Hey Mr, Green, Should I feel guilty using the garbage disposal in my condo sink? --Gary in Sarasota, Florida

Like its menacing cousins the power mower and the leaf blower, the garbage disposal is a howling metallic tornado of superfluous technology that replaces kinder, gentler, and healthier tools in the name of convenience. The pulverized crud whirled through disposals and into wastewater increases the level of pollutants, requiring extra treatment before the effluent is safe enough to be released.

It's impossible to calculate how much food waste Americans slice and dice down the drain, but we still trash about 27 million tons of it each year--around 16 percent of all municipal garbage sent to dumps. If composted, this annual waste would be transformed into a gorgeous 9 million-ton pile, a veritable Mt. Olympus for gardeners. (Once, when I was engaged in the leveraged folly of a second mortgage, the property appraiser condescendingly noted that the kitchen lacked a garbage disposal and dismissed my genteel offer of a compost-bin visitation. No hope of thinking inside the bin when a guy can't even think outside the disposal.)

Since you're in a condo, you probably don't have a compost bin, but you might want to experiment with one of the indoor composters now available. Use the results on houseplants or give it to a gardener who will, I hope, gratefully reward you with fresh vegetables and bouquets.

Hey Mr. Green, Which salmon is safe to eat? --Eileen in Burbank, California

Wild Alaskan or Pacific salmon is better than the farmed kind, both for the fish and for the offshore habitat. Turns out what's good for the deep is good for the diner: Farmed salmon, including most labeled "Atlantic," contain significantly higher levels of dioxin, PCBs, and other potential carcinogens and endocrine disruptors than do wild salmon. Neither wild nor farmed specimens usually contain hazardous levels of mercury, though many other fish do. To download a handy reference guide to potentially dangerous or overfished seafood, go to sierraclub.org/mercury/fishguide.pdf.

Hey Mr. Green, I'm only 13, and I really want to help save the environment. But donating money feels like somebody else is doing the work for me, and recycling has become routine. What else can I do? --Alex in Boulder, Colorado

The bad news is we adults are leaving a complicated mess for your generation. But you're never too young to advocate for nature. Adam Werbach, who was the Sierra Club's president at age 23, started his environmental activism at 8. He also founded the Sierra Student Coalition, whose summer camps for high school and college students help them start campus groups and run effective campaigns. To learn about these and similar opportunities, go to ssc.org/resources. Earth 911, the EPA's Environmental Kids Club, Kids for a Clean Environment, and the Natural Resources Defense Council's Green Squad all offer useful information for you computer-savvy whippersnappers.

And spread the word. If you kids pestered your parents as much about saving the planet as you do about getting cell phones, iPods, and video games, you'd probably start an environmental revolution.

Read more advice from Mr. Green, including his Web-only mailbag, and submit your own environmental questions at sierraclub.org/mrgreen.

Mr. Green illustration by Melinda Beck; used with permission.