BHP Group has written down its Jansen potash project in Saskatchewan by $2.3 billion and raised its cost estimate to $6.9 billion. The project, which has been in development for over a decade, is the latest example of how mining investments can balloon in cost long after initial plans are made, according to Bloomberg (18 June 2026).

A writedown happens when a company admits an asset on its balance sheet is worth less than it previously thought. In this case, BHP's internal calculation of what Jansen is actually worth — taking into account fair value and the cash it will generate — now falls short of what the company had recorded by $2.3 billion. It is an accounting reality, not a guess. The number is now locked into BHP's financial statements.

Why the cost keeps climbing

Jansen was first given the go-ahead for its initial stage back in 2021, but money has been flowing into the project for much longer. Each time BHP has revised upward what it will cost to build, the returns investors were promised have shrunk.

The reasons are straightforward. Building a deep potash mine in Saskatchewan requires engineering skill in one of mining's toughest technical challenges. Labour is scarce there. Materials — steel, concrete, equipment — cost far more now than they did before the pandemic. None of these pressures have fully eased.

What makes this different from typical project overruns is the sheer duration. A project that stays over budget for years, adding billions in cost, signals something deeper than bad luck. It raises a real question about whether the original plan was realistic.

The potash price problem

Potash is fertiliser — a bulk commodity whose price swings based on what a handful of large producers decide to do. Nutrien and Mosaic control most North American supply; Russia and Belarus hold major reserves too. Unlike BHP's iron ore or copper, which have diverse buyers and longer production lives, potash demand is tied tightly to global farming and food production.

BHP is betting on Jansen as a 30-year asset. Over that timescale, the logic holds. Over the next five years, the math is much tougher.

When potash spiked above $900 a tonne in 2022, the original Jansen numbers made sense. Now the price has settled around $300–$350 per tonne. Every $50 swing in price meaningfully changes what return the project will actually deliver — on a $6.9 billion investment, that matters enormously. Analysts will now rebuild their models using these new prices. BHP will face hard questions about which price assumptions it believes are realistic.

The balance sheet and board-level pressure

The $2.3 billion writedown is non-cash, meaning it does not immediately crimp BHP's dividend or operating cash flow. But it does reduce reported profit, and it raises the odds that BHP's board will reconsider the total investment, including plans for a second expansion stage.

The bigger issue is internal. BHP has been under sustained pressure since its failed attempt to buy Anglo American in 2024, with investors questioning how the company picks long-duration, capital-intensive projects. A mine that costs more at every checkpoint is difficult to defend when the board is also evaluating quicker-payback copper expansions that need less capital. The company has not signalled any plan to halt Jansen, but the optics are becoming harder to explain.

A sector-wide pattern

Mining companies that diversified into potash or similar agricultural commodities during the commodity boom of the 2000s and 2010s have, with rare exceptions, found these assets more capital-hungry and less profitable than expected. Interestingly, BHP avoided a bid for Potash Corporation of Saskatchewan in 2010 due to shareholder and political concerns — then later entered the same space through Jansen. That contradiction in strategy is not lost on observers.

The potash market remains structurally sound for decades. But the path from here to a profitable operation at Jansen requires potash prices to hold, costs to stabilise, and BHP's capital discipline to hold firm. The $6.9 billion figure, paired with a price environment far weaker than 2022's peaks, creates a narrower margin for error than most investors assumed when Jansen was first sanctioned.