Joint Seminar
Sponsored by:
Department of Chemical and Biological Engineering
and
Wanger Institute for Sustainable Energy Research (WISER)
October 16, 2013
Perlstein Hall 131 – Auditorium
3:15 pm - 4:30 pm
Jonathan D. Trent, Ph.D.
OMEGA Project Scientist
Bioengineering Branch, NASA Ames Research Center
and Adjunct Professor, UC Santa Cruz
Are Biofuels a “Fuel’s Paradise”?
Abstract
Of all the proposed alternative feedstocks for making biofuels, microalgae, with high growth rates and high
yields of oil, have become a focus attention. Microalgae species that can be grown on domestic wastewater
are of particular interest to avoid competing with agriculture for water and fertilizer. To economically
produce algal biofuels, culturing facilities must be close to wastewater treatment plants to avoid pumping
water long distances. Unfortunately, traditional cultivation methods using open ponds or closed
photobioreactors (PBRs), is impossible in most cities because wastewater plants are embedded in urban
infrastructure and excavating thousands of hectares of ponds or installing PBRs near existing wastewater
plants would be prohibitively expensive. For coastal cities however, it may be possible to cultivate algae
offshore by redirecting offshore wastewater outfalls to a system we call “OMEGA” (Offshore Membrane
Enclosures for Growing Algae).
In the OMEGA system, freshwater microalgae are grown in flexible, clear plastic PBRs attached to floating
docks in naturally or artificially protected bays. Wastewater and CO2 from coastal facilities provide water,
nutrients, and carbon. The surrounding seawater maintains the temperature inside the PBRs and provides
environmental control of the cultivated algae that escape (i.e., if a PBR module accidentally leaks, the
freshwater algae that grow in wastewater cannot compete in the marine environment). The salt gradient
between seawater and wastewater can be used for forward osmosis (FO) to concentrate nutrients and
facilitate algae harvesting. Both the algae and FO clean the wastewater, removing nutrients as well as
pharmaceuticals and personal care products. The economics of the OMEGA system are supported by
biofuels production, wastewater treatment, carbon sequestration, and aquaculture, while the OMEGA
system is powered by local renewable sources, including solar panels, wave generators, and wind turbines.
The feasibility of OMEGA was investigated over the last three years with support from the California
Energy Commission and NASA. Floating prototypes were developed and tested for continuous algae
growth, wastewater treatment, biofouling, and impact on marine animals. A techno-economic analysis
indicated the requirements of a full-scale system. The plans for the next phase of OMEGA will be
discussed.