If debate in the Senate last week over some relatively non-controversial energy measures was any indication of things to come, we can expect fireworks over energy policy when legislators return from their two-week April recess.

The Senate Energy and Natural Resources Committee took up the first four components of its pending energy package last week, focusing on job-training programs, efficiency standards for appliances, improvements to industrial efficiency, and protection of water resources. The four separate measures flew through the mark-up process with little discussion. But post-recess, the committee expects to take up more controversial elements of legislation — including oil and gas drilling, nuclear power, coal technologies, grid upgrades, and financing for renewables.

Even the relatively calm session last week offered insight into how messy it could get. During discussion of the non-controversial amendments, Sen. John McCain (R-Ariz.), a long-time supporter of nuclear power, redirected the conversation to his concerns about the Obama administration’s intention to cut off funding for the nuclear-waste repository at Yucca Mountain.

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“I am an ardent proponent of nuclear power, but I believe that the administration has closed out the technology,” McCain said. He pledged to offer amendments to the energy package to support the nuclear industry.

Idaho’s freshman Sen. Jim Risch (R) echoed those concerns about nuclear power, as did Lisa Mukowski (R-Alaska) and Byron Dorgan (D-N.D.). Energy and Natural Resources Chair Jeff Bingaman (D-N.M.) cut off the discussion and assured his fellow committee members that they’ll be given time to discuss nuclear power and Yucca Mountain at length in the near future.

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During the same session, Sen. Bob Menendez (D-N.J.) offered an amendment to an efficiency measure that would direct the Department of Energy to study the possibility of creating an “Energy Superstar” label to designate the most efficient appliances on the market. Currently the DOE gives appliances and office equipment the Energy Star label if they meet certain efficiency standards. Menendez said an “Energy Superstar” program could “encourage manufacturers to produce the best in their class.”

But though the proposal only called for study of the idea, not actual implementation, it tipped off a flurry of debate.  Murkowski, the committee’s ranking Republican, suggested that the new label might plunge the nation down a slippery slope of confusing efficiency labels. “Then do we have a Megastar?” she asked. Risch seemed to call for the end of the Energy Star program altogether. Menendez’s amendment was approved, but the squabbling over it and other minor measures doesn’t bode well for more complex energy negotiations.

Bingaman is taking the lead on the energy package in the Senate, which right now is looking like the most action we’ll see from that chamber for a while on energy and environment. The House is moving forward on a comprehensive energy and climate plan, but the Senate is focusing on energy and leaving climate by the wayside for now.

Senate Environment and Public Works Chair Barbara Boxer, who last year shepherded a climate bill out of her committee, has even pitched the idea that the climate portion of a plan could just show up in an energy package after a conference between the House and Senate later this year. As we’ve noted before, the Senate will have a tough time passing a climate plan. Sixty votes will be needed to break filibuster, and Democrats hold just 58 seats (they might hold 59 if the fiasco in Minnesota is ever resolved). And among the Democrats, a number of moderates have serious reservations about regulating greenhouse-gas emissions.

The Energy and Natural Resources Committee approved all four components of the energy package debated last week:

Bingaman has been gradually rolling out the various elements of his energy package, and the more contentious portions are likely to come out in the weeks following recess. After mark-up in his committee, they’ll move to a vote in the full Senate, where even more sparks can be expected.