Greenwire: From cap and trade to chemicals reform to offshore drilling, 2010 was marked by pitched environmental battles that Congress left unsettled as the clock wound down. But some of the season’s most intense political jockeying has come over a $7 billion project that lawmakers can neither approve nor veto. The 1,700-mile Keystone XL pipeline would carry up to 900,000 barrels per day of Canadian oil sands to Texas refineries, nearly doubling U.S. imports from a crude reserve ranked as the …