It's FAB: Cleaning Water and Producing Energy

cat_harvesting.jpgA system linking clean water, bio-energy and strawberries is in full operation on the grounds of the City of Santa Rosa Laguna Regional Wastewater Treatment Plant.

Called FAB, for Fuel from Aquatic Biomass, it is a collaborative research project led by the City's Project Development Manager Dell Tredinnick and Sonoma State biology professor Michael Cohen that is developing a low-cost sustainable system applicable for businesses or small municipalities that generate organic wastes.

The project is an illustration of Buckminster Fuller's observation: "Pollution is nothing but the resources we are not harvesting. We allow them to disperse because we've been ignorant of their value."

The project has gained national recognition with four awards, most recently the Theodore Roosevelt Environmental Award from the Association of California Water Agencies, and has garnered support from a variety of sources, including the California Energy Commission and the Bay Area Air Quality Management District.

The FAB process begins with treated wastewater passing through two channelized aquatic wetlands, constructed by local green builder R.S. Duckworth, that remove residual nitrate and other components, such as pharmaceuticals. SSU graduate student Caden Hare, recipient of the prestigious Switzer Environmental Fellowship, is working with undergraduate Linden Schneider to investigate the relative contributions of aquatic vegetation and microbes to the scrubbing efficiency of the constructed wetlands.

strawberries.jpgSome of the pharmaceutical load in treated wastewater, such as excreted birth control medicine, has the capacity to bind estrogen receptors, thereby causing abnormalities in sexual development of fish and other wildlife.

Research by graduate student Rachel McCormick, who is also a laboratory technician at the treatment plant, has shown that a one-day retention time in the wetlands lowers the estrogen mimicking activity of the water by approximately 80%.

The plants and algae in the wetlands create biomass that can be harvested for energy production. Another virtually unlimited source of vegetation is the invasive aquatic weeds that clog the Laguna de Santa Rosa.

"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". To this end, research of SSU graduate student John Kozlowski seeks to optimize anaerobic digestion of the vegetation mixed with agricultural by-products from nearby Hanna winery and local dairies.

A recent feedstock that has been added to the mix is the highly digestible glycerin waste derived from biodiesel production at Yokayo Biofuels in Ukiah; a gallon of this waste provides sufficient methane to meet an average day's natural gas demand of a Sonoma County resident, according to Cohen.

At the treatment plant, methane from twin experimental digesters supplies a generator that charges electric vehicles used on site. In the key moment at a recent ceremony to dedicate the digesters, Rep. Lynn Woolsey flipped the generator power switch and was driven off by Hare in a bioenergy-powered vehicle. "This is a simple system," said Cohen. "Using conservative estimates Sonoma County could supply a quarter of its natural gas demand by anaerobic digestion of local organic wastes. Germany is now on track to supply 20% of their demand by 2020".

Some Sonoma County businesses, including Simi and Clos du Bois wineries, already utilize anaerobic digestion for treating organic-rich wastewaters. 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 from PG&E. Nonetheless, 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 in the US, and therefore lower costs, for dumping organic wastes. Secondly, unlike Europe, we have no governmental incentive 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 utilized as a soil amendment. SSU graduate student Aaron Agostini is investigating these solids for their capacity to suppress pathogens of strawberry 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 substra

Project manager Tredinnick commented that it was particularly fitting to have Rep. Woolsey's in attendance at the opening ceremony considering that he met Cohen and Hare at a town hall meeting on global warming organized by her office in 2006. Rep. Woolsey displayed a clear enthusiasm for the FAB project in promising to do her best to find further funding for expansion and thereby lower local dependence on imported fossil fuels.
labgroup.jpgThe group, in the photo above (from left to right): Shaun Horne, Linden Schneider, Aaron Agostini, Mike Cohen, Caden Hare and Rachel McCormick.

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