When soils
or groundwater are contaminated, cleanup can be very expensive.
Traditionally, contaminated soils are either:
excavated and buried as hazardous waste;
temporarily excavated, “washed,” and returned to the
site;
treated with engineered microorganisms that break down organic
contaminates (bioremediation), or;
capped with imported fill.
It is generally agreed
that phytoremediation techniques can reduce costs anywhere from fifty
to ninety-eight percent compared to traditional remediation. Phytoremediation
is also less expensive than bioremediation, a technique itself considered
to be cost-saving. Growing plants on site is several hundred times
cheaper than growing an equivalent weight of bacterial biomass. Plants
are easier to propagate and do not require sterile growing conditions,
organic nutrients, or the laboratory facilities necessary for growing
bioremediation microorganisms (aspb).
An example of the kind
of cost savings possible is discussed in the EPA Phytoremediation
Handbook: The authors have estimated that the 30-year costs of remediating
a 12-acre site contaminated with lead are as follows:
$12,000,000 for excavation and disposal
$6,300,000 for soil washing
$600,000 for installing a soil cap
$200,000 for phytoremediation (installation and maintenance)
The cost savings
are less dramatic, but still significant, in other remediation projects.
When groundwater is contaminated, phytoremediation is estimated by
GWRTAC to cost less than half what traditional “pump and treat”
technologies do. Groundwater plumes controlled by the hydraulic action
of fast-growing poplars are many times cheaper to install and maintain
than a system of constructed dams, levees, and drainage pipes to control
contamination of nearby groundwater.
The tradeoff,
however, is in time and maintenance. While costs are lower overall,
phytoremediation techniques are far from a “quick fix.”
Plants— especially trees—take years to mature to their
full remediating potential, and sites must be monitored and maintained
for many years to ensure human and ecological safety. It is therefore
imperative that a source for constant funding be secured in advance
to ensure a complete and conscientious maintenance plan for the duration
of the remediation project.