This is another article that I have written for Our Green Earth but the web editor doesn’t seem to be checking his emails at the moment. I’ll be taking this post offline when (if) he adds it to the site so as not to have duplicate content on the web, but for the meantime, here you go…
The petrol, diesel and jet fuel that we use in today’s vehicles is made up of hydrocarbons – long chains of hydrogen and carbon molecules that when broken in the process of combustion, release energy. Energy is stored in the bonds of these molecules, so it follows that the longer the chain of the molecule – the more bonds there are – the more energy it will store and therefore release upon burning.
Getting biofuels such as bioethanol and biodiesel from plant-based feedstocks such as wheat, sugarcane, algae or even less conventional materials such as melons and old furniture, (see the articles “Algae As A Feedstock For Biodiesel Production” and “Watermelon Bioethanol Production”) is a relatively easy process and, indeed, biofuels of this type are becoming increasingly common and widespread.
Biofuels burn more cleanly than petrol and diesel and so are better for the environment because they only release the carbon dioxide that the plant itself used for photosynthesis. This is in contrast to fossil-derived fuels that, when burnt, unleash millions of year’s worth of stored carbon on our ecosystems.
A problem with bioethanol however, is that it is a very short hydrocarbon molecule. This means that, gallon for gallon, it does not release very much energy and so is unsuitable for our high energy-driven transport requirements. In fact, most of the bioethanol-powered vehicles on our streets run on a blend of ethanol and normal petrol – better for the environment, but only a little.
New research from the University of Wisconsin-Madison could have found a solution to this problem. Using a chemical called gamma-valerolactone (GVL), a derivative of the sugars found in biomass, they have worked out how to create jet fuel – exactly the same kind of jet fuel that is normally distilled from crude oil, but using a renewal source of agricultural waste instead (1, 2).
GVL is currently produced on a small commercial scale for its use as a component of perfumes (2). It can also act just as well as ethanol when used as a blending agent with petrol (1). This, however, does not solve the problem of creating a fuel that is man enough for our planes, trains and high-performance automobiles (3).
The Wisconsin-Madison team have developed a system whereby GVL can be decarboxylated and oligomerized (1). In layman’s terms, this means that the GVL molecule can have its oxygen molecules removed to leave just carbon and hydrogen, then these short-chain hydrocarbons can be joined together to form long chains – remember, the longer the chain, the greater the potential energy output when combusted.
Laboratory tests have proved highly successful and, what’s more, the conversion of GVL to jet fuel is relatively inexpensive. The equipment and catalyst materials required are nothing fancy and the yield of final product is high. Another benefit of this process is that the only waste product, carbon dioxide, is almost pure and can be harvested to feed into other chemical processes, unlike the impure emissions from fossil fuel-burning power stations that cannot be recycled (2).
The only pitfall in this seemingly wonder-process, is that GVL is expensive to make from the original plant feedstock (1). However, fuels derived from GVL have so far only been produced on a small scale and, the researchers have claimed, with investment and further research into developing the technology on a larger scale, an affordable way to mass produce high energy fuels could soon be realistically achieved (2).
1. Bond, JQ, Alonso, DM, Wang, D, West, RM, Dumesic, JA, Integrated catalytic conversion of gamma-valerolactone to liquid alkenes for transportation fuels, Science (327) 1110 – 1114, 26th February 2010
2. New process yields high-energy-density, plant-based transportation fuel, press release from the University of Wisconsin-Madison, 25th February 2010
3. Sanderson, S, From plant to power, Nature (461) 710 – 711, 8th October 2008