ASU Expert Touts Solar- and Microorganism-Based Bioenergy as Best Approach

Perhaps there is no greater societal need for scientific know-how than in finding new ways to meet future energy demands. Skyrocketing gas prices, an uncertain oil supply, increasing demand from around the world, and the looming threat of climate change have made identifying and developing realistic energy alternatives a national priority.

For Biodesign Institute researcher Bruce Rittmann, the threat of global warming also presents a significant opportunity for innovation and fresh solutions to today's energy challenges.

"Beginning with the Industrial Revolution, the unprecedented expansions of human population and economic activity have been based on combusting fossil fuels," said Rittmann. "Today, fossil fuels provide 80 percent of the energy needs to run human society worldwide: 34 percent petroleum, 32 percent coal, and 14 percent natural gas."

In a new Perspective article published in the journal Biotechnology and Bioengineering, Rittmann points the way toward developing bioenergy as the best realistic alternative to meet our current and future energy needs while cutting back on the use of fossil fuels. Rittmann directs the Center for Environmental Biotechnology and is a professor in the Ira A. Fulton School of Engineering's Department of Civil and Environmental Engineering.

"The only way that human society has a realistic way of slowing and reversing global warming is bioenergy; and it has to be bioenergy that is done right," said Rittmann, who leads many of Biodesign's sustainability-themed research projects. "Most critically, we need to be able to have bioenergy sources that work on a very, very large scale."

Besides the scalability issues of bioenergy, any technologies developed must also be able to produce energy while minimizing damage to the environment or affecting the world's food supply.

For Rittmann, the most obvious renewable-energy solution – one that passes the tests of scalability, environment, and food – stems from the very factor that makes life on Earth possible: the sun.

"The good news is that we have plenty of energy from the sun. Every day, the sun sends to the earth's surface about 173,000 terawatts of energy, or more than 10,000 times more that is used by human society. So, we have a lot of what we like to call 'upside potential' for capturing sunlight energy."

Up to now, harnessing the energy of the sun has proven to be technically and socially challenging. In particular, approaches to make biofuels from crops such as corn have been met with skepticism in recent days.

"When people think of capturing sunlight energy in biomass, they focus on plants, which are familiar. However, plants are quite inefficient at capturing sunlight energy and turning it into biomass that can be used a fuel," Rittmann explains. As a result, plants could provide only a tiny fraction of our society's energy needs. "Obviously, we need the plants for producing food and sustaining natural ecosystems. Plants simply fail the scalability, environmental, and food tests."

In contrast, microoganisms, the smallest forms of life on Earth, can meet the scalability and environmental tests. Rittmann sees a vast untapped potential of using microbes in service to society to meet our energy challenges.

"Photosynthetic bacteria can capture sunlight energy at rates 100 times or more greater than plants, and they do not compete for arable land," Rittmann said. This high rate of energy capture means that renewable biofuels can be generated in quantities that rival our current use of fossil fuels.

In addition, non-photosynthetic microorganisms are capable of converting the energy value of all kinds of biomass, including wastes, into readily useful energy forms, such as methane, hydrogen, and electricity.

"Microorganisms can provide just the services our society needs to move from fossil fuels to renewable biofuels," said Rittmann. "Only the microorganisms can pass all the tests, and we should take full advantage of the opportunities that microorganisms present."