You probably have heard about ethanol and biodiesel, liquid fuels made from plants rather than petroleum. They use a renewable resource, and burning them doesn't contribute to global warming. But can you make gasoline directly from plants? As we hear from VOA's Art Chimes, scientists are learning how to do just that.
Some promising research programs suggest several ways to get gasoline out of plant material, according to William Schultz, with the National Science Foundation and the University of Michigan.
"What we are going to do is change a biofuel, such as poplar, switchgrass, corn stover (which is just the part of the corn we don't normally eat) and others, and by one of three processes – gasification, pyrolysis, or deconstruction – produce precursors to green gasoline."
Those "precursors" are chemical molecules similar to what is found in crude oil, molecules that can be refined to produce gasoline.
Schultz mentioned that there are at least three different ways to get from plants to gasoline. Gasification is the oldest, and has been used to convert coal to gasoline, but it is expensive and not very efficient.
Pyrolysis uses heat and chemical catalysts to promote the conversion of plants to gasoline. It is efficient and can even use waste paper as its raw material, but so far can only produce some components of gas.
A third process uses sugars, which can be easily derived from plants. It is being developed at a company called Virent Energy Systems. Company founder Randy Cortright says their process produces gasoline that's actually better than what you can buy at a service station.
"We did an analysis of this, of our green gasoline versus just standard unleaded gasoline we got at the gasoline station across the street. We have the same components in there. In fact, it's actually got a higher octane and some preferable blending component that you can utilize."
Cortwright says Virent's plant-based process can also produce chemicals that can be used to make plastics and pharmaceuticals, just like petroleum. It can also produce jet fuel, noting that ethanol is a poor choice for aviation fuel since a liter of ethanol packs less energy than a liter of gas.
"You don't have the energy content there," Cortwright explained. "While you can burn ethanol in your automobile, you would not take ethanol and put it on an airplane because it has a lower energy content. And ideal fuel right now is a hydrocarbon fuel, and what we're looking at is, the hydrocarbon doesn't have to come from petroleum. It can come from biomass, and that's what we're doing with our process."
For its briefing on green gasoline, the National Science Foundation decorated a meeting room with some of the plants that might fuel the 21st century energy economy.
"If you look at some of these plants around here, what we're trying to do is take the non-edible portion of the plants," said University of Massachusetts chemical engineering professor George Huber. "This is the fastest [growing] and most abundant form of plant material, and produce green gasoline, green diesel, and green jet fuel.
Huber pointed out that it's not enough just to turn plant biomass into gasoline, you have to do it efficiently and economically to compete with petroleum.
"Making a fuel – it's a commodity. You have to have a very highly optimized and integrated process to make a profit. You're competing against petroleum oil that's been around for over 100 years, and the petroleum industry has developed and they've learned how to economically refine crude oil. Now we need to learn how to economically refine biomass resources."
Huber said one factor favoring biomass-based gasoline is that the chemical production process should be quicker than the biological process used to make ethanol from similar raw materials.
Like gasoline made from crude oil, burning green gasoline produces carbon dioxide, a greenhouse gas. But there's virtually no net impact on climate because the CO2 released comes from CO2 absorbed from the atmosphere when the plant was growing.
Although green gasoline is still in the research stage, William Schultz of the National Science Foundation pointed out that it is building on technologies that have been around for a long time.
"Many of the processes that we're considering have been around for a century. I guess it just hadn't been thought that we could do the same things with switchgrass as has been done with coal 50-100 years ago. Making it into liquid fuels is more of a challenging process, and I think we're really close, and I think that everyone who is involved in this sees how close we are. So it's not a technology that's 20 years away. I think we think it's 5-10 years away."
And one more thing: Schultz points out that while the chemical process for making green gasoline still has a long way to go, so does the breeding of plants specifically designed to be turned into fuel. Breeding has improved wheat, corn, and other crops over thousands of years. Improvements can also be expected in the undomesticated plants that would go into biofuels.
Large, industrial facilities may one day be making gasoline, jet fuel, and maybe even plastics and medicines from plants. And smaller facilities might end up right where biomass is grown.
a farm that produces primarily food crops, just its waste product might be
enough to produce more energy than they need. Perhaps you could do enough
energy from the waste products from the food production that you could make a
farm energy-self sufficient, even if it's not a biofeedstock energy
producer," added William Schultz of the National Science Foundation, which
is funding research on green gasoline.