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I'm always confused why we aren't pyrolyzing refuse and reusing the hydrocarbons in them. It's energetically and monetarily expensive, but both costs are more
by jaggederest 8y ago
I'm always confused why we aren't pyrolyzing refuse and reusing the hydrocarbons in them.
It's energetically and monetarily expensive, but both costs are more or less paid for by the output products and input products, as far as I am aware. And you get out fairly high quality fuels.
- pmiller2 8y agoMy guess is that you may end up with more than just hydrocarbons, and then you have to dispose of those waste byproducts. You certainly wouldn't do this to electronic waste, but, perhaps, if you could guarantee a pure stream of plastics, you could make it work.
- jaggederest 8y agoWell, one of the major problems is that if you pyrolyze PVC you get hydrochloric acid as a byproduct, but you can extract that by washing. These are known, operating plants, they just aren't operational here, for whatever reason.
- supertrope 8y agoAir pollution is worse than landfills. Incineration increases our exposure to heavy metals and dioxins. Burning plastic is a fairly nasty process and can only be done "cleanly" at very high temperatures. Trash also contains stuff like batteries that explode when burned.
- jaggederest 8y agoNot incineration. Pyrolysis, in an anoxic environment. It's the same process by which syngas is produced, except that the results are longer chain carbons and thus just have to be cracked and distilled rather than Fischer-Tropsch'd into usable feedstocks. You use about 30% of the input mass of organics to power the process (usually the lightest fraction that is equivalent to syngas), and the result is about 10% waste material and 60% usable mass fractions in the fuel-to-wax range, just like a normal oil refinery.