The State of California has a Low Carbon Fuel Standard (LCFS) regulation which mandates that California’s transportation fuels should be at least 10 percent less carbon intensive by the year 2020. The LCFS does not mandate the adoption of any particular fuel, but it will likely drive
"Keystone" – the wedge-shaped stone piece at the apex of a masonry arch which is the final piece placed during construction and locks all the stones into position, allowing the arch to bear weight.