First spotlighted by NorthBay biz in “Algae: America’s Next Super Fuel?” (Feb. 2009), the FAB process begins by passing partially treated wastewater through two channelized aquatic wetlands, constructed by local green builder R.S. Duckworth, that remove residual nitrate and other potentially harmful components such as pharmaceuticals.
Some of the pharmaceutical load in treated wastewater can adversely affect native wildlife. Excreted birth control medicine, for example, has the capacity to bind estrogen receptors, thereby causing abnormalities in the sexual development of fish and other creatures. Research by graduate student Rachel McCormick, a laboratory technician at the treatment plant, has shown that a one-day retention time in the FAB wetlands lowers the estrogen mimicking activity of the water by approximately 80 percent. A team is investigating the relative contributions of aquatic vegetation and microbes to the overall scrubbing efficiency of the constructed wetlands.
The plants and algae in the wetlands create biomass that can be harvested for energy production. “The most efficient way to harness the energy held in this vegetation,” says Cohen, “is to feed it to anaerobic digesters and produce methane gas.” SSU graduate student John Kozlowski has been researching ways to optimize anaerobic digestion of the vegetation mixed with agricultural byproducts from nearby Hanna Winery and local dairies. Another virtually unlimited source of vegetation is the invasive aquatic weeds that clog the Laguna de Santa Rosa.
A recent feedstock that’s been added to the mix is the highly digestible glycerin waste derived from biodiesel production at Yokayo Biofuels in Ukiah; according to Cohen, a gallon of this waste provides sufficient methane to meet an average day’s natural gas demand of a single Sonoma County resident. At the treatment plant, methane from twin experimental digesters supplies a generator that charges electric vehicles used onsite. At a May 10 ceremony to dedicate the digesters, Rep. Lynn Woolsey flipped the generator power switch and was later driven off in a bioenergy-powered vehicle. Project Manager Tredinnick commented it was particularly fitting to have Woolsey in attendance, considering he met Cohen and me at a town hall meeting on global warming, which was organized by her office in 2006. Woolsey displayed a clear enthusiasm for the FAB project in promising to do her best to find further funding for expansion.
Some Sonoma County businesses, including Simi and Clos du Bois wineries, already use anaerobic digestion for treating organic-rich wastewater. Both companies have found that, within a few years, the system pays for itself by reducing water treatment costs and generating energy that would otherwise need to be purchased. “This is a simple system,” says Cohen. “Using conservative estimates, Sonoma County could supply one-quarter of its natural gas demand by anaerobic digestion of local organic wastes. Germany is now on track to supply 20 percent of its demand by 2020.”
Compared to Europe, anaerobic digestion has yet to become a widely disseminated technology in the United States. One major reason is the comparatively large amount of available space—and, therefore, lower costs for dumping organic waste—in the United States. Second, unlike Europe, there are no governmental incentives in place for rewarding the carbon offsets that anaerobic digestion generates.
Another benefit of the anaerobic digestion process is that the nutrient-rich solids remaining after digestion can be used as a soil amendment. SSU graduate student Aaron Agostini is investigating these solids for their capacity to suppress root rot and support plant growth. Funded by the California Strawberry Commission, this research is conducted in collaboration with Dr. Mark Mazzola of the USDA Agricultural Research Service. SSU graduate student Mia Maltz’s research is finding that the solids stimulate microbial degradation of diesel in contaminated soils, especially when combined with spent mushroom growth substrate.
In all, the FAB project is a marvelous illustration of R. Buckminster Fuller’s observation: “Pollution is nothing but the resources we aren’t harvesting. We let them disperse because we’ve been ignorant of their value.”
