The cost of a diaper and other trash

Seattleites are enthusiastic recyclers, and they can do more. But in recycling there is a law of diminishing returns, and each step needs to justify itself.

Overall, the garbage not recycled costs the city $50 a ton to put on a train and send to Oregon. That means that any recycling that costs less than $50 a ton is worth doing. The current recycled share is 44 percent, which includes most of what is worth doing, but not all.

The city has a study that says it could increase the recycled share to 72 percent, but the director of solid waste, Tim Croll, says some of that is too expensive. One is composting of pet waste, which is estimated to cost $1,700 a ton. Another is subsidizing cloth-diaper services in order to cut down on used disposable diapers. That pencils out at more than $2,000 a ton.

Another is a ban on plastic shopping bags. The current alternative, says Croll, is a cornstarch bag that biodegrades into little waxy pellets that aren't good in compost. The cost for a ton of garbage saved is more than $2,000. It is an amount that would tend to get rolled into the price of groceries, which makes us wary of supporting it.

The best opportunity is in recycling the construction and demolition waste generated by builders. Nail-scarred studs can be chipped and used for boiler fuel. Broken wallboard and metal can be recycled. Some of this is done today without subsidy because it pays; with some incentives, a much larger sorting station could be built.

The study estimates that a program to encourage recycling of construction and demolition waste would cost only $2 a ton and could increase the share of municipal garbage recycled by nearly 5 percentage points, making it hundreds of times more cost-effective than banning plastic bags.

Another 2 to 3 percent of garbage could be recycled, the city estimates, if garbage workers picked up large items at curbside. But that would mean a ban on private dumping at the transfer stations, and Mayor Greg Nickels rejected that. The inconvenience is too painful. Let it wait.

As time goes on, the limits on what it makes sense to recycle will change. More things become possible. For now, the city's target of 60 percent by 2012 is about right.