Sustainability and Chemicals
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3.1 Solvent Use[edit | edit source]
According to the EPA, the use of solvents contributes to our greenhouse gas emissions in the form of volatile organic compounds, usually hydrocarbons. Your fume hood simply extracts the solvent from the lab and evaporates it into the atmosphere. Chemical compounds in the solvents we use become pollutants when they enter the environment through off-gassing or disposal with potential adverse impact on our ecosystems. The definition of what a pollutant is evolves over time as we learn more about our impact on the environment.
Before undertaking conservation treatments that involve solvent use, please consider ways to alter your technique to use less solvents or less toxic solvents. The AIC Health and Safety Committee has created an excellent and thorough document on use and disposal of solvents. Among the recommendations in the document is the following:
- consider use of alternative materials
- order only what you need
- use only what you need
- reuse what you can
Other handy suggestions are:
- Find the least toxic alternative (see 3.2 Solvent Choice and 3.3 Environmentally Friendly Solvent Substitutions below).
- In your treatments, look for alternatives to petroleum based products such as water based systems, gels, and steam. (Gel systems often use a larger amount of a less toxic solvent.(Stavroudis 2010))
- Read through suggestions in specialty group sections of the AIC wiki to direct you to the most effective and least wasteful treatment procedure. For example, Chapter 15: Hinge, Tape, and Adhesive Removal in the Paper Conservation Catalog Wiki gives information about the specific adhesives found in different products and suggests non-solvent techniques for reducing them.
- Find a better use of chelators and surfactants requiring less clearing and/or clearing with less toxic solvents.(Kronkright 2010)
- Keep your math figures so that you can easily mix up a small batch of a solvent mixture in the future, rather than relying on an easy, but larger, measurement each time.
- Improve solvent storage to reduce or eliminate evaporation.
- Do not leave solvent containers open. Self-closing solvent dispensers cut down on evaporation.
- Try to pour from small containers, reducing spills and evaporation in the transfer.
- Clean brushes in used solvent rather than new solvent.
Chris Stavroudis. 2010. Personal communication
Dale Kronkright. 2010. Personal communication
3.2 Solvent Choice[edit | edit source]
How much does the choice of solvent impact impact the environment? Just as conservators have a list of solvents to try in order of least toxic to most toxic, or least polar to most polar, we wanted to make a least green to most green solvent list, but we quickly realized that ranking the environmental impact of solvents is complicated. There are multiple factors to consider and the data available is incomplete.
Even when we switch to more ‘natural’ substitutions (e.g. xanthan gum), it is often difficult to find, even in the MSDS, exact toxicological, ecological, or disposal information. Some manufacturers are starting to provide this information with their products but it is still uncommon.(Daly-Hartin 2010)
Any new solvents used in conservation will have to be vetted to ensure that they are safe to use on and around valuable objects. For the time being, therefore, we will focus on what we know about solvents commonly used in conservation. We chose the top 11 from Chris Stravroutis' list of solvents most used in the conservation community (Chris Stavroudis 2000) and made a chart that takes into account manufacture, environmental impact, disposal implications, and recycling possibilities. The data for columns I - IV comes from the EPA and columns V and VI are based on research done in Switzerland. The chart is not complete, and reflects the current underdeveloped pollution rating system. The EPA ratings are geared towards US industry and the Swiss ratings consider European disposal and recycling standards, which are not entirely relevant to current US practices.
Below the chart is an explanation of the data in each column.
|Evaluation of Environmental Impact of Top Solvents Used in Conservation|
|Solvent||Health Hazard Ranking||Environmental Hazard Ranking System||Regulatory Coverage; solvent listed on at least _ lists||Total Environmental Releases in USA pounds/year||EHS Score Combined||LCA Score CED/kg Solvent|
|Acetone||Not Recognized||<10||3||No data||3.1||21|
|Ethanol||Not Recognized||<4||2||No data||2.6||18|
|Denatured Alcohol||Not Recognized||<4||2||No data||NA||NA|
|Toluene||Developmental Toxicant||<2 out of 10||8||64,619,053||3.4||20|
|Ammonium Hydroxide||Respiratory Toxicant||<3||2||151,805,024||NA||NA|
|Xylenes||Not Recognized||<3 out of 10||6||43,243,515||3.4||20|
|Isopropanol||No data||<1 out of 8||3||3.1||20|
|Mineral Spirits||No data||<3||2||No data||NA||NA|
|VM&P Naptha||No data||<3||1||No data||NA||NA|
|Hydrogen Peroxide 52% conc||No data||<2 out of 5||3||No data||NA||NA|
|Stoddard Solvent||No data||<3||2||No data||NA||NA|
* Note: all are high volume chemicals with production exceeding 1 million pounds per year in the USA except for hydrogen peroxide, which is listed here as “used in at least 8 industries.” This GoodGuide Scorecard was recommended as a website for comparing solvents by a contact at the EPA. (Austin 2010) More about GoodGuide can be found here. 
Column I (Health Hazard Ranking) reflects the EPA ratings according to industrial standards, based on relative exposures to large quantities of solvents, as found on the EPA website.  The environmental hazard system can be difficult to use for solvent comparisons, especially when trying to apply to art conservation uses. For example, it rates hydrogen peroxide (scored at 52% concentration, not the normal 3% concentration used in conservation) as a worse environmental hazard than toluene, due to its explosive quality at such high concentrations. The “No data” criteria in each of the EPA data columns refers to data that the EPA views as “not toxic enough to comment on.
Column II (Environmental Hazard Ranking System)is based on the GoodGuide Scorecard pollution information “Toxics Release Inventory”.  This system ranks 650 chemicals according to 40 different criteria such as air releases, health effects, and ozone depleting potential. (Austin 2010)
Column III (Regulatory Coverage; solvent listed on at least _ lists) addresses the amount of EPA regulatory lists that a solvent appears on. The higher the number, the more environmentally polluting the solvent is rated.
Column IV (Total Environmental Releases in USA pounds/year) was also found on the Solvent Scorecard. 
Column V (EHS Score Combined) and Column VI (LCA Score CED) report information taken from work at the Zurich Institute for Chemical and Bioengineering, which resulted in a 2007 publication called What is a green solvent? A comprehensive framework for the environmental assessment of solvents by Christian Capello, Ulrich Fischer, and Konrad Hungerbuhler.  The method they developed considers multiple aspects of environmental toxicity. It is promising because it categorizes the issues into two groups: EHS-environmental, health and safety (column V); and LCA- life cycle assessment (column VI), scored according to the cumulative energy demand (CED) required to produce 1 kilogram of the solvent. For both the EHS and LCA, the higher the score, the worse the solvent. To generate their data, they created Ecosolvent -Tool, a computer program .
Note: The CED can differ from country to country or processing plant to processing plant, depending on the disposal method -either distillation or incineration, the amount of carbon recovery attained in the disposal process and the amount of solvent recycled or reused. Solvent recycling is the highest variable because it differs country to country and processing plant to processing plant. In Switzerland, they have a 90% carbon recovery rate. In the USA there is no data for recovery, but equipment is available for institutional use to recycle used solvents -relying on the private institution to take action.
In Switzerland, and other European nations, credits are given for solvent distillation because solvent recovery of 90% is assumed, so the higher the carbon fraction of a solvent, the higher environmental credits from solvent incineration. (Capello, Fischer and Hungerbuhler 2007) In the USA, this type of point system has not been established. The EPA pollution control division is hoping to develop a resource that links private companies, allowing individuals and institutions to buy recycled solvents. These would be as clean as “virgin” solvents, but have less environmental impact on the production-end of the lifecycle.
A few generalizations can be made concerning solvent “greeness.” The production of solvents that are closest to their petrochemical base only require few process steps, resulting in less environmental impact from cradle to grave. Solvents with names made up of more than 8 letters are usually worse offenders than those with shorter names- tetrahydrofuran has higher EHS and LCA scores than ethanol. Solvents that are water based, or water-soluble are less polluting in their production and disposal.
Other notes on solvents:
Ammonia: occurs naturally and is produced by human activity. It is a colorless gas with a distinct odor that can be dissolved in water and quickly turns back into gas when exposed to oxygen. It is used as a fertilizer in agriculture.
Debra Daly-Hartin. 2010. Personal communication
Chris Stavroudis. 2000. Solvent/Hazardous Materials Usage Survey
Information on the Scorecard Pollution Rating System and EPA solvent recycling program was based on telephone conversations and emails with Sharon Austin, US EPA, Office of Pollution Prevention and Toxics Chemical Engineering Branch, Washington, DC.
Christian Capello, Ulrich Fischer and Konrad Hungerbuhler. 2007. “What is a Green Solvent? A Comprehensive Framework for the Environmental Assessment of Solvents.” www.rsc.org/greenchem (February). 
citation to Monona Rossol’s The Artists’ Complete Health and Safety Guide, esp. pg 95 with a table called Common Solvents and their Hazards
3.3 Environmentally Friendly Solvent Substitutions & Alternatives[edit | edit source]
Green chemistry technologies are developing substitutions to the petroleum based products that we use. These technologies, supported by the EPA, aim to reduce waste, eliminate "end-of-the-pipe" treatments, offer safer products, reduce use of energy and resources, and supply the consumer with more competitive materials that produce less pollutants. (EPA Green Chemistry page) 
While newer solvents are being developed, it is worthwhile to consider whether a milder traditional solvent can be substituted in some situations.
Alfonsi et al, in a 2008 article in Green Chemistry , broke commonly used solvents into three categories: Preferred; Usable; and Undesirable. Shown here:
|Ethyl acetate||Methyl t-butyl ether||Dichloromethane|
|Methyl ethyl ketone||2-MethylTHF||Dimethyl formamide|
|Dimethyl sulfoxide||Dimethyl acetate|
Most of the solvents used in conservation fall in to the first two categories. For those that do not, substitutes are suggested. For example, benzene can be replaced by toluene and hexanes can be replaced by heptane.
An excellent resource for solvent selection is the National Archives Solvent Solver  program which uses the principles of Teas Fractional Solubility Parameters to help the user design a mixture of solvents that will have the same properties as a more toxic solvent. For example, mixtures of heptane, acetone and ethanol can be used to make toluene or THF substitutes. Note: this program will work with Windows 95 or later (including Windows 7), but is not Mac compatible.
The Green Chemical Alternatives Purchasing Wizard from the Massachusetts Institute of Technology is another program for finding green alternative solvents .
This Department of Labor/OSHA website entitled 'Transitioning to Safer Chemicals' has a good bibliography on the topic. 
Regarding Specific Substitutions for Solvents in Conservation
Acetone: has negligible ground level ozone forming properties, is a good alternative to other, more toxic chemicals. It is an acceptable substitute for ozone depleting compounds.
Xylene: There has been some discussion on the Conservation DistList ( search: 'alternative to xylene') about substitutions for xylene in B-72 mixtures. Polypropylene glycol methyl ether was one of the solvents suggested.
Regarding Solvent Alternatives
In some cases it is possible to use alternative treatment methods that minimize the use of solvents. For example, solvent baths of acetone, ethanol, and/or aromatic hydrocarbons are traditionally used to strip protective lacquers from polished metal. Removal of cellulose nitrate, a lacquer commonly used to protect silver from tarnishing pollutants, can be accomplished with steam at about 30 psi. The steam removal process is even more efficient if the object can be pre-soaked in warm water. Minimal use of solvent (acetone) is required to remove remaining traces of lacquer after the steam-cleaning process. In fact, steam stripping of cellulose nitrate lacquer results in a more thorough removal of the material from the metal surface than the use of solvents, either by bath or swab (Thickett and Hockey 2003). Steam is not an effective way to remove acrylic lacquers.
Ankersmit, Hubertus A., and Robert van Langh. 2002. 'The removal of lacquers from silver by steam. 'In Contributions to Conservation, edited by J. A. Mosk and N. H. Tennent, 1-9. London: James & James.
Thickett, David, and Marilyn Hockey. 2003. 'The effects of conservation treatments on the subsequent tarnishing of silver.' In Conservation Science 2002, edited by J.H. Townsend, K. Eremin, and A. Adriaens, 155-161. London: Archetype.
Regarding Substitutions for Solvents in Art
It is worthwhile, as conservators, to be aware that artists are also looking at ways to reduce solvents use. The following websites describe possible solvent substitutions or alterations in technique for making art:
R. Bissett. The Secret to Oil Painting Without Solvents. Retrieved Feb. 2014. [www.buildart.com/secret_paint_without_solvent.htm]
Nontoxic Print: Nontoxic Printmaking, Safe Painting & Printed Art. Safe Solvents (2014). Retrieved March 2014. 
Regarding Substitutions for Specific Surfactants
Consult the MSDS for specific environmental hazards before using a surfactant. See Stavroudis, Chris. January 2009. Sorting Out Surfactants. WAAC Newsletter (31)1: 18-21  and Stavroudis, Chris. September 2012. More from CAPS3: Surfactants, silicone-based solvents, and microemulsions. WAAC Newsletter (34)3: 24-27 
Triton X- line of surfactants: Use of the Triton X-line is not recommended, as its degradation products adversely affect the environment. (It is an endocrine disruptor that can harm humans, fish, and other organisms). Triton 100X and Triton XL-80N are discontinued. Proper disposal of bulk Triton X products is required.
Surfonic JL-80X: Considered the ‘safe’ non-ionic replacement for discontinued Triton X-100 and Triton XL-80N. According to the MSDS, it is considered moderately toxic to aquatic life but it is not considered hazardous waste. Its biodegradability is undetermined.
ECOSURF EH-line of surfactants: EH-9, EH-6, and EH-3 are non-ionic, low toxicity, and soluble in both water and low polarity solvents. The surfactant is readily biodegradable but the secondary solvent is not. EH-9 may be used a replacement for Triton X-100 or Triton XL-80N.
Surfactant use and disposal tips:
- Do not dispose of surfactants (even the EH-line) in water or soils.
- Order small bulk quantities, as very little is typically used.
- Work in multiples of the surfactants' CMC (Critical Micelle Concentration) to avoid excess quantities.
- According to Chris Stavroudis, emulsions should be allowed to dry and residue disposed of as solid waste, as the water/solvent mixture will complicate most solvent waste collection programs. For disposal of large emulsion amounts, contact a waste disposal service for further instructions. Additionally, if the emulsion separates- or can be made to separate (perhaps by adding salt)- the organic phase can be removed and combined with waste solvents.
Information About the Sustainability of Conservation Materials[edit | edit source]
Benzotriazole (BTA, C6H5N3) has been popularly employed as a copper alloy corrosion inhibitor since the 1960s, yet it is highly toxic and possibly carcinogenic.
- BTA should only be used in labs with proper extraction, access to safety glasses, and chemical resistance gloves.
- BTA should never be applied in the field.
- BTA is harmful to aquatic life and must be disposed of as toxic waste.
- Objects previously treated with BTA should be considered potentially toxic and handled accordingly.
Alternatively, cysteine (C3H7NO2S) - an amino acid present in proteins and enzymes - is currently being evaluated as a non-toxic, environmentally-friendly replacement for BTA. The -NH2 amino group and -SH thiol group in cysteine promotes the material’s affinity to copper, allowing cysteine to form a stable, oxygen-inhibiting film on the metal surface that can inhibit over a wide pH range. While cysteine did not outperform BTA during initial assessments, it may prove more stable than BTA in the long-term as well as in high RH environments.
See Gravgaard, Mari and Jetti van Lanschot. 2012. Cysteine as a non-toxic corrosion inhibitor for copper alloys in conservation. Journal of the Institute of Conservation, 35:1, 14-24.
Orvus WA, an anionic surfactant commonly used in textile conservation, is an environmentally friendly alternative to a variety of non-ionic surfactants currently or historically used. Orvus WA paste “is not ‘hazardous’ within the meaning of the OSHA Hazard” and “is a biodegradable surfactant” that can be disposed of down the drain or sewer without harmful effects to the environment. Non-ionic surfactants such as Dehypon LS45 TM, Synperonic N, Synperonic 91/6, Triton XL-80N, Triton X-100, and Imbentin C135/070 have a variety of toxic components that prevent it from being safely and easily disposed of, and in some cases are no longer produced due in part to their negative toxicological effects.
Proctor & Gamble “Material Safety Data Sheet – ORVUS WA Surfactant Paste.” Issue Date: 2/99. http://talasonline.com/photos/msds/orvus.pdf
De, Silva M, and Jane Henderson. "Sustainability in Conservatin Practice." Journal of the Institute of Conservation. 34.1 (2011): 5-15. Print.
Gregory Smith, “Triton,” e-mail to DistList mailing list, instance: 19:11, Wednesday, August 17, 2005, http://cool.conservation-us.org/byform/mailing-lists/cdl/2005/1090.html
Fields, John A, Andrew Wingham, Frances Hartog, and Vincent Daniels. "Finding Substitute Surfactants for Synperonic N." Journal of the American Institute for Conservation. 43.1 (2004): 55. Print.
Ian Gibb et al, ‘Greener Cleaning of Large Textiles’ (paper presented at Going Green: Towards Sustainability in Conservation, British Museum, London, April 24, 2009) in de Silva, Megan, and Jane Henderson. 2011. Sustainability in conservation practice. Journal of the Institute of Conservation 34(1): 5-15
Dicholormethane-based Paint Strippers
Julia Barton and Rachel Swift, ‘The Big Ban: Preliminary Research into Finding a Non-toxic Alternative to Nitromorsw’ (paper presented at Going Green) in de Silva, Megan, and Jane Henderson. 2011. Sustainability in conservation practice. Journal of the Institute of Conservation 34(1): 5-15
Supercritical Carbon Dioxide is a "relatively non-toxic, inert, and easily disposed of by-product of fermentation" (de Silva and Henderson, 2011). It is also non-flammable. Liquid carbon dioxide has been used on ethnographic objects for the removal of contaminants.
Michaela Sousa et al., ‘The Art of CO2 for Art Conservation: A Green Approach to Antique Textile Cleaning’, Green Chemistry 9 (2007): 943–7.
Barry Kaye, David Cole-Hamilton, and Kathryn Morphet, ‘Supercritical Drying: A New Method for Conserving Waterlogged Archaeological Materials’, Studies in Conservation 45 (2000): 233 – 62.
Achim Unger and Helene Tello, ‘Handle with Care: the Dry Cleaning and Decontamination of Ethnographical Objects with Liquid Carbon Dioxide’, in Preprints of the ICOM Committee for Con- servation (ICOM-CC) 15th Triennial Meeting, New Delhi, India, September 22 – 26, 2008, vol 1 (London: James and James, 2008), 207.
de Silva, Megan, and Jane Henderson. 2011. Sustainability in conservation practice. Journal of the Institute of Conservation 34(1): 5-15
Treatments for Iron Objects
Stephanie Hollner et al., ‘Environmentally-Friendly Treatments for the Protection of Iron Artefacts of the Cultural Heritage against Atmospheric Corrosion’, in Metals 07, Interim Meeting of the ICOM-CC Metal Working Group, Amsterdam, September 17 – 21, 2007 (Amsterdam: ICOM-CC Metals Working Group, 2007), 64–70 in de Silva, Megan, and Jane Henderson. 2011. Sustainability in conservation practice. Journal of the Institute of Conservation 34(1): 5-15
Sustainability, Water Purification and Use[edit | edit source]
What techniques are used to purify water?
Tap – On demand source; no feedwater waste occasional lab use, general office use, potable, sanitation Quality and content varies according to location Contains VOCs and microbial contaminants Boiling water will kill microorganisms, however it does not remove dissolved ions or particulates.
Filtered – On demand source; occasional lab use, potable Two chief filters of use to conservators are particulate filters and activated charcoal filters.: Amount of feedwater waste correlates with type of filter used. Waste is generally lower than distilled, deionized or reverse osmosis processes. Varying degrees of VOCs and microbial contaminants are removed depending on the filter employed.
Distilled – prepared by heating tap water to create steam. The condensate is collected as product. Distilled is not an on demand source, so it must be made in advance and stored. If the storage container is not made of an inert material, plasticizers will leach out of it and recontaminate the water. Distillation removes all metals, anions, cations, and microorganisms. Distillation eliminates nearly all VOCs. Distillation produces small amounts of water very slowly and uses large amounts of energy and is wasteful of water. Up to 95% waste of feed water; 5% pure product
Deionized can produce moderate volumes of purified water on-demand. While it doesn't produce absolutely pure water, it is convenient and quick, and may be sufficient for many applications. It is an excellent system for removing dissolved solids and gases, although it has a generally poor rating for other impurities. Amount of feedwater waste is much lower than distilled or reverse osmosis, however filters that are re-usable require considerable amounts of water for cleaning purposes. For ultrapure product, deionization systems are often combined with reverse osmosis (RO) systems.
ElectroDeIonized (EDI) water is a continuous water treatment process that removes ionizable species from liquids using voltage applied across a cell. It differs from conventional deionization techiniques in that it is does not require the use of acid, caustic soda, or other chemicals. Deionization can be done continuously and inexpensively using electodeionization.
Reverse Osmosis – depending on system, approx 75% of feedwater is recovered as pure water. While the percentage of feedwater to recovered water is large, the process is very efficient in removing contaminants: RO can remove mineral salts as well as contaminants such as bacteria and pesticides. Reverse osmosis eliminates nearly all VOCs and provides high quality purified water which is suitable for many routine laboratory purposes Product may be prepared in advance and stored for use. The amount of water on demand may be limited by the size of the storage container. If the storage container is not made of an inert material, plasticizers will leach out of it and recontaminate the water.
High Efficiency Reverse Osmosis (HERO) is a proprietary system originally developed to provide ultrapure water. This process was developed for the microelectronics industry. HERO has several potential advantages over conventional RO including greater water recovery – between 95% to 99 %, higher quality product, higher quantity output, and generally lower costs. This is achieved by chemical pretreatment of the feed water undergoing RO. More efficient system than RO, so costs are about 20%–40% less than operating a conventional RO system.
ElectroDeIonization (EDI) is commonly used in conjunction with reverse osmosis (RO) process for ultrapure water. The combination is known as Reverse Osmosis ElectroDeIonization (RO/EDI). Feedwater is first treated by RO. Recovered water is then sent through an electrodeionization cell where voltage is applied across the cell. Output is ultrapure water.
Ultraviolet oxidation is another method that works well as an addition to other systems. It does a good job eliminating bacteria. It works by the use of ultraviolet radiation at the biocidal wavelength of 254 nanometers, which is ‘murder’ on bacteria.
For more in depth discussion of water quality and application, see the Paper Conservation Catalog, [[[BP_Chapter_16_-_Washing#16.3_Materials_and_Equipment| Chapter 16 Water; Quality/Purity]] (pp. 13 – 16 or 16.3.1).
How sustainable are these purification techniques?
The Sustainability Committee has published tables about Water Purification Methods and Environmental Considerations with information that address the following factors:
- Water discarded during purification (ratio of feed water to purified product)
- Energy to run purification equipment
- Energy to make purification equipment and bottles
- Raw materials to make purification equipment and bottles
- Disposal of spent filters, equipment, and empty storage containers
To download these tables, go here: Water Charts
When to use purified water and when to use tap water?
Tap water quality varies by region, and if contaminants are a concern it can be tested. The examples of activities that can be done with tap water assume standard drinkable tap water in the United States.
- Rinsing silver
- Rinsing salt contaminated ceramics and stone, except for the last few rinses
- Inpainting on fill material
- Other examples? Email us at email@example.com
Often purified water is necessary in conservation treatments, but not always. Here are a few examples of activities that do require purified water:
- Mixing reagents
- Salt test solutions
- Sample preparation
- Paper conservation treatments may need purified water, depending on the region and the contaminants in the water. Some conservation use primarily tap water after having the water tested.
- Other examples? Email us at firstname.lastname@example.org
Another way to go green is to reduce your water use. Here are some ideas of ways to conserve water:
- If you have an eyewash station, it has to be run regularly to ensure the water is clean and working properly. While it is running, the water can be used to rinse glassware.
- More info and ideas at The Columbia Water Center.
Tse, Season. Water quality for treatment of paper and textiles. Technical Bulletin 24. Canadian Conservation Institute [Institut canadien de conservation], 2001.
3.5 Disposal: Evaporate, Dump, or Dispose as Hazardous Waste?[edit | edit source]
Below are some articles on this complicated topic:
- Some Information on Chemical Compatibilities with Regard to Waste This excellent resource was created by the Health and Safety Committee.
- 'Hazardous Waste: Where on Earth Should it Go?' This article was originally published in Vol. 38 No. 2 of AIC News, March 2013. 
- Waste Disposal created by Golden Artist Colors  talks about considerations for disposing of waste in general and also has specific guidelines for disposing of unused acrylic paint.
Many waste management companies will recycle used solvents through distillation if possible. It is also possible to purchase a machine and recycle the solvents yourself. This might be a good option for a lab that generates a sizeable amount of solvent waste. The University of Minnesota has created an excellent website  that discusses the factors to consider, such as 'Can the distilled solvent be used again for the same process at your company?' (an important question in conservation). Here are some companies that offer such products.    (We do not know anyone who uses one, and would love to hear from you if you do. Please email us at email@example.com)