Sunday, September 30, 2012

Miscanthus for fuel?






Species name: Miscanthus sinensis

Common name: Chinese silver grass, Eulalia grass, Suzuki grass

Location: Ontario

As you can probably guess, this species of ornamental grass is native to Asia (China, Korea, Japan and Taiwan). It is a very popular ornamental grass species in North America, if not the most popular. There are about 15 different varieties that are widely grown with varying selected characteristics; this variety (along with a couple of others) has purple flower bracts. Another variety that I've previously blogged about is the infamous zebra grass, which you can read all about HERE.

I'm actually surprised at how many people believe that grasses don't have flowers, just because they don't have a structure that you would traditionally believe to be a flower. Any plant that produces a fruit must have a flower (but not every plant that produces a seed; pine trees, for example, produce seeds but no flowers. Instead the seeds are produced in a cone), and the fruit of a grass has a special name called a caryopsis. The caryopsis of any edible grass species is what we eat: the oatmeal you have for breakfast is the oat caryopsis, the grain that is ground to make flour for your morning toast is the wheat caryopsis, and the rice that you cook for your stir-fry is the rice caryopsis. As a general rule, any flower that's not overly flashy is probably pollinated by wind, since they make no effort to attract insects (through scent, colour, mimicry, etc.).

Miscanthus grasses are very successful reproducers in temperate ecosystems. They produce a huge number of seeds, and can spread through the soil via underground rhizomes. Recently, the suggestion has been made that perhaps they would make a good biofuel alternative compared to corn, since we eat corn and we don't eat Miscanthus. Instead, we could use corn for food (both for us and for livestock), and make fuel out of Miscanthus. A good idea in theory, but the problem is that we make bioethanol currently out of actual corn fruit (the corn caryopsis!) which is full of sugar and easily fermentable by yeast. We do not make bioethanol from corn husks or the green parts of the plant. This would involve turning plant cellulose into sugar, then the sugar into ethanol. Completely possible, but incredibly expensive and slow. The same would have to happen with Miscanthus; this makes the process currently economically a moot point. Any benefit we would get from growing Miscanthus instead of corn would be outweighed by the obscene price it would cost to build cellulose reactors. Until we can find an economically viable way to turn cellulose into sugar, producing bioethanol will always be a very expensive process. Expensive because corn is expensive to grow (unlike Miscanthus which grows like a weed with no chemical or labor inputs) but also because we're diverting perfectly edible food out of the food production chain.