Green building materials manufacturer Serious Materials will retrofit all 6,514 windows in the Empire State Building to quadruple their energy efficiency -- but without discarding the 26,000 panes of existing glass.

Tech companies, in California and across the world, are among the highest-ranking firms in a new sustainability assessment. But while some of these companies are strong on initiatives, the industry lacks systematic, holistic approaches to greening.

It is becoming increasingly common for companies to measure and report the water they consume within their four walls. Yet they rarely track all the water used to make the electricity powering their operations. It's called the forgotten water footprint, and it's about to get a lot more attention.

The kickoff to IBM's third-annual Pulse expo showcased how the company has its eyes on making the world's cities connected, automated and efficient, through hardware and software innovations and new partnerships with Johnson Controls and Ricoh.

Bacardi Ltd., the world's largest privately held spirits company, cut greenhouse gas emissions 9.2 percent in the last fiscal year by increasing efficiencies and the use of renewable energy, while KPMG LLP shrank its carbon footprint in the U.S. by reducing air travel, use of electricity and waste.