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Comment by tda | Hacker News Reader

Plastic waste should be burned for heat and/or electricity in an incinerator. Every other usage/disposal method seems like a waste to me. Instead of burning fossil fuels directly, we get much more value from them if we first turn it into some plastic product, and only then burn it. And as long as we keep burning fossil fuels for heat and power, let's not wate out attention on recycling (downcycling actually) plastics as we can much better burn the old and make fresh new plastic from the fossil fuels we didn't have to burn because of that.

When we are not relying on fossil fuels anymore for heat and power (which is hopefully sooner than later), only then we need to start looking into plastic recycling

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This is actually the "best" answer for our plastics problem. There was an NPR/Planet Money podcast on it recently here: https://www.npr.org/2020/09/11/912150085/waste-land and there are plenty of other sources that all agree on this premise. I have worked in waste management a few years ago and recycling is not the long-term solution.

Why do we want to put the plastic's carbon into the atmosphere instead of back into the ground where it came from?

Because then we can avoid pumping oil out of the ground and burning that.

The hydrocarbons are going to get burned one way or another, you can just trade one type for another types.

> you can just trade one type for another types

You cannot replace most oil-based fuel with incinerators. So I'll disagree there.

The utility of oil-based fuels is the energy density in combustion. Burning plastic doesn't come close to the same exchange.

> The utility of oil-based fuels is the energy density in combustion. Burning plastic doesn't come close to the same exchange.

The energy density of plastic (by weight, not volume) is virtually identical to that of oil.

Yes, the machine used to burn oil vs plastic looks different, but coal plants can burn plastic without much modification - and they would be much much cleaner than coal when they do so.

> The energy density of plastic (by weight, not volume) is virtually identical to that of oil.

Oil-based unleaded fuel is not oil. You probably could run trains on plastic. That's if you didn't mind hot plastic raining down around the tracks as the coal dust and soot did when we used it for trains.

We don’t burn oil though. We burn natural gas, in highly-efficient turbines. Burning oil and coal is obsolete technology that we are trying to phase out.

Even more to the point: we can avoid digging coal from the ground, which burns even dirtier than plastics trash.

And even in the lofty goal end state of zero fossils, if it's not a complete collapse back to medieval tech (and population numbers), we would likely end up with biomass based plastics serving as packaging and the like at the upper end of that carbon's energy slope, before utilizing the remaining bound energy in an incinerator.

Biodegradable properties of grown plastics are only a last line of defense against pollution when collection has failed.

You do have significant differences between noxious fumes and clean burning between burning plastic vs burning fossil fuels. The energy captured from the burn is obviously not the same - same reason you can't just set fire to a "bowl" of plastic.

What noxious fumes? Plastics are very clean burning if you do it properly (which isn't hard to do).

They burn MUCH MUCH cleaner that coal for example.

> The energy captured from the burn is obviously not the same

There is nothing obvious about it. I don't understand what you mean? Plastics have around the same energy density as oil.

Whether we should burn, recycle, or dump plastic into a landfill depends entirely on the relative amount of energy generated and CO2 emitted by those different options. Just because plastic and natural gas both are/come from hydrocarbons doesn’t mean that burning them produces anywhere near the same amount of emissions per MWh, or that the economics would be at all close.

And if you are proposing the construction of new power plants to burn trash, your justification also has to explain why that would be preferable to building wind/solar instead

>And if you are proposing the construction of new power plants to burn trash, your justification also has to explain why that would be preferable to building wind/solar instead

An easy to grasp reason is that we still can't viably store energy for long enough periods for wind and solar alone to work. Also solar and wind might not work so well everywhere.

That’s a favorite talking point of climate deniers, but even once storage becomes a concern this proposal is only one of many possible options. What I’m pointing out is that this thread doesn’t actually contain any quantitative argument why burning trash is competitive with, let alone superior to, credible alternatives

Doesn't burning plastic produce large amounts of toxic off gassing?

My understanding is that incinerators don't just release the output. The exhaust is pumped back into the system and dealt with somehow. The extent to which the release is "dealt with" is the tricky part.

I'm going to guess that large amounts of CO2 is a byproduct and is vented.

CO2 is bad but not toxic at all. It's inert. The toxic ones are toxic because they still have some energy left and the earlier you pull out that energy the better. Preferably in a plant that puts that energy to some form of use.

Have you been under a rock for the last 20 years?

Yes , it does. Burning plastic without somehow accounting for that is a terrible idea.

Is there a way to mitigate this, or make use of the waste gasses?

Mitigated in Japan. After dioxin gate, any incinerator must be run at high temperature. https://www.japan.go.jp/tomodachi/2015/winter2015/advanced_w...

>At the plant, the garbage is first mixed with a large crane so that all the different kinds and sizes of items are uniformly distributed for easier burning. Next, the waste is incinerated at extremely high temperatures, over 800°C (1,472°F). This reduces not only the volume to 1/20 of what it was but also the amount of dioxin gases produced by incineration. Multiple provisions are made to prevent gases and harmful substances emitted during incineration, such as sulfur oxide and particulate matter, from being emitted outside the facilities. Chimneys of waste incineration plants emit vapor—not smoke—that does not contain harmful substances. Heat energy produced by the incinerator is used to supply the electricity needs of the entire facility, with any remainder being sold (earning approximately JPY 9.8 billion annually, or USD78.6 million, in income from electricity). High-temperature water is also supplied to neighborhood swimming pools and tropical plant greenhouses.

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See also: Sweden also incinerates waste for heat and electricity, and a few years ago there was a story about how they ran out of trash and had to buy more trash from their neighbors.

See my other comment as well as this HN thread: https://news.ycombinator.com/item?id=20551946

No, they produce water and CO2. Nothing toxic, unless you don't give enough air (so obviously make sure to give enough air).

This isn't some theory - right now, today, lost of plastic is being burned, and it works just fine. They try to keep is off the radar because of misinformed people thinking it's bad.

this is widely promoted (incinerator to energy) and widely disliked (state of the air in industrial locations around the world) .. not a new idea

I think just about all household trash in the Netherlands is incinerated. And as far as I know the exhoust fumes are manageable, but definitely not something to live next to. Just like any other fossil fuel run powerplant by the way.

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