If food waste were a country, it would be the third-highest greenhouse-gas emitting nation behind the US and China. That’s because 40% of all food grown in the world goes uneaten each year, according to a World Wildlife Fund report from last year. And when food ends up in landfills, it produces huge amounts of greenhouse gases. So it’s no surprise then that apps designed to combat food waste – by giving consumers the opportunity to purchase leftover, expiring or misshapen food at discount prices – have become increasingly popular in recent years. Some of these apps have millions of…