the propane industry sees an opportunity to seize a share of the auto sector. Its representatives are working hard to convince public officials to switch to propane-fueled school buses, which they claim are “near-zero emissions” vehicles that are better for kids and the climate.
Except — that’s not true. Propane is still a polluting fuel: While it is refined differently than diesel and natural gas and combusted in uniquely styled engines, it still has a measurable impact on air quality and the climate. If PERC’s deceptive marketing to children, parents, and school administrators is successful, the propane industry threatens to lock in fossil fuels and their polluting emissions for another generation of schoolchildren.
I don’t think you need to hedge with “generally”, I’m going to say it always has combustion products, and CO2 is the most benign gas product you can really hope for. In this case you’re burning carbon and hydrogen with oxygen to create carbon dioxide and water, and there really is a limit to how much energy you can extract from each molecule reacted. There’s no way around that, it’s a physical limitation.
I don’t know what kind of reaction doesn’t have by-products, maybe antimatter annihilation.
Fusion reactors have helium by-product which can be harvested I guess.
Point is you need to get pretty exotic and leave the realms of chemistry to get something with “near zero emmissions”.
The closest thing I can thing of is hydrogen, burning it just makes water, which while still a by-product, is the cleanest and least harmful product of I’m pretty sure any combustion reaction
Oh that’s true actually, you could probably call that emissions free in the sense that it really is harmless. I don’t know how I overlooked that tbh.
A lot of people are afraid because hydrogen fuel cells have a tendency to go boom, in terms of catastrophic failure.
There’s the going boom factor and the fact there is no good pressure vessel that can stop the hydrogen from slowly leaking out through the walls.
Also looking that up I just discovered this:
https://www.euractiv.com/section/energy/news/scientists-warn-against-global-warming-effect-of-hydrogen-leaks/
“Hydrogen is such a potent indirect greenhouse gas that it “could undermine the climate benefits of decarbonisation efforts,” warned Ilisa Ocko, a senior climate scientist at the EDF”
So… that creates a new problem before it gets out the tailpipe.