There is a blog post today on Forbes online that summarizes a new paper in the journal of Environmental Science and Technology. (http://blogs.forbes.com/energysource/2010/04/07/report-says-algal-biofuels-may-not-cut-carbon-emissions-but-read-more-closely) This summary inspired me to read the original article, which suggests that the environmental impacts resulting from the production of algal biofuel are greater than that of traditional crops.
The article by Clarens, et al. from the University of Virginia (http://pubs.acs.org/doi/abs/10.1021/es902838n) says that if the nitrogen and phosphorous needed for growth need to be mined and carbon dioxide used to enhance growth is added from compressed gas transported to the site of the algae culturing, then the carbon dioxide emitted in the process is greater than that sequestered by the algae growth. Not surprising. The authors then say that if you grow algae on waste water (for the N and P) and with flue gas for the enhanced carbon dioxide for growth, then you can side step the negative carbon balance. If you read my other posts, you'll see I fully agree. We have to be recycling waste water and carbon dioxide if algae will ever be a part of a sustainable system.
The authors make assumptions for their model that include growing algae in raceways that are aerated with paddle wheels and fertilizers are used as flocculants. Harvesting is a combination of flocculation and centrifugation, which is an old idea and a very power hungry one. I like the idea of this kind of energy balance modeling, but it would be nice to see the results with a new and more innovative cultivation approach.
No comments:
Post a Comment