Trash rocks can be used as benches, tables, sculpture bases, landscape accents, and walls. A family living in one location over time could build a castle out of their trash. I would expect trash rocks to have good thermal insulation, useful in both hot and cold climates.
I'm big into recycling and built my whole house out of recycled nylon fishnet and cement, a material I call nylon-cement. For many years I eliminated all my trash right at home using trash rocks.
Ideally, I would like to see a chemist develop a way to recycle some of our plastic trash and make a mesh material like fishnet out of it that could be plastered with cement.
Recycling is all about mining trash; converting waste into something useful. If we separate our trash first and put it into separate trash rocks we would know where to look for specific recyclable materials in the future when we need them. In the meantime, why not enjoy living around all the trash we generate?
Step 1: Scoring the Fishnet
Then I found the free fishnet mother load of all time right under my nose, the StarKist tuna factory. They were very helpful to me in saving used fishnet that the boats wanted to get rid of. Discarded netting is a trash disposal problem for the factory, so we helped each other out.
After getting it home, the fishnet was opened out, cleaned off, rolled up and stored outdoors. It smelled "fishy". Given a month or two of exposure to rain and air it was completely user-friendly. Fortunately, I live in the country, where I can do this without offending the noses of neighbors.
Good luck finding a source of your own. Fishing ports and fish farms are good places to start looking for used fishnet. Ready-made trash sacks that can be plastered with cement should be available for this idea to really take off. Sewing your own sacks allows you to make different sizes of trash rocks, but ready-made sacks would save some time and effort.
http://agriculture.exportersindia.com/aquaculture/fishing-nets.htm This is a link to manufacturers of fishnet. Most are in the Orient.
http://www.thomasnet.com/nsearch.html?cov=NA&what=Netting&heading=53680203&navsec=prodsearch A search for "netting" on Thomasnet can come up with U.S. manufacturers.
Step 2: Sewing the Sacks
I use nylon twine to do the stitching with. When protected from sunlight by the cement, nylon will last a long time.
Step 3: Fill the Sack
Step 4: Site Preparation
If you are putting the trash rock on the ground, you might want to dig a little nest for the trash rock to sit in. Throw some cement in the hole before setting the sack of trash in it. That gives you some foundation, and might prevent animals from burrowing up into the trash from underneath.
As with building any rock wall, keep in mind how the next row of rocks will sit on the row you are working on. Plan ahead to avoid problems.
Step 5: Mixing the Cement
(The same 1, 2, 3 will help you remember how to mix concrete: one part cement, two parts sand, three parts gravel. )
You can mix small amounts of cement in containers, or in a wheelbarrow. I usually mix a sack at a time on a patio area with a square end shovel.
To do that, mix the dry materials first. Then shape the pile like a volcano and add water to the hole in the middle. Mix it and add more water if needed. Try not to add too much water. It is easier to add more water later than it is to patch up a too juicy mix with more dry material.
Depending on the size of the mesh of the fishnet you are using, you might want to have the mix be drier or wetter. Larger mesh might accept a drier mix, where a thinner mix would fall through the holes. With fine mesh, you might want a wetter mix for better penetration.
Step 6: Plastering the Sack
When you stroke upward, the trowel makes a sort of "V" shaped pocket in which the cement on the trowel rests. If you stroke downward the "V" is upside-down and the cement tends to fall on the ground. After the cement is up, it can be stroked in different directions without much problem.
You might want to brush the surface of the cement after it starts to harden up some, in order to knock off any sharp bumps that might interfere with plastering the next layer, or applying the color coat. Quite often, to get adequate thickness, you have to plaster the rock twice. The second coat is easier, because the first coat is solid at that time.
Step 7: Colorizing
Pigments, powdered or liquid, can be added to the cement used in plastering the trash rocks. Pigments cost money, though. Less pigment is used if plastering is done with uncolored cement and a thin layer of colorized cement is then brushed onto the surface. That is what I usually do.
When exposed to sun and rain cement will slowly wear away. The thicker the pigmented layer, the longer it will last. Colorized cement can be brushed on with a broom head or big house brush. One can also fling cement from a brush to create irregular spotty effects.
Exposed to the weather, even un-pigmented cement can become beautifully colorized by nature as algae grows on it.
I haven't colorized any trash rocks yet, but this photo shows colored cement effects on the wall of a house. I added some concrete acrylic fortifier to the cement to hopefully make it more weather resistant.