Using just CO2, sunlight and water – and some math right off Einsteins’ blackboard — researchers come up with a potential game-changing technology for making renewable fuels. The hunt is on for technologies that use carbon dioxide and non-potable water since they are available in such tantalizing abundance. So, lets dig into one of the most interesting ways to make renewable fuels to appear in a month of Sundays.
The National Science Foundation’s division of Emerging Frontiers in Research and Innovation, widely known as EFRI, made a $2 million grant to a group of researchers led by Lehigh chemical and bioengineering professors Steve McIntosh and Bryan Berger — in a project that aims to make methanol using only carbon dioxide, sunlight and water.
The project utilizes a new low-cost technology that McIntosh and Berger developed to produce low-cost quantum dots from bacteria.
Er, Quantum Dots?
OK, let’s do a little science backgrounder here. A quantum dot is a really tiny crystal — so small (in the 5 to 50 nanometer range, at the low end roughly equivalent to the smallest transistor ever made) that the crystal begins to exhibit properties associated with quantum mechanics.
Specific to fuels, when a photon, arriving on planet Earth after an eight minute journey from the Sun, happens to strike a quantum dot (instead of say, a plant’s light harvesting mechanism) — it produces an excited electron (which is to say, an electron in a higher energy state than the garden variety electrons that power your computer).
Two things make this effect important for the production of fuels. First, there’s no limitation imposed by photovoltaic or photosynthetic efficiency — you get one electron for every photon. Second, the Lehigh team has theorized that these excited electrons catalyze the removal of hydrogen from water and carbon from CO2, and produce methanol in a continuous flow process.
That theory is what is being tested under the EFRI grant.
What Makes It Low Cost?
Quantum dots were discovered several decades ago, and are today employed in industrial applications. But the use of them is severely constrained by the high cost of producing them, using rare-metal catalysts, toxic solvents, and high temperature process conditions.
In a foundational bit of work that preceded this EFRI grant, McIntosh and Berger demonstrated their novel method for producing quantum dots in bacteria. In the EFRI project, an expanded research team will use quantum dots in tandem with a series of yeast-synthesized enzymes — providing the energy to a process that will create methanol from the aforementioned carbon dioxide and water.
There are a variety of outcomes worth noting — should the technology prove out.
First, one has a perfectly good, densified means of transporting captured energy — which is to say, more economically feasible than transporting gases, and more energy-efficient than transporting electrons.
Second, one has an energy system based on abundant materials — which is to to say, CO2, sunlight and water — instead of comparatively scarce resources such as sugars or fossil fuels.
Third, the high photon efficiency could prove to surpass not only current biological processes for making fuels; it could prove more efficient in utilizing solar energy than solar PV technology.
Fourth — and this is looking well down the line — here’s a pretty decent theoretical system for generating liquid fuels on neighboring planets like Mars, to fuel return trips.
OK, It’s a Renewable Fuel, but is It a Biofuel?
As the Digesterati point out from time to time, because biofuels are usually renewable fuels, many people equate the two terms. But not all renewable fuels are biofuels, and not all biofuels are renewable fuels.
As we see it, a biofuel is a fuel made using a biologically based process — so, for example, Calysta Energy makes biofuels by using biocatalysts to make fuels from fossil methane. But, in this example, Calysta is not making renewable fuels.
In the case of companies like Joule — and with this technology — though they are not using biomass (rather, using the same sources that plants use: sunlight, water and CO2) they are using biological processes. In this case, yeast-based enzymes and quantum dots made in bacteria. Voila, biofuels.