Light Cue 23

Solar Sunday is my weekly roundup of renewable energy and energy efficiency news from around the web.

Bugs Are Getting Worked Out Of Bioethanol Production

f the biofuel known as bioethanol is to make a major contribution to our fuel supplies, then we may well require the assistance of some tiny insect helpers, says Michael Scharf, an assistant professor of entomology at the University of Florida, Gainesville.

In a review to be published in Biofuels, Bioproducts & Biorefining, Scharf and his colleague Aurélien Tartar describe how the enzymes produced by both termites and the micro-organisms that inhabit their gut – known as symbionts – could help to produce ethanol from non-edible plant material such as straw and wood.

“Through millions and millions of years of evolution, termites and their symbionts have acquired highly specialised enzymes that work together to efficiently convert wood and other plant materials into simple sugars,” says Scharf. “These enzymes are of the most value to bioethanol production.”

Current bioethanol production processes tend to use edible plant materials, such as starch from corn (maize) and sugar from sugar cane, which contain easily accessible sugar molecules that can be fermented to produce ethanol. However, using food crops to produce ethanol has proved highly controversial, with bioethanol being blamed for much of the recent rises in food prices.

The non-edible parts of many plants also contain a large number of sugar molecules, which could potentially be used to produce ethanol. But the problem is that these sugar molecules are far less accessible. This is because they’re locked up within a substance known as lignocellulose, which provides structural support for plant cell walls.

Breaking this substance up into its component sugar molecules is far from easy. One approach involves pretreating the lignocellulose by heating it in combination with acids or bases and then exposing the pretreated material to various enzymes. Another approach is very fine grinding followed by enzymatic treatment.

Termites, on the other hand, don’t seem to have too much trouble digesting wood and other lignocellulosic materials into their component sugars, as many homeowners can attest. The termite appears to favour the fine grinding approach in combination with its own unique set of enzymes. These enzymes are secreted by both termites and the symbionts that colonise their gut, and act on the lignocellulose that has been chewed to very small particle sizes by the termite.

Space Age Solar

Ben Bova, the president emeritus of the National Space Society, recently suggested an incredible solution to the world’s energy crisis. Instead of taking solar panels and sticking them on your roof, he wants to send photovoltaic arrays off into space and beam solar energy down to earth. Since they are constantly exposed to the sun, such solar power satellites could provide a continuous stream of 5-10 gigawatts of energy!

In a recent Washington Post article Mr. Bova explains that the technology is not as farfetched as one would think. We already know how to send materials into space, and we have built large superstructures in zero-gravity environments (think the space station), so perhaps building a giant solar collector in space is not entirely out of the question.

His proposal is to build and launch solar power satellites – large photovoltaic arrays that constantly convert sunlight into electricity and use microwaves to beam that energy back to earth-bound receiving stations. According to Mr Bova, a single one of these satellites would send enough energy to power all of California. Since one would need a large surface to collect all of this energy, the best locations for receiving stations are dry areas such as the Nevada Desert or the Sahara.

Although the costs involved are fairly astronomical, the technology exists today, and this is not the first space-bound solar proposal that we have seen. So, what do you think – should someone give it a try?