STARKVILLE, Mississippi—“By the time it gets here, David, it’s no longer my poop,” says microbiologist Todd French with conviction. “I don’t want you to think there’s solid turds coming in over there. When we get it as sludge, it’s far removed from what it was when it left your body. That’s all bacteria that has grown and fed off this stuff.”

French is trying to reassure me. We’re gazing down into a concrete vat filled with a churning tide of gray and green water at the Ernest E. Jones Wastewater Treatment Plant in Starkville, Mississippi. A gust of wind kicks an odor off the frothy surface; a spittle-sized drop of foam has hit my lip. Students in French’s program must get hepatitis shots and boosters before helping French in his audacious quest to convert sludge like this into biodiesel; I furiously rub my finger over the spot, removing as many dermis layers as possible.

But French tells me he’s ingested “mouthfuls” of the water without ill effects. “You don’t have to worry about getting anything… too much,” he says.

French, it should be clear, has a very different perspective on sludge. He takes a sniff of the ripe air around us. “That’s money,” he says. “That’s what it smells like.”

Luckily, when we hop back into French’s SUV, there’s a bottle of Purell in his car.

French, a 48-year-old associate professor at Mississippi State University (MSU), has convinced the school and the US Department of Energy to build him a Sustainable Energy Research Center—a large building designed around French’s novel ideas about converting sewer sludge into biodiesel. Based on numbers from French’s pilot project, if 50 percent of US wastewater treatment plants used his extraction process, the country could generate nearly 2 billion gallons of biodiesel a year. Although that’s only 0.5 percent of the national diesel demand, French believes it can still revolutionize our economy in the process. So I came to Starkville to find out how.

Sweet sludge

French doesn’t fit the professorial stereotype. He first picks me up in his SUV—ATV in tow—after an unsuccessful crossbow hunting trip.

“We hang out and cook at night. You get a little wild,” he says about time spent outdoors with friends. “You know how that old saying goes that precedes every redneck wreck: ‘Hold my beer and watch this’?”

The GPS on his dashboard announces politely, “In two-tenths of a mile, keep left.”

“Ah, shut up,” he says. “I just need you to show me the miles.”

French spent some wild days after high school working the lumber yards in Natchez, Mississippi—a rough patch in his life that nearly undid the straight-A student with full-ride scholarships. Knowing that his talents were being squandered, French eventually enrolled in pharmacy school, where he took a microbiology class. The cyclical nature of organic matter consumed his thoughts.

“The possibilities of what bacteria and microorganisms could do is unlimited,” he tells me, driving north on this forested highway. “And that’s what I fell in love with.” He focused his obsession at the US Army Corps of Engineers in Vicksburg, where his job was to fingerprint microbes used to clean the environment. He later found an outlet for his curiosity as an associate professor at MSU, where he teamed up with chemical engineers Rafael Hernandez and Mark Zappi.

The three of them attended an energy convention in 2002, and, during a presentation, an elemental chart of biocrude oil was projected. French leaned over to his colleagues and said, “You find me a cheap carbon source, and I can make all the biodiesel fuel you ever wanted.”

Zappi was quick to point out the problem: there weren’t any cheap carbon sources.

Bacteria might seem like a good option. They double rapidly, and cell membranes contain phospholipids with two long-chain fatty acids of hydrogen and carbon. These fatty acids are “saponifiable,” which means that they can be used to make fatty acid methyl esters (FAMEs), greasy stuff that could lead to vegetable oil. If you could invent a way to raise the fat content in bacteria, you could extract a decent amount of this oil, which could then undergo transesterification for fuel production. Samples taken to French’s lab verified that a mixture of FAMEs could meet international requirements for biodiesel. But growing bacteria in the massive quantities needed for fuel was expensive.

Six months later, when Zappi and Hernandez were doing consulting jobs at wastewater treatment plants, French brought up the carbon issue again. This time, Zappi’s tone changed. “Why would I grow bacteria?” he said. “A wastewater treatment plant has to pay to get rid of that excess sludge.”

David MacNeal



Scientists had tried for years to repurpose sewage for use in energy production. Wastewater is 97 percent water; the other three percent is a sludge composed of oils, paper, plant nutrients, human feces, and bacteria. Lots of bacteria. The problem is that without any tampering, sludge is only about 4 to 5 percent fat.

“But then I found some yeast and bacteria,” says French, “that could gain 60-70 percent fats on a dry weight basis” within the sludge after being fed sugars and nutrients. Soon, monetary investment came in from the Department of Energy, and by 2011, French had a research pilot facility to ferment gunk from the sewer and make biodiesel. Working with the EPA, French has since replicated results at multiple sewer plants.

Today, with a wife and three kids, French is trying to commercialize his sewage conversion technology through Bio Energy Spectrum Solutions. He and business partner Rafael Hernandez hope it will be enough to secure their children’s future. But for French especially, the company is a playground for him to seek new renewable sources. “My whole world is about what I can have fun with,” he says.

But cheap oil is causing problems.

“Right now—shit.” French shakes his head. “Two-dollar-a-gallon diesel is too tough for our technology to compete with.”

Listing image by David MacNeal