I understand that this is not the solution, we need to phase out gas-powered engines in order to reduce carbon emissions by 50% by 2030, and I understand that the filters would have to be changed and washed/recycled/disposed of constantly and couldn’t just sit on the tailpipe clogging up, I just don’t understand why a filter would be useless, wouldn’t it help just a little? Would it just ruin the cars? What about rooftop carbon capture devices? Is there nothing we can do to reduce pollution and carbon output from our current combustion engines?
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We do. They’re called catalytic converters. But any filter is going to obstruct the emissions which has an impact on engine efficiency, so there is a trade off.
We do, it is called a catalytic converter and it reduces emissions a great deal, but they do wear out eventually and replacing them is not cheap.
Most of the emissions are otherwise too small to be caught by a regular filter, they are smaller than viruses even. Methane carbon dioxide, nitrous oxide are some of the smallest molecules out there.
CO2 is a gas like oxygen or nitrogen; you can’t trap it with a filter, it’ll pass right through. Filters are only good for particulate matter like soot. If you want to trap a car’s exhaust CO2, you need an airtight barrier.
Cars put out a much larger volume of CO2 than you probably imagine. Burning a gallon of gas creates 8.887 kg of CO2, which at a density of 1.87 kg/m^3 takes up 4.75 cubic meters of space—*1,255 times larger than the gallon of gas you started with.* You’d need to tow around a miniature blimp full of CO2 to contain your car’s carbon output.
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We do. Cars are less polluting than lawn mowers now. You get to a point where if you’re exhaust is too restrictive the care will not run. I suppose you maybe could put a maintenance item like a filter you clean/replace every 1000 miles but then people will just take them off and claim they get better performance(whether it’s true or not) so they don’t have to pay to replace it or keep up on it.
Others mentioned the reasons filtering wouldn’t work, but as far as rooftop carbon capture devices, trees work pretty well.
A lot of people are talking about catalytic converters, but a more “true” filter would be Diesel Particulate Filter, or DPF. They act like an actual filter, filtering exhaust soot from diesel engines. The thing is that said filter needs to be cleaned somehow, as a clogged filter would not only increase emissions, but also reduces engine power and reduces fuel efficiency. Some filters requires replacement, but the vast majority would “recharge” by raising exhaust temps, which would burn the captured soot. Issue is that this requires burning extra fuel, which would hurt fuel economy. There’s also claims of DPF systems being unreliable and being very expensive to repair, although I haven’t personally owned a diesel vehicle long-term.
There’s also other systems in place, such as recycling exhaust gasses back inside the engine’s intake (EGR system), much better engine control electronics, modern “fast burning” combustion, etc. Modern cars are nothing like old carbureted pickups of several decades ago.
Brilliant
These days, cars run clean enough that there isn’t any particulate carbon (smoke particles) coming out of the tailpipe. The carbon comes out of the tailpipe in the form of CO2, which is a gas, and can’t be caught by a mechanical filter. You could use a chemical filter, but cars put out a LOT of CO2, and you would need an absolutely huge filter, which would fill up with CO2 quickly and need to be replaced very frequently. It would also be very expensive to make these sorts of filters.
[Jeremy’s CO2 Greenhouse | Top Gear](https://www.youtube.com/watch?v=nz-Q-4RUd28)
Awesome little segment and Clarkson is always a hoot. But it does seriously highlight a potential technology and what the drawback is which is cost and replacement interval and the added weight which would burn even more fuel at the end of the day. The rocks featured are **Soda Lime Crystals** which do work in a high school chemistry class way but will not ever be a viable solution.
This is not to say that there aren’t other technologies out there that might be able to make a significant difference.
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