Jansen is slated to be the world’s largest potash mine, twice the size of its closest rival. With a total estimated cost of some $14-billion, it’s a brazen bet by Australian mega-miner BHP Billiton Ltd. that the crop nutrient will be the world’s most important mined commodity for decades as farmers struggle to boost food production for a hungry planet. The Jansen project is on a scale not seen before in the industry. BHP is developing a potash deposit nearly the size of Montreal. It will be the first major new mine the industry has seen in decades. The company describes it as a 70-year bet on potash.