Another solution for the Great Pacific Garbage Patch

From Flickr Creative Commons - emilymcmc

I’ve briefly mentioned the Great Pacific Garbage Patch here before. It consists of a vast quantity of particulate plastic, floating in the middle of the Pacific Ocean (there’s similar ones in other oceans too).

There’s a lot of people out there who have come up with ideas for cleaning it up, including several with ideas to build floating islands out of recycled plastic.

I just came across something that might be easier and cheaper to implement.

There’s a substance called pykrete which is ice mixed with sawdust (or some other kind of fibre). You may have seen the episode of Mythbusters where they fired bullets at it (they bounced off) and then built a boat of the stuff.

Materials like pykrete can be made out of a wide variety of substances (in this case small bits of plastic) suspended in water and then frozen; the results can be stronger than concrete, and (obviously) lighter than water. The only problem is keeping it cold.

My idea is as follows:

Build a mold in the shape of a pipe. Use plastic particles dredged out of the ocean and filtered pure water to make a pykrete pipe from the mold. The result will look like a PVC pipe (except colder).

Freeze the pipe into the middle of a larger cube of pykrete.

Join frozen blocks together so that the pipes connect.

A small amount of infrastructure can then keep the pycrete cold, even in hot weather:

  • Attach a pumping station and refrigeration unit, and run low temperature brine through the pipes to keep the whole thing cold.
  • The pumps can be run by solar panels sitting on top.
  • Once the platform is large enough (and thick enough), put on an insulating layer and top it off with a few meters of topsoil. Then build on it. Or plant crops.

I haven’t looked at this in detail, but I think it can be made into a self-sustaining system fairly easily, once the platform is large enough to support a water recycling system, a refrigeration unit, a pump, and something to power it all. I don’t think it would be particularly expensive to bootstrap a project like this either.

For reference: there’s estimated to be around 5kg of particulate plastic per square kilometer of water in the Gyre. A boat with a large dredge and a small water filtration system could make a few big blocks of pykrete per day. Within a few weeks, it might be possible to build a big enough platform to move all of the equipment over, and to continue operations from it instead.

UPDATE: I’d like to try building a small scale model to see if this is feasible. Location would be a lake somewhere in Southern Ontario (if someone has a cottage that could work, please let me know). I’d be interested in hearing from anybody who wants to help out – particularly if they have access to a refrigerated shipping container.

5 responses on “Another solution for the Great Pacific Garbage Patch

  1. Sol

    Yeah, I dunno if it would stay frozen, the whole thing might be in constant need of slow repair. What’s the average air and water temperatures around there? Could be tricky… Maybe just a giant floating barge with an opening in the hull that dredges in the plastic and then feeds it to a huge on-board recycling plant, and then sell the recovered plastic. But that might not be cost effective…

    1. Anonymous

      There was a fairly large boat make out of pykrete somewhere in Canada during WW2. After they turned off the refrigeration unit, it took three hot summers before it completely melted.nnI think reasonably cold brine (i.e. freezing point of very salty water is a few degrees below zero Celsius) running through the system could keep it frozen on a permanent basis.nnThe energy requirements for running the refrigeration and pumping the refrigerant could easily be run by a relatively small passive solar system. nnAdd in some kind of system to suck plastic out of the surrounding ocean, and a little bit of equipment to partially automate creating new blocks, and this could easily be bootstrapped.nnOr alternatively the blocks could be melted and the plastic stripped out and recycled at leisure later on.

    2. Anonymous

      Oh and I ran numbers on this plan vs a generic cleanup/recycle plan. I think my idea would cost less than $2 million to bootstrap, and a minimal annual cost (maybe even a profit) going forwards. I even did a parts list. :)

    3. Anonymous

      Any human structure is in constant need of slow repair.nnAs long as the circulation ducts stay open – and they’ll probably occasionally need clearing out due to ice crystals forming – the whole structure is going to be pretty stable, even in the tropics.nnAnyhow, the idea is intended to be a cost effective way to build a great big floating platform made out of recycled garbage – and to capture some mind-space in the process. Whether the platform is later replaced with something lower maintenance is a different story.