When you order that barbecue sandwich at the drive thru, or sit back from that roast beef dinner Sunday evening, how much of it remains in your wrapper or on the plate?

Well, the U.S. Department of Agriculture is concerning itself with that information as it tries to assess how much food Americans waste and the challenge of cutting that waste.

When I was a kid, lo those many years ago, Mom was concerned with us eating what we were given. "You need to clean your plate, "she would say, "There are starving children in China who would love to have what you have."

Made sense at a time when kids expended huge amounts of energy playing and working outside. But, today, watching our waistlines makes more sense and tailoring our caloric intake to our health needs trumps starving children in China - although I'm sure they still exist.

The result is that we tend to take larger portions than Mom or our doctor wants us to ingest and we leave a lot of it on the plate, especially in restaurants, where portion control might not be the best. So, a good deal of good food winds up in the landfill or down the garbage disposal.

The USDA has noted that food is the single largest component of municipal solid waste, accounting for over 20 percent of landfills by weight. In the landfill, it rots and creates methane gas 21 times more potent than carbon dioxide. Landfills, the USDA said, are the third largest source of methane in the U.S.

Working with the U.S. Environmental Protection Agency (EPA), the USDA has created the U.S. Food Waste Challenge. The effort challenges producer groups, processors, manufacturers, retailers, communities and other governmental agencies to join in the fight to:

* REDUCE food loss and waste;

* RECOVER wholesome food for human consumption; and

* RECYCLE discards to other uses, including animal feed, composting and energy generation.

In launching the Challenge in June, the USDA said food waste in the U.S. is estimated at roughly between 30 to 40 percent of the food supply. In 2010, for instance, an estimated 133 billion pounds of food from U.S. retail food stores, restaurants and homes never made it into peoples' stomachs. The amount of uneaten food in homes and restaurants was valued at $390 per U.S. consumer in 2008, more than an average month's worth of food expenditures.

The goal of the Food Waste Challenge is to band organizations and individuals together to lead a shift in how we think about and manage food and food waste. The Challenge includes a goal to have 400 partner organizations by 2015 and 1,000 by 2020.

Among the wide range of activities the USDA plans are programs to reduce waste in school meal programs, educate consumers about food waste and food storage, and develop new technologies to reduce food waste.

How can you help? Go to usda.gov/oce/foodwaste/index.htm. It will require a concerted effort across the nation to get waste under control and tailor our food supply to our actual needs, making more wholesome food available at a better price for all of us.

I'll see ya.