Oil from Algae?
There was recent news about the discovery of 200 marine dead zones all over the world. These dead zones occur when water becomes devoid of oxygen because algae have consumed it. The algae create the oxygen deficit because of their ability to prosper in polluted water that kills off all other marine life but them. With no competitors or predators to curb their numbers, the algae are free to grow uncontrolled and consume oxygen.
But there is an upside to algae’s ability to grow so quickly. Because they grow in specific environments, sensitive to salinity, sunlight, acidity, temperature and nutrients, algae’s growth can be controlled and even augmented. That means that one of the most promising new uses for algae is the production of vegetable oil – bio-diesel.
Using photovoltaics and solar heat collectors, producers potentially could cultivate algae in fish ponds or tanks, creating the ability to produce bio-diesel locally, thereby saving biomass transportation to remote fermentation and distillation facilities, and drastically reducing embodied energy.
The key to getting the biomass fuels costs down, is to devise highly efficient production methods, with few expensive inputs. That is a huge engineering challenge, but not insurmountable in light of many current investigators working on the technology. This effort by many poorly financed people is ongoing around the world, rather than by well- financed mega-corporations.
Analogous to the aluminum industry’s attempts to curb energy costs, the move towards algal production of biofuels is a result of high petroleum costs. At one time aluminum was more expensive than gold until cheap, abundant hydroelectric, geothermal, or petroleum energy was available for its energy-intensive production. But as energy becomes more expensive, the cost of aluminum has risen drastically – thus, the value of recycled aluminum.
Building a low cost algae-based energy infrastructure, is now quite possible. Waterproof light emitting diodes strung in chains across the interior of large insulated steel tanks and pumped in CO2 can accelerate algal growth. Harvesting and pressing the oil from the algae can be done approximately every 72 hours. The biomass residue (algal cells less the oil) is potentially an animal feed, depending on the species of algae.
This combination of fuel production and animal (secondary protein) feed could offer great economic stability to impoverished developing countries and remote agricultural communities.
The development of this technology is dependent on low-energy methods at every step of the production process and must be operated on photovoltaic power. For example the energy required to distill alcohol from water-based fermentation broths equals nearly 2/3 of the energy contained in the alcohol product. However, by using a solar-powered alcohol still, youe can eliminate nearly all of that otherwise wasted distillation heat input.
A combination of solar thermal collectors and photovoltaics can be designed to separate water from the fermentation broths, and then go on to separate the fusel oils (propanols, butanols, pentanols and heaxanols) from the ethanol.
The entire process is driven by solar radiation collected in several high-vacuum, thermal solar collectors. The vacuum is permanently sealed in, and thus requires no vacuum pumping power. The collectors have a ultra high-efficiency selective solar adsorption coating, and are 97-percent efficient, reflecting a mere 3 percent of the sun’s energy.
The solar thermal collectors achieve temperatures high enough to boil off the water, and then successively distill the individual fusel-oil alcohol fractions, using no additional electrical inputs whatsoever (except for a tiny photovoltaic array that generates a few milli-watts to run an ultra-low energy microprocessor control system to regulate and control the solar fractional distillation process).
Although it is certainly not a backyard process by any means, it still could be within the reach of a farm or community co-op.
Algal production of bio-diesel offers many benefits over ethanol production from sugar- bearing crops. Ethanol production is dependent on sugar content from the feedstocks. These feedstocks can be sugar beets, cane sugar, corn, sorghum or water hyacinth. The sugar is fermented to produce alcohol. There is no reason why algae could not be used to produce ethanol as well. The problem with sugar-based ethanol production is the transportation of huge biomass tonnage to massive, costly, central distilleries, and then the transportation from the distillery to dispensing outlets.
The rapid growth rate of algae, coupled with low capitalization of facilities and ability to harvest every few days, could help algae become a more prominent fuel source. Competing with sugar crops that are harvested at most twice per year and then processed with expensive equipment should give a very competitive advantage to algal-sourced bio-diesel.
One big question is whether the auto industry will foresee the eventual dominance of bio-diesel and start producing more vehicles that can run on it.