Brandon Rotavera, an assistant professor with appointments in the College of Engineering and the Department of Chemistry in the Franklin College of Arts and Sciences, took home UGA’s Fred C. Davison Early Career Scholar Award in 2021 for his physical chemistry research in next-generation combustion systems. In this interview, he discusses his research and how he believes combustion technologies will continue to play a major role as society grapples with energy needs and the environmental impact of transportation technologies.
What drew you to this field of research?
I love road racing, like the MotoGP circuit, and for a short period of time I raced motorcycles at the amateur level. I fell in love with the idea of engines and high performance, that sort of thing. That was my original motivation, and then I started to realize that transportation—really, the way we rely on combustion as a source of energy—touches more of our everyday lives than most people probably realize.
When you go to the store and purchase something, there’s a transportation cost embedded in the price of that item. So, there are economic arguments one can make around the importance of sustainable transportation energy. Currently, about 95% of our transportation energy comes from hydrocarbons—pure petroleum derivatives. Petroleum is a form of energy that is of finite supply. We continue to augment petroleum with biofuels that can be produced renewably and make the actual combustion process better, while also using less petroleum.
What do you mean by “better combustion?”
There are two parts. One is efficiency: How much power can you produce for a given input? How can we arrive at a scenario where we produce more power from less fuel? That’s the efficiency argument. And then there are environmental ones. Combustion sometimes gets labeled as “dirty.” So when I say “better,” I mean can we take some kind of fuel source, renewable or not, and use less of it to generate more engine power while minimizing environmental impact?
What you can’t get away from with combustion of hydrocarbons and most biofuels is the generation of CO2. But there are a number of solutions to this—carbon capture being just one technology. Modern biofuels are generally produced from conversion of inedible crops—crops that will grow on arid land incapable of food production—so that takes some of the CO2 out of the air and makes biofuels less “carbon intensive.” Meaning, less net CO2 is produced compared to using petroleum-derived fuels.
Are there different categories of biofuels?
There are two main categories. When we say “biofuel,” this does not mean one specific fuel. It means we’re taking something that’s produced through a biogenic process and converting it into fuel that is energy dense, safe and transportable. One category is when you take something like methane—or even CO2—and convert it, catalytically or through some other process, into a synthetic hydrocarbon compatible with jet fuel, for example.
The other category is oxygenated biofuels. These come from inedible plant crops. By their nature, being derived from plants that have cellular walls containing lots of oxygen, the fuels produced from these sources have some degree of oxygen content. That oxygen is bonded to hydrocarbon structures in different ways, and that can completely change the fundamental steps of the combustion process.
There’s been significant technological investment from the Department of Energy, National Science Foundation and other agencies, as well as the private sector, to bring society to a point where we have a multi-pronged strategy for sustainable transportation energy. This is a major credit to the scientific enterprise that has real impact on day-to-day life.
You hear estimates about global petroleum reserves lasting another 50 years, 60 years. The real answer is nobody knows how much petroleum is left in the ground, and for me personally, it’s somewhat irrelevant. If we have the ability to develop an energy infrastructure that meets societal demands and complements, or in the longer term becomes better than, petroleum-based energy, then that’s clearly the direction to go.
Can you describe one or two of your current projects?
Two core projects we’re working on right now, one funded by DOE and one by an NSF CAREER award, aim to advance combustion chemistry knowledge. The DOE project is funded by the Gas-Phase Chemical Physics program and focuses on comparing combustion mechanisms of molecules that contain oxygen. We want to know, at the molecular level, the steps that a biofuel follows as it undergoes combustion at high pressures and temperatures in the range of 450–1,200 degrees Fahrenheit.
The NSF project is funded by the Combustion and Fire Systems program and takes up fundamental questions on the chemistry of cyclic ethers. These are molecules where one oxygen atom is bonded to two different carbon atoms connected in a ringed structure. They’re useful as biofuels, but they’re also formed as intermediates in hydrocarbon combustion. When a hydrocarbon reacts with oxygen, it doesn’t go straight from fuel and air to CO2 and water. There are, in fact, thousands of intermediate steps along the way, and cyclic ethers are one of those steps. And so that project focuses on the competition between the ether breaking apart on its own, versus adding an oxygen molecule and reacting in a different direction. Which seems like a pretty simple question, but it’s one that’s actually very challenging to study.
Do you work with computational models or lab experimentation to study these questions?
Both. Probably about 60% of our efforts are on the experimental side, and about 40% are on the computational side. Both are complementary of each other. The normal process is, we write a plan for and then conduct a series of experiments and interpret the results using a variety of diagnostics. Then, for a more nuanced description, or to make that experimental information useful to other people, we conduct computational work that supports the development of chemical reaction models.
Those models are useful for companies like Ford, GM, Caterpillar, Convergent Science and others that want to build better engines. In order to test a new technology, it’s just faster and cheaper to have a reliable computer model that can completely describe the combustion process, rather than cutting metal, building equipment and testing.
What are some of the biggest barriers to having biofuels play a more prominent role in everyday life?
Certainly not all, but a lot of the issues biofuels face are related to perception and communication, in my view. Ethanol was initially produced from corn, and there was a little bit of misinformation where—to use some hyperbole—some people thought that ears of corn were being pulled off shelves at the supermarket to produce ethanol. That did not happen. I would argue that those who were in favor of ethanol at that time lost that so-called “food versus fuel” argument in the early 2000s.
This is why I was making the point earlier about describing biofuels as being produced from inedible plant crops that can be grown on arid land, right? You’re taking something that you can’t eat, and it’s grown on land that you can’t use from a soil-quality standpoint. None of these technologies are taking food off anybody’s table.
All this to say, surprisingly the barriers are not overwhelming on the technological side. I’m less concerned about our scientific ability to answer hard challenges, and I’m more concerned with winning the public narrative and the politics—especially in light of electric vehicles being heralded in some arenas as “the environmental solution.” In a recent seminar that I gave, I highlighted some of the counter arguments against this narrative. What’s more is that most people view electric cars as something new. They are not. While Elon Musk is a household name, Oliver Fritchle, who built the first electric car over 100 years ago in 1906, is almost certainly not.
Governments and policymakers must recognize that there is no silver bullet. I don’t think combustion is the singular answer for everything, and batteries absolutely have a place in the future, particularly in hybrids. It’s a combination of strategies and technologies that is most effective in providing clean transportation energy, just like in a financial portfolio. You always hear about diversifying your investments. It’s the exact same thing for energy technologies. A colleague of mine, who recently authored a book on this topic, coined a phrase to reflect this—“the future is eclectic”—and he is absolutely right.