Globe and Mail: On a late-spring day beneath a warm prairie sun, some 6,000 construction workers and 30 cranes are at work on a $12-billion expansion to Royal Dutch Shell PLC’s upgrader to boost its capacity for processing oil sands bitumen. A short drive across the massive industrial complex near Fort Saskatchewan, Alta., a gravel lot sits largely empty — an idle crane, some pickup trucks, and a row of portable offices. It is, however, home to a controversial idea: This undeveloped lot is the …