Plants clean water, waste then used to generate energy
[caption id="attachment_21115" align="alignright" width="252" caption="Phase I. Aquatic plants scrub wastewater in channels before being harvested for methane production."][/caption]
SANTA ROSA – Launching today is the significant second phase of the Fuel from Aquatic Biomass, or FAB, project at the Santa Rosa Laguna.
Funded by grants of $75,000 apiece from the Bay Area Air Quality Management District and the California Energy Commission, FAB demonstrates the ability of native water plants to scrub residual pollutants and endocrine disrupters from treated wastewater and then be harvested to produce methane in an anaerobic digester.
"A farming county like Sonoma could provide 25 percent of its natural gas from digestible wastes," said Dr. Michael Cohen, biology professor at Sonoma State University.
He and graduate research assistant Catherine Hare began looking into the possibility of producing gas from nutrient-absorbing aquatic water plants several years ago.
[caption id="attachment_21116" align="alignleft" width="216" caption="Phase II."][/caption]
They met Dell Tredinnick, Santa Rosa city project developer, at a climate change conference in 2005.
"The results they were getting were incredibly positive," said Mr. Tredinnick. Subsequently Santa Rosa funded the initial expansion of the project to the Laguna Treatment Plant with $50,000.
There biology students from Sonoma State University dug six 20-foot-long channels, diverted secondarily treated wastewater into them and planted natives like marsh pennywort, Azola (mosquito fern), duck weed and algae.
"Our measurements show the plants, as they grow, reduce nitrates by 30 percent to 40 percent a day," said Ms. Hare. "And even more importantly, they reduce estrogenic activity by 80 percent."
Estrogens, or endocrine disruptors, are chemicals that can mimic or block hormone activity in the endocrine system, causing adverse biologic changes in animals, perhaps eventually in humans. Their presence in drinking water is very small but growing.
[caption id="attachment_21117" align="alignright" width="217" caption="Phase III."][/caption]
With demonstrable scrubbing results from the aquatic biomass in place, FAB now moves on to the methane production phase, which has drawn the interest of the Bay Area air quality management agency and the state energy commission.
They've funded two experimental-sized 1,500-gallon biodigesters, capable of processing about a bale of vegetation a day.
"They're small but hungry," said Ms. Hare. "I've learned to operate a fork-lift to feed them with enough agricultural waste."
Like a human stomach, the digester's colonies of organisms partially convert the biomass to methane gas. The gas is captured and fed into a small electricity-producing plant, funded by the grants.
Only half the biomass is converted into gas; the rest is compostable, ready to dig into a vegetable bed. Or in this case, strawberry beds. The California Strawberry Commission got into the act as well, providing eight raised beds and an initial harvest of berries to celebrate the success of Phase I.
"We're not doing this for our own benefit," said Mr. Tredinnick. "We already produce methane from our treatment plant. But we want to show that a small community or a farming operation can provide its energy from its own waste."