In 2010, Nnaemeka Ikegwuonu, a Nigerian social entrepreneur, won a Rolex Award for Enterprise for creating a radio station advising smallholder farmers. Today, around 40 per cent of Nigeria’s produce rots in the heat before it can be sold. In a country ranked 107th out of 113 countries on the Global Food Security Index – and where more than 88 million people face food insecurity while 12 per cent are undernourished – this wastage is a huge problem. To combat this, Ikegwuonu has created ColdHubs, a network of solar-powered, walk-in cold rooms that is revolutionizing Nigeria’s food supply chain. His solution is helping farmers to keep their produce fresh until it can be sold.