This time it’s San Francisco, one of the first cities in the country to adopt a mandatory composting and recycling ordinance. The city has even moved to implement fines of up to $1,000 to buildings, mostly large waste producers, that fail to comply with the law. The hope is that by 2020, none of San Francisco’s annual two million tons of solid waste will make its way to a landfill.

Ambitious? Certainly. But how do they plan to deal with all of...