Thermal Depolymerization
 

Okay, so I was just running some random thoughts through my head, and I realized that I really liked the Doc's idea of using trash to produce energy... Maybe not 1.21 gigawatts from a Mr. Fusion, but you never know.

I was wondering if it would be possible to make a portable thermal depolymerization device that runs off of the waste heat from the car's engine. Even diesels lose a huge amount of energy through thermal waste, and I'm wondering if that waste energy could be used to convert plastics and other trash items into a fuel that could be used to... ta da... run the diesel engine.

It might be a little beyond the abilities of someone trying to put together a home-brew type system, but one never knows... So, what to you guys think? Possible? Even worth trying? There are, literally, tons of fuel just lying around. :eek:

I run my diesel off recycled vegetable oil. The process to make diesel fuel from that requires far less energy input than TDP, and because I have a fuel tank, I can travel 600 miles before refueling. No need to make it portable.

What sorts of "trash" do you think a thermal depolymerization unit can use, and what sort of fuel do you want from it?

But to point out the obvious, there is a strictly limited supply of waste vegetable oil. Used to be that restaurants had to pay to have it hauled off. Now they sell it to biodiesel companies, and people get arrested for stealing it: Cooking-Oil Theft: 2 Men Charged In Arlington Waste-Oil Scheme

Well, here are a few points:

It doesn't HAVE to be portable; however, it does require a huge amount of thermal energy. ICE are very inefficient, and most of that inefficiency is lost in thermal energy. Recouping even a moderate percentage of that energy in the form of fuel could be a good thing.

In terms of trash, why not plastics? They seem to be the most readily available, filling up landfills everywhere, taking forever to break down, etc.

As for fuel type, it could be heating oil, or fuel to run the vehicle that is processing it.

And the biodiesel is a good tangent. Just as jamesqf said, previously, companies were having to pay people to haul it off... Now they can't help getting rid of it. Maybe the same will be true of these plastics that are choking up the environment?

Mine does not seem to be particularly limited, it's been free and more than enough for almost 10 years. But you are correct in the larger perspective.

I was just trying to get some specifics, if you had some in mind. Typically TDP will give combustible oils, and most people don't drive vehicles that can use them. By burdening a vehicle with a portable unit, you lose a lot of load capacity for not much gain.

I'd be all for recycling plastics in other ways, but that carbon came from fossil sources, and I don't think we should be burning it, even in a clean way. That carbon, if not re-used as plastic, should go back into the ground and get re-sequestered.

Also I'd imagine you'd need a pretty consistent standard of recycled plastic and it would need to be melted into pellets that could be fed from a hopper. You're talking about 'cracking' the long organic chains into liquid fuel, preferably in one heat-driven step, yes?

Might work on a large vehicle like a artic (semi) where weight isn't so much of an overhead and there's lots of heat to play with.

How about gasifying the waste (from pellets) then using the product gas and adding this to the intake (a bit like a wood-gas generator, but with a denser fuel-stock). What reaction would occur if the plastic was reacted in a stream of superheated steam?

It would be real easy to run natural gas or bio gas intake fumigation on a diesel.
So easy its already being done.

That only works as a fuel supplement. You still need the source of ignition to be a diesel oil.

Being done in a large scale already:
Waste-to-Biofuels Facility :: City of Edmonton