photo by Future-PhD. via flickr
We've written about the enthusiasm for algae-based biofuels a number of times, but this is first time I've seen reference to this angle on the green fuel's production. Using waste carbon emissions from coal-fired power plants to grow the algae.
Given that it is green conventional wisdom (as well as my personal belief) that we should be doing everything possible to reduce coal burning as much and as quickly as possible, I am torn by this development.
CO2 from coal burning absorbed by algae
The practice, which is being tested by NRG Energy from Louisiana runs like this: rather then sending carbon emissions up the smokestack, the CO2 is used to grow algae, which then can be harvested and used as biomass for re-firing in the plant or converted into liquid biofuels for transport. Renewable Energy World estimates that two million tons of algae would be required to capture one million tons of CO2.
Sounds like a prudent enough idea, right? But what will enough algae be able to be grown to offset a significant portion of the coal plant's emissions? Since the average 500 MW coal-fired plant produces approximately 3 million tons of CO2 emissions per year, each would have to generate 6 million tons of algae to absorb it all. Given the production stats for the first commercial algae plant this might be possible.
photo by Bruno D Rodrigues
An excuse to keep burning coal?
Or it could all just be a ruse to expand the use coal. A quote from David Crane, NRG's chief executive, seems to hint at this: "Coal is—and will remain—the premier domestic fuel source for power generation purposes in the United States for the foreseeable future. This means it is incumbent on us not only to build new coal plants using technology which limits or eliminates greenhouse gas emssions but also to find the best way to retrofit the country's existing fleet of coal plants for post-combustion carbon capture."
To me this statement makes the assumption that the best way forward is simply a tweak of business as usual, consumption as usual, energy use patterns—rather than attempting to address the base problem: consumption levels of energy in the developed world are well beyond those which are ecologically sustainable.
While algae biofuels offer much promise, is expansion of them which is enabled by the continued deployment and expansion of one of the most polluting forms of energy ever deployed really a good idea?
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