A Citizen’s Guide to 

Thermal Desorption

What Is Thermal Desorption?

Thermal desorption removes organic contaminants 

from soil, sludge or sediment by heating them in a 

machine called a “thermal desorber” to evaporate the 

contaminants. Evaporation changes the contaminants 

into vapors (gases) and separates them from the solid 

material. Many organic contaminants can be removed 

by thermal desorption. These include volatile organic 

compounds or “VOCs” and some semi-volatile organic 

compounds or “SVOCs.” VOCs such as solvents and 

gasoline evaporate easily when heated. SVOCs require 

higher temperatures to evaporate and include diesel 

fuel, creosote (a wood preservative), coal tar, and several 

pesticides. Thermal desorption generally is not used to 

treat metals but can partially remove metals like mercury 

and arsenic, which evaporate at the temperatures 

sometimes reached in thermal desorption.

A thermal desorber is not the same as an incinerator, 

which heats contaminated materials to temperatures 

high enough to destroy the contaminants. (See A 

Citizen’s Guide to Incineration [EPA 542-12-010].)

How Does It Work?

Thermal desorption involves excavating soil or other 

contaminated material for treatment in a thermal 

desorber. The desorber may be assembled at the site 

for onsite treatment, or the material may be loaded into 

trucks and transported to an offsite thermal desorption 

facility. To prepare the soil for treatment, large rocks or 

debris first must be removed or crushed. The smaller 

particle size allows heat to more easily and evenly 

separate contaminants from the solid material. If the 

material is very wet, the water may need to be removed 

to improve treatment. This water removed may require 

treatment using other methods.

The prepared soil is placed in the thermal desorber to 

be heated. Low-temperature thermal desorption is used 

to heat the solid material to 200-600oF to treat VOCs. 

If SVOCs are present, then high-temperature thermal 

desorption is used to heat the soil to 600-1000oF.

Gas collection equipment captures the contaminated 

vapors. Vapors often require further treatment, such 

as removing dust particles. The remaining organic 

vapors are usually destroyed using a thermal oxidizer, 

which heats the vapors to temperatures high enough 

to convert them to carbon dioxide and water vapor. At 

some sites with high concentrations of organic vapors, 

the vapors may be cooled and condensed to change 

them back to a liquid form. The liquid chemicals may 

be recycled for reuse, or treated by incineration. If the 

concentrations of contaminants are low enough, and 

dust is not a problem, the vapors may be released 

without treatment to the atmosphere. 

Often, treated soil can be used to fill in the excavation 

at the site. If the treated soil contains contaminants that 

do not evaporate, such as most metals, they may be 

disposed of and capped onsite, or transported offsite to 

an appropriate landfill.

How Long Will It Take?

Thermal desorption may take from a few weeks to a few 

years. The actual cleanup time will depend on several 

factors. For example, thermal desorption may take 

longer where:

• The contaminated area is large or deep.

• Contaminant concentrations are high.

• The soil contains a lot of dust, clay, or organic

material, which causes contaminants to stick to the

soil and not evaporate easily.

Contaminated

Material

Oversized 

Objects

Removed

Thermal

Desorber

Treated 

Material

Vapor

Treatment

System

Concentrated 

Contaminants

for Disposal

Cleaned

Vapors

Thermal desorber heats contaminated material to evaporate 

contaminants.
United States Office of Solid Waste and EPA 542-F-12-020

Environmental Protection Emergency Response September 2012

Agency (5102G) www.epa.gov/superfund/sites

www.cluin.org

Example

High-temperature thermal desorption 

was used to clean up contaminated 

soil at the Industrial Latex 

Superfund site in New Jersey. 

From 1951 to 1983, Industrial 

Latex manufactured rubber and 

adhesives, contaminating soil 

with SVOCs, PCBs, and arsenic.

From April 1999 to June 2000, 

about 53,600 cubic yards of 

contaminated material were 

excavated to depths of up to 

14 feet. Materials greater than 

2 inches in diameter were 

removed before placing the soil 

in the desorber and heating 

it to 900°F. About 225 tons of 

contaminated soil were treated 

each day. A small amount of 

treated soil had to be placed 

back in the desorber a second 

time to meet cleanup goals for 

PCBs, SVOCs, and arsenic. 

The cleaned soil was used to 

backfill the areas that had been 

excavated. 

Vapors from the desorber passed 

through scrubbers and filters that 

removed dust particles and a 

filter that removed contaminant 

vapors. Air quality was monitored 

daily to make sure the air 

released from the desorber met 

permitted levels. 

For More Information

For more information about this 

and other technologies in the 

Citizen’s Guide Series, visit:

www.cluin.org/remediation

www.cluin.org/products/citguide

www.cluin.org/ThermalEx

NOTE: This fact sheet is intended solely as general 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.

• A lot of debris must be crushed or removed.

• The capacity of the desorber is small. (Most thermal desorbers can clean over

25 tons of contaminated material per hour.)

These factors vary from site to site.

Is Thermal Desorption Safe?

Thermal desorption has been safely used at many Superfund sites. EPA makes 

sure that materials are handled properly at each stage of the process. Workers 

take measures, such as covering loose soil, to control dust and vapors during 

excavation and treatment. If necessary, they collect and treat the gases that are 

produced in the desorber. 

How Might It Affect Me?

Excavating soil and other contaminated materials for thermal desorption 

involves the use of heavy machinery, such as backhoes and bulldozers, which 

may be noisy. Excavation of soil and sediment may release dust and vapors into 

the air but this is controlled with covers, foam, or water. Nearby residents and 

businesses also may see increased truck traffic when excavation equipment 

and thermal desorption systems are delivered to the site. If an offsite desorber is 

used, truckloads of soil must be transported from the site to the desorber.

Why Use Thermal Desorption?

Thermal desorption is typically used to clean up soil that is contaminated with 

VOCs and SVOCs at depths shallow enough to reach through excavation. 

Thermal desorption may be 

faster and provide better 

cleanup than other methods, 

particularly at sites that 

have high concentrations 

of contaminants. A faster 

cleanup may be important if 

a contaminated site poses 

a threat to the community 

or needs to be cleaned up 

quickly so that it can be 

reused. 

Thermal desorption is being 

used or has been selected 

for use at over 70 Superfund 

sites across the country.

Onsite thermal desorber.