The Biofuel Potential of Elephant Grass
What’s a big fluffy-looking grass that could be one of the answers to dwindling fossil fuel supplies? The answer is Miscanthus – also known as elephant grass.
Elephant grass (Miscanthus × giganteus) has been getting a bit of interest from the biofuel boffins since as early as the 1980s. And it’s got a fair bit of promise. It’s not an oil-producing plant but it does make a good feedstock for ethanol.
Elephant grass is a perennial (plant it once and then it just keeps on going) that grows from rhizomes (that’s big fat roots). It puts out fresh shoots every spring, grows up to 3 metres high in summer. In the autumn, it starts to go to sleep, sending a lot of the nutrients (including nitrogen and carbon) underground to the soil and the roots (and also smothers a few weeds with the shed leaves). This leaves tall stems that are kind of like bamboo standing. These stems are harvested in late winter or early spring before the new leaves start poking up again, and it’s the stems that get used as an ethanol feedstock. Then the cycle begins again.
Now, there are a number of issues that have to be tackled when it comes to finding a good plant source of biofuel. Firstly, there’s the land issue. There’s only a certain amount of arable land in the world, and with the global population growing the way that it is, we’re going to need quite a lot of it to feed us all (we probably also need to do something about the amount of food that gets wasted every year, but that’s another story). Then come the issues with water: again, there’s only so much fresh water out there at any one time for people and animals and plants to use, even if the water cycle means that it all keeps circulating. And you’ve got pesticides: if a crop gets a lot of pests eating it, then farmers need to dump on the pesticides, which (a) takes up a lot of resources and (b) puts a whole lot of junk into the soil and water.
It’s an added bonus if a plant used as a biofuel feedstock is pretty easy-care. That way, it doesn’t mean that the farmers use heaps of diesel in the process of ploughing, sowing, harrowing, weeding, fertilising and harvesting. Plants that have other benefits also get big tick marks.
Stems of elephant grass ready for harvest at the end of winter.
So how does elephant grass stand up?
Elephant grass has a high yield per hectare. This means that for every acre of elephant grass planted, you get a maximum of 25 tons of biomass (depending on the exact variety) that converts to over 3000 gallons of ethanol – better figures than you get for corn grown for biofuel and heaps better than timber. It’s not a food crop for humans or for animals. This means that on one hand, it will take up land that could be used for growing food. On the other hand, it means that it won’t drive up the price of food, like corn grown for biofuel can. It needs a moderate amount of water, but it’s pretty undemanding regarding other inputs. Because it’s a perennial plant, it doesn’t need to be re-sown every year. It also smothers weeds and puts some organic material back into the soil, meaning that you don’t need pesticides and it cuts down on the amount of fertiliser needed for a good crop – although a wee bit of fertiliser will be needed for best results. All a farmer has to do, more or less, is stick it in, water it and harvest it at the right time.
And is there anything else that elephant grass is good for? It can be used as a substitute for coal in coal-fired power plants (one US plant breeder claims that 1 acre of elephant grass can power two typical US households for a year). The stems also get used for kitty litter, bedding for racehorses, paper and composites (eco-friendly plastic substitutes). Unfortunately, these aren’t by-products of the biofuel industry. However, the tall green stands does provide cover for wildlife during summer. It can also be used as an ornamental plant – although it’s a bit on the large side!
Elephant grass grows reasonably well in the more temperate parts of Australia. In fact, a close relative of M. × giganteus (Miscanthus sinensis – also known as zebra grass) is considered to be an invasive weed in Victoria and New South Wales. Let’s hope the powers that be don’t just spray it off but make the most of it! Elephant grass, however, is a hybrid, so it’s not likely to spread as invasively, as the seeds aren’t fertile.
Safe and happy driving,
Megan
Level 2, 9 Help Street
Paul says:
That was very interesting, thanks for sharing.
June 24th, 2015 at 6:19 pm
Rob Clark says:
This sounds like a perfect idea, especialy if some of the unused land, ie; swamp land on the outskirts of Tooradin could be used to grow the Elephant grass. That way would leave the usual arable land free for it’s normal use.
June 25th, 2015 at 6:24 pm