Uganda wastes staggering amounts of fresh fruit and vegetables every day. Such losses are a big food security issue here and elsewhere in Africa. The waste is not just heartbreaking for producers and consumers. It is also creates methane gas, a big driver of climate change, and poses a danger to public health. To help prevent food loss, Makerere University in the capital Kampala is training students in food processing and preservation. And a tiny innovation, also spawned at the university, might have an even bigger impact.  Inventor Gift Arnold Mugisha's nano-sachets could help extend the shelf life of fresh, perishable produce by weeks. He is hoping to scale up find distribution across the country's food industry.