Last week’s topic was why corn ethanol is an environmental loser.

But are all biofuels losers? No. Some can be winners. One of those is called cellulosic ethanol.

What Is Cellulosic Ethanol?

All ethanol — whether it is corn or cellulosic — is the same chemical compound: C2H5OH. You might recall from elementary chemistry courses that the “OH” group at the end of the formula indicates that the compound is an “alcohol.” Alcohols can have varying numbers of carbon atoms. Alcohol with two carbon atoms is called “ethanol.” The other alcohols are generally too toxic to be ingested, and thus ethanol has been the libation of choice down through the ages. (Ethanol used as fuel is rendered nonpotable.)

So corn ethanol and cellulosic ethanol don’t signify different types of ethanol, but rather the different material (or feedstocks) used to produce them.

Why Cellulosic Ethanol Can Be an Environmental Winner

Corn ethanol is produced from kernels — actually only a small part of the corn kernels — the sugars and starches. Herein lies one of the limitations of corn ethanol. You see, sugars and starches comprise a tiny fraction of the corn plant’s mass — about 2-15%. Because only a small fraction of a plant is used to make corn ethanol, the amount you can produce is limited.

Cellulosic ethanol is a different story. Most of the dry biomass — as much as 80% — is typically made up of cellulosic material — the stuff that makes the plant sturdy. So you can make a lot of ethanol using a plant’s cellulose instead of its sugars and starches. (By the way, even if the cellulosic material comes from corn, we still call it “cellulosic ethanol.” Corn ethanol is made solely from the sugars and starches of the corn kernel.)

The Major Advantage of Cellulosic Ethanol

Our guts are unable to digest cellulose, so we typically throw away that part of crops. A lot of it is left on the field or disposed of as agricultural waste. For corn, the cellulosic material includes the corn stover — the leaves and stalk — and the cob.

Remember what made corn ethanol such an environmental negative? A main reason is that it requires that land being used to grow food (or left as forests or grassland) be converted to growing an energy crop. And that leads to lots of global warming pollution.

This is not a problem for cellulosic ethanol — we can simply use the agricultural waste from food crops to make the ethanol and thereby avoid all those emissions.

Why We Can’t Fill Our Tanks With the Cellulosic Stuff … Yet

Unfortunately, right now, producing cellulosic ethanol on an industrial scale is too expensive. Unlike converting a plant’s sugars and starches to corn ethanol, making cellulosic ethanol requires that we first break down the cellulosic material. But because this material is what makes a plant sturdy, the atoms in these compounds are strongly bonded together and that makes them hard to break apart. The processes we have available today to do this are too expensive to make cellulosic ethanol commercially competitive.

But that will likely change. Scientists and engineers are working to make a commercially viable form of cellulosic ethanol. Some are developing new chemical processes; others are trying to genetically engineer new microbes that can “ferment” cellulose into ethanol like normal microbes that ferment sugars into ethanol. (The U.S.Department of Energy is helping fund six biorefineries.)

Cellulosic Ethanol Could Help Cut U.S. Global Warming Pollution

By my own estimates, agricultural and forest wastes could supply as much as 35 billion gallons of ethanol per year, saving up to 76 megatons of global warming emissions per year. (These results are somewhat larger than but consistent with other recent estimates (e.g., see Smith et al. 2004).) Such savings would cut a little less than 5% of all our heat-trapping pollution and about 15% of the emissions from the transportation sector.

By mid-century, cellulosic ethanol could supply as much as 86 billion gallons of ethanol, saving a little more than 180 megatons of global warming pollution per year — or almost 12% of America’s total global warming pollution and about 35% of the emissions from the transportation sector.

These are significant numbers. But to reach such levels we would need to grow bioenergy crops such as switch grass. Such cultivation, in turn, would require converting lands for this purpose, and that could raise some of the problems discussed in last week’s post.

The Bottom Line of Biofuels: There Are Winners and Losers

The saying “waste not, want not” applies to biofuels. The best biofuels are made from agricultural or forests wastes or from plants cultivated on degraded or marginal lands. The product from such feedstocks — cellulosic ethanol — is where we should be directing our entrepreneurial energies.

Read more about Dr. Bill Chameides, Dean of the Nicholas School of the Environment and Earth Sciences at Duke University.

See also:

CleanTechnica: Gene from Cow’s Stomach Engineered to Create More Affordable Biofuel

Gas 2.0: Mascoma Update — Cellulosic Ethanol Company Adds $10 Million From Marathon Oil

CleanTechnica: First Sustainable Ethanol to Mass Market?

Who doesn’t want to be green? But beware of automobile ads claiming environmental benefits from home-grown ethanol. Almost all U.S. ethanol comes from corn and, as a fuel, corn just isn’t as “amaizing” as they say.

“What if we could live green by going yellow?” one TV spot asks. “What if we could lower greenhouse gas emissions,” it continues, promisingly, “with a fuel that grew back every year?” Sounds great doesn’t it? Sorry folks, it’s just not so.

With corn ethanol, we are barking up the wrong stalk. This so-called yellow fuel is not green and the rush to it is misguided. The negatives of turning corn into fuel far outweigh the positives. First a little background.

A short history of ethanol

Ethanol has been around for a long time. Some of the earliest forms of life on Earth — anaerobic bacteria — used fermentation to produce ethanol and in the process extracted energy to drive their metabolic functions. In prehistoric times humans fermented grains and other biomass to make ethanol. Most of you have encountered ethanol in your lives — in beer, or wine, or the harder stuff. Ethanol is simply alcohol.

Using ethanol as a fuel dates back to the nineteenth century. It powered some of the earliest automobiles, including Henry Ford’s first car, the Quadricycle. Interest in reviving and expanding the usage of ethanol in cars today has grown, in part, because of its perceived climate benefit.

When we burn fossil fuel, excess carbon dioxide (CO₂), the chief global warming pollutant, is released to the atmosphere. This, at least in principle, should not be the case for ethanol or other biofuels (fuels produced from plants and wastes). When ethanol is burned, its carbon is converted to CO₂, just as in fossil fuels. But because the carbon in biofuels is pulled directly from the atmosphere via photosynthesis, it would seem that burning ethanol does not, in and of itself, represent a net source of new CO₂ to the atmosphere. (See the Department of Energy’s diagram below.)

As it turns out, it’s not that simple.

Why ethanol is not effective at fighting global warming

To get the whole picture you have to consider ethanol’s entire life cycle — the energy inputs and global warming pollution arising from every step in the production process, such as:

• cultivating and harvesting the crop,
• refining the crop to ethanol, and
• its transportation to market.

Corn is a particularly hungry crop — it requires lots of water and nitrogen fertilizers. The application of fertilizers creates nitrous oxide. Though it’s called laughing gas in the dentist’s office, in the atmosphere it is no laughing matter — nitrous oxide is about 120 times more potent than CO₂ at trapping heat.

As you can start to see, corn ethanol is ineffective at fighting global warming. A research team from Princeton University led by Tim Searchinger pointed out an obvious but little appreciated fact about biofuels in a recent study. Growing crops for fuel requires cropland dedicated to that purpose. That can create a market imbalance.

For example, the seemingly simple decision to grow corn instead of soybeans creates a demand for soybeans that can only be met by someone else adding cropland to grow soybeans. Typically this entails destroying important rainforests or grasslands. This transformation of land spews huge reservoirs of carbon stored in that land into the atmosphere in the form of CO₂, leading to further global warming. It is mind-boggling but probably true: U.S. farmers growing more corn drives the destruction of tropical rainforests in Brazil as more land is converted to soybeans. Now that’s a global economy.

The Searchinger team’s results suggest that when land-use changes are factored into the equation any possible climate benefit from corn ethanol is canceled out. Searchinger’s models stunningly show that it would take 167 years of continuous corn ethanol production before it would begin to switch from a climate loser to a climate helper. That’s way too long to wait with global warming bearing down on us.

So, for the huge environmental price of growing corn for ethanol, what do we get? An increase in the very emissions we need to reduce — the precise opposite of what is needed.

The silver lining of biofuels: Degraded or abandoned land and waste

While ads might encourage you to go green by going yellow, I recommend caution. Given the present source of ethanol in the U.S., it is a bad environmental bet. Going yellow isn’t easy either. Sure you can buy an E85 car (one that runs on a mix of 85% ethanol and 15% gasoline). The car companies would love you to because they get a break from the federal government on meeting national fuel economy standards. But try filling your new car with ethanol. As of January 2007, there were only about 1,100 E85 pumps in the U.S. My own take on this is that we could accomplish a lot more, a lot faster by zeroing in on fuel economy.

So that’s the bad news about corn ethanol. But there is a bright spot on the biofuels landscape; it involves using biomass waste and growing feedstocks on land that stores very little carbon. We’ll discuss these solutions in our next post. Stay tuned.

Read more about Dr. Bill Chameides, Dean of the Nicholas School of the Environment and Earth Sciences at Duke University.

See also:

Green Options: The Big Dark Cloud in the Ethanol Silver Lining

CleanTechnica: First Sustainable Ethanol to Mass Market?

Gas 2.0: First Cellulosic Ethanol Plant Goes Online, Makes Fuel from Wood Waste

Everyone knows we need green energy to fight global warming. But there’s another big reason to tap renewable power sources –- not enough water.

Large swaths of the Southwest and Southeast are in the throes of debilitating droughts. North Texas and Oklahoma’s recent dry spell dragged on from 2003 to the spring of 2007 (more on U.S. droughts). Droughts have even wiped out entire civilizations like the Anasazi (see Jared Diamond’s Collapse and Eugene Linden‘s Winds of Change).

But today’s water problems are far more profound than those of the Anasazi. The huge quantities we use — unprecedented in human history — make us more vulnerable to drought. Our water woes stem from an ever-increasing demand for water to slake the thirsts of a growing population on the one hand and to irrigate crops to feed that same population on the other.

Few people appreciate that yet another sector is clamoring for more water — the power industry. Fortunately we have the technology to wean this one from our dwindling supplies.

Another water hog: Conventional power plants

Have you noticed that power plants tend to be located near rivers, lakes or oceans? Do you know why? Easy, they need lots and lots of water.

Conventional and nuclear power plants, like the coal-fired plant pictured here on Lake Erie, are usually located by a lake or river because they need lots of water to operate. NREL/David Parsons

Coal-burning, natural gas-fired and nuclear power plants (which together produce about 90% of the country’s power) all generate electricity through a thermal process. They burn fossil fuels or split atoms to generate heat to boil water. The resulting pressurized steam turns a turbine that drives a generator that produces electricity.

It’s a process that produces lots of waste heat, which must be dissipated to keep the plant from overheating. So in addition to the source of water needed to make the steam (usually the nearby river or lake), even more water, generally much more than that required to make the steam, is needed to cool things down.

Because water is so integral to conventional and nuclear power production, strained water supplies put energy production at risk. A case in point is the Corette Power Plant in Billings, Montana, which siphons water daily from the Yellowstone River to produce electricity. The plant needs the river flow to be above 1,500 cubic feet per second to stay online. A recent dip below this level prompted a shutdown.

Unfortunately, this is not anomalous. Reduced water supplies are wreaking havoc across the country, fueling debate and water wars. A list of troubles includes:

• Florida’s Polk County trying to generate electricity without drying up wells,
• the decade-long fight between Alabama, Florida, and Georgia over who gets to draw how much water when (see this recent AP report and CNN video) and
• the receding waters of the once majestic Rio Grande, which failed to reach the Gulf of Mexico during much of 2001 and 2002.

Prognosis: Global warming means less water

Predicting the precise impacts of global warming is difficult, but by almost all indications things are not going to be pleasant. More specifically, there is a strong scientific consensus that water will be a big casualty of climate change. Higher temperatures will cause soils to dry out faster, making us more prone to long stretches of drought.

If this comes to pass, it could devastate our water system as increasing demands compete for a shrinking supply. Even without droughts, a warmer world will stress conventional power plant operations. The water used for cooling plants, which must be returned to its source after cooling, cannot be so hot that it undermines the river’s or lake’s ecosystem.

Severe heat waves can render cooling systems inoperable and cause shutdowns of power plants at the very time when demand for electricity is often the highest. During the 2007 heat wave, for instance, the Tennessee Valley Authority had to shut down a nuclear reactor because of high temperatures in the Tennessee River. Similar episodes have occurred in Europe.

We’re all too familiar with power outages and brownouts during hot spells, when the power grid is stressed to capacity. Global warming could make these events commonplace.

Among existing solutions, green power is the most potent

But it does not have to be that way. Weaning our power system off water would make it less prone to disruptions from shortages and rising temperatures while leaving more water available for municipal and agricultural needs.

Photovoltaic power plants, like this SunEdison plant in Colorado, draw very little water to generate electricity. As the world continues to wrangle over dwindling water supplies, green power could be a powerful solution. NREL/Steve Wilcox

A small number of tweaks to our current system is helping staunch the slowly evolving water crisis, but more needs to be done. Newer plants are being designed to use less water. Unfortunately, such efficiency doesn’t help the hundreds of old plants supplying much of our power. Alternative cooling methods are also being pursued, with several plants using dry or air cooling. But while such technology exists, a scant 600 plants worldwide use it.

Renewable energy offers a wide window of hope. Green power sources like wind and solar photovoltaics require tiny amounts of water. While such green solutions comprise only about three percent of our electricity, this could change and almost certainly must if we are to meet rising demands for drinking water and irrigation in a warming world.

Some say that green energy won’t be able to provide a significant portion of our electricity needs. But solving big problems usually requires thinking out of the box. Now I am just a dean, albeit at a great university, so what do I know about business, you might ask? I certainly wouldn’t suggest taking investment advice from me, but my guess is that the time is ripe for investing in green power. And high time it is.

Read more about Dr. Bill Chameides, Dean of the Nicholas School of the Environment.