technology for use until the next-generation feedstocks fulfill biofuels' real promise. Nonfood plants rich in cellulose or even residual waste diverted from landfills may define the biofuel future. …