
Please click here to download the Flash plugin


Eau de chip shop!

Smelly old chip fat with bits of floating gunk going for free…anyone? Well, you could pour it down the drain, throw it out, or use it in your car. Yes, use it in your car! Diesel cars can be converted to run on old vegetable oil for about £700. Diesel is well over a pound a litre and old chip fat is free. Not a bad deal eh!

Green and free, so what’s not to like?

Let’s see, fancy driving around in a car that smells like a chip shop? Or spending hours filtering out the gunky bits from litres of vegetable oil? But some people do manage to get past these problems (or maybe put up with them). In fact, vegetable oil is a potent ‘bio fuel’ and people have been using old chip fat as a greener substitute for fossil fuels for years.

Car powered by chip fat

Why don’t we use it all the time?

Chip fat, and all hydrocarbons, is made of hydrogen and carbon atoms. If we could get the hydrogen atoms out of these molecules we could use them as a really good clean fuel. This is because hydrogen contains lots of energy. React it with oxygen and that energy is released with a big bang and a little bit of water as a waste product. It is just about the perfect fuel.

The problem is that it would take a lot of energy to split the hydrogen away from the carbon because it would have to be heated to very high temperatures, over 800°C. Then you would have to mix it with steam in the presence of a metal catalyst. The catalyst is what causes it to split into hydrogen and carbon dioxide.

This method would use more energy than you can get out of the hydrogen to heat it in the first place. Also, you would get a lot of green house gas that is thought to be most responsible for global warming. So really, it’s not very green at all.

Bring on the cavalry, well Leeds University scientists

These researchers have come up with a way of doing splitting the hydrogen and carbon without using too much energy.

How could they do it?

The trick is to take a nickel catalyst and blast it with air. This causes it to react and forms nickel oxide. The process is exothermic, that means it gives out heat and lots of it! It can take the start temperature of 650°C and boost it to over 800°C. This may not sound like very much, but it’s a huge saving in energy. The less you have to pay to raise the temperature, the more cost effective the process will be. The chip fat and steam mixture now react to produce hydrogen and carbon dioxide in the usual way.

But the best trick is saved till last. A special ‘sorbent’ material is used to absorb the carbon dioxide. Sorbents have huge surface areas and a structure like a microscopic sieve to trap and hold unwanted molecules. This also helps sustain the reaction so that it will run indefinitely. Hey presto, cost effective hydrogen from a waste material.

The best part of all is that it looks as if the process will work just as well in tiny reactors that could be built into a filling station, or giant industrial plant that could cope with thousands of tonnes at time.

Refilling with oil

The big questions:

What are bio fuels?

Are bio fuels really ‘green’?

Why isn’t hydrogen used as fuel more often?