Recovering usable petroleum from oil sands is about seven times more difficult than getting it from other sources, but rising energy costs have caused a flurry of new investment into this energy source. Canada's recoverable reserves are estimated to be about 165 billion barrels, making this the largest known source of petroleum in areas that are friendly to the US. The Chinese are hopping in as well. The cost of $20/barrel may have once been a significant issue, but with today's oil prices, there's still plenty of room for profit. Problems that still have yet to be addressed are the large amounts of wastewater generated (up to four barrels for every barrel of oil), and substantial CO2 emissions. Mining this stuff sounds like messy work, but the days of simply drilling a hole in the ground and waiting for oil to spray out are probably nearing an end.