P&D, you said, "because lenders don't share in the upside, they typically want certainty".
Sure lenders want certainty but every day, businesses borrow money (successfully) to set up or increase production capacity with no signed contracts for the products because market demand is predictable, including for fertilizers and fuels. The economy would grind to a halt if businesses had to pay 100% cash up front for business capacity expansions.
I was thinking the difference here from a typical business is the huge upfront capital costs. While market demand is predictable, prices are not. Note that in the power business, it took merchant plant developers years to convince banks to finance large projects without long term contracts with electric utilities. When they finally started doing this, the industry overbuilt and prices collapsed leaving large independent power producers like Calpine bankrupt and bankers scratching their heads over the billions owed.
I am not familiar with how fertilizer is sold but some sort of hedge program going out a least a couple years seems to be required. If fertilizer prices are correlated with natural gas, perhaps they could use gas futures to hedge some of the risk. But with no hedge, would you take on the fertilizer price risk for 20 years for only an 8% return?