United States
                  Environmental Protection
Office of Solid Waste and
Emergency Response
EPA 542-F-01-003
April 2001
 &EPA       A Citizen's  Guide
                  to Thermal  Desorption
   The Citizen's Guide  Series
   EPA uses many methods to clean up pollution at Superfund and other sites. If you live, work, or go to school
   near a Superfund site, you may want to know more about cleanup methods. Perhaps they are being used or are
   proposed for use at your site. How do they work? Are they safe? This Citizen's Guide is one in a series to help
|  answer your questions.
                    What is  thermal desorption?

                    Thermal desorption removes harmful chemicals from soil and other materials (like sludge and
                    sediment) by using heat to change the chemicals into gases. These gases are collected with
                    special equipment. The dust and harmful chemicals are separated from the gases and dis-
                    posed of safely. The clean soil is returned to the site. Thermal desorption is not the same as
                    incineration, which uses heat to destroy the chemicals.

                    How does it  work?

                    Thermal desorption uses equipment called a desorber to clean polluted soil. Soil is exca-
                    vated and placed in the desorber. The desorber works like a large oven. When the soil gets
                    hot enough, the harmful chemicals evaporate. To get the soil ready for the desorber, workers
                    may need to crush it, dry it, blend it with sand, or remove debris. This allows the desorber to
                    clean the soil more evenly and easily.
                                                             clean air
                       polluted soil
                                                         cleaned soil
                                                          tested for
                                                  clean soil
                                                                polluted soil
                              returned to site
                               disposed of safely
                              • or cleaned using
                               another method

For  more
write the Technology
Innovation Office at:

1200 Pennsylvania Ave.,
Washington, DC 20460

or call them at
(703) 603-9910.

Further information also
can be obtained at
www.cluin.org or
                          During each step of the process, workers use special equipment to control dust from the soil
                          and collect harmful gases that are released to the air. The polluted gases are separated from the
                          clean air using gas collection equipment. The gases are then changed back into liquids and/or
                          solid materials. These polluted liquids or solids are disposed of safely.

                          Before returning the cleaned soil to the site, workers may spray it with water to cool it and
                          control dust. If the soil still contains harmful chemicals, workers clean it further by placing it
                          back in the desorber. Or they may try other cleanup methods instead. If the soil is clean, it is
                          returned to the site. If the soil is not clean, it is sent to a landfill.

                          Is  thermal  desorption safe?

                          Thermal desorption has been used at many sites over the years. EPA makes sure that materials
                          are handled safely at each stage of the process. EPA tests the air to make sure that dust and
                          gases are not released to the air in harmful amounts. EPA also tests the soil to be sure it is clean
                          before it is returned to the site. All equipment must meet federal, state, and local standards.
                              How        will it         ?
     Thermal desorption systems can clean over 20 tons of polluted soil
     per hour. The time it takes to clean up a site using thermal desorption
     depends on:
      •     the amount of polluted soil
      •     the condition of the soil (Is it wet or dry? Does it contain a lot of debris?)
      •     type and amounts of harmful chemicals present
     Cleanup can take only a few weeks at small sites with small amounts of chemicals. If the site
     is large and the chemical levels are high, cleanup can take years.
Why  use  thermal  desorption?

Thermal desorption works well at sites with dry soil and certain types of pollution, such as fuel oil,
coal tar, chemicals that preserve wood, and solvents. Sometimes thermal desorption works where
some other cleanup methods cannot—such as at sites that have a lot of pollution in the soil.

Thermal desorption can be a faster cleanup method than most. This is important if a polluted site
needs to be cleaned up quickly so it can be used for other purposes. The equipment for thermal
desorption often costs less to build and operate than equipment for other cleanup methods using
heat. EPA has selected thermal desorption to clean up 59 Superfund sites.
NOTE: This fact sheet is intended solely as general guidance and information to the public. It is not intended, nor can it be relied
upon, to create any rights enforceable by any party in litigation with the United States, or to endorse the use of products or services
provided by specific vendors. The Agency also reserves the right to  change this fact sheet at any time without public notice.