It's scrap, not trash, and it's also one of America's top exports

International scrap dealers educate our reporter on the language of our leftovers.

One thing you learn quickly if you hang around scrap merchants is not to refer to the materials in which they trade as "trash" or "garbage" or "junk."

At a recent convention here of the Bureau of International Recycling (essentially the global forum for scrap dealers) I drew some very sharp looks and a reprimand or two before I got the message.

Of course, the traders are right. If scrap was indeed trash it would not be worth anything. And scrap is certainly worth something. In fact, according to a recent Bank of America-Merrill Lynch report, the global waste and recycling business is worth $1 trillion a year. And it could be worth double that by 2020.

"Where there's muck, there's brass," runs an old Yorkshire adage.

People in the know at the conference told me that a lot of the participants were millionaires at least. But they work in the shadows of the world economy, attracting little attention.

Did you know, for example, that trash – I mean scrap – was America's top export to China in 2011? (Though maybe not for long, because of new Chinese regulations.)

There is one synonym for "scrap" that its devotees more or less allow – "waste." But, as I was reminded by Surendra Borad, an Indian businessman whose company, Gemini, handles more scrap plastic than any other firm, "waste is not waste until it is wasted."