How green is your detergent?
"Biodegradability" refers to the degree to which a substance can be decomposed by the action of bacteria and other living organisms, such as fungi. Chemicals that do not biodegrade quickly can gradually accumulate in the environment and harm living organisms at several levels in the food chain.
Pure soaps stand out as the best choice environmentally, as they are 100 percent biodegradable and contain no phosphates. (See "How Much Phosphate?" on the next page.) In addition, they can be extracted more easily at the sewage plant. However, they may not wash satisfactorily in hard water areas and may need to be combined with water softeners such as borax or washing soda. The grease emulsified by soap may be liberated when sewage is pumped into the sea, eventually forming scum on beaches.
These days even mainstream laundry detergents are designed to be more biodegradable. Many countries now have biodegradability standards, which may dictate, for instance, that 80 percent of the detergent must biodegrade within twenty-eight days. However, often these standards do not address the biodegradability of all the ingredients. Low-phosphate or phosphate-free detergents are also available, although the problem of phosphates in detergents is not a clear-cut one.
Manufacturers of alternative brands offer detergents with plant surfactants (dirt-removing molecules) that they claim are 100 percent biodegradable. These brands often omit a number of additives such as whiteners.
In many countries detergents are required to be biodegradable, but that is a qualified term. In Australia, the standard says that surfactants classified as "biologically soft" must be 80 percent biodegraded in twenty-one days. "Biologically hard" surfactants must biodegrade by 50 percent in twenty-one days. Pure soap and soap flakes are considered to be 100 percent biodegradable, and surfactants that are 100 percent biodegradable in seven days have been developed.