The Blade filter is, however, somehow supposed to decrease CO2 emissions as well, by “up to 12%“. This strikes me as a very peculiar claim. What’s it doing with the CO2? Cracking it to carbon that stays in the filter and oxygen that’s released?
Let’s assume, for the sake of argument, that this near-magical feat is in fact what it’s doing. Doing this with nothing but exhaust heat to work with would, I think, be a Nobel-prize-winning achievement, but never mind. How much carbon would the thing actually have to catch, even if you replaced it every 7000 miles on the dot?
Well, the carbon dioxide molecule contains two oxygen atoms (atomic weight 16) and one carbon (atomic weight 12). So by weight, it’s about 27.3% carbon.
7000 miles of driving is 11265 kilometres. If you’re driving a car which emits a mere 100 grams of CO2 per kilometre, it’ll emit a total mass of 1126.5 kilograms of CO2 over that period. The total mass of the carbon atoms in that much CO2 is 307.2 kilograms. Let’s say that in this case the Blade’s “up to 12%” CO2 catching turns out to mean “6%”. 6% of 307.2 kilograms is 18.4 kilograms.
So if there isn’t eighteen kilograms of soot in the filter when you replace it, you haven’t caught six per cent of the carbon.
Note that carbon also isn’t very dense. Even diamond only weighs about 3.5 grams per cubic centimetre. So even if the magic filter turned the magically extracted carbon into diamonds, you’d still end up with 5267 cubic centimetres, 312 cubic inches, of them clogging up the filter in the above situation. Graphite is only about 2.2 grams per cubic centimetre; that’d be 8379cc, 511 cubic inches, 2.2 US gallons, all somehow having to fit in the filter.
You could deal with the gallons of carbon clog by just burning off the carbon, but that would of course defeat the purpose of collecting it in the first place. Or you could just blow the soot out the exhaust pipe, but this would increase particulate matter emissions, which the Blade, you’ll recall, is meant to reduce.
As far as improved fuel economy goes, it’s uncontroversial that you can reduce the fuel consumption of internal combustion engines by restricting the air intake or, less elegantly, the exhaust. Restricting air intake is exactly what you’re doing whenever you don’t have the throttle wide open.
