; (ii) waste gas or industrial tail gas that would otherwise be flared, incinerated, or vented; (iii) a pressure drop in any gas for an industrial or commercial process; or (iv) any other form of waste heat resource as the Secretary may determine. (B) Exclusion The term qualified waste heat resource does not include a heat resource from a process the primary purpose of which is the generation of electricity using a fossil fuel. (4) Waste heat to power technology The term waste heat to power technology means a system that generates electricity through the recovery of a qualified waste heat resource. (b) PURPA definitions Section 3 of the Public Utility Regulatory Policies Act of 1978 ( 16 U.S.C. 2602 ) is amended by adding at the end the following: (22) Combined heat and power technology The term combined heat and power technology means the generation of electric energy and heat in a single, integrated system that meets the efficiency criteria in clauses (ii) and (iii) of section 48(c)(3)(A) of the Internal Revenue Code of 1986, under which heat that is conventionally rejected is recovered and used to meet thermal energy requirements. (23) Qualified waste heat resource (A) In general The term qualified waste heat resource means— (i) exhaust heat or flared gas from any industrial process; (ii) waste gas or industrial tail gas that would otherwise be flared, incinerated, or vented; (iii) a pressure drop in any gas for an industrial or commercial process