Thermo-Economic Valuation of Industrial Waste Heat: A Pricing Framework Based on Natural Gas Substitution Under Operational Variability

A thermo-economic valuation framework is proposed to assign an economic value to industrial waste heat streams. The methodology integrates thermodynamic heat-quality degradation, represented through logarithmic mean temperature difference (LMTD)-based thermal decay, with market-indexed valuation using natural gas substitution benchmarks. To account for operational uncertainty, a Monte Carlo simulation and a two-state Markov chain were implemented to represent stochastic dispatch conditions of natural gas engines within an industrial park configuration. The results indicate that operational variability has a limited influence on waste heat valuation compared with the dominant effect of natural gas price indexation and transport-distance-related thermal degradation. Under the representative case study conditions, supplier revenues ranged from approximately USD 60,000 to USD 320,000 per year depending on prevailing gas prices, while consumers achieved estimated energy cost reductions between 22% and 62%. An exergy-based comparison was additionally performed to contextualize the thermodynamic quality of the recovered heat stream. The proposed framework provides a practical methodology for evaluating industrial waste heat under localized energy exchange and fuel substitution applications.