Toward More Efficient Biofuel Production
During World War II, in some environments soldier’s uniforms and tents suffered from “jungle rot,” consumed by a canvas-eating fungus. It is fungi like that, as well as other microbes, that are the object of intense study by scientists seeking to find more efficient ways to make biofuels.
Biofuels like ethanol and biodiesel can be made simply enough from a multitude of plants and organic materials. The problem is, the process isn’t very efficient. Depending on the feedstock used, producing fuel from these sources may consume more energy than it yields. Or it may release an excess of greenhouse gases. Or it may require growing crops for fuel instead of food.
To overcome these problems, biologists are looking for easier ways of breaking down the cellulose that makes up the bulk of the plant material on Earth.
Cellulose is tightly bound chains of sugar molecules, designed so plants can be rigid. It’s what keeps trees, corn, and almost all other plants that grow above ground standing upright rather than growing as formless puddles. Those sugar molecules can be fermented into ethanol, but only if the chains holding them together are first broken. Breaking those chains is easier said than done.
Heat is one option, but it doesn’t do a complete job, and it’s expensive; it takes energy to generate the heat.
Cellulose can be broken down with chemicals, but that complicates the process. Those chemicals will either have to be removed or will contaminate the end product, leading to hazardous emissions when the fuel is burned.
A cleaner but more difficult option is to use enzymes. This is where the canvas-eating fungus comes in. It turns out the fungus secreted an enzyme that broke down the cellulose in the canvas of the tents and uniform materials.
However, it’s difficult to overcome the natural recalcitrance of the cellulose to being disassembled. Even the enzymes of the canvas-eating fungus can only partially break the cellulose into sugars. Fortunately there are other microorganisms that also secrete cellulosomes, natural multi-enzyme complexes that disassemble the hemicellulose and lignin protecting the cellulose. Unfortunately, these too are only partially effective.
Thus, scientists are working hard to find ways to both increase the potency of the microbes and their enzymes, and to reduce the resiliency of plant’s cellulose. Of course, that could have unanticipated drawbacks.
Consider the potential for disaster if engineered microbes — super-efficient at breaking down cellulose — gained access to the wild and began attacking crops and trees, causing them to simply collapse where they grew. Or if the engineered strains of plants designed to be easily broken down and fermented inadvertently crossed with natural species in the wild, causing them to begin fermenting while they were still in the field.
Is this merely unfounded fear mongering by technophobes? Not really. Humans have a long and dark history of turning seemingly bright ideas into dismal failures.
Think about the rabbits introduced into Australia in the 18th century as a food source, and now considered one of the country’s most serious pests. Or the two million tires dumped in the ocean off Fort Lauderdale, Florida as the basis for a new coral reef, which instead killed marine life and damaged existing natural reefs. Or the drug Thalidomide, once used by pregnant women as an antiemetic to alleviate morning sickness, but soon found to cause terribly disfiguring birth defects.
This is not to say we shouldn’t pursue more efficient ways of producing biofuels, merely that we must be cautious. It is horror scenarios like this that scientists working on the biofuel conundrum must keep in mind. If they do, and if they can successfully — and safely — overcome the technical issues they face, the farmer’s field may soon replace the oil field as our primary source of fuel. Let’s just hope we don’t create more problems than we solve.