Materials Characterization Paper

In Support of the

Advanced Notice of Proposed Rulemaking –

Identification of Nonhazardous Materials That Are Solid Waste

Spent Solvents and Related Materials

December 16, 2008

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1.	Definition of Spent Solvents

A solvent is a material used to dissolve or dilute another substance.
Examples of solvent use include degreasing, cleaning, and fabric
scouring, use as diluents, extractants, and reaction and synthesis
media.  A spent solvent is a solvent that has been used at least once
and cannot be used again for its original purpose without being
processed, due to contamination during its use.  This analysis addresses
only solvents that: 1) have potential fuel value (i.e., organic
solvents), and 2) are not considered hazardous under RCRA. Specifically,
this paper targets non-hazardous, non-halogenated, solvents.
Non-halogenated solvents include a variety of organic chemicals
(hydrocarbons, alcohols, ketones, esters, etc).

2.	Annual Quantities of Spent Solvents Generated and Used

Sectors that generate spent solvents: 

A wide range of non-hazardous spent solvents are generated by a large
number of industries.  Generators of spent solvents can include
industries that use solvents, industries that recycle or process spent
solvents from other sources, and, in some cases, industries that
manufacture solvents. Facilities in the following NAICS industry sectors
focus specifically on the manufacture or management of solvents: 325998
– Recycling services for degreasing solvents (e.g., engine, machinery)
manufacturing; 325132 – Solvent dyes manufacturing; 324110 –
Solvents made in petroleum refineries; and 811111 – Automotive repair
and replacement shops.

Solvents are typically used in the following industries and
applications: coatings, cleaners, inks, adhesives, pharmaceuticals,
agricultural and food uses, personal care, automotive, microelectronics,
and aerosol products (American Chemistry Council 2008). 

Quantities and prices of spent solvents generated:   

Due to the wide variety of solvents produced and used, it is difficult
to characterize the quantity or prices of spent organic non-hazardous
solvents generated in the U.S.  Only a fraction of all solvents produced
return to the market as spent solvents; many are recycled and reused on
site by generators.  Total annual production of solvents exceeds 10
billion pounds (5 million tons) per year (Paint and Coatings Industry
2006).  This suggests that the total quantity of solvents that require
replacement could also be roughly five million tons per year.

The limited information available on markets for spent solvents focuses
on hazardous solvents; these are commonly used as fuel, and they are
“priced” to be less expensive to the generator than the avoided cost
of hazardous waste disposal, which can range from $0.41 to $2.13 per
gallon (Environmental Technology Council 2004).  

Trends in generation of spent solvents:  

Information on trends in generation of spent solvents is difficult to
assemble given the range of products and management options. National
demand for solvents is expected to rise by one percent a year to 12.5
billion pounds in 2010 (Paint and Coatings Industry 2006). However, as
interest in recycling, reuse, and waste minimization increases, and the
costs of reuse decrease, this projection may not hold.

3.	Uses of Spent Solvents

Combustion uses of spent solvents:  

Solvents with sufficient calorific value and minimal contamination can
be readily used as fuel in a range of boilers, furnaces, and kilns. 
However, readily available information suggests that non-hazardous
solvents do not represent a significant alternative fuel source.

Portland Cement Association data indicated that the BTU value per pound
of spent solvent varies due to the wide variety of solvent types
(Portland Cement Association 2007).

Solvents that are considered hazardous under RCRA frequently have fuel
values that are similar to coal.  Hazardous waste, as estimated by the
Assessment of the Potential Costs, Benefits, & Other Impacts of the
Hazardous Waste Combustion MACT Final Rule Standards, and the Economic
Analysis for the Proposed Emission Comparable Fuel rule (based on the
information contained in the hazardous waste constituent survey), has a
heating value between 12,200 and 13,500 Btu per pound.   In fact, a
number of these solvents appear to meet the definition of hazardous
waste because they are characteristic for ignitability, suggesting that
there is a strong correlation between hazardous solvents and high
fuel-value solvents.  This may suggest that non-hazardous solvents are
typically less valuable as a fuel source, but the variation among
solvents makes it difficult to draw any specific conclusion.

Non-combustion uses of spent solvents:

Most spent solvents can be reprocessed and recycled for use again in
their original form. Facilities that produce spent solvents may choose
to install recycling equipment in an effort to cut costs on virgin
solvent purchases (see, for example, Ohio EPA 2004; and NSBDCBEP). It is
difficult to estimate the quantities of non-hazardous spent solvents
disposed or kept in storage because they originate in many locations,
and are likely managed in a number of different ways.  It appears,
however, that recycling is a viable option for a significant percentage
of non-hazardous solvents.

4.	Management and Combustion processes

Types of units using spent solvents

It is possible that some non-hazardous, organic, solvents may have Btu
values that would give them value as a fuel source.  Hazardous solvents,
whose generation and management is tracked in the Biennial report, are
burned as fuel in a variety of liquid-fuel industrial boilers and cement
kilns.

One limitation concerning burning solvents may be the design of
combustion equipment.  Bullard (2007) notes that boiler and burner
manufacturers and other companies that support commercial and industrial
boilers have only limited experience with burning hazardous or
non-hazardous waste solvents. These boiler/burner supportive industries
are more familiar and more interested in working on projects involving
traditional fuels like natural gas and distillate, since this is the
fuel overwhelmingly in use in industry (Bullard 2007). 

Cement kilns are experienced at burning hazardous waste solvents, along
with a range of other liquid wastes.  However, an industry contact noted
that EPA’s introduction of the exclusion rules in the 1990s that
removed materials with high Btu values, when used as fuels, from the
definition of solid waste, have resulted in more energy recovery from
solvents on-site at manufacturers; as a result, solvents have diminished
as a fuel source in the cement industry (Guerra 2008).  

An EPA document source concerning industry impact information of boilers
suggests that some nonhazardous waste burning cement kilns use, among
various other secondary fuels, spent lubricants and solvents (EPA 2008).
These data are not sufficiently broken down to attribute any energy
savings information to spent solvents specifically. 

Sourcing of spent solvents:

Spent solvents originate in many locations, and a national-level
collection and distribution system does not exist for all types of
solvents.  However, census data indicates that recycling of solvents is
widespread.  Recycling services for degreasing solvents (e.g., engine,
machinery) manufacturing includes 1,188 facilities that are involved in
the management of secondary solvents.  This does not address the on-site
recycling and fuel recovery activities that take place at generators. 

Processing of spent solvents:  

In some cases, only minimal processing is required to reuse spent
solvent on site, since it is not always necessary to have 100 percent
purity (Ohio EPA 2004). Alternatively, some types of solvents may not be
suitable for reuse even after significant processing (including physical
and chemical processes to remove impurities) and therefore must be
managed through an alternate method, including being used in a different
process or sold to another company for use. 

State regulatory status of spent solvents use as ingredient:  

At this stage, we have not identified any states that have specifically
granted a beneficial use designation for the use of spent solvents as
fuel, but we have not performed an exhaustive investigation of state
activities and regulations.

5.	Commodity Composition and Impacts

Composition of spent solvents:  

The composition of spent solvents can vary widely depending on the
original chemical structure and the solvent, and the substance with
which it was first used.  To be useful as a non-hazardous fuel source,
solvents must have carbon (i.e., be organic).  However, other
constituents are difficult to characterize because they are based
largely on the specific process (e.g., cleaning production equipment) in
which the solvent was originally used.

Impacts of spent solvents use:

Data from the Portland Cement Association notes that the Btu value per
pound of spent solvent varies (Portland Cement Association 2007), but
when it can be used as an alternative fuel, it offsets use of primary
fuels.

Benefits associated with use of spent solvents as fuel include avoided
risks associated with disposal, cost savings associated with avoided
disposal and recovery of energy, and the avoided environmental impacts
associated with production of energy from “virgin” non-renewable
sources when solvents are used instead.

The specific lifecycle impacts of spent solvents used as a fuel are not
evaluated here because of uncertainties in lifecycle scenario
development.  For example, it is difficult to identify the fuel (Btu)
value and emissions factors associated with a “typical”
non-hazardous organic solvent that is suitable for fuel. In addition,
spent solvents may substitute for a variety of fuels; the choice of fuel
often depends on location specific-factors such as the location of the
combustor in relation to fuel supplies, and on the design of the
specific combustion unit. Avoided upstream impacts depend heavily on the
specific fuel being displaced in the lifecycle scenario.

References

Personal Communication with Erika Guerra, Holcim Ltd., August 26, 2008.

American Chemistry Council, “Solvents Industry Group: Solvents
Explained.” 2008. Available at
http://www.americanchemistry.com/s_acc/sec_solvents.asp?CID=1483&DID=558
6

Bullard, Jack L., P.E. “Determining the Technical Feasibility of
Firing Waste Solvent in an Existing Industrial or Commercial Boiler.”
Continuing Engineering Education Journal. Article #0015. 2007. Available
at: http://www.ceejpublishing.com/Articles/0015.htm

Environmental Technology Council, “May 2004 Incinerator and Landfill
Cost Data,”  2004. Available at: http://www.etc.org/costcurvey8.cfm

Nevada Small Business Development Center Business Environmental Program
(NSBDCBEP), “Solvent Recycling at Crumrine,” CS- FY9501018.
Available at: www.nsbdcbep.org/pdf/case/Crumrine.pdf

Ohio EPA, “Onsite solvent recycling equipment,” Office of Pollution
Prevention. September 2004, Number 9. Available at:
www.epa.state.oh.us/opp/solvents/fact9.pdf

Paint and Coatings Industry, “U.S. Solvents Demand to Exceed 12
Billion Pounds in 2010,” July 1, 2006. Available at:
http://www.pcimag.com/Articles/Industry_News/515aaeb98e85c010VgnVCM10000
0f932a8c0____

Portland Cement Association, “Beneficial Reuse of Materials in the
Cement Manufacturing Process.” PCA R&D Serial No. 2868. p. 8. 2007. 

United States Environmental Protection Agency (EPA). 2008,
“Identification of Nonhazardous Materials That are Solid Waste.  EPA
Exhibit 1: Preliminary Estimate of Total Non Hazardous Secondary
Materials Used Annually in Boilers and Kilns.  Sept.  24, 2008

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