Algae Could Help Fuel the Future. But It's Not Easy Being 'Green'

by Melina Walling (Arizona Republic/AZ Central) ... Scientists in Arizona have been cultivating algae for several years, but this time, ASU researchers are working on a project with the city of Mesa in hopes of turning wastewater byproducts into fuel and other products. They want to harness the way algae naturally works to coax another use out of the gases that would otherwise be emitted as a result of the necessary process of breaking down human-produced wastewater.

"... We’re using waste as food for the microalgae,” said Justin Flory, the associate director of research in the Center for Negative Carbon Emissions at Arizona State University and the manager of the algae project.

Algae-based biofuels and products have been a dream for researchers and companies for several years, including for teams at ASU and the University of Arizona. In 2007, the Energy Independence and Security Act called for 36 billion gallons of renewable fuels, including microalgae-based biofuels, by 2022. Algae biofuels are not yet produced commercially, according to the EPA.

Now, as the need for energy independence and security grow more urgent in the U.S., algae still isn’t being produced at a scale large enough to power cars, planes or anything else that requires energy. Meanwhile, many scientists say we need to electrify everything, fast, to meet climate goals, with the potential for dire consequences if we don’t.

Flory and other Arizona researchers think algae will play an important role in the move to a sustainable future. In the uncertain zone between where we are now and complete decarbonization, they say algae-based biofuels offer solutions for some of the toughest problems of the energy transition. Those include, for instance, addressing the limitations of intermittent power sources like solar and wind, reducing the impact of heavy transportation like cargo ships and, of course, improving the sustainability of unavoidable emitting processes like treating wastewater.

But for algae to reach its potential, its cultivators are up against big challenges. There are biological hurdles: Much like growers of agricultural crops on dry land, algae farmers need to achieve ideal conditions to maximize yields (and some even want to use genetic modification). Then there’s the task of converting a pond of green gunk into fuel, a design problem that engineers, chemists and other scientists are still trying to perfect.

Algae projects are most sustainable when combined with other processes, like wastewater treatment, something big companies and investors aren’t always aligned with.

Another decision for researchers growing algae, including Arizona teams, is whether to grow algae in environments that are open or closed to the outside world. To grow the vast amounts of algae needed to produce biofuels on a large scale, cultivators need big ponds. Smaller, closed systems tend to work well, but the size is limited, and they’re more expensive. When ponds are outside, wind could contaminate the algae or introduce dust.

“Arizona is a great place for (algae cultivation) because of how much sunlight we have,” Ogden said. But in the desert, water usage is a big concern. “At some point we might get a water problem, because there’s a lot of evaporation off of there."

That’s something Flory and his team hope to address by working directly with a wastewater plant. Since the process already involves reclaimed water, it’s less of a burden on water systems.

When the microalgae “eat” the waste from the anaerobic digesters, they do two useful things. They leave behind a purer form of methane (another type of gas) that can be pumped into existing natural gas systems as “renewable natural gas.” And they also grow more of themselves, creating “biomass,” which can eventually be converted into biodiesel or other products like fish feed or even synthetic materials used to make sneakers.

Casey Norton, a spokesperson for ExxonMobil, did not answer when asked about whether the company was working on integrating processes like wastewater treatment as part of its algae biofuel strategy. Instead, he described the work with Viridos on developing genetic tools for better cultivation, as well as other biofuel projects not using algae, which some scientists have pointed out have the potential to be land-intensive and inefficient.

“Algae is one part of our portfolio approach to researching, developing and deploying lower-emissions technologies,” he said in an email. READ MORE