TAIZHOU, China – At the edge of one of the many pig farms spread across the vast, unbroken floodplains of Taizhou, a two-hour drive north-west of Shanghai, a pair of square, 4m pools of acrid-smelling ochre liquid hold the key to cutting costly soya bean use in half. The pools hold a swill of cheaper, locally sourced ingredients, which can include bran, pumpkin vines and wine lees. But it is fermented – like yogurt – so the proteins are already broken down and easy to digest, lessening the need for the higher-quality proteins in soy, 80 per cent of which…