PR-312-12206-R01 FTIR Formaldehyde Measurement at Turbine NESHAP and Ambient Levels
Authors: Drayton Paul , Panek Jeffrey , McGrath Tom , McCarthy James 
Published: August 2023

Since formaldehyde is ubiquitous (e.g., naturally formed through atmospheric chemistry even if not directly emitted), there is also the potential that atmospheric levels and atmospheric chemistry are not adequately understood.� That avenue of investigation may provide important information that could be important in assessing formaldehyde health risk, source contribution, and ultimately regulatory criteria for gas-fired combustion sources.� In 2002 and 2003, the pipeline industry conducted turbine formaldehyde testing using refined FTIR methods and a dedicated measurement system, which indicated exhaust formaldehyde below 100 ppb and near the method detection limit.� Anecdotal data from that test program showed ambient levels similar to turbine exhaust in some cases.� For example, during the industry test program, a serendipitous finding observed that ambient formaldehyde concentrations varied and were independent of turbine operation.� Instead, naturally occurring emissions from an adjacent corn field appeared to spike the ambient concentration to levels higher than formaldehyde exhaust levels, depending on whether there was direct sunlight or shading from a cloud (i.e., due to �naturally occurring� formaldehyde from vegetation and/or other organics and ambient photochemistry that forms formaldehyde).� Evidence of �high� ambient formaldehyde levels (relative to turbine exhaust) would be a powerful counterargument to restrictive formaldehyde regulations.

If ambient levels are similar to (or higher than) in-stack formaldehyde for turbines, then a NESHAP requiring catalytic control of turbine formaldehyde results in a significant burden without� environmental benefit, while also negatively impacting turbine efficiency and environmental impacts associated with catalyst construction, installation, operation, cleaning, and disposal.�

Similarly, if ambient formaldehyde is significantly higher (in at least some circumstances) than currently available ambient data suggests, there could be implications for perceived formaldehyde risk and the basis, need for, and stringency of formaldehyde reductions from turbines or other combustion sources.� In a more far-reaching impact, ambient FTIR data could provide additional insights on atmospheric reactions that not only impact formaldehyde issues, but also ozone (and NOx control issues) because of the importance of formaldehyde and hydrocarbon chemistry in ambient ozone formation.

These determinations are challenged by the ability to accurately measure formaldehyde at levels less than 100 parts per billion (ppbv).� Ambient measurements rely on �batch methods� subject to error (due to the inherent instability and reactivity of formaldehyde), and those methods do not provide real-time continuous results.� Extractive Fourier Transform Infrared (FTIR) methods were developed for combustion exhaust formaldehyde measurement, but measuring the ultra-low levels from turbines, commensurate with the NESHAP standard of 90 ppb, is challenging.� This project was intended assess ambient formaldehyde levels as compared to the NESHAP standard and acquire additional ambient measurement data using FTIR testing.