What is trigeneration?

 
Cogeneration is a technique allowing the production of heat and electricity in a single process. Heat can be distributed either as steam, at high pressures, or as hot water. A heat and power cogeneration plant works with turbines or gas engines. Natural gas is the primary energy most commonly used to operate cogeneration plants. But renewable energy sources and waste can also be used .

If the waste heat (or a part of it) is used for cold generation -by the well-known absorption and adsorption cycles- we have a trigeneration process. Generally, combined processes of electricity production through thermal processes (power plants) and waste heat exploitation in other applications are called poly-generation processes.