Solar Energy of the Green Variety
NPR has a nice article discussing how much energy the sun provides the earth when compared to how much we use each year. Basically, the amount the sun provides (86,000 terawatts/year) far outweighs the energy we use (15 terawatts/year). The only problem is that we don’t have the technology to properly harness and store all this energy. Therefore, the author argues that we should look to photosynthesis to properly store all this power.
And what is the best plant out there to do this? Algae.
Meanwhile, it turns out that there’s a great way to make oil from sunshine. It’s called photosynthesis. Plants absorb sunlight and use the energy to convert atmospheric CO2 into organic products. Indeed, that’s how our current hydrocarbon reserves were generated in the first place: with the aid of geology, the ancient products of photosynthesis were crushed and converted into oil and coal.
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Most land plants don’t make oil except in their seeds; the CO2 they fix goes largely into making shoots and roots and walls and starch, material that can be converted into ethanol but not into oil. But there’s a diverse and abundant population of photosynthetic organisms, collectively called the algae, that can be induced to make the likes of olive oil, oil that can fly jet airplanes just fine.
So, full disclosure: About two years ago I started up some experiments in my lab that related to algal biodiesel, and they worked, and I now have funding from the Department of Energy to pursue these leads. Having studied the sex life of a particular green soil alga, Chlamydomonas reinhardtii, all my research life, during which we made lots of cool discoveries that had no planetary impact whatsoever, it’s a trip to be asking interesting questions of Chlamy that are potentially also relevant.
When you deprive Chlamy of nitrogen, it bloats up with triacylglycerides (TAGs) until it looks like a fat-guy cartoon. (The image accompanying this blog shows this, where the red is chlorophyll fluorescence and the yellow comes from a dye that fluoresces yellow when it’s embedded in TAGs.])Same goes for marine diatoms: they all but burst with TAGs when deprived of silicon. Chemists can take these TAGs and readily convert them into transportation fuels. Better yet, the fat-extracted algae can be dried down and fed to chickens.
The algal biodiesel field is in its infancy. The solar industry is booming by comparison. There are daunting problems to be solved: how to grow enough cells and maximally elicit their TAG potential; how to protect them from the predators that make their way into cultivation ponds; how to harvest the TAGs. But there are also very smart engineers and start-up companies thinking hard about how to implement this potential source of fuel.
