I’ll bet you know families that refuse to eat any left-overs. Instead of saving perfectly good food for later in the day or the next day, the entire assortment of the unfinished meal is dumped into the garbage can.

Maybe it’s because I grew up on a farm in the 1950s and 60s, the one thing we were taught was not to waste food, or anything for that matter. There was always plenty of food, and you were expected to eat what mother prepared.

A recent newspaper article reminded me that 40 percent of edible food in the U.S. is wasted, according to the U.S. Dept. of Agriculture. That includes food wasted on farms, restaurants and retail markets. The figure is 21percent in homes, a staggering 120 billion pounds.

The most food is wasted in the summer. Overall, 25 percent of fresh fruit is dumped, 24 percent of fresh vegetables, 23 percent of meat, 31percent of fish and seafood and 20 percent of dairy products.

The report said we are not inclined to waste unhealthy foods like bakery, candy, packaged snacks and other sugared sweets. We wouldn’t think of tossing a warm beer but it’s okay to toss a half-eaten beef roast or a slightly over-ripe bunch of bananas. Not at my house!

Another article the same day reminded me that the world population is expected to reach 9.7 billion by 2050, 33 percent more people than are on the planet today, according to projections from the United Nations.

About two-thirds of those people will live in cities. The migration from the countryside to the cities is already under way. It’s the biggest movement of humans in the history of the planet, the UN report says.

That has the planners of the future wondering how to get food from the farms to the people who live thousands of miles away. Those city-dwellers will demand that their food be fresh daily and still affordable.

Major investments are now being made into environmental-engineering companies that are using a “closed-loop” gardening system that aims to use compost and rainwater runoff to support “vertical farms” just on the outskirts of metro areas.

These companies want to grow vegetables in smaller places, such as walls, rooftops, balconies, abandoned lots. The high-density vertical growing systems have many advantages, but they face major challenges.

So far, they only grow organic leafy greens, such as kale, arugula, lettuce, herbs and wheatgrass. Maybe suburban families with large backyards will lease fenced-in space to farmers to raise livestock, such as cows, pigs and chickens?