Sunday, December 4, 2011

The Future of Transportation

Scientists have engineered E. Coli to eat switchgrass and produce transportation fuels. These fuels can be used with the existing infrastructure:
Researchers with the U.S. Department of Energy (DOE)'s Joint BioEnergy Institute (JBEI) have engineered the first strains of Escherichia colibacteria that can digest switchgrass biomass and synthesize its sugars into all three of those transportation fuels. What's more, the microbes are able to do this without any help from enzyme additives.

"This work shows that we can reduce one of the most expensive parts of the biofuel production process, the addition of enzymes to depolymerize cellulose and hemicellulose into fermentable sugars," says Jay Keasling, CEO of JBEI and leader of this research. "This will enable us to reduce fuel production costs by consolidating two steps -- depolymerizing cellulose and hemicellulose into sugars, and fermenting the sugars into fuels -- into a single step or one pot operation."

Advanced biofuels made from the lignocellulosic biomass of non-food crops and agricultural waste are widely believed to represent the best source of renewable liquid transportation fuels. Unlike ethanol, which in this country is produced from corn starch, these advanced biofuels can replace gasoline on a gallon-for-gallon basis, and they can be used in today's engines and infrastructures. The biggest roadblock to an advanced biofuels highway is bringing the cost of producing these fuels down so that they are economically competitive.

Unlike the simple sugars in corn grain, the cellulose and hemicellulose in plant biomass are difficult to extract in part because they are embedded in a tough woody material called lignin. Once extracted, these complex sugars must first be converted or hydrolyzed into simple sugars and then synthesized into fuels. At JBEI, a DOE Bioenergy Research Center led by Berkeley Lab, one approach has been to pre-treat the biomass with an ionic liquid (molten salt) to dissolve it, then engineer a single microorganism that can both digest the dissolved biomass and produce hydrocarbons that have the properties of petrochemical fuels.

"Our goal has been to put as much chemistry as we can into microbes," Keasling says. "For advanced biofuels this requires a microbe with pathways for hydrocarbon production and the biomass-degrading capacity to secrete enzymes that efficiently hydrolyze cellulose and hemicellulose. We've now been able to engineer strains of Escherichia coli that can utilize both the cellulose and hemicellulose fractions of switchgrass that's been pre-treated with ionic liquids."
Producing biofuels from agricultural waste using engineered bacteria seems to be the most promising avenue of transportation fuels in the future. See this: Corn gene boosts fuels from switchgrass:

Many experts believe that advanced biofuels made from cellulosic biomass are the most promising alternative to petroleum-based liquid fuels for a renewable, clean, green, domestic source of transportation energy. Nature, however, does not make it easy. Unlike the starch sugars in grains, the complex polysaccharides in the cellulose of plant cell walls are locked within a tough woody material called lignin. For advanced biofuels to be economically competitive, scientists must find inexpensive ways to release these polysaccharides from their bindings and reduce them to fermentable sugars that can be synthesized into fuels.

An important step towards achieving this goal has been taken by researchers with the U.S. Department of Energy (DOE)'s Joint BioEnergy Institute (JBEI), a DOE Bioenergy Research Center led by the Lawrence Berkeley National Laboratory (Berkeley Lab).

A team of JBEI researchers, working with researchers at the U.S. Department of Agriculture's Agricultural Research Service (ARS), has demonstrated that introducing a maize (corn) gene into switchgrass, a highly touted potential feedstock for advanced biofuels, more than doubles (250 percent) the amount of starch in the plant's cell walls and makes it much easier to extract polysaccharides and convert them into fermentable sugars. The gene, a variant of the maize gene known as Corngrass1 (Cg1), holds the switchgrass in the juvenile phase of development, preventing it from advancing to the adult phase.

"We show that Cg1 switchgrass biomass is easier for enzymes to break down and also releases more glucose during saccharification," says Blake Simmons, a chemical engineer who heads JBEI's Deconstruction Division and was one of the principal investigators for this research. "Cg1 switchgrass contains decreased amounts of lignin and increased levels of glucose and other sugars compared with wild switchgrass, which enhances the plant's potential as a feedstock for advanced biofuels."

Lignocellulosic biomass is the most abundant organic material on earth. Studies have consistently shown that biofuels derived from lignocellulosic biomass could be produced in the United States in a sustainable fashion and could replace today's gasoline, diesel and jet fuels on a gallon-for-gallon basis. Unlike ethanol made from grains, such fuels could be used in today's engines and infrastructures and would be carbon-neutral, meaning the use of these fuels would not exacerbate global climate change. Among potential crop feedstocks for advanced biofuels, switchgrass offers a number of advantages. As a perennial grass that is both salt- and drought-tolerant, switchgrass can flourish on marginal cropland, does not compete with food crops, and requires little fertilization. A key to its use in biofuels is making it more digestible to fermentation microbes.
And this: New advanced biofuel identified as an alternative to diesel fuel

Researchers with the U.S Department of Energy (DOE)'s Joint BioEnergy Institute (JBEI) have identified a potential new advanced biofuel that could replace today's standard fuel for diesel engines but would be clean, green, renewable and produced in the United States.

Using the tools of synthetic biology, a JBEI research team engineered strains of two microbes, a bacteria and a yeast, to produce a precursor to bisabolane, a member of the terpene class of chemical compounds that are found in plants and used in fragrances and flavorings. Preliminary tests by the team showed that bisabolane's properties make it a promising biosynthetic alternative to Number 2 (D2) diesel fuel.
And this: Advance towards producing biofuels without stressing the global food supply:
Scientists in California are reporting use of a first-of-its-kind approach to craft genetically engineered microbes with the much-sought ability to transform switchgrass, corn cobs, and other organic materials into methyl halides — the raw material for making gasoline and a host of other commercially important products. The new bioprocess could help pave the way for producing biofuels from agricultural waste, easing concerns about stress on the global food supply from using corn and other food crops.
The problem with electric cars is that the extension cord would be inconveniently long. Electric cars need to store their energy on board with batteries. Batteries run down and need to be recharged, limiting the range:

...But a better battery doesn't seem to be in the offing anytime soon. As Fletcher explains, physics, politics, and the price of gasoline have always conspired against the improvement of battery technology. Fletcher's book is hopeful—he investigates a number of promising technologies that might theoretically challenge the dominance of fossil fuels. But many of them are a long way from fruition, and the history of failure in the battery industry doesn't inspire confidence. We might get a better battery someday, and if we do it will probably come from China, which has become the hub of advanced energy production. But don't hold your breath.

The fundamental problem with batteries is the existence of gasoline. Oil is cheap, abundant, and relatively easy to transport. Most importantly, it has a high "energy density"—meaning that it's phenomenally good at storing energy for its weight. Today's best lithium-ion batteries can hold about 200 watt-hours per kilogram—a measure of energy density—and they might theoretically be able to store about 400 watt-hours per kilogram. Gasoline has a density equivalent of around 13,000 watt-hours per kilogram.

The only reason electric cars might one day compete with cars that rely on internal combustion is that gasoline engines are highly inefficient; nearly all of the energy stored in gasoline is lost to heat. But gasoline makes up for that flaw with another advantage: When your car's out of gas, you can refill it in a few minutes. With today's electrical infrastructure, batteries need many hours to recharge. There's some hope that we might one day install fast-charging stations across the country, but the researchers Fletcher interviews point out that this is a daunting challenge. The battery in today's Tesla roadster needs about four hours to charge. If you wanted to charge that battery in 15 minutes, you'd need a 200-kilowatt electric substation feeding the charging station. "Your house takes 1 kilowatt," one expert tells Fletcher. "If you want to have something like a gasoline fuel station that is all electrical, you're talking about multimegawatts of power at that station. And I just don't see that happening."

Neither do I. So what's the answer? Fletcher's book ends with a look at the most far-out research in the battery world—the lithium-air battery. In this design, lithium and carbon combine with oxygen from the air to form a system with a staggering potential to store energy. In theory, the lithium-air battery could store 11,000 watt-hours per kilogram, which makes it, Fletcher says, "the best chance battery scientists have to beat gasoline." A lithium-air battery could allow a car to drive 500 miles before recharging. With that range, you wouldn't need a nationwide system of quick-charging stations. You could drive pretty much wherever you wanted all day, and then recharge your car at night.

But lithium-air is the cold fusion of the battery world—a would-be game-changer that has the unfortunate downside of being impossible to achieve (probably).
Better batteries will save the world. Too bad they're impossible to make (Slate).

In fact, batteries may not be needed at all, many feel that future electric cars will be powered by ultracapacitors:
Hang around the energy storage crowd long enough, and you’ll hear chatter about ultracapacitors. Tesla Motors chief executive Elon Musk has said he believes capacitors will even “supercede” batteries.

What is it that makes ultracapacitors such a promising technology? And if ultracapacitors are so great, why have they lost out to batteries, so far, as the energy storage device of choice for applications like electric cars and the power grid?

Ultracapacitors also have two metal plates, but they are coated with a sponge-like, porous material known as activated carbon. And they’re immersed in an electrolyte made of positive and negative ions dissolved in a solvent. One carbon-coated plate, or electrode, is positive, and the other is negative. During charging, ions from the electrolyte accumulate on the surface of each carbon-coated plate.

Unlike capacitors and ultracapacitors, batteries store energy in a chemical reaction. Ions are actually inserted into the atomic structure of an electrode (in an ultracap, the ions simply cling). This is an important distinction, because storing energy without chemical reactions allows ultracapacitors to charge and discharge much faster than batteries, Schindall explained. And because capacitors don’t suffer the wear and tear caused by chemical reactions, they can also last much longer.

Put simply, ultracapacitors are some of the best devices around for delivering a quick surge of power. Because an ultracapacitor stores energy in an electric field, rather than in a chemical reaction, it can survive hundreds of thousands more charge and discharge cycles than a battery can.

Despite offering a huge leap over regular capacitors, ultracaps still lag behind batteries when it comes to energy storage capacity. Ultracapacitors (which are also more expensive per energy unit than batteries), can store only about 5 percent of the energy of comparable lithium-ion batteries. And that, said Schindall, is a “fatal flaw” for many applications.

It would be technically possible, for example, to use ultracaps instead of lithium-ion batteries in cell phones, with some serious benefits: You would never have to replace the ultracapacitor, said Schindall, and the phone would recharge very quickly. But the phone wouldn’t stay charged for very long at all with today’s ultracapacitors—perhaps as little as 90 minutes, or five hours max, Schindall said.

Ultracapacitors are very effective, however, at accepting or delivering a sudden surge of energy, and that makes them a good partner for lithium-ion batteries, Schindall explained. In an electric car, for example, an ultracapacitor could provide the power needed for acceleration, while a battery provides range and recharges the ultracap between surges.

Think of it this way: The ultracapacitor is like a small bucket with a big spout. Water can flow in or out very fast, but there’s not very much of it. The battery is like a big bucket with a tiny spout. It can hold much more water, but it takes a long time to fill and drain it. The small bucket can provide a brief “power surge” (“lots of water” in this analogy), and then refill gradually from the big bucket, Schindall explained.
How ultracapacitors work and how they fall short.

It's important to note that the vast majority of urban dwellers drive less than 30 miles a day - easily in the range of electric cars. And electric cars can charge at night when there is less demand for electricity. Density also allows efficient intallation of recharging stations, and of course the infrastructure to deliver electricity already exists. There is nothing new about electric cars, they've been around ever since the electric motor was perfected. Here's an ad for an electric car from 1912:


So will we see liquid fuels made from cellulose-digesting bacteria? Or will we see electric cars? My feeling is both - electric cars will come to dominate cities and urban areas, while biofuels will become the standard for the transportation industry (you cannot move freight from coast-to-coast using electric semis).

Of course, the major downside to biofuels is we will be limited by the photosynthetic activity of the planet. In other words, we will need to live within the earth's solar budget, not the earth's massive savings account of undeground fossil fuels that we've been burning for a century. And there is other competition for land and water for the feedstock for fuels, even if we use switchgrass and agricultural waste. No matter what we do, there will be less fuel available. No technology can save us from that fact.

So here's what you're also going to see: higher fuel prices, denser cities, walkable neighborhoods, bicycling, public transportation, jitney, and car sharing programs. You're also going to see the economy shrinking to a size compatible with our energy resources.

On a side note, one of the major problems with renewable energy is storing it. Thermal energy storage is a promising way to do that:

http://www.scientificamerican.com/article.cfm?id=how-to-use-solar-energy-at-night

http://cleantechnica.com/2008/03/27/solar-thermal-electricity-can-it-replace-coal-gas-and-oil/

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.