The steps involved in mining and processing Canada's tar sands to produce oil offer an example of why unconventional fuels can be less attractive than traditional fuels, in terms of the amount of energy they yield versus how much is invested in producing them. First comes energy-intensive logging, digging, hauling, crushing, washing and heating of the sand-laden raw product to separate out the tarlike bitumen (inner ring). An on-site refinery called an upgrader must then cook the bitumen to turn it into regular crude oil, which is eventually transported by pipeline and sometimes tanker. Another method requires energy to create steam that melts the bitumen underground. Of course, all the operations require human labor (second ring). Distant refineries consume still more energy to turn the crude into gasoline and other fuels. Cleanup afterward includes water purification and land reclamation, both of which require yet more energy. Traditional drilling, extracting and refining conventional crude oil demand much less energy investment.