Wedge information I could find in relation to heat is as follows: 1 wedge could be achieved by using the best technology available in all new and existing buildings. (US "Energy Star program" have achieved 1/40th of a wedge in 2003. If there was an increase of 25% efficiency in all new and existing residential and commercial buildings, it would achieve a wedge worth of emissions reduction.
Some methods used include polygeneration which uses simultaneously generate electricity and heat, increasing efficiency. Other much smaller methods of trying to limit carbon emissions as applied to developing worlds include substituting coal for sugar cane or corn. Using this technology and applying it to the