Renewable energy enthusiasm is at an all time high. Unfortunately, the logistics of the energy source most widespread in commercial deployment, ethanol, are not as green nor as economically sound as one might hope. The biofuel ethanol is currently produced from sugar from crops such as corn and sugarcane. The high price of gasoline has created a catch-22 situation in which people want to buy ethanol to save money on lower gas prices, but if they do so they will raise the price of food crops and have to pay more at the supermarket.
Worse yet, ethanol's net carbon output is stated in some studies to be worse overall than gasoline's, due to the extra carbon cost needed to harvest the sugar crop and drive the conversion. And the social situation is no rosier; a UN expert called biofuels "a crime against humanity" and has stated that they are contributing to starvation and war worldwide.
With all the challenge associated with the current less-than-savory state of biofuels, some researchers are rising to the occasion and considering how to fix the biofuel infrastructure. The journal Nature Review Genetics carries a large study in next month's edition, which explores in depth advances and possibilities that genetic engineering holds to help produce cellulosic ethanol.
Cellulose is an abundant plant sugar which makes up the cell walls of plants. It consists of long chains of individual glucose sugar molecules which could be converted to ethanol, but it is difficult to break these chains apart. If it was easy to break apart cellulose, it would open the door to mass production of ethanol from crop waste, yard waste, and other sources, such as the non-crop plant switchgrass, greatly raising the promise of the resource.
Current cellulosic efforts focus on harvesting cellulose digesting enzymes from fungi and bacteria. While this is one possible method, the study suggests that another more promising method would be to genetically engineering plants to store cellulose digesting enzymes within safe compartments within the cell. When the plant was initially processed these enzymes would be released and would start breaking down the cellulose.
Other suggestions in the study are genetically engineering non-food cellulose source crops such as switchgrass to be taller. Another idea is to add more cellulose mass to plants by duplicating genes for cellulose production catalyzing enzymes. Yet another possibility is to reduce the enzymes that catalyze cellulose cross-linkages to make the cellulose easier to digest.
Another salient document to the future of the ethanol industry was published by the Global Invasive Species Programme (GISP) this week. The GISP published a cautionary set of recommendations (PDF) about potential ethanol crop candidates. Since fast growth and endurance of a variety of climates are desirable characteristics for such a plant, it is unsurprising that GISP states that nearly all the candidates are invasive species, which could have the detrimental environmental effect of killing native plants and harming ecosystems. The exceptions, it states are food crops used for their cellulose, including wheat, peanuts, and soy
The GISP advocates risk assessments and cost/benefit analyses. They say that a certification system should be in place to ensure responsible agriculture. Finally, they suggest that when possible native species be used to produce the biofuel.
The AAAS journal Science published an editorial that is also pertinent to the future of biofuels. It discusses the bacteria that produce the cellulose-digesting enzymes. It says that other symbiotic bacteria could help to foster the growth of plants with useful chemical character. Further they could be used to sequester carbon. The key, the post concludes is to gain a better understanding of how the carbon cycle works in bacteria.
While ethanol certainly fairly deserves criticism for its current implementation, these new efforts promise a new responsible face for the ethanol industry. While they may take some time to be implemented, it is exciting to see the interest in the scientific community. The best part about these developments is if achieved, they would have the end effect of saving the consumer money, something the vast majority of consumers want.