Closing time approaches, waiting staff collect plates littered with leftovers and chefs sweep up spoiled ingredients. This routine, repeated in restaurants across the developed world, means $80bn (£56bn) of food is wasted annually. London-based startup Winnow is tackling the problem with its smart meter for food waste. Since opening in 2013, the business has saved its customers £2m and reduced carbon emissions from the hospitality sector by 34,000 tonnes. Co-founder Marc Zornes, who researched food…