Phytocap Technology
Landfill final covers have traditionally been constructed from low permeability materials (eg compacted clay, geosynthetic clays and geomembranes) that are intended to resist the percolation of water into the waste zone.
Phytocaps, in contrast, are vegetated soil covers that control percolation through a water balance mechanism. Phytocaps are also known as ‘water balance covers’, ‘evapotranspiration covers’, ‘store and release covers’ and ‘alternative covers’. The phytocap’s lightly compacted soil layer stores moisture during rain events and the sun and plants remove the water from the soil by evapotranspiration, returning it to the atmosphere. These water balance mechanisms work with, rather than against nature.
These different mechanisms are illustrated in the following diagrams.
Phytocaps also reduce fugitive emissions of anaerobic landfill gases through the diffusion and enhanced oxidation of the gases as they pass through the biologically active root zone.
Over a decade of quantitative research and demonstration in the USA and Australia has shown that phytocaps can often provide an excellent and cost-effective alternative for final landfill closures. More recent commercial application of the technology in the USA has provided further confirmation.
Compared to traditional clay caps, phytocaps can often provide a number of environmental and economic benefits, including:
- more effective control of percolation and fugitive methane emissions;
- lower construction and maintenance costs; and
- more aesthetic and sustainable final landforms and land end use.
The attached document (Phytocap Technology - PDF) provides further detail on the development of the technology, its relative performance, implications for design and PhytoLink’s design approach.