Monday, March 2, 2009

Algae, A New Energy Source?

With transportation uses of energy on the rise in the United States and currently 25-30% of total US energy accounted for by transportation uses, petroleum is almost solely relied upon to fill these needs. However, with petroleum costs rising, green house emissions gasses increasing in amount and decreasing the ozone layer, alternative fuel sources and their respective processes have been formed, researched, and tested. One of these processes is the Fisher-Tropsch process. Established in the 1920s by two German scientists, this process was created in order to convert coal to diesel fuel. Now, research has found feedstocks other than coal that can be used in this process. Biomasses, such as algae have become probable feedstock resource for this process.

With the Fischer-Tropsch (FT) process the fuel created is a very high performing diesel that greatly resembles that of conventional diesel. All properties of the fuel generated by the FT process are the same as conventional diesel. The only difference is that the toxicity of the fuel from the FT process is a little less. Also, the functional unit is 1 gal of FT diesel = 1 gal of conventional diesel.

From feedstock to finished product, many steps occur during the process. Converting the feedstock to a finished product via the Fisher -Tropsch process requires other processes to take place. These processes include making fertilizers for the cultivation of the algae, dewatering the wet algae in order to produce dry algae, gasifying the algae to extract CO2, H2, and other trace elements, and finally using the syngas formed by CO2 as a feed for the Fisher-Tropsch process to make diesel. Below a flow diagram illustrates the process of converting the algae to the fuel.
As you can see, this is a very interesting process that can show some promising attempts for alternative energy resources. However, a lot of energy is required in order to have this process work. Because of this, this process is still not a viable resource. More research is needed in order to make this process possible.

algae:biodisel. (n.d.). Greenfuels: CO2 rich fuel gas. Retrieved May 2, 2008, from http://seekerblog.com/‌archives/‌20061010/‌greenfuels-biodiesel-from-algae/

Sears, J. (2008, February 19). Strategic road to commercialization: food and fuel from algae [Brochure]. AFOSR Algae Oil for Jet Fuel Production Workshop: A2BE Carbon Capture. Retrieved May 2, 2008, from
http://www.algaeatwork.com/‌page_attachments/‌AFOSRfinalA2BE.pdf

Stranges, D. A. (2008, May 2). Discussion of current Fisher-Tropsch process plants. Interview presented at Texas A&M University, Telephone.

3 comments:

czak said...

I am curious about the step outlined in the posted diagram as "Gasification of Algae...". My understanding is that syngas has to be broken down into CO2 and H2 in order to be used in the production of other chemicals. I'm assuming that this would be what occurs at the refinery for the production of FT diesel. It seems to me that the gasification process would more likely produce a syngas, not CO2 and H2 that must be combined into syngas only to be broken up again later. My basis for this comment is that in the UT combustion labs we use a Porous Media reactor to convert biofuels to what we call syngas (a gaseous mixture chiefly composed of CO2 and H2) which is then separated and used for various purposes. Although we have not tried algae oil yet, based on previous experiments, we expect similar syngas production. If anyone has any idea as to why the algae gasification process would produce CO2 and H2 separately and even better why that would be a bad thing, I would appreciate a response. Otherwise, I think that this diagram and its creator might be mistaken.

Brodie Black said...

This post mentioned that toxicity of the fuel from the FT process is "a little less" than conventional diesel. I would point out that FT diesel actually emits significantly less pollutants, with particular emphasis on its low emission of sulfur and particulate matter. However, I'm not sure if this translates equally when different feedstocks are used.

Some general comments on FT diesel emission properties can be seen at
http://www.afdc.energy.gov/afdc/fuels/emerging_gas_liquids_benefits.html

David Wogan said...

Casey brings up a great point: gasifying the algal biomass will end up producing syngas (CO and H2), which can then be further processed into F-T products.