Biodiesel Production from Algae
Here is another interesting renewable alternative to fossil fuels: biodiesel fuel from algae.
The Office of Fuels Development, a division of the Department of Energy, funded a program from 1978 through 1996 under the National Renewable Energy Laboratory known as the "Aquatic Species Program". The focus of this program was to investigate high oil yield algaes that could be grown specifically for the purpose of wide scale biodiesel production. Some species of algae are ideally suited to biodiesel production due to their high oil content (some as much as 50% oil), and extremely fast growth rates. From the results of the Aquatic Species Program, algae farms would let us supply enough biodiesel to completely replace petroleum as a transportation fuel in the US (as well as its other main use - home heating oil).
Of course, the major drawback to biodiesel fuel is that burning it still causes the same pollution problems as fossil fuels. However, there has been some creative thought about at least some aspects of this problem.
The program targeted coal and other fossil fuel fired power plants as the main sources of CO2. Typical coal-fired power plants emit flue gas from their stacks containing up to 13% CO2. This high concentration of CO2 enhances transfer and uptake of CO2 in the ponds. The concept of coupling a coal-fired power plant with an algae farm provides an elegant approach to recycle of the CO2 from coal combustion into a usable liquid fuel.
Biodiesel fuel has significant problems to face before if becomes a sustainable energy source, but it does provide a renewable resource that can at least recycle CO2 created by other sources. It is worth keeping an eye on this project.