Historical Use of Chlorinated Solvents and Their Stabilizing Compounds - Environmental Investigation and Remediation - page 20

TABLE 1.11
Solvent Mileage by Machine Type

Perchloroethylene Consumption
per 1000 kg of Clothes Cleaned Machine Type

First-generation transfer 78-100 kg (8-10%)

Second-generation dry-to-dry 77-94 kg (8-10%)

Third-generation closed loop 20-40 kg (2-4%)

Fourth-generation closed loop with refrigeration 10-20 kg (1-2%)

Fifth-generation closed loop with vapor locks 10-20 kg (1-2%)

Source: Mohr, T.K., et al., 2007, Study of Potential for Groundwater Contamination from
Past Dry Cleaner Operations in Santa Clara County . Santa Clara Valley Water
District, San José, CA.

target for the dry-cleaning industry as a whole. Therefore, i fth-generation machines provide a
5-10-fold improvement in solvent mileage compared to i rst-generation machines (USEPA, 1995).

1.1.1.4.7 Self-Service Coin- Operated Dry- Cleaning Machines
Self-service coin-operated dry cleaners were introduced to the market in the early 1960s. Coin-operated
machines were usually located in self-service laundries and were operated by consumers. The coin-
operated machines are small dry-to-dry machines with 8 to 10 pounds clothing capacity that used
perchloroethylene. These machines were inefi cient, and maintenance issues invariably led to spills
and emissions violations. Coin-operated dry-cleaning machines were prohibited beginning in 1994.
Table 1.11 summarizes the perchloroethylene mileage for i ve generations of dry-cleaning machines.

1.1.1.4.8 Chlorinated Solvents Used for Dry Cleaning
By 1915, carbon tetrachloride provided a nonl ammable alternative to the hydrocarbon solvents
used for dry cleaning at the time. It was used by the majority of dry cleaners in the United States in
the years prior to World War II. Carbon tetrachloride was replaced by perchloroethylene and TCE
as dry-cleaning and degreasing solvents because they are less toxic, easier to recover, and easier to
ship. By 1950, three times as many dry cleaners were using perchloroethylene compared to those
using carbon tetrachloride. Carbon tetrachloride is no longer used in the dry-cleaning industry.
TCE was i rst used as a dry-cleaning solvent in Germany in the 1920s and was introduced in the
United States for this purpose in about 1930. TCE was more easily reused and cleaned faster and
more safely than carbon tetrachloride. However, TCE damaged certain types of i bers and synthetic
substances. Because of human toxicity and photochemical reactivity concerns, TCE is no longer
used in the dry-cleaning industry (Johnson, 1973).
Perchloroethylene was introduced to the U.S. dry-cleaning industry in the late 1930s.
Perchloroethylene became the solvent of choice for most small dry cleaners because it is not l am-
mable, it safely cleans virtually all types of fabrics without damaging the material or bleeding dyes,
and it is less toxic than carbon tetrachloride. As of 1952, the dry-cleaning industry used 80% of the
perchloroethylene produced. However, from that point forward, such usage decreased; from 1972 to
1975, perchloroethylene usage for dry cleaning decreased from 75% to 63% of the total production
(Doherty, 2000a). The decline in perchloroethylene consumption corresponded to improvements in
dry-cleaning equipment and vapor-recovery systems, as well as to trends toward wash-and-wear
clothing. In 1975, one 55-gallon drum of perchloroethylene cleaned 8000 pounds of clothing,
whereas in 1993, the same amount cleaned 16,000 pounds of clothing. By 1990, however, only 50%
of the perchloroethylene produced was used for dry cleaning. Improved efi ciencies in handling and
recovery have caused dry-cleaner perchloroethylene consumption to substantially decrease although
perchloroethylene still dominates the U.S. dry-cleaning industry.