For decades, combined heat and power (CHP) has been promoted and embraced as a cost-effective technology for meeting on-site thermal and electric needs more efficiently and with fewer emissions than separate procurement of those resources. But climate change concerns are leading to a reevaluation of CHP’s benefits. Significantly, natural gas, the most common fuel for CHP and until recently regarded as an environmentally preferable “bridge fuel” in the energy transition to renewables, is increasingly being reexamined amid calls for deep decarbonization and emerging clean energy policies that limit the use of natural gas. Given this trend, electrification has gained traction as a net zero carbon energy strategy. With natural gas being a preferred fuel for CHP, policymakers and others are beginning to question CHP’s role in a cleaner, more electrified future. However, CHP fueled by low carbon fuels such as renewable natural gas and hydrogen may be a more viable path to decarbonizing industrial processes that are difficult to electrify due to technology limitations or cost, and for applications where energy resilience is a critical requirement. This paper seeks to add clarity to a complex issue. It offers a framework for assessing industrial applications where natural gas CHP will provide significant GHG reductions in the near term and provide a more economic and practical path to deep decarbonization in the long term through a transition to low carbon fuels.

Emissions from the potential installation of distributed energy resources (DER) in the place of current utility-scale power generators have been introduced into an emissions inventory of the northeastern United States. A methodology for predicting future market penetration of DER that considers economics and emission factors was used to estimate the most likely implementation of DER. The methodology results in spatially and temporally resolved emission profiles of criteria pollutants that are subsequently introduced into a detailed atmospheric chemistry and transport model of the region. The DER technology determined by the methodology includes 62% reciprocating engines, 34% gas turbines, and 4% fuel cells and other emerging technologies. The introduction of DER leads to retirement of 2625 MW of existing power plants for which emissions are removed from the inventory. The air quality model predicts maximum differences in air pollutant concentrations that are located downwind from the central power plants that were removed from the domain. Maximum decreases in hourly peak ozone concentrations due to DER use are 10 ppb and are located over the state of New Jersey. Maximum decreases in 24-hr average fine particulate matter (PM2.5) concentrations reach 3 microg/m3 and are located off the coast of New Jersey and New York. The main contribution to decreased PM2.5 is the reduction of sulfate levels due to significant reductions in direct emissions of sulfur oxides (SO(x)) from the DER compared with the central power plants removed. The scenario presented here represents an accelerated DER penetration case with aggressive emission reductions due to removal of highly emitting power plants. Such scenario provides an upper bound for air quality benefits of DER implementation scenarios.