Coal is an abundant and relatively inexpensive energy resource that is available almost everywhere in the world. It is essentially wood that's been cooked for 300 million years.
What if termites, a wood-eating insect usually seen as a pest, held the key to transforming coal into cleaner energy for the world?
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Until now, the use of coal as an energy source has been framed as a polarizing debate between environmental advocates and those supporting jobs and economic growth. Extracting energy from coal by burning it releases toxic pollutants into the air that contribute to respiratory illnesses. This has given coal the reputation for being "dirty." However, it is not the coal that is dirty, but the way that we extract energy from coal.
And that's where termites come in. They live to eat wood and are able to extract energy from it, thanks to a few thousand microbes living in their gut—their gut microbiome. Those same microbes can digest coal to methane, the primary component of natural gas.
Our research team at the University of Delaware (UD) has co-developed a comprehensive coal biotechnology solution that has the potential to turn the coal debate on its head—to radically transform the reputation of coal to a "clean and green" invaluable resource.
The technology takes advantage of a community of thousands of microorganisms from the termite gut, with each microorganism contributing to one or more steps in the intricate and complex biochemical process of "digesting" coal. The extraction of biogenic methane from coal is the combined result of thousands of surgical nicks by enzymes derived from over a million genes present in the termite gut microbiome.
Understanding where coal comes from makes it easier to see why termites have a role to play in this technological transformation. Eons ago, trees and other plants from the huge forests that once covered the earth died and fell into swamps. Layers upon layers of this vegetation were subjected to high pressure and temperature from geologic forces, eventually forming seams of coal at depths of 1,000 feet or more.
According to the U.S. Energy Information Administration, 90.7 percent of all the fossil fuels worldwide lie in deep, unmineable coal seams, followed by mineable coal at 4.8 percent, natural gas at 2.3 percent, and oil at 2.2 percent. (It is worth noting that the United States has the largest proven reserves of coal.)
In the American Chemical Society journal Energy and Fuels, our research team describes a quantitative computer model that was developed to simulate the step-by-step process by which termite-gut microbes produce biogenic methane from coal.
First, the coal is converted to large poly-aromatic compounds, then it is further degraded into fatty acids, next into organic acids, and finally into methane. The UD model was validated using above-ground experimental data from ARCTECH, a research company based in Centerville, Virginia. The company has been working with these microbes for the past 30 years and have been successful in getting their patented microbes to convert coal to methane gas above ground. They have also used the residual coal to produce humic matter, a beneficial organic fertilizer.
The availability of the termite gut microbes, along with the UD computer model, allows for the implementation of the technology below ground.
Natural gas present below ground is already being successfully extracted commercially using technologies such as fracking and coal-bed methane (CBM.) However, previous commercial attempts to "accelerate" the biogenic production of methane below ground by injecting nutrients have failed.
Why should the use of termite gut microbes be any different? Because we have successfully addressed the biochemical complexity of making a community of microbes work together outside a termite gut environment.
The UD computer model provides insights on the metabolic bottlenecks and nutritional needs of the various microbes and makes it feasible to successfully commercialize the below-ground process.
The technology has major environmental ramifications and has the potential to alter the economic and political landscape in many U.S. states. The environmental footprint of coal is reduced by eliminating air pollution caused by burning coal above ground and also decreasing the side-effects of mining. Moreover, only half as much carbon dioxide per unit of energy is generated by burning methane compared to burning coal. Microbial mining also gives us access to much more of the unmineable coal resources than is possible with just human mining.
We are talking about a realistic path for reviving the coal industry and bringing back coal-related jobs. Nature has provided us with the microbes and the UD computer models can uncover key factors and limitations that have previously impeded commercialization. The technology is ready to be implemented and can play a significant role in the transition to an era of clean energy.
Prasad Dhurjati is a Professor of Chemical & Biomolecular Engineering with joint appointments in the Department of Mathematical Sciences and Biological Sciences at the University of Delaware.
The views expressed in this article are the author's own.
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