Just a nit: beer never had loads of NO2. So-called "nitro" pours are pushed with nitrogen gas (N2), not NO2. This is a good thing, since NO2 is rather toxic: https://en.wikipedia.org/wiki/Nitrogen_dioxide
That's an apples-and-oranges comparison. The system you cite differs from the one under discussion in several ways; the most important of which are:
1. The cited system does not include a light-harvesting component. It merely postulates that the required energy could be generated from photovoltaics. This would introduce additional cost and complexity along with an efficiency hit.
2. The cited system comprises a bacterium in conjuction with an electrode-supported catalyst, whereas the system under discussion is solely an engineered bacterium.
Finally, it is not correct to refer to cadmium and cysteine as feedstocks. They are components of the catalyst, and they are not consumed during catalysis. The only feedstocks for both systems are CO2 and water.
>That said, relying on a fuel source that requires CO2 as
>input seems just as potentially destabilizing to the global
>carbon cycle as relying on a fuel source that produces CO2
>as byproduct.
Not really. Using CO2 to generate a fuel which then liberates CO2 when it is consumed ends up being CO2-neutral, which is exactly the way to go.
You've got a lot of it right, but you're missing the key advance described here, which--if true--is pretty wild.
Taking a step back, in 2016, this group did cover a bacterium with tiny semiconductor nanoparticles (specifically CdS) just as you say. That work is described here: http://www.pnas.org/content/113/42/11750.full In short, the semiconductors act as mini-solar cells, converting light into electrical current. The bacteria then use that electricity to convert CO2 into acetic acid. That already is pretty cool.
However, what they claim now is that they don't even need to make the semiconductor nanoparticles. They can simply grow the bacteria in an environment containing cadmium and sulfur sources and the bacterium will synthesize it's own cadmium sulfide coat, and use it for photosensitization.
This is really pretty wild. Bacteria will often incorporate various elements from their host medium, but the generally use them to make biomolecules, not semiconductors. Right now, this is just being presented at a conference, but it will be very interesting to see the details when the full paper comes out.
That may be the origin of this particular phrasing, but the idea is much older:
In 1973, the artist Richard Serra made a film called Television Delivers People which declares "You are the product of TV" [0]
Key to Noam Chomsky's _Manufacturing Consent_ (1988) is the idea that advertising-supported media caters to the desires of the advertiser, not the media consumer [1]
I won't pass judgement on whether 410 micrograms/kg is an "unbelievable" amount, but I will just mention that it is 410 parts per billion, or less than 1 ppm.
Some background and context from someone tangentially related to the field:
1. The overall idea here is to take an intermittent energy source (e.g. solar power) and "store" it as chemical fuel, in this case hydrogen and oxygen. This is what plants do, and we can also view fossil fuels as resulting from the "storage" of millions of years of solar energy. Note also that you get the water back when you burn the hydrogen, so there is no net consumption of water, it's just a carrier.
2. While you can split water without a catalyst, most of the energy gets wasted as heat, so this is not a great way to go if you're trying to do energy storage.
3. Efficient catalysts exist for this reaction, but they are based on rare and expensive metals, typically Pd, Pt, and Ir. As a result, there has been a search for catalysts involving "first-row" metals such as Fe, Co, Ni, etc.
4. There are variety of metrics for an electrocatalyst (efficiency, stability, cost, etc), but it's a fair bet that if this were significantly better than state-of-the-art, it would be in Science or Nature rather than PNAS.