Consider how we get milk from cows: 1. Grow lots of cows. 2. Grind them up. 3. Extract the milk from the mixture. Or did we find a better way?
The standard approach to algal fuels is to grind up the cells and then extract their oil from the mixture. This takes lots of energy to get energy (the oil). The cost of doing this is part of what makes algal fuels expensive. Instead, perhaps we should think of each algal cell as a little cow.
Diatoms are algae that are particularly good at making lots of oil. Their oil includes many low molecular weight alkanes and related molecules. They naturally create everything from propane to jet fuel, or at least molecules a chemical step or two away from the ones we like to burn. Perhaps we could use selective breeding and/or genetic engineering to get diatoms to maximize production of the type of oil we want. There are about 200,000 species of diatoms to start from.
A diatom biofuel solar panel might look much like an electric solar panel, but it would contain live diatoms in water, with some means of milking them. The oil droplets might rise spontaneously to the top, or be separated by a continuous flow centrifuge run by an included electric solar panel.
The advantages of diatom solar panels are many:
- Local, rooftop production of gasoline, perhaps as easy as electric solar panels.
- No use of cropland to produce biofuels in competition with food.
- Works on buildings or nonarable land.
- Solves the energy storage problem: we know how to safely handle gasoline, and can use it any time of night or day. (Solar and wind power require battery or dam storage to use when the sun isn’t shining or when the wind isn’t blowing.)
- The energy density of gasoline far exceeds that of batteries: 44.4 MJ/kg versus only 0.17 MJ/kg for lead-acid batteries, i.e., 260 times higher.
- We would not have to switch from the mature technology of the gasoline engine to electric or hydrogen run automobiles.
- Batteries last only 5 years, while gasoline lasts indefinitely until used.
- Gasoline can be used to run automobiles, trucks and tractors, and heat and cool homes.
- Gasoline can be used to generate electricity.
- Gasoline would be equally available everywhere, including remote communities, at equal cost everywhere.
- Diatom biofuel solar panels would have zero carbon footprint.
- Oil would no longer be a factor in international relations, altering our whole economic system and toppling dictatorships.
In 2009 Dick proposed that diatoms be grown in solar panels and the oil be extracted without killing the diatoms. The work continues in an international collection of scientists in India (lab of Vandana Vinayak), France (lab of Benoît Schoefs), Georgia and Texas, USA (labs of Kalina M. Manoylov and Ali Beskok, and retired diatomists: Mary Ann Tiffany, Stephen Nagy, Richard Gordon). And it’s interdisciplinary: diatomists, algal physiologists, microscopists, nanofluidics engineers, and a theoretical biologist. Research continues on this idea. Some progress includes ways to get living diatoms to give up their oil without much effort on our part.
Other methods being tested include centrifugation, direct electric current, and titanium dioxide coating of live diatoms.
One problem is that the conditions in a solar panel could get extreme, especially in terms of high temperatures. Fortunately, diatoms are already extremophiles. Diatoms adapted to live in high temperatures already exist. We are presently culturing diatoms from Hot Lake in the state of Washington, USA, the hottest lake in the world where temperatures reach 55C. We will need to survey in situ oil contents of many hot springs diatoms to select the best.
Many practical aspects of making diatom solar panels will have to be addressed:
- There is a large literature on the ecology of microcosms, enclosed chambers that receive only light energy, but none specifically on diatoms in microcosms.
- What other organisms (bacteria, etc.) should we allow to live in diatom biofuel solar panels?
- Will diatoms in a microcosm recycle the nutrients, including silica, from their dead companions?
- With removal of oil, what nutrients, if any, will need to be replenished? Some might partition into the oil.
- Will diatoms continue to produce oil if milked at stationary phase in a microcosm?
- Can we build microcosms for diatoms that are gas permeable, allowing CO2 in and O2 out, while retaining water?
Dick presented this (via Skype) as his second talk “Progress Report on Diatom Biofuel Producing Solar Panels” at the VI-th Vereshchagin Baikal Conference September 7 – 12, 2015, Irkutsk, Russia. The first talk was on diatom motility. Motile diatoms in diatom biofuel solar panels might be able to seek optimal lighting or temperature conditions, if we designed the panels to allow for this.
- Ramachandra, T.V., D.M. Mahapatra, Karthick B. & R. Gordon (2009). Milking diatoms for sustainable energy: biochemical engineering versus gasoline-secreting diatom solar panels. Industrial & Engineering Chemistry Research 48(19, Complex Materials II special issue, October), 8769-8788.
- Gordon, R. & B.J. Poulin (2012). Quitting cold turkey: rapid oil independence for the USA. In: The Science of Algal Fuels: Phycology, Geology, Biophotonics, Genomics and Nanotechnology. Eds.: R. Gordon & J. Seckbach. Dordrecht, Springer: 3-20.
- Vinayak, V., R. Gordon, S. Gautam & A. Rai (2014). Discovery of a diatom that oozes oil. Advanced Science Letters 20(7-9, Special issue: National Conference on Nanotechnology and Renewable Energy, Jamia Millia Islamia, New Delhi, April 28-29, 2014), 1256-1267.
- Vinayak, V., K.M. Manoylov, H. Gateau, V. Blanckaert, G. Penchreac’h, J. Hérault, J. Marchand, R. Gordon & B. Schoefs (2015). Diatom milking: a review and new approaches. Marine Drugs 13(5), 2629-2665.