There is no perfect energy source. Each and every one has its own advantages and compromises. This series will explore the pros and cons of various energy sources. Learn about other forms of energy generation here.
Algae–based biofuel is a new energy source that has been getting a lot of attention lately. Certain types of algae contain natural oils that can be readily distilled into a vegetable oil or a number of petroleum-like products that could serve as drop-in replacements for gasoline, diesel, and jet fuel.
But because it’s a bio-fuel, it is essentially carbon-neutral because the carbon emitted when it is burned had just recently been absorbed as food, which means that the net CO2 emission is essentially the same as if the algae had never been grown. That does not include CO2 utilized in production. Industry claims assert that algae-based bio-diesel has a GHG footprint that is 93 percent less than conventional diesel. Some algae production is sited near sources of CO2 such as power plants, in a kind of symbiotic relationship. Algae-based fuel yields considerably more energy per unit area than other bio-fuels. It can also be grown on land otherwise unsuitable for agriculture. The technology is quickly moving out of the lab and into commercial scale production. A number of companies developing refineries include Solazyme, Sapphire Energy (which just last week announced another $144 million in funding) and OPXBIO. Aviation trials with several airlines including United and Qantas have been successfully completed using fuel blends of up to 40 percent algae-derived fuel.
Algae was initially raised in large shallow ponds which produced about 5,000 gallons per acre-year and required a fair amount of water to compensate for evaporation. More recently, companies have migrated to vertical photo bio-reactors (PBRs) that are gravity fed, with no evaporation, and in which 85 percent of the water is recycled along with excess nutrients and CO2.
Here is a list of pros and cons for algae-based biofuels.
- Bio-based fuel with essentially carbon neutral combustion
- Drop in replacement for petroleum-based liquid fuels
- Inherently renewable
- Absorbs carbon dioxide as it grows
- Both waste CO2 and wastewater can be used as nutrients
- Higher energy per-acre than other bio-fuels
- Can be grown on land unsuitable for other types of agriculture
- Scalable: Study found that 17 percent of U.S. oil imports could be met with algae
- Investments are being made
- Production is presently scaling up (Navy buying 100,000 gallons this year)
- Research has been underway for 50 years
- Need to be grown under controlled temperature conditions
- Requires a considerable amount of land and water
- Cold flow issues with algal biofuel
- Some researchers using genetic engineering to develop optimal algae strains
- Requires phosphorus as a fertilizer which is becoming scarce
- Fertilizer production is carbon dependent
- Relatively high upfront capital costs
- Not clear yet what the ultimate cost per gallon will be. Presently too high.
In summary, algae-based bio-fuel is a promising energy source that is in the latter stages of development. A number of issues related to the ultimate cost of the product need to be resolved, but there is a good deal of research money going into this as production is beginning to scale up. Land issues can be addressed using marginal land. Water can be recycled in reactors. Cold flow issues might result in the fuels being blended with other fuels or possibly additives. Fertilizer issues could be addressed using waste streams, thereby recycling the critical nutrients. Time will tell, though I believe this is an important technology to watch.
Original post available here.