Phytocapping.com

Phytocapping is a new sustainable landfill capping system.  Essentially, it involves covering a waste disposal site with a layer of soil about a meter deep and planting trees, grasses or other vegetation on top of it to achieve a variety of ecological benefits.

Phytocapping Keeps Pollutants Out Of Groundwater

When a waste disposal site is full, the decomposing solid waste must be kept relatively dry to avoid landfill leachate pollution.  For this reason, a landfill cover is constructed to reduce percolation of water through the waste.  These covers are normally constructed of geosynthetic clay liners, compacted clay barriers or geomembranes.  Using any of these methods, a conventional landfill cover is quite expensive to construct and is also unsustainable as it is susceptible to deterioration over time.

Although still in it's experimental phases, phytocapping offers the promise of a natural solution to this problem.  In early phytocapping experiments, mature trees planted on a filled landfill were shown to soak up more water from the soil than fell in rain.  This keeps the waste dry and the groundwater clean while making the landfill far more attractive.

Phytocapping Reduces Methane & Oderous Gases

As the solid waste in a landfill decomposes, methane gas and other greenhouse gases are released into the soil.  They naturally find their way to the surface and into the atmosphere.  This contributes to the global greenhouse gas load as well as producing an unpleasant odor.  The conventional landfill cover helps stop these gases from escaping but of course, over time the cover deteriorates and the gases are free to escape once more.

Initial experiments with phytocapping suggest that the rhizosphere (root) zone of the phytocap can oxidise methane and other odorous gases.  In addition, a mulch or compost layer surrounding the plants will further oxidise these gases so that little or no gas is left to escape into the atmosphere.

How Does Phytocapping Work?

Phytocapping utilizes the principal of water balance instead of trying to create an impermeable layer to keep water out.  The soil layer acts like a sponge to absorb and hold water when it rains.  Then when it's not raining, the water evaporates up through both the soil and the leaves of the plants.  In this way, the heat of the sun pumps moisture from the soil into the atmosphere and keeps the leachate from percolating into the waste layer.

 

While the research into phytocapping is still fairly new, it appears that it could be a far better solution to solid waste containment than the conventional landfill cover.