Investing in a policy-mandated market, you might think, should make for a comfortable ride. …Yet, as the ructions in the European biofuels market show, that is not necessarily the case. …Shell on Tuesday announced it was temporarily suspending construction work at its 820,000 tonnes a year biofuels facility in the Netherlands, amid technical challenges and concerns about the current market slump. BP has recently scaled back its own biofuel plans, pausing work on two planned refineries. Meanwhile, Finland’s Neste, the world’s leading producer of sustainable aviation fuel and biodiesel, warned on profits in June. One problem is that biofuel demand relies on government mandates. Biodiesel and green jet fuel cost two to three times as much as comparable fossil fuel-derived products. Consumption is driven by the commitments European countries have made to “blend” a small but growing percentage of green fuel into the traditional kind.