Cellulose ethanol pioneer receives US$100,000 Lemelson-MIT Award for Sustainability

Dartmouth College Engineering Professor and Mascoma co-founder Lee Lynd is honored for 25 years of inventive achievements and research into biofuels. He received the first-ever US$100,000 Lemelson-MIT Award for Sustainability for a career that ultimately led to the development of one of the most promising cellulose ethanol production processes - a process configuration known as 'consolidated bioprocessing' (CBP) which allows the transformation of biomass into ethanol in one single step by using special ethanogenic microbes. A look back at the way Lynd came to this technique can teach us something about the challenges ahead.

Lynd and his colleagues’ inventions are at the forefront of advanced technologies for converting biomass feedstocks into motor vehicle fuels. Lynd is being recognized for these inventions, as well as his vision and long-term advocacy of biofuels as a sustainable alternative to fossil fuels.

“Decades ago, Lee Lynd started doing something about global warming and the rapid depletion of the world’s non-renewable energy resources,” said Merton Flemings, director of the Lemelson-MIT Program. “He continued to experiment and pursue his ideas even when the conventional wisdom said they couldn’t be done.”

“Lee’s groundbreaking research has driven forward the public policy debate, the business world, and the fundamental science of bioenergy,” said Nathanael Greene, a senior policy analyst at the Natural Resources Defense Council, and one of Lynd’s nominators for the $100,000 Lemelson-MIT Award for Sustainability. “His work has helped frame our basic understanding of the sustainable potential for bioenergy and especially biofuels.”

A ‘Harebrained Idea’ from a compost heap
In 1977, while an undergraduate biology major at Bates College, Lynd spent a summer working on an organic farm in North Reading, Massachusetts and was struck by how much heat a compost heap could generate. “I said, my goodness, that pile of grass and whatnot is four-feet high, and if you put a thermometer down into the bottom of that, it’s 150 degrees Fahrenheit,” he recalled.

At first, Lynd thought about using compost heaps as a source of heat. Although he soon realized that was not promising, the idea of using biology to produce energy stayed with him. “An initially harebrained idea can lead you to something worthwhile if you run with it for awhile,” Lynd said.

As Lynd’s vision for biofuels took shape in the late 70s, he realized that cellulose-utilizing bacteria that produced ethanol were known, and that production and utilization of cellulosic biofuels could involve a sustainable carbon cycle with no net emissions of carbon dioxide. These initial insights have served him well over several decades of continuous focused effort, during much of which the world showed little enthusiasm for renewable fuels. “I think the thing that served me the best is clarity of purpose,” he explained. “For decades when biofuels were not popular, I thought the topic was exciting and important, and so I worked on it anyway.”

Step-by-step progress toward a big idea
In the United States today, fuel ethanol is derived from corn, which is available in limited quantities and consumes substantial amounts of fossil energy as currently produced. “On the other hand,” Lynd observed, “cellulose is the most abundant organic compound on the face of the Earth and production of fuel from cellulosic biomass displaces far more fossil fuel than is required to produce it.”

Lynd has identified one-step fermentation of cellulosic biomass into ethanol or other biofuels—a process configuration known as consolidated bioprocessing (CBP)—as a potentially transformative breakthrough for low-cost processing:
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While the vast majority of research on processing cellulosic biomass has focused on separately-produced enzymes used in multi-step biological processing, Lynd's group is the most active worldwide in research on the one-step, CBP approach.

“Developing a microbe that can convert cellulosic biomass to ethanol can be approached in one of two ways,” said Lynd. “Either start with organisms that are able to grow well on biomass and modify them to produce ethanol better, or start with organisms that produce ethanol well and modify them so that they can grow on biomass.” Lynd’s group is investigating both approaches. His group has recently engineered thermophilic bacteria – similar to those present in the compost heap that captured his imagination years before – to produce ethanol as the only fermentation product. Working in collaboration with colleagues at the University of Stellenbosch, South Africa, the group has also engineered yeast to grow on cellulose.

“Originally, we were motivated to look at CBP by process engineering considerations – fewer tanks and fewer process steps,” said Lynd. “However, as we have learned more about how microorganisms utilize cellulose, we are finding additional, biological, advantages to the CBP strategy.”

“Microbes grow on cellulose by producing cellulase enzymes, which hydrolyze cellulosic biomass into sugars that can be fermented to ethanol,” he explained. “Producing cellulases requires expenditure of the cell’s energy currency, a molecule called ATP.” A key doubt about the feasibility of CBP was whether ethanol producing microbes could produce enough ATP to make cellulase in sufficient quantities to allow rapid cellulose hydrolysis. Lynd’s group showed, however, that a naturally-occurring cellulolytic bacterium actually has several ATP-generating mechanisms that are specific to cellulose utilization and that these mechanisms more than compensate for the ATP requirement of cellulase synthesis.

In an additional development, the Lynd group showed that cellulase enzymes are several-fold more effective when they are present on the surface of a metabolically-active cell as compared to when the enzymes act independently of cells. “Nature has solved many of the challenges associated with microbial cellulose utilization, which we are gradually discovering,” said Lynd.

Largely as a result of Lynd’s efforts, the potential of CBP has been increasingly recognized of late. For example, a recent DOE roadmap states, “CBP is widely considered to be the ultimate low-cost configuration for cellulose hydrolysis and fermentation.”

“The difference of opinion is how long it will take,” said Lynd. “Most people still think CBP is a decade off, but I think we can get there much faster than that.”

A Mission to commercialize biofuels
Recently, there has been a renewed interest in alternative fuels, especially after oil reached $70 a barrel in the wake of Hurricane Katrina and the political instability in the Middle East. In 2006, with Series A funding from Khosla Ventures and other financiers, Lynd co-founded a start-up company called Mascoma Corporation to advance technologies such as consolidated bioprocessing and make fuel production from cellulosic biomass a commercial reality.

In his nomination letter for the $100,000 Lemelson-MIT Award for Sustainability, renowned venture capitalist Vinod Khosla said he has become a “big believer” in the ability of ethanol to reduce America’s dependence on petroleum. “While corn-based ethanol is a great start toward this goal, the ability to convert cellulosic feedstocks to ethanol is the Holy Grail,” he wrote.

In addition to Lynd’s invention work, he is also one of the leading analysts and advocates addressing the need to develop and adopt alternative fuels. He co-led a multi-institution research project that produced the seminal report, “Growing Energy: How Biofuels Can Help End America’s Oil Dependence,” published in 2004 by the National Resources Defense Council. Lynd was also the biofuels industry representative on an advisory committee to the Executive Office of President Clinton on reducing greenhouse gas emissions from personal vehicles, and has twice testified before Congress.

Lynd is also an inspiring mentor to others. He manages the only graduate fellowship program in the general energy field, and has supervised dozens of students who share his passion for alternative fuels.

“Energy is and always has been important,” he said. “Right now, it’s the critical issue of our time and a huge determinant of human well-being and prosperity. In the future people will look back and judge us by how well we responded to this challenge.”

In addition to the $100,000 Lemelson-MIT Award for Sustainability, the Lemelson-MIT Program also named Timothy M. Swager as the 2007 winner of the $500,000 Lemelson-MIT Prize today. Swager is the Department Head and John D. MacArthur Professor of Chemistry at the Massachusetts Institute of Technology. He is being recognized for inventing a range of materials and devices using original molecular-based designs, including sensors with increased sensitivity that are ideal for detecting explosives.

From May 2-5, Lynd and Swager will participate in the first-ever EurekaFest, a multi-day celebration of the inventive spirit presented by the Lemelson-MIT Program in partnership with the Museum of Science, Boston.

Image: Clostridium thermocellum, an anaerobic, thermophilic, cellulolytic, and ethanogenic bacterium capable of directly converting cellulosic substrate into ethanol.

More information:
Lynd has published extensively about the processes he developed, but a good overview of CBP can be found in the following open access article:

Lee R. Lynd, and Yi-Heng Percival Zhang, "Cellulose utilization by Clostridium thermocellum: Bioenergetics and hydrolysis product assimilation", Proceedings of the National Academy of Sciences, May 17, 2005 | vol. 102 | no. 20 | 7321-7325