William & Mary

Rebooting algae

Under the microscope

Under the microscope:  Melosira algae look like a string of beads on a necklace. Each bead is small—maybe 20 microns—but full of oil. New pyrolysis techniques have made more efficient biofuel conversion possible.

New processes, new patent power up our biofuel initiative

William & Mary scientists are rebooting their algae biofuel initiative, aiming to build on opportunities brought about by new processes, new funding and newly patented apparatus.

The biofuel collaboration involves a number of researchers from both William & Mary’s Williamsburg campus as well as the university’s Virginia Institute of Marine Science. An earlier incarnation, known as the Chesapeake Algae Project, or ChAP, was a partnership that involved a number of external collaborators, including the Norwegian energy corporation Statoil.

The initiative retains the original concept of the ChAP initiative. The goal remains to engineer an environmental “twofer,” removing excess algae from waterways—and the excess nutrients from land runoff that the algae take up—and then using the harvested algae as fuelstock.

Trying to prevent more dry Toledos

The recent water emergency in Toledo, Ohio, was caused by excess algae growth in Lake Erie, Toledo’s source for drinking water—exactly the kind of situation that the technology being developed at William & Mary will help to prevent.

Bill Cooke, a physics professor involved in the algae collaboration, says that conservative numbers show that the process is capable of producing a harvest of 150 tons of dry algal biomass per year from an acre of water surface area. He added that new pyrolysis-based techniques, developed at the National Renewable Energy Labs in Golden, Colorado, allow the collaborators to project a yield of 2,000 gallons of liquid fuel from the anticipated 150 tons of dried river goo.

Manos explained that pyrolysis is a versatile process, allowing the production of a wide variety of fuels—liquid and gas—as end products. “Green” gasoline at any octane you choose, butanol, diesel and others can all be produced by applying chemical engineering methods to algal biomass.

“Through pyrolysis, you create what amounts to a substitute for natural gas. That natural gas substitute essentially modifies the hydrocarbon content of your biomass,” Manos said. “This process allows you to treat that gaseous product as a fuel in itself or to turn that product into a liquid fuel through chemical engineering methods. We’re totally agnostic about the kind of fuel that could be ultimately produced.”

As algae giveth biofuel, algae also taketh away harmful substances from the environment. The stuff contains quantities of phosphorus and nitrogen, nutrients that, in excess, help to form “dead zones” in the Chesapeake—as they do in Lake Erie’s western basin, where Toledo draws its water. The 150 ton-per-acre yield is projected to contain about one percent nitrogen and ten percent phosphorus.

The economics of nutrient removal

And there is money in nutrient removal. Much of the nitrogen and phosphorus coming into the Chesapeake comes from non-point sources—essentially developed land. A movement to reduce the surplus nitrogen and phosphorus going into the Bay has resulted in the emergence of nutrient credit trading arrangements. In nutrient credit trading, a developer of a property would buy credits, generating cash that usually goes to pay a farmer to stop farming a portion of his land, thereby reducing the runoff of nutrients into the waterways.

By contrast, the algae biofuel process removes nutrients that are already in the ecosystem, because, as Manos says, “It cleans the water in much the same way that an oyster cleans the water.” The nitrogen and phosphorous leave the water along with the algae that has sequestered it.

The current nutrient trading markets make removal of nitrogen and phosphorous a potentially lucrative byproduct for the algae biofuel initiative. For example, Cooke says the cost for removing phosphorus from the ecosystem is around $20,000 a pound. Algae sequesters a surprising amount of phosphorus and an acre of substrate surface can grow a lot of algae.

“We should produce about 400 pounds of phosphorus per acre, per year,” Cooke said. “Capturing those remediation savings, together with the potential cash flow from future credits, that’s a crop with a pretty good yield.”

For algae farmers to reap a good return, the nutrient credit system must be extended to incorporate the value of extraction of nitrogen and phosphorus from the water. Right now, only “upstream” remedies, such as land banks and sewer system improvements, qualify for credits. “It’s a broken piece of public policy,” Manos said. “And it needs to be fixed.”

Advantages of using wild algae

The William & Mary approach offers a number of advantages as compared to other green fuel initiatives. Growing wild algae neither uses potable water nor requires the use of agricultural land that could otherwise be used for growing food crops, as is the case of corn- or switchgrass-based operations. Growing wild algae is much less resource-intensive than the more common method of selecting, then carefully cultivating a specific algal species.

“The standard approach is to grow a specific species of algae that you want to grow because you know it will produce a lot of lipids to produce biodiesel,” Cooke explained. “So once you decide what algae you want to grow, you put it in a raceway to keep it separate from everything else and you have to feed it nutrients and give it sunlight and all it needs to grow, then harvest it.”

Physics students Mitchell Polizzi ’16 and Neal Parker ’16 install harvesting apparatus on the algae project’s York River flume at the VIMS Boat Basin.The William & Mary team has designed platforms that float in ponds, streams and other waterways, places that are already algae-rich. “We grow algae in these environments partly because the algae wants to grow so badly in these environments,” Manos says.

The free-floating algae diatoms form colonies on quarter-inch polyethylene screen substrates that are suspended from the floating platform. Jason McDevitt, the university’s director of technology transfer, worked to secure a patent on aspects of the platform design.

McDevitt explained that the patent hinged on a simple design innovation. The researchers had found that, contrary to expectations, the algae were just as happy growing on vertical screens as they were on screens placed horizontally.

“It’s a different approach from what other people are doing,” McDevitt said. “Other approaches grow algae on horizontal mats; we grow it on vertical mats. This vertical configuration allows us to have more growth substrate per square meter of surface area, because we grow down into the water.”

The patent lists core members of the algae biofuel initiative as inventors: Cooke and Manos, plus Gene Tracy, Chancellor Professor of Physics; Karl Kuschner, research scientist in William & Mary’s physics department; and Emmett Duffy, the Loretta and Lewis Glucksman Professor of Marine Science at VIMS. Duffy also serves as director of the Smithsonian Institution’s Tennenbaum Marine Observatories.

It’s mostly Melosira

The scientists have found from work at platforms at Lake Matoaka and in the York River that the algae population isn’t as diverse as they first thought. An initial census of the York River growth logged hundreds of types of algae, but Cooke said that measurements by research scientist Charlotte Clark revealed that 80 percent of the growth was represented by a single species of Melosira.

“If you were to look at a strand of Melosira, it looks like tiny little beads on a necklace,” Cooke said. “It looks like a long chain of beads and each bead is maybe 10 to 20 microns in diameter.”

Even though the algae are cooperative when it comes to growing, the stuff doesn’t harvest itself. Harvesting algae by hand is tedious, wet, muddy work, even at experimental quantities. Supported by funding from the Virginia Center for Innovative Technology, Cooke is working on prototype underwater harvesters.

“It’s important to have underwater harvesters, because when the algae is under water it’s bushy,” Cooke said. “It sticks out. It flops around. But when you pull it out of the water, it drops down, it turns to goop and when you scrape it off, you scrape off most of the base crop.”

The goal for the harvester is to devise a kind of small subaquatic lawnmower, a mechanism that will not only trim the Melosira closely, leaving enough on the substrate to regrow, but also collect the harvest.

In addition to the harvester development work, the Center for Innovative Technology also allowed the researchers to bring to the team Kurt Stephenson, an agricultural economist from Virginia Tech. Manos hopes to secure additional funding to cap the algae biofuel initiative.

“We’ve done several years of preliminary work, funded by Statoil. We have three contiguous years of algal growth to look at,” he said. “Now we hope to be funded by the Department of Energy or other entity to get the final aquacultural figures to actually operate a business from this.”