This post was written by Paul O’Callaghan, founding CEO of the Clean Tech consultancy, O2 Environmental Inc. and lecturer on Sustainable Energy at the BC Institute of Technology.
There was much furore recently surrounding the story ‘Joule Biotech comes out of stealth with sun-powered biofuel’.
The premise is that the technology can take solar energy and use it to convert carbon dioxide directly into fuel. A one stop-shop to soak up carbon dioxide and produce a biofuel.
Having dug into it a little, the conclusion I came to is that it’s not as radical as it sounds. It is basically directed photosynthesis: same principle as oil from algae, or biofuels. The overall efficiencies are likely to be 10 times lower than that from solar PV processes, but, in terms of where biofuels are heading, it is on the right track.
The press release included the following:
“The SolarConverter captures the sun and is fed carbon dioxide and combine inside where a solution of brackish water and nutrients exist with photosynthetic organisms—secreting the SolarFuel,” Joule’s CEO Bill Sims said, describing the end-product as a hydrocarbon-based fuel, not a biofuel.
Points to Note:
1. This is a solar powered system.
2. Its a Biological system
The input energy into this system is incident solar radiation. This varies from place to place but in North America a reasonable average year round figure would be 200 Watts per m2.
So that’s what you have to work with. That is what is referred to as Primary energy.
Solar panels are about 10% efficient, so you get 10% of that 200 Watts of incident power as useful energy, converted into electrons, which is the energy carrier. Electricity is a versatile energy carrier, but difficult to store. Hence why high energy density liquid fuels are so good in transportation. They are an energy carrier, or ‘Secondary energy’.
What is described here is the production of a secondary energy carrier via photosynthesis.
This is exactly what Oil from Algae is. Algae are fast growing unicellular organisms, certain species of which produce large quantities (50%) of oil as a percentage of the total cell weight. The algae oil is very like diesel, so you can produce biodiesel.
The Joule Biotech system is using a photosynthetic organism also. They don’t say whether it is an algae, plant cell cultures, or some new genetic hybrid, but either way, I don’t think they will have improved on millenia of evolution in terms of the net efficiency of the photosynthesis process, i.e. how much of the solar energy the living organism is capable of capturing.
Compared to other plants, the photosynthetic efficiency of algae is very high – almost 3 times that of sugar cane for instance. Compared to solar energy, however, the energy efficiency of algae is very low – around 1 percent, while solar panels have an efficiency of at least 10 percent, and solar thermal gets 20 percent and more.
So the absolute efficiency of the Joule Biotech system at converting solar energy into chemical energy is likely to be similar to algae or other high yield plants.
So why go with Joule Biotech Vs Solar PV?
1. Carbon sequestration – this could be the tail wagging the dog. There is business to be made in tieing up CO2. Overall this is carbon neutral, but if you take the CO2 from a stack, there may be a credit there.
2. There is a demand for alternative liquid fuels
Even if Solar PV is a more efficient method of capturing solar energy, it produces electricity and we still run our transport fleet on liquid fuels. You could take Solar PV and use the electricity produced to synthesize hydrogen or other chemical fuels such as methyl hydrate, but the overall accumulated losses might make a Joule Biotech type option more favorable.
3. The alternative chemicals produced are likely to be a higher value than the fuels produced.
What Joule Biotech may have, and this is one of the challenges with oil from algae, is engineered a system which works. The challenges are maintaining a pure cell culture on an on-going basis. If you want high yield of a certain product, you need pure cultures. That raises challenges when you try and do it on a large scale, particularly if you need to expose it all to sunlight.
The other way to go is low yield open ponds. This is a mixed culture, low efficiency, low yield process. You accept that you get a lower yield but it’s cheaper to build. So, on a cost per unit of fuel produced, it may be the same. It’s like the debate between high efficiency PV solar and low efficiency solar. What matters is the unit cost per watt of capacity. The fuel is free, so low efficiency is fine, the capital cost per watt of installed capacity is key.
The other challenge with producing fuel from photosynthetic bio-organisms is getting the fuel out afterward, the extraction and purification process. You have cells and what you want is pure fuel. Perhaps Joule Biotech have something unique to offer in this regard as well.
Overall, in terms of where the biofuels market is heading, Joule Biotech appear to be on the right track. The ability to be able to produce multiple different products, different fuels and different chemicals is key. This allows you flexibility. As the demand or price of one product increases, you can alter your output to match market demand.
The future of biofuels appears to be the interlinking of technology platforms to allow the use of multiple feedstocks, to produce multiple products. Vinod Khosla has invested in a large number of Biofuel companies which all synergise and interlink.
In terms of feedstock, Joule Biotech are using carbon dioxide and sunlight. It’s a biofuel with an accelerated path, less steps, from biology to fuel and the option to tailor it to produce different fuels.
Joule’s CEO Bill Sims says that the end-product they produce is a ‘hydrocarbon-based fuel, not a biofuel’. I think that is semantics. They still use a living organism to carry out the chemical synthesis to produce the fuel product.
This means that they have some of the same issues and challenges as other bio-based processes.
1. Cells need phosphorus
I wrote about Peak Phosphorus in a previous blog. This is a big issue. The cells used by Joule Biotech will need nutrients. Phosphorus is a non-renewable resource and one of the big challenges for biofuels, both first generation and second generation, is that if you are growing a crop, be it switch grass, sugar cane or algae, you need phosphorus. Now in the case of Joule Biotech, they may be able to keep recycling this back into the system and keep a closed loop going. If this is the case, that would be great.
2. Water is required
All living cells need water. Sure, they may be able to function on wastewater, brackish water or saltwater, but you need to provide them with water.
Check out Leave the Algae Alone for an excellent piece on this.
The idea of converting solar energy into chemical energy is an excellent one. Biofuel based processes are one way of doing this.
If one could avoid the biology altogether that would be even better. Check out Blue Fuel Energy for some interesting ideas on how to chemically synthesise a chemical energy carrier using renewable energy. Its still at a very nascent stage, but it stacks up very well as an overall concept.