I generally see her after dark: an old woman in a conical Vietnamese hat, making the rounds in my neighborhood the night before our weekly trash pickup. She is out in all kinds of weather, checking the bins that residents have set out on the curb, helping herself to the aluminum cans. I’ve smiled and nodded hello once or twice, but she looks right past me and moves on. I figure she’s too busy working to lose any time on pleasantries.

The woman engages in one of mankind’s oldest means of employment: picking through rubbish, looking for things of value in other people’s discards. Winslow Homer portrayed such scavengers — recyclers, we’d call them today — in “Scene on the Back Bay Lands, Boston,” an 1859 engraving of trash-pickers sorting through the landfill that eventually became one of Boston’s most elegant neighborhoods.

Such “private sector recycling is as old as trash itself,” notes Clemson University economist Daniel K. Benjamin, who reproduces the Homer image in “Recycling Myths Revisited,” a new monograph for PERC, the Montana-based Property & Environment Research Center. Homer’s Back Bay foragers were poor people who sifted through rubbish not because it was politically correct or required by law, but because it was a productive use of their time.

It left them better off. Similarly, the woman I see in my neighborhood pulls beverage cans out of trash bins not because she believes recycling is virtuous, but because there is a 5 cent deposit on them and behind that a natural market demand for aluminum cans.

By contrast, she doesn’t take the toothpaste tubes, or Styrofoam cups that people have thrown out, because there is no natural market for them. That doesn’t mean those items couldn’t be recycled. It means that they’re not worth recycling. To put it in environmental terms, recycling such rubbish would be a waste of resources.

Most of the stuff we throw out — aluminum cans are an exception — is cheaper to replace from scratch than to recycle. “Cheaper” is another way of saying “requires fewer resources.” Green evangelists believe that recycling our trash is “good for the planet” — that it conserves resources and is more environmentally friendly. But recycling household waste consumes resources, too.

Extra trucks are required to pick up recyclables, and extra gas to fuel those trucks, and extra drivers to operate them. Collected recyclables have to be sorted, cleaned, and stored in facilities that consume still more fuel and manpower; then they have to be transported somewhere for post-consumer processing and manufacturing. Add up all the energy, time, emissions, supplies, water, space, and mental and physical labor involved, and mandatory recycling turns out to be largely unsustainable — an environmental burden, not a boon.

“Far from saving resources,” Benjamin writes, “curbside recycling typically wastes resources — resources that could be used productively elsewhere in society.”

Popular impressions to the contrary notwithstanding, we are not running out of places to dispose of garbage. Not only is US landfill capacity at an all-time high, but all of the country’s rubbish for the next 100 years could comfortably fit into a landfill measuring 10 miles square. Benjamin puts that in perspective: “Ted Turner’s Flying D ranch outside Bozeman, Mont., could handle all of America’s trash for the next century — with 50,000 acres left over for his bison.”

Nor do modern landfills — which are regulated by the Environmental Protection Agency — pose a threat to human health or the environment. They must be sited far from wetlands and groundwater, thickly lined with clay and plastic, covered daily with fresh layers of soil, and equipped for drawing off the methane gas created by decomposition. Eventually they are capped, landscaped, and turned into public parks or other open space.

Recycling makes many people feel good, but feelings are not the best test of environmental soundness. When it makes more sense to recycle than to throw something away; government compulsion isn’t needed. And when recycling is a profligate use of natural and human resources, government mandates can’t change the fact. Big Brother can force you to recycle your garbage, but that doesn’t make garbage-recycling green.

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