Eco-Experts Answers Your Environmental Questions
Get help with detergent, home heating and flea control questions.
January/February 2004
By Natural Home Staff
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Carol Steinfeld
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Detergents in graywater
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Is graywater containing Wisk detergent safe for lawns and plants? The detergent, called Wisk Action with Colorhold, is labeled “biodegradable with no phosphorus and safe for septic systems.”
—Kitty Jansen Arena, Wisconsin
Carol Steinfeld replies:
Most soaps and detergents won’t kill plants outright. Some even feed them. However, some ingredients can clog plants’ “arteries.” Soaps emulsify soils, microbes, and liquids, detach them from surfaces, and act as a surface action agent (surfactant) to reduce water’s surface tension, making it “wetter.” Detergents go a step further, detaching and binding up particles so they can be washed away.
Many soaps contain sodium hydroxide. This increases the amount of sodium in the graywater, while the hydroxide raises the pH, or alkalinity. Sodium can inhibit water and nutrient transport in some plant cells and change the osmotic balance. In other words, sodium causes hypertension in plants, just as it can in humans.
Wisk only lists its ingredients in general terms, but it appears that it will not harm gardens irrigated with graywater. If you are planting salt-sensitive plants, look for potassium-based laundry soaps instead. Potassium is a fertilizer and a beneficial nutrient. Most liquid soaps are made with potassium hydroxide. Potassium hydroxide serves as an excellent grease remover; it works by turning grease into soap. Tri-potassium phosphate (TKP) is a powerful cleaner that is used on sewer pipes and automotive engines.
Citrus oil soaps are also a good choice for graywater gardens. Laundry powders (both detergents and soaps) often contain caking agents such as silicates to keep them powdery, even in products labeled “natural” or “organic.” These and other additives called “builders” do not decompose and can clog graywater-irrigated gardens.
Phosphate laundry detergents are banned by most states because phosphorus can pollute surface water with nutrients. But your plants will eat it up.
Carol Steinfeld is co-author of The Composting Toilet System Book (Chelsea Green, 2000) and conducts workshops on composting and composting toilets.
Home heat conversion
Many homes in rural North Carolina and Virginia are heated with propane gas. I object to the odor and the expense of the fuel. Is it economically and/or physically feasible to change a 1,500- to 1,700-square-foot home’s heating system from propane gas to natural gas, or even to an electric heat pump? I hope to do this in conjunction with (at least passive) solar heat capabilities.
—Elissa Ornato via e-mail
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