Oil sands | Alberta Canada | Nancy Pelosi

Oil sands | Alberta Canada | Nancy Pelosi

The boom times are back at Alberta’s oil sands.

What environmentalists describe as one of the worst emitters of greenhouses gases on earth has shaken off the recession. Its massive oil extraction projects now employ 27,700 workers — 3 percent more than the previous peak in 2008.

It’s a sign that the United States’ gluttonous appetite for the tar-like mix of bitumen and sand isn’t expected to subside any time soon. America, after all, is pretty much the only client for what President Barack Obama’s advisers once derided as Alberta’s “dirty” oil.