FACTBOX-U.S. presidential candidates on environment

(Reuters) - Environment and energy issues have gained prominence in the 2008 U.S. presidential contest, with Pennsylvania's Democratic primary voters going to the polls on Tuesday, Earth Day, as crude oil prices neared a record $120 a barrel.

Here is what the candidates are saying about energy and the environment:

* CLIMATE CHANGE

New York Sen. Hillary Clinton, Democrat - Cut U.S. greenhouse gas emissions to 80 percent below 1990 levels by 2050 through cap-and-trade system; require all publicly traded U.S. companies to file report on climate change risks with the Securities and Exchange Commission.

Illinois Sen. Barack Obama, Democrat - Cut carbon dioxide (CO2) emissions to 80 percent below 1990 levels by 2050; reduce emissions to 1990 levels by 2020; require fuel suppliers to cut carbon content by 10 percent by 2020.

Arizona Sen. John McCain, Republican - Favors cap-and-trade CO2 approach; sponsored legislation in 2007 to cut emissions by 30 percent by 2050.

* OIL USE

Clinton - Cut foreign oil imports by two-thirds from 2030 projected levels, more than 10 million barrels per day.

Obama - Reduce overall oil consumption by at least 35 percent, or 10 million barrels per day, by 2030 to offset imports from OPEC nations.

McCain - No specified targets. Has said he will unveil "a national energy strategy that will amount to a declaration of independence from the fear bred by our reliance on oil sheiks."

* VEHICLE FUEL ECONOMY

Clinton - Boost corporate average fuel economy standards, or CAFE, to 55 miles per gallon (4.28 l/100 km) by 2030, offer $20 billion in "green vehicle bonds" to help U.S. automakers meet standards, invest in plug-in hybrid technology.

Obama - Double fuel economy standards in 18 years, give automakers tax credits to retool plants and invest in advanced lightweight materials and new engines.

McCain - Has not specified CAFE targets. Voted against energy amendments in 2003 that would have boosted CAFE to 40 mpg (5.88 l/100 km) by 2015.

* BIOFUELS

Clinton - Make 60 billion gallons (273 billion l) of biofuels available for trucks and cars by 2030.