One problem facing many communities and governments is that landfills are becoming overcrowded and/or a city is running out of additional sites for garbage disposal. The sanitary landfill represents an improvement on road-side dumping, but it is ultimately a huge environmental liability for any city or operator. Landfills almost always leak a toxic ooze of chemical, radiological and bacterial pollution.

Increased energy costs and climate concerns have led many landfill operators to harvest methane which is given off from decomposing garbage. Likely more profitable and environmentally beneficial would be to begin to mine these sites for valuable metals and hydrocarbons.

Get this: Today's average gold mining operation sifts through a ton of material to gather 14 grams of gold. At today's market price ($900/oz), this is worth approximately $27.

We could achieve the profitability of a gold mine if we could recovery any ONE of the following amounts in a ton of landfilled material (a ton!):

25 lbs of aluminum (1.25% by weight)

9 lbs of copper

25 lbs of lead

4 lbs of tin (0.2% by weight!)

While today many of these things are recycled, older landfilled material undoubted contains far more of these materials. It would also be considerably cheaper to process loose landfill waste than to blast into solid rock to get gold ore.

So, how do we recover these materials? Landfill material is sent into a processing facility where it is first ground up, and fed into a methane digester. This will convert organic material (leaves, paper, wood) into useful fuel. Remaining materials are then placed into a large tank, which fills with water (from a closed-loop system) and is agitated. Metals sink to the bottom, and are screened out. Plastics rise to the surface, and are recycled or pressed into composite fake-lumber products (e.g. Trex decking). Remaining material is replaced in the landfill at a considerably small volume and lower toxicity. Methane is captured quicker (as material is processed vs. over 30-50 years as an in situ landfill), resulting in a higher NPV for this resource. Over time, the landfill site can be rehabilitated for other uses such as parkland.

If the economics are favorable, this should be a self-supporting activity. Landfill operators would license miners who would be bound to process the entire landfill (not just richer pockets within).

Chris Larson

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