Achieving cost savings through ozone treatment in laundry disinfection
Washing laundry is a significant use of water in the average home, accounting for 15% to 40% of the overall water consumption in a typical household. Using ozone for laundry can help reduce detergent use and make laundry less time consuming, more affordable and more eco-friendly.
There are many factors that contribute to the amount of money that can be saved by using ozone for laundry, including the number of loads of laundry done per week, the weight of laundry per wash, the number of cycles the machine runs and water temperature. It is important to examine each of these to understand how ozone in laundry use can help a family.
According to the U.S. Environmental Protection Agency (EPA), the average family of four washes nearly 480 loads of laundry per year, which is more than a load per day. According to Minol Water Services, washing a load of clothes uses about 30 gal of water. The U.S. Geological Survey states that newer washing machines (typically front loaders) may use 25 gal per load, but older models may use up to 40 gal per load. That adds up to more than 12,000 gal of water used per year, on average, just to wash clothes.
The amount of water used per wash is calculated by measuring a clothing load in pounds per cubic foot. Most washing machines will note a water factor in their owner’s manuals. According to the Consortium for Energy Efficiency, the water factor for washing machines is claimed to be the number of gallons needed for each cubic foot of laundry, in which lower water consumption is indicated as being more efficient. The other element to take into consideration is the modified energy factor (MEF) provided by the washing machine manufacturer. Energy Star or Federal Standard are the two most common energy-efficiency standards. The MEF indicates how many cubic feet of laundry can be washed and dried with only 1 kilowatt-hour (kWh) of electricity. Typically, the higher the MEF, the more efficient the machine.
The heating cost per gallon of water that goes into doing laundry is another consideration, as this has one of heaviest impacts in terms of savings. Hot water in a washing machine does not actually get hot enough to kill bacteria or viruses. Dr. Chuck Gerba of the University of Arizona presented research showing that after swabbing 100 washing machines, more than 60 were found to test positive for coliform bacteria, an indicator of fecal contamination. Another 20 of the machines contained Staphylococcus bacteria. Gerba also confirmed that the laundry bacteria primarily come from underwear, but also include bacteria often found on dishcloths and sponges. He also looked at what happens to bacteria during washing and drying. He used three pathogenic bacteria for his tests: E. coli, Salmonella and Mycobacterium fortuitium, a common bacterium that causes skin infections.
Simulating typical home laundry practices using warm water washes, the researchers observed that after washing, bacterial contamination was found throughout the clothing and on the machine itself. The bacteria left behind even showed up in subsequent wash loads.
The heat from the dryer also did not kill all the bacteria. The E. coli was eliminated, but the other two bacteria, although reduced, were still present.
Many also wonder how well their laundry detergent is working. A CBS news report claimed to find the “dirty secret” of the laundry business: “We’re all guilty of overdosing. If you’ve ever filled a washing machine with clothes you felt could use an extra boost of cleaning power, you may have added more than the recommended amount of detergent.” Because washing machines are becoming more energy- and water-efficient, adding too much laundry detergent can leave a film on clothes.
A detergent is a chemical substance used to break up and remove grease and grime. Water alone cannot clean clothes because it does not attach to molecules of grease and dirt. Detergent is different. The surfactants it contains are made of molecules that have two different ends. One end is strongly attracted to water; the other is attracted to oily substances such as grease. Because detergent is designed to attract dirt, wearing overdosed clothing can make it dirtier faster, resulting in doing laundry more often and ultimately costing more money.
Formula for Savings
A mathematical equation can help homeowners determine how much their washing machines are costing them on average. This equation varies by washing machine and region in terms of cost, but it provides a good average.
On average, a washing machine uses 18 gal of water per wash cycle and there are two cycles per load, totaling 36 gal of water per load of laundry.
On average, the water inlet temperature is 77°F. To prevent scalding accidents, the hottest water allowed in most homes is typically 120°F. The difference between the two is 43°F.
It takes approximately 8.34 btu to heat 1 gal of water 1°F.
Thus, the formula is as follows: 1°F x 8.34 btu x (120°F-77°F) = Number of btu per gallon of laundry.
This equates to 358.62 btu per gallon to simply heat the water going into an average washing machine. With an average of 36 gal of water per load of laundry, the total amount of heat used is 12,910.32 btu. The conversion back to kilowatt-hours equates to 3.784 kWh per load of laundry. This varies based on the type of washing machine used.
The average kilowatt-hour cost also varies by location. In the state of Maryland, it is $0.13.7, thus $0.13.7 x 3.784 kWh per load = $0.51 per load of laundry just in heating costs.
For a family of four completing 480 loads per year, the energy cost alone would be $244.80.
The cost of laundry detergent also adds up. A 50-oz bottle of Tide Total Care laundry detergent says it does 32 loads per container, so to complete 480 loads per year, a family would use 15 containers. Each 50-oz bottle costs $19.99, for a total annual cost of $299.85 (not including tax). Adding in the cost of bleach, fabric softeners and stain treatment sprays brings the total to approximately $440.
Considering all of the costs, a family of four could spend $700 per year on laundry.
Ozone use in a laundry routine can save money in many of these areas. A 104-room California hotel conducted a two-month study to compare traditional laundry with an EcoTex ozone laundering system. It found the annual costs of ozone versus traditional laundry were less in the categories of electrical (30% savings), natural gas (81% savings), chemicals (21% savings), water (26% savings) and labor (39% savings). A 2012 hotel study titled “Ozone Laundry – 95 Room Hotel Payback Study” showed similar results and savings of almost $780 per month. It found that the ozone laundry system saved more than 47% of fuel costs for boiler and dryer operation, with a 74% savings for the boilers (hot water) alone. In addition, the system eliminated softener costs, reduced electrical costs for the washers and dryers by about 13%, and reduced linen replacement costs by 10%.
Furthermore, ozone has been shown to effectively control, disinfect and/or eradicate microorganisms normally found in soiled laundry in many studies. For example, one study found that several microorganisms, such as E. coli and many types of viruses, were eradicated within minutes by ozone cold water laundering. The same was found for two “superbugs”: methicillin-resistant Staphylococcus aureus and C. difficile. These bacteria often are resistant to traditional hot water laundry processes. However, disinfection is a time-dependent process. Ozone is effective in killing bacteria in three minutes and viruses in six minutes. In this aspect, ozone laundry systems outperform traditional systems. It is recommended that laundry wash cycles be 10 to 12 minutes long to determine a concentration over time value that is the recommended method to report compliance with EPA disinfection requirements for drinking water.
Detergent-less laundry systems can save money and time. A detergent-less laundry system consumes around 25 watts of electricity—less than the average light bulb consumes when running. For these systems, no hot water is required, saving energy and money. Due to the elimination of hot water, clothes do not need to be sorted by darks and lights, whites and colors. Clothes feel softer and fluffier because no soap is left behind in the fabric. The life of the fabric itself is extended, because detergents can cause fiber shredding. The rinse cycle will work as a second wash cycle. Detergent-less laundry systems ultimately will improve the performance of the washing machine and end the need to purchase cleaners.