Hannon Armstrong Sustainable Infrastructure Capital has its hands in both kinds of green. The real estate investment trust (REIT) provides securitized funding for environmentally friendly infrastructure projects. It is a key provider of financing for the US government's energy efficiency projects. Hannon Armstrong focuses on energy efficiency, clean energy (solar, wind, geothermal, biomass), and other sustainable projects, including water and communications, that improve energy consumption and the use of natural resources. It works with Honeywell, Ingersoll-Rand, Johnson Controls, and Siemens. Formed in 2012 to be a REIT, the company went public in 2013, though it traces its roots to the 1980s.