FACTBOX: Timeline, comparison of U.S. climate bills

WASHINGTON (Reuters) - Democrats on the U.S. Senate Environment and Public Works Committee approved their version of a climate change bill as the panel’s Republican lawmakers boycotted the vote.

Here is a possible legislative timeline:

* OTHER COMMITTEES: Several other Senate committees will debate, modify and vote on the bill and closed-door negotiations with the White House, Senate Republicans and moderate Democrats are being led by Senator John Kerry.

* FULL SENATE VOTE: The full Senate will then vote on the bill shaped by the committees, which will likely not happen until next year and it will probably be altered again when it is on the Senate floor.

* OVERCOMING FILIBUSTER: Sixty of the Senate’s 100 members would have to support a controversial bill to block a filibuster, while the House only needs a simple majority to pass legislation.

* DIFFERENCES BETWEEN CHAMBERS: Differences between the Senate and House climate bills would have to be worked out to win over enough lawmakers in both chambers to approve a compromise climate measure.

* OBAMA SIGNATURE: Only then could a final climate bill be sent to President Barack Obama to sign into law, which again is not expected to happen until sometime next year, if the process does not bog down along the way.

* ECONOMIC WORRIES: With Americans worried about economic issues, it will be more difficult for lawmakers to vote for a climate bill in 2010, which is a congressional election year.

Here are key similarities and differences between the bills passed by the House and the Senate environment panel:

* EMISSION REDUCTIONS: The Senate shoots for a 20 percent cut in smokestack pollution by 2020. The House bill sets a 17 percent reduction from 2005 levels. Some moderates in the Senate will try to lower the goal to 14 percent. Both bills have the same long-term goals: an 83 percent cut in U.S. carbon pollution by 2050.

* CAP AND TRADE: Both the House and Senate bills envisage a system under which the government would put limits, continually declining, on the amount of carbon pollution from stationary sources like power plants, oil refineries and other factories. Companies would need an annual permit for every ton of carbon pollution they release into the atmosphere. Facilities that don’t use all of their permits could trade, or sell them, to companies that need more.

* FREE POLLUTION PERMITS: Eighty-five percent of the pollution permits companies would have to obtain would initially be given away by the government, with 15 percent sold, under the House bill. In 2026, many of the free permits would begin switching to those that must be sold. The Senate bill has a 75 percent-25 percent split between free versus auctioned permits.

* ALLOCATION OF PERMITS: The Senate and House bills give 30 percent of all free permits to local electric distribution companies, 15 percent to cement, steel, glass and other big energy-using firms, 9 percent to local natural gas distributors, 3 percent for companies making electric and advanced technology vehicles and about 2 percent for oil refiners.

The free permits are designed to ease industry’s burden in the early years of cap and trade and prevent large energy price increases for consumers. Electric utilities and natural gas interests are asking the Senate for more free permits.

* PRICE COLLAR: Both bills try to prevent wild fluctuations in future carbon prices by sketching out price floors and $28 ceilings. As time goes by, the Senate bill would allow the price to go higher than the House-passed bill.

* TRADE PROTECTIONS: The House bill would protect U.S. energy-intensive industries from foreign countries’ exports in future years if those countries do not take certain climate-control steps. Industrial-state senators want to add similar or tougher protection language in the Senate bill.

* NUCLEAR POWER: The House bill leaves this industry out in the cold. In an attempt to broaden support in the Senate, Kerry-Boxer has a nuclear provision that includes provisions for training more workers in the industry. But Senator John McCain, a big nuclear power proponent, wants much more to help the industry build new plants.

* NATURAL GAS: The Senate bill has incentives to encourage coal-fired power plants to switch to natural gas. The House bill does not.

* RENEWABLE ENERGY: The House bill requires 20 percent of U.S. electricity to be generated by renewables like wind and solar, with 5 percent coming from improved energy efficiency standards by 2020. The Senate bill is expected to add energy legislation that sets a lower 15 percent standard by 2021.

Reporting by Tom Doggett and Richard Cowan