Solvent Table
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| Evaluation of Environmental Impact of Top Solvents Used in Conservation | ||||||
|---|---|---|---|---|---|---|
| I | II | III | IV | V | VI | |
| 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 rated on the Scorecard as “used in at least 8 industries.”
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.
Discussion of the Chart:
The health hazard ranking column reflects the EPA ratings according to industrial standards, based on relative exposures to large quantities of solvents. *
The data listed in the environmental hazard ranking column is based on the United States’ Environmental Protection Agency (EPA) 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.*
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 (only 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.*
Regulatory Coverage addresses the amount of EPA regulatory lists that a solvent appears on. The higher the number, the more environmentally polluting the solvent is rated. *
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.” (****)
Further explanation of these categories could not be found on the Scorecard/EPA website.
The two last columns report information taken from the Swiss chemists’ data derived from their Ecosolvent -Tool (computer program.)* In this program, each solvent is given a score from 1-9 based on the solvent’s environmental, health and safety impact (EHS) from cradle to grave. Each solvent is also rated according to its life cycle assessment (LCA) based on the cumulative energy demand (CED) required to produce 1 kilogram of solvent. For both the EHS and LCA, the higher the score, the worse the solvent. In the article the two scores for each solvent are combined in one chart. Five of the top ten solvents from Stravroudis’ list are rated. The Ecosolvent-Tool rates the conservation top 10 solvents with similar low scores. Solvents such as formaldehyde, formic acid and cyclohexane have much higher scores. Only the published solvents were included. We have asked the Ecosolvent-Tool authors to calculate the EHS and LCA for the remaining 5 of the Stravroudis top ten solvents and we hope to include that data in our publication.
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. Need to double check)
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.** 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.
*Data for Scorecard was found on the US EPA website
** this data is taken from an article by Christian Capello, Ulrich Fischer and Konrad Hungerbuhler, “What is a Green Solvent? A Comprehensive Framework for the Environmental Assessment of Solvents” www.rsc.org/greenchem February 2007.
- Chris Stavroudis’ Solvent/Hazardous Materials Usage Survey taken in 2000 was the basis for solvent ranking according to conservator use.
- Information on the US EPA 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.
