A wave of contaminated fuel that has clogged and damaged engines on hundreds of oil tankers and container vessels in the past months has pushed shippers to demand stricter quality controls around the world. The calls are shining a light on the notoriously opaque shipping fuel sector, where any contamination can spread quickly and be difficult to trace back to its source. That is because large volumes of fuel oil are blended with so-called cutter stocks by suppliers and sold on through an extensive network of middlemen before finding their way into ships’ fuel tanks. This tide of dirty fuel comes when the shipping industry, the backbone of global commerce with over 90 percent of the world’s traded goods transported on the oceans, is bracing for an unprecedented shift […]