Plants Act as Green Caps at Landfills

Layers of very thick vegetation can be a very effective means of preventing landfills from releasing large amounts of carbon dioxide (CO2) and methane into the atmosphere, a new test study at the Rockhampton's Lakes Creek Landfill in Australia recently showed. Using methane capture towers can be prohibitively expensive if the methane quota needed for efficient production is not reached.
 

Covering the pits with hardened clay is also a bad option in warm weather, as the material can easily crack and allow water to infiltrate. The new process, known as phytocapping, implies covering the wastes with soil and growing very dense vegetation on it. These plants would act as a double filter, first trapping carbon and methane and converting them to oxygen, and secondly stopping rain from infiltrating the soil and accelerating the decay of the trash.
 

Certain plant species have to be used for optimum effect, and the soil depth carefully chosen, so the earth doesn't get eroded. The depth of the top layer has to also be carefully selected, as a too thick one could mean that the gases will spread and not get trapped by the plants.
 

A 1400 mm thick layer of soil could reduce methane emissions alone by 45 percent, as opposed to a 700 mm thick one, the test site has shown. The team in charge of the project, led by Kartik Venkatraman and Nanjappa Ashwath, both working with the Department of Molecular and Life Sciences at Central Queensland University (CQU), in Rockhampton, Australia, tested various species of plants and types of soil before coming up with a sustainable combination.
 

"The establishment of phytocaps would offer an additional and economical way of reducing methane emission from landfills," say the researchers. Other benefits include lowering the costs of operating a landfill and improving the aesthetic look of disposal sites near large cities. New wildlife corridors would also be created, to sustain and nourish animals and birds.