Garbage disposal guilt - disposal vs. the trash can for perishable wastes

Vegetarian Times, Jan, 1996 by Jeanne Rattenbury

Is using a garbage disposal more environmentally responsible than throwing perishable waste in the trash?

YOU'VE RAISED a complex question, one whose answer depends largely on where you live and how waste is managed in your community. At issue are the potential negative impacts that table scraps have wherever they end up, so let's review the options. If you throw last night's salad out with the rest of your trash, it will be hauled to either an incinerator or a landfill. According to Joanna Hoelscher, program director for the Illinois office of Citizens for a Better Environment, incineration is probably the worst option because "food doesn't burn well at all. So much of organic material is wet." The more wet material present in an incinerator (along with such eminently recyclable items such as paper and plastic, not to mention such lethal commodities as batteries and household cleaners), the more time the incinerator will spew all sorts of nasty toxins into the air you breathe.

Although landfills don't seem to be much more pleasant, they do provide a better final resting place for kitchen garbage at least in theory. In a properly designed landfill, organic material decomposes, which helps mitigate one of the problems with landfills: they fill up, necessitating that more of them be built. Occasionally, however, poor landfill design prevents biodegradable material from meeting its destiny (we've all heard some variation on a hot dog found still intact wrapped in a 1940s newspaper). More troubling is that wet organic material exacerbates the real problem with landfills leaching of toxic materials and contamination of groundwater. Although landfills have protective plastic liners that are designed to prevent leakage, a 1992 study by the El Macero, Calif.-based consulting firm G. Fred Lee and Associates concluded that leakage is inevitable. Dangerous heavy metals and other poisons are much less likely to seep through the landfill's protective barrier when dry than when wet, says Hoelscher.

When you use a garbage disposal, organic material ends up either in a water-treatment facility or in a septic tank. Publicly owned treatment works (POTWs) are designed to deal with food waste (after all, that's what fecal matter essentially is), so it's OK to send your table scraps their way, according to Christopher Magruder, environmental policy coordinator for the Milwaukee Metropolitan, Sewage District. Doing so adds to "biochemical oxygen demand," however; in other words, more oxygen needs to be pumped into the water to feed the microorganisms that break down organic material. If this oxygen need isn't met, problems may result downstream. Magruder says the added demand isn't substantial though, and facility operators keep on top of the amount of oxygen that must be added. True, somewhat more energy is expended (as it is when you use electricity to run your disposal), and energy consumption certainly has environmental ramifications, so using a disposal is not an entirely guilt-free proposition.

Nor should it be a careless one. Not everything that's put into a disposal can be broken down by microorganisms, and whatever is left behind will ultimately have to be removed from either the POTW or your home septic system. Many septic-system professionals advise against using disposals; extra waste means your system has to be cleaned more often. Coffee grounds and egg shells, for instance, will not decompose. "They just take up space," says Jim Wheeler, an environmental engineer with the U.S. Environmental Protection Agency.

The "sludge" that settles at the bottom of the POTW generally meets one of two ends: it's landfilled, with all of the above repercussions, or it's used as fertilizer (in which case it is known as a "biosolid"). In theory, using biosolids this way is a fine idea, but in practice they may be tainted with toxins, says Hoelscher. Unfortunately, many individuals and businesses dump materials into the wastewater stream that biologically active POTWs are not well suited to deal with, such as motor oil, paint thinner and industrial chemicals. Those toxins can get mixed up with the biosolids that are then spread on the soil that grow the food we eat, leading to a not-so-pretty picture.

What's the best solution? You guessed it: composting. Composting eliminates the middle man in returning nutrients to the earth, and expends no fossil-fuel generated energy in doing so.