University Times

Take some wastewater. Add a little carbon dioxide and sunlight. Grow plants like algae that are composed of large quantities of lipid oil. Extract the oil and — viola! — you have biodiesel, a much cleaner alternative to petroleum that’s made from environmentally deleterious fossil fuels.

It’s not quite that simple, of course, but that’s the basic process and those are the necessary ingredients to create an alternative and in many ways superior energy source, while at the same time reusing waste products, said Amy Landis, assistant professor in the Department of Civil and Environmental Engineering, who spoke on “Waste to Fuels: Using Coal Refuse and Municipal Wastewater to Produce Advanced Biofuels.”

Her talk was part of the Science 2011 scientific forum held on campus last week.

Landis’s work has illustrated the environmental tradeoffs of transitioning to bioproducts from petroleum-derived commodities.

“One area I focus on is sustainability,” Landis said. “Most of our transportation fuel now is produced from fossil fuels”; supply is finite, “so it’s unsustainable,” she said.

“And instead of just having waste, we’re trying to get rid of waste by reusing it,” she said.

A number of plants have been shown to be a rich source of biofuel production, for example, converting corn to ethanol. “Other useful plant life are soybeans, switchgrass and especially algae,” Landis said.

“But just because it comes from a green plant, it does not necessarily yield clean biofuels. And you have to consider all the input of energy that’s included in the process of making corn into ethanol. How do you harvest plants? You use tractors. What do tractors run on? Fossil fuels. How about pesticides? We put pesticides on all our crops. What do we make pesticides out of? Fossil fuel.”

So the process of developing alternative energy sources itself uses up energy resources, she noted.

“Instead, what we’re looking into are advanced byproduct synergies,” that is, reusing wastewater and other byproducts to reduce fossil fuel energy consumption and need, she said.

“Take wastewater. We make a lot of it in the U.S. We use a lot of chemicals and fossil fuels to treat our wastewater. In fact what we tend to do is take a lot of the nutrients out of the wastewater to make it cleaner. We spend a lot of money and energy removing algae from wastewater,” Landis said.

“So instead of getting rid of the nutrients when we clean our wastewater, our team built a laboratory version of a wastewater treatment plant. It turns out we can grow algae in seven days and improve the water quality. We need to stop thinking about waste as waste,” she said.

“We can do more. Electricity produces a lot of CO2. We need CO2 to grow algae. So let’s combine these systems. What else is out there? The coal mining industry generates CO2. When we mine coal, it affects the air [and land], but also the water, which captures heavy metallic material, making it very acidic, enough to turn the water [murky],” Landis said.

“What if we could grow plants on that land and reduce the acidic content so that the next generation of biofuels improve the soil, hopefully by growing the plants on marginal land? So we took some mine refuse — that’s the stuff that’s left over and usually found in piles, called gobs, outside abandoned mines.”

Her lab team then tried to grow canola — another plant suitable for producing biodiesel — on the gobs in their greenhouse. “Nothing grows on these gobs, these are dead areas. But, we thought, let’s start using another waste product from another industry to enable the plants to grow and eventually make biodiesel,” Landis explained.

She said that due to ongoing negotiations with her team’s industrial partners, she was not at liberty to name the industry or the waste byproduct. But, that waste, her team discovered, neutralizes the soil, making it nonacidic. “We make a little more neutralized soil and we’re able to grow crops on these gobs,” Landis said.

The water content of the gobs also improved, she noted. “When we harvest these plants, they’re actually taking up some of the heavy metal in the gob pile, so we’re remediating the soil. We’re not only growing biofuel crops, but we’re improving the water at the same time.”

The next challenge, she said, is ensuring that no toxins are carried over into the biodiesel product as a result of this process, something the team currently is working on.

“Mine remediation needs to have a sustainable design,” Landis said. “At a brownfield site near Pittsburgh, we’re growing biofuel crops on marginal land, on greyfields. So far, we’re not seeing any contamination in the plants, so we’re excited that we can improve abandoned land while growing valuable crops,” she said.

“But there’s more: We think not only can we use other waste products to add to our mining sites to grow biofuel, we can also use some of the waste products in the algae system as fertilizer. We also know that we can use wastewater in electrical power plants, so we’re really looking at a lot of different synergies, with the goal of lowering the carbon and environmental footprint.”

—Peter Hart