Consolidated bioprocessing: a revolution in biofuels development
by Jeremy Fordham <jeremyfordham08@gmail.com>
In 1956 M. King Hubbert, a geoscientist working with the Shell research laboratory, developed a controversial theory of petroleum production that rocked the oil industry. The model, known today as the Hubbert Curve, was widely criticized at the time. In a nutshell it predicted that overall petroleum production in the U.S. would peak sometime between the mid-sixties and early seventies. Scientists and oil speculators thought he was crazy and dismissed his model as irrelevant and poorly constructed, especially because Hubbert was reluctant to publish the methods and equations behind his theory. Then, in late 1970, United States petroleum production actually did peak. A few years later the U.S. entered an energy crisis characterized by high gas prices and a frenetic rush to find new resources in places like Mexico and elsewhere.
Lots of people mistake the actual implications of Hubbert’s theory, which he later developed to predict a world petroleum production peak around the year 2000. Since the oil industry is fragile and dependent on things like wars and the shape of the global economy, this prediction is subject to much more variability and fluctuation than normal. What is certain, however, is that mass implementation of renewable energy systems is a viable alternative to consuming depletable petroleum-based resources. In the last couple decades, renewable energy initiatives have skyrocketed all around the world. Britain recently finished building the world’s largest offshore wind farm, which is a daring and trend-setting achievement for the country. All across the world academic programs have cropped up in attempt to instill interest in this now-blossoming realm. While online PhD programs have yet to come to full scale, places like Loughborough University in the U.K. are helping people gain extensive and professional expertise in this field from their own homes. Renewable energy is an infectious ideal that has effectively swept the entire world.
Biofuels are a particularly interesting form of green energy because they don’t require the construction of a secondary infrastructure for use. You can take biodiesel created from algae and put it directly in your gas tank, just like ethanol derived from corn-based biomass can be added directly to gasoline to improve its octane number substantially. Many companies have attempted to take advantage of everything from solar algal systems to gasification reactors that turn woody biomass (woodchips, etc.) into heat and fuel oil. Unfortunately, these reactor systems can cost upwards of $100 million, which is a lot of money to invest in something that hasn’t yet proven its power. Biofuel researchers are working hard to break through the barrier holding this industry back from macroscopic economic viability, and by far one of the most creative, and cost-effective, recent developments is consolidated bioprocessing.
Microorganisms are incredibly abundant and diverse, especially in their metabolic functionality. Consolidated bioprocessing takes advantage of this versatility. To obtain ethanol from a plant like sugarcane, a factory must grind the biomass, heat it up, feed it to microorganisms that can degrade cellulose into glucogenic byproducts and then feed those sugars to another set of microorganisms that can digest them to create ethanol. Cellulose is a crystalline molecule that is critical to a plant cell’s structure, so it is hard for microbes to break down naturally.
This is a very complicated and sensitive bioprocess that requires lots of temperature-controlled reactors and expensive grinding equipment. Consolidated bioprocessing, then takes this entire concept and minimizes the components needed to create ethanol from biomass, by genetically engineering one microorganism to both break down a plant’s cell wall (cellulose) and ferment its constituent sugars. This eliminates the need for an expensive grinder and for separate reactors that contain different microbes with different functions.
The genetics are approached in many interesting ways. A microorganism that is capable of degrading crystalline cellulose but incapable of fermenting its sugars, for instance, could be engineered with alternative metabolic pathways that allow it to use molecules like glucose, xylose and arabinose (components of cellulose) to create ethanol. This is typically done by introducing homologous genes into the target microbe’s DNA that cause it to develop novel fermentation pathways. Alternatively, a microbe that is widely used as a fermentative species (yeast, for instance) could be engineered with genes that give it the ability to break down plant material, which it cannot do naturally. This “super microorganism” would only need one reactor to function optimally in a biofuel production system.
The macroscopic consequences of this difficult genetic manipulation are astounding. Engineers can save millions of dollars by eliminating more than half of the reactors involved in biofuel processes if they create a microbe that can “do it all.” This drives down operating costs and ultimately makes the price tag on a biofuels plant that much more bearable. Companies like the Mascoma Corporation and Qteros (who actually discovered their own microbe in the wild) are working rigorously to develop technologies that rely on consolidated bioprocessing to make biofuel production worth the cost. They are making great progress.
The USDA is also actively involved in this research, so it will be interesting to see where things go in the next decade. Solar and wind technologies are still very expensive and bulky, so biofuels have an outstanding opportunity to outshine them as a resource whose implementation will be relatively transparent.
While nobody knows the exact date and time that petroleum will run out, the overarching point is that someday it will be gone, whether it’s 30 or 300 years from now. Biofuels have an opportunity to slow this depletion and are sure to come to the forefront of renewable energy in time, so be on the watch.
