What happens to the toxic byproduct from burning the waste?
How is the energy harnessed, stored and ultimately used?
Why aren’t more countries doing this? Limitations?
Thanks
In: Other
Garbage is burned just like coal would be, which heats water to make steam that turn a turbine to produce electricity. If you hear things hot enough the ‘toxic’ stuff burns or breaks down, what comes out the chimney is mostly CO2 and water vapor. Ash then goes to a dump.
The downside is that all the carbon is now in the atmosphere, and some bad stuff does come out the chimney.
There are plenty of drawbacks to the waste-to-energy process.
1. The “waste” has to be properly sorted, since not everything can just be incinerated. This takes time, money, and energy.
2. The vast majority of the waste energy releases carbon dioxide, so it’s no better than coal.
3. Transportation of physical material costs a lot, and since it’s not *nearly* as energy-dense as, say, coal, oil, nat gas, nuclear fuel, etc, the transportation costs are rather considerable.
4. It’s not reliable–if your energy source depends on a steady flow of trash, that sets up a whole lot of perverse incentives.
For the most part, garbage is burned, so the energy is coming from heat. There are carve-outs–some plastics can be broken down (and releases energy) and biomass can be harvested, but it’s mostly just heat.
That said, the *main* allure of this is that this is garbage that has to be gotten rid of anyway. Like #3 above is going to happen whether or not it’s being used for energy. It’s not particularly efficient or good as an energy source, but if it’s stuff we have to do anyway, why not at least get some energy out of it?
Waste incinerators aren’t like a normal fire, it runs at far higher temperatures which converts most stuff to carbon dioxide. Some byproducts have to be filtered before release. Newer incinerators don’t release much beyond carbon dioxide into the atmosphere but it isn’t zero.
Energy is generated because combustion releases heat and that heat is used to heat water into steam which runs a steam turbine to produce electricity. It isn’t stored and is sent into the electrical system like any other power generator.
Properly constructed waste incinerators are fairly expensive to build and to run. The energy it produces can offset some costs but it is far from paying for the incinerator’s operation. The alternative to incineration is to landfill (other than some potential for recycling). So in areas with limited landfill or landfills that are really far away, incineration might be the best option. Broadly speaking though, recycling and reducing waste is the preferred option.
The same way coal plants turn rocks into usable energy. They burn the garage, and use the heat generated to no water. The boiling water turns to steam which spins a turbine to generate power.
I’ve done some reading about Tire and Plastic Derived Fuels (TDF; PDF) lately.
TDF plants generally operate in one of 2 ways. The first is shredded rubber as an additive to or direct coal replacement. This is the most efficient way to collect energy from tires as it consumes the entire product as it burns. The ash contains toxic metals that are used in the vulcanization process of the rubber and needs to be handled appropriately. The second is destructive pyrolysis of rubber to liquid / gaseous fuels like propane, butane, gasoline, diesel etc. These could then be used as fuel oils to generate electricity or fuel transport, stoves etc. The heavier oils can also be used as lubricant base stock. It’s essentially recovered crude oil.
PDF has largely the same story but the resulting oils tend towards the lighter end of the spectrum.
Other organic based trash like wood, paper and cardboard that can’t be recycled are used in much the same way, either pyrolyzed and stored as a saleable fuel or burned directly in a solids burner.
They turn landfill into skyfill.
Out of sight, out of mind, plus the heat can be turned into power.
Next door we’re spending power to try and extract carbon from the atmosphere to put it in the ground.
Go figure.
Garbage is essentially just very lousy fuel with a ton of water and pollutants. Setting up a proper waste plant can be a challenging engineering task, and the electricity production is not always so great. What is great about waste plants however is the amount of hot water you can produce from it, which is why countries with wide scale district heating are often very good at waste plants.
Toxins in waste can be of multiple sources. But if it’s biological or chemical then in most ways the burning removes the poisonous part. Things like heavy metals are of course still a problem, and but heavy metals gets collected in the ash leftover from burning the waste. So in a sense the waste plant also helps separate out toxins.
The energy is harnessed like any other powerplant, via good’ol boiling water to spin a turbine. However the electric efficiency is not very high due to the lower quality of the fuel, however you still get a lot of good quality hot water out of it, that countries with district heating can sell to consumers to heat their homes
Think about the steam engines on a train. You dump coal into the furnace and it fuels the engine using heat energy.
Same thing, but much bigger.
In fact, nuclear works the same way too, using heat to essentially run a steam engine. It’s not quite that simple, but it’ll give you a fair idea.
Latest Answers