The U.S. House approved the controversial $8.1 million energy bill Thursday, April 21. Now it’s up to the Senate to come up with its own version.

The House version of the bill includes several controversial provisions, including one allowing for oil drilling in the Alaskan National Wildlife Refuge, sometimes called ANWR. Another measure provides protection against lawsuits for producers of methyl tertiary butyl ether, or MTBE, a clean-air additive for gasoline that some claim is polluting the nation’s water supply.

Senate Republicans say they want to have their version of the bill ready for a vote by the end of May, while Democrats have vowed to fight both the ANWR and MTBE provisions.