Dear EarthTalk: Some drycleaners I've seen offer "wet cleaning" as opposed to dry cleaning. What's the difference? Is it better for the environment? -- Elizabeth Connelly, Tampa, Fla.

The dry-cleaning industry has come under attack in recent years for its use of perchloroethylene ("perc"), a noxious chemical solvent that does a good job cleaning and not damaging sensitive fabrics, but which is also considered a hazardous air contaminant by the U.S. Environmental Protection Agency and a probable human carcinogen by the International Agency for Research on Cancer.

Also, exposure to perc can irritate the skin and has been associated with central nervous system disorders. Drycleaners are required to reuse what perc they can and dispose of the rest as hazardous waste, but there are still concerns about contamination at and around sites that don't follow best practices. California has banned the use of perc by drycleaners beginning in 2023, and several other states may follow suit.

Given the issues with perc -- and the fact that most of the nation's 34,000 commercial drycleaners still use it -- many consumers are demanding greener ways to get their fine clothes and fabrics clean. So-called wet cleaning -- whereby cleaning professionals use small amounts of water, non-toxic detergents and conditioners, instead of perc and other harsh detergents, inside specially designed machines to get fine garments and other fabrics clean -- is one of the most promising alternatives.

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"The garments are agitated in the computerized wet cleaning machine just enough to extract the dirt and grime, but not enough to alter the structure, size or color," reports the website Earth911.com. "The garments are then transferred to a high-tech drying unit that (that) automatically stops once the prescribed level of moisture is reached." Earth911.com adds that after drying, wet cleaned garments are pressed, hung up and bagged for pickup by or delivery to customers, just like at the drycleaners.

The EPA is encouraging drycleaners to make the switch to greener solvents through a cooperative partnership with the professional garment and textile care industry. The agency's Design for the Environment Garment and Textile Care Partnership recognizes the wet cleaning process as "an environmentally preferable technology that is effective at cleaning garments."

Another green alternative to perc is also starting to catch on: Using pressurized carbon dioxide to get fabrics clean. CO2 exists as a gas at low pressure but turns to liquid at higher pressure and can serve as a solvent in tandem with non-toxic soap to get materials clean. "Clothes are placed in the dry cleaning machine drum and cool CO2 is pumped in until, at high pressure, (it) becomes a liquid," reports Corry's, a leading drycleaner in the Seattle area. "After the wash cycle is complete the CO2 is filtered, and the pressure is released spontaneously converting the CO2 back to a gas from a liquid. The CO2 then goes back into the holding tank. The clothes are left clean, smelling fresh, cool and perfectly dry."

There are other greener processes out there as well. If a new cleaner opens up in your neighborhood, chances are they are using something cleaner than perc. Or they should be. So make sure to go in and ask.

Contacts: Earth911.com, www.earth911.com; Design for the Environment Garment and Textile Care Partnership, epa.gov/dfe/pubs/projects/garment/; Corry's CO2 Cleaners, www.corrysco2cleaners.com.

Dear EarthTalk: What are the greenest light bulbs to use? I hear there has been a lot of backlash against compact fluorescents because they contain mercury. -- Peter Roscoe, Hershey, Pa.

A decade ago, incandescent bulbs were just about the only game in town, despite their inefficient use of electricity to generate light and their primitive technology that had not changed since being invented some 125 years ago. But now that is all changing fast, with phase-outs of incandescents going on in Australia, Brazil, Venezuela, Switzerland and the European Union, with Argentina, Russia, Canada and the U.S. following suit shortly. The U.S. passed legislation in 2007 to increase the efficiency of light bulbs sold in the U.S. by 25 percent or more by 2014, and then by as much as 60 percent more by 2020.

For decades, those concerned with energy savings have been touting the benefits of compact fluorescent lamps over incandescents. CFLs use only one-fifth of the electricity of incandescents to generate the same amount of light, and they can last six to 10 times longer. But CFLs' cooler color and inability to be dimmed have made them less desirable. Another hindrance to the widespread adoption of CFLs has been their higher cost (though most consumers would save plenty in energy costs over the life of a bulb). Also, CFLs contain mercury, a dangerous neurotoxin that is released when the bulbs break. And once CFLs do burn out they must be disposed of properly to avoid releasing mercury into the environment.

Given the issues with CFLs, LEDs, short for light emitting diodes, are beginning to come on strong. These highly efficient bulbs don't generate heat like incandescents, which helps to keep air conditioning costs down as well, and can last five times longer than CFLs and 40 times longer than incandescents. Tiny LED bulbs have been around for years in specialized applications, such as stadium scoreboards, but lighting engineers got the idea to cluster them and use reflective casings to harness and concentrate their light for residential use. In recognition of the LED's potential, the U.S. Department of Energy set up a special "solid-state" LED lighting R&D program to hasten the advance of the technology.

In comparing the total cost to run three different types of 60-watt equivalent bulbs for 50,000 hours (factoring in the cost of the both bulbs and electricity), the EarthEasy website found that LEDs would cost $95.95, CFLs $159.75 and incandescents $652.50. The 42 incandescent bulbs tested used up to 3,000 kilowatt hours of electricity compared to 700 and 300 for CFLs and LEDs respectively. However, despite the savings, most consumers are loath to spend $35 and up for an LED bulb, even though it will save more than $500 in the long run, when a traditional incandescent bulb right next to it on the shelf costs $1.

There are other newer technologies in the works. Seattle-based Vu1 now sells highly efficient bulbs based on its Electron Stimulated Luminescence technology, whereby accelerated electrons stimulate a phosphor coating on the inside of the bulb, making the surface glow. One of Vu1's 65-watt equivalent bulbs retails for under $20 and uses a similar amount of energy as an equivalent CFL. And incandescents aren't out of the efficient lighting race altogether just yet. Top bulb makers recently released new versions that use as much as a third less electricity to operate, complying with 2012's new federal standards, and are promising newer models still that will run on even less energy.

Contacts: DOE Solid-State Lighting Program, www1.eere.energy.gov/buildings/ssl/; EarthEasy, www.eartheasy.com; Vu1 Corporation, www.vu1corporation.com.

EarthTalk is by Roddy Scheer and Doug Moss of E -- The Environmental Magazine (www.emagazine.com). Send questions to: earthtalk@emagazine.com.