One of the most promising methods to clean the ground is using phytoremediation techniques. These techniques introduce the use of plants that hyperaccumulate or absorb larger than normal amounts of heavy metals in soils, and hence they are called hyperaccumulators. These plants have the ability to concentrate the dangerous metals in their stems, shoots, and leaves, and then these parts are collected and can be recycled or disposed.
How is this possible? The concept is the following: researchers have isolated a gene found in a specific type of fern, Pteris vittata, that increases the tolerance against arsenic by up to 100 to 1,000 times more than other plants. This specific gene encodes a protein that stores the toxic metal away from the cytoplasm, so it can't hurt the plant. No similar gene has ever been found in other plants, however researchers, at least in theory, could put them in any organism to help cleaning soils and contaminated water.
The technology can be used for both small and large sites. Treatment for gardens and backyards can be addressed using simple home gardening techniques, whereas lumber storage areas can be treated with larger scale agricultural techniques. In particular, Edenspace Systems Corporation has developed such a technology with the help of EPA's SBIR Program. The company's aim is mostly focused on individual homeowners. There are indications that there is a strong customer interest in phytoremediation of soil arsenic deposited from CCA-treated wood, with a projected U.S. market of $162-$194 million.
Despite the great potential, the disposal of harvested plants is a major problem. Arsenic cannot be destroyed by recycling the plants, and the toxic metal returns to the soil or water eventually. Therefore, one of the best tactics for heavy metal accumulating plants is to incinerate them and dispose of the ashes instead of disposing of the contaminated soil directly. Homeowners can store low quantities of harvested ferns in watertight containers and dispose of them the same way as regular trash. It is suggested however, that larger quantities handled by businesses and municipal parks should be sent to suitable waste landfills.