Issue Date: October 31, 2011
The Cold Facts
To reduce the energy cost of washing clothes, chemistry may not be enough.
Procter & Gamble has three goals for making its laundry products business more environmentally sustainable over the next 10 years. The consumer goods giant wants 25% of its laundry raw materials to be derived from renewable resources and to use 20% less product packaging. It’s also pushing for 70% of all clothes to be cleaned in cold water.
All laudable targets, according to Dawn French, P&G’s director of laundry R&D in North America, but reaching the third one will have the biggest impact on the environment. The third goal is also the most difficult, she acknowledged, because unlike the other two, achieving it is in the hands of the consumer—not P&G.
French made the case for cold-water washing at Cleaning Products 2011, a conference sponsored by IntertechPira in Washington, D.C., earlier this month. Part of her pitch was a plea to chemical companies that supply P&G with raw materials to consider wash temperature when developing new ingredients.
Coincidentally, a study released during the week of the conference throws some cold water on the push to make detergents work efficiently at ambient water temperatures. The study found that the energy saved by washing in unheated water is much less than that derived from cutting the time clothes spend in the dryer.
Today, 40% of U.S. laundry is washed in cold water, French said. She cited a P&G calculation that 4% of the energy consumed in the U.S. would be saved if all laundering were done in cold water. “Heating that water takes a lot of energy, and that energy creates its own environmental footprint,” French pointed out.
P&G’s means of promoting the switch is Tide Coldwater laundry detergent, launched in 2005. At the time, the company told C&EN that it contains a hydrophobic surfactant system to solubilize oily soils in cold water. It said the liquid version uses a combination of protease and carbohydrase enzymes that are particularly effective on insoluble soil residues in cold water. The powdered version, it said, contains high levels of a cold-water bleach activator.
Despite the specialized formulas, P&G and others in the detergent industry have yet to perfect cold-water washing, French acknowledged. “The reality is that there are gaps today, and these are gaps we must commit to fixing,” she told attendees.
Heat works synergistically with detergent ingredients to get clothes clean, French pointed out. “Thermal energy is real,” she said. “It does help our chemistry.”
Because surfactants, the workhorse ingredients in laundry detergents, struggle to hydrate fabrics in cold-water conditions, French said, “we must preferentially pick surfactants that can do this at a lower temperature.” Branched surfactant molecules have a better solubility profile, she explained, and short surfactant chains dissolve stains faster than long ones.
Soil-dissolving enzymes work better at warm temperatures but can be optimized to work at cold temperatures, she said. And stain-resisting polymer additives are a boon to cold-water formulas because their performance is relatively unaffected by temperature.
The typical buyer of detergents has good environmental intentions, French said. “She wants to do what is right, but she’s not going to accept a personal trade-off to do it.”
To help P&G develop effective detergents that consumers will buy, French asked chemical suppliers to determine whether the ingredients they are developing work well in cold water. Some are heeding the call. In describing a new anti-graying polymer, Jan Shulman, a group leader for fabric and surface care at Dow Chemical, said tests of the polymer’s effectiveness did in fact take place at ambient water temperature.
On the other hand, when Neil Renninger, chief technology officer at Amyris, discussed a new surfactant based on the biobased raw material farnesene, he presented performance data collected at 100 °F. Acknowledging French’s call for low-temperature results, he speculated that the branched nature of the surfactant should make it relatively active at low temperatures.
Jesper Duus Nielsen, a senior R&D manager at the Danish enzymes producer Novozymes, told attendees that his firm has spent years developing enzymes that work in cold water. “We’re seeing enzymes evolve from being an add-in to being a cooperating ingredient you need to get the low-temperature cleaning the consumer wants,” he said.
Enzymes are expensive ingredients used in premium detergents, but Nielsen pointed out that the added cost they tack on at the supermarket is offset at home when consumers save money by washing in cold water. And a Novozymes study found that washing with an enzyme-containing detergent in cold water gets clothes cleaner than washing with a no-enzyme detergent at high temperatures.
Overall, Nielsen said, if everybody in the U.S. turned their washing machine dials from hot to warm and from warm to cold, between 16 million and 20 million tons of carbon dioxide emissions would be averted each year. “Cold is the goal,” he said.
That may be true for washing clothes, but on the day that the cleaning products conference began, the environmental and energy research firm Cadmus Group released a study concluding that the detergent industry’s environmental efforts may be inconsequential. Cadmus found that heating water to wash clothes uses only a modest amount of energy compared with drying clothes in an electric clothes dryer.
“Hot-water use in washing clothes is moderately important,” said David Korn, a principal at Cadmus, “but we found that households only use hot water about 13% of the time.”
According to Korn, because the majority of the energy is consumed during the drying process, “potential savings arise in reduced operation of the clothes dryer—not the washer.” The firm didn’t study gas-based dryers because of the difficulty of metering gas use.
Cadmus isn’t discouraging further development of cold-water detergents. But after concluding that 81% of the electricity used to do laundry is consumed by the dryer, the research firm said emphasis should be on maximizing water removal during the washing machine’s spin cycle to reduce the amount of time clothes must spend in the dryer. ◾
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