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Grass Used as Fuel Source

Transcript: Robyn Williams on The Science Show
ABC (Australia) – Broadcast: Sat 24 Sep 2005, 12:00am

Note: This is an old interview, but an interesting one nonetheless. Robyn and Dr Stephen Long (Department of Plant Biology & Crop Sciences, University of Illinois at Urbana-Champaign) discuss the use of Miscanthus as a fuel source when the project was in the early stages.

Robyn Williams: Well, we continue to burn coal in our power stations – but why not use grass instead? Professor Steve Long from Illinois is keen. He calculates that burning elephant grass could provide half his state’s needs – or more.

Steve Long: Well, if we assume 30 tons per hectare and we have had yields of 60 tons per hectare, then if 8% of the land was turned over to this crop we would generate enough biomass to generate about half of the state’s electricity use.

Robyn Williams: That includes of course, the great city of Chicago, lots of people.

Steve Long: Yes, exactly.

Robyn Williams: So it’s a very substantial contribution?

Steve Long: It is, yes.

Robyn Williams: Would this be able to grow in many other places – in Europe, in Asia, in Australia for example?

Steve Long: Well, actually Europe has been the pioneer with growing this and they have had trials from Sicily right up into southern Sweden, and in all of those locations they’ve achieved respectable yields. As you move into the Mediterranean climates, of course this would affect Australia in particular, then the yields go down because you can’t achieve 60 tons per hectare, even with a very efficient crop, without significant water input. But Australia may have significant areas of surplus land. I think for a country like Australia this type of crop is particularly promising.

Robyn Williams: And it’s called elephant grass; of course, there’s more than one elephant grass. What’s its technical name?

Steve Long: It’s technical name is Miscanthus and that’s why we’ve tended to use that as the common name as well, because as you say, there are other elephant grasses and indeed some of these are grown in pastures in Australia.

Robyn Williams: And what’s the advantage of it? Unlike coal you’re not making a net addition to the CO 2 in the atmosphere.

Steve Long: Yes, this is the major advantage in Kyoto terms and global change terms, that as the plant grows through the summer it’s removing carbon dioxide from the air to make its biomass. When you burn it in a power station you release that carbon dioxide back to the atmosphere. So electricity generation or heat generation is not adding carbon dioxide to the atmosphere; there’s no net effect on the atmosphere, whereas if you burn coal you’re taking the coal out of the ground, you’re burning it, and you’re adding carbon dioxide to the atmosphere.

Robyn Williams: How do you burn the grass. Do you dry it off and just pop it in the burner or what?

Steve Long: Yes, it is a perennial but it produces an annual crop of stems, rather like reeds or savannah grasslands. The grass grows up and then in the autumn it dies back. The farmer harvests it after it’s died back, so essentially he’s harvesting the dried above ground material, so that’s cut and baled. In most cases the idea is that the bales will be burnt in a power station.

Robyn Williams: Wouldn’t it be more sensible to grow a crop like sugar cane where you’ve got a product and then you burn what’s left over?

Steve Long: Well, that is another option but of course we’re thinking here about crops for temperate zones and the major advantage you have there is, during the autumn period as the plant dies back it’s moving its nutrients below ground. So that nitrogen is very energy expensive, you need to essentially combust a lot of fossil fuel to make your nitrogen even for some sugar cane plantations. So when it dies back and moves the nitrogen below ground you’re essentially saving the farmer having to put fertiliser on and making this more energy efficient.

Robyn Williams: I see, so the grass you use doesn’t deplete the soil itself?

Steve Long: Exactly, in fact what has been shown in Europe is it actually adds organic matter to the soil quite significantly.

Robyn Williams: So what’s been the take up of this? You said that it’s been pioneered in Europe, is it actually running a substantial amount of power stations yet?

Steve Long: There are two power plants in Britain which are now starting to use Miscanthus. Government has subsidised farmers to plant Miscanthus, so it is looking at meeting part of its Kyoto targets by burning Miscanthus and other biomass crops. Britain is actually probably in the lead at present on this. In the Midwest there’s a great deal of interest from farmers, obviously this is a crop they see requires less work than their existing crops, they’re very interested in finding a third crop, particularly one which might restore their soil organic matters. But really to get this underway it does need government intervention to encourage power plants to cover the initial costs for farmers to actually plant it. But beyond that we believe then it will be economically sustainable because if we look at those yields and the cost of fossil fuels in power plants then we can see that it could already be economically viable.

Robyn Williams: And it won’t be a worry about being a monoculture which then, if you like, runs wild in some way as we’ve seen so often before?

Steve Long: This particular Miscanthus is called Miscanthus giganteus. It’s actually a hybrid between two species, so it’s rather like crossing a donkey with a horse: what you get is strong but it’s completely sterile. I mean that is deliberate, because something which produces 60 tons of dry matter per hectare is clearly a very vigorous plant, so we don’t want that running wild and this is why the material we are using is sterile.

Robyn Williams: And you’re not going to tell me that the seed is sold by Monsanto or something?

Steve Long: Well, of course there is no seed. It’s actually planted from rhizomes and those rhizomes are available from a number of sources in the public domain.



Presenter: Robyn Williams / Producer: Polly Rickard / Producer: David Fisher