Eli5: why can’t we burn all our garbage and filter out all the toxic fumes?


I understand it’s probably a more complex issue, but could it be similar to a 4th grade science project where you filter water through a bottle with a variety of rocks, sticks, moss etc?

In: 1

Because you can filter out large chunks of debris from water using filters, but can’t filter dissolved salt out.

Filtering toxic fumes is equivalent to that, when toxic molecues are pretty similar to air molecules when it comes to their abilities to pass through a filter.

Ultimately, even when burned with a plasma arc, some of our garbage is still very toxic to us like mercury, cadmiun, nuclear waste, etc. We will still need landfills or some kind of hazardous waste storage.

Japan is doing something along the lines of your post with plasma waste converters/recyclers. Garbage gets sorted, recycled, where the leftover is burned and syngas is collected.

There’re already garbage disposer that burn several safe-ish burnable garbage. But the operation is quite energy intensive. Combine this with how to collect the garbage and categorize it into what can or cant be burn can also be quite troublesome.

We can and we do, in waste incineration plants (sometimes called waste-to-energy plants). Usually non-flamable garbage like rubble and metal is sorted out and then rest can be burned. Biohazard garbage is only burned, it is illegal to do anything else with it.

Proper waste managment is:
1. Avoiding waste production,
2. Re-using (like cleaning glass bottle to be used again),
3. Recycling (like using smashed glass bottle as a raw material for glass production),
4. Using waste as fuel (that is the step you are asking about),
5. Proper and safe storage (landfill);

So in other words we try to organise our waste managment everywhere where it is economically viable in such a way, that every type of waste that can be burned and cannot be reclaimed as a material/ raw resource is in fact being burned.

This is actually something that is happening already. With the caveat that it’s not really possible to ENTIRELY filter out the toxic fumes entirely.

Trash incinerators create a massive amount of heat, which means that you can use it to create steam, that pushes on a turbine on a generator. I.e, most trash incinerators are actually electrical power plants, trash is just the fuel.

Another thing you can use the steam water for is that you can use it for central heating. In cities where the climate requires that you heat your house for 8 months or more per year, it’s financially sound to sell hot water so that many, many homes and businesses can use the energy for heating instead of having their own combusting heat source in the building.

If you want to be a bit blunt, it’s only in this kind of setup that a trash incinerator is particular environment friendly.

– When you compare the combustion of trash with burning something biological, like a rest product from the timber industry.

– when you compare the incinerators exhaust fumes to the less clean fumes you would have had if every building in the entire city would have had to burn oil, natural gas or firewood for heating.

In other words, even if you think about it, it’s not a great idea. It’s just that it’s an idea that is a lot better than digging a large hole in the ground and making a landfill of trash, but to be convinced that it IS a better idea, you need to produce things that you would otherwise have exhaust from, when you compare the exhausts you get from trash.

One reason that the equation is a bit fiddly is that trash is not really a homogen and predictable product. Incinerators more or less CONSTANTLY add a hint petroleum to the process to maintain the exhaust *temperature* that their cleaning equipment needs to function as intended.

It’s a complex system, with quite many factors that speak both for and against.