In-situ measurements of greenhouse gases and NH3: mobile laboratories, agricultural emissions, and low-cost sensors

Fri, Jun. 30th 2023, 14:30-16:00

Bât. 714, P. 1129 Visio Zoom, LSCE Orme des Merisiers

The topic of this seminar will be an overview of ground-based in-situ measurements of greenhouse gases and NH₃. Novel instruments developed at Princeton University will be discussed: 1) open-path laser spectrometers for high-resolution (10 Hz) measurements, 2) low-cost optical gas sensors for sensor networks. The second half of the seminar will present results of an application of open-path laser spectrometers. The spectrometers were mounted on top of an electric vehicle from 2021-2022, and we measured facility-integrated emissions of greenhouse gases (CO₂, CH₄, N₂O) and NH₃ from 207 dairy cow farms in California, representing 2.4% of the total dairy cow population of the United States (US). The measurements show that emission inventories based on current IPCC guidelines underestimate N₂O by at least a factor of 2.5, on average. CH₄emissions are underestimated by roughly a factor of 2. NH₃emissions agree with the emission inventories when downscaled from the total emissions for the state of California. A second, parallel study was performed for 107 wastewater treatment plants, representing 6.9% of total US wastewater flow by volume. We find that both CH₄ and N₂O emissions from the wastewater sector are underestimated by a factor of 2.7. These two studies are the most comprehensive measurement campaigns of greenhouse gas and NH3 emissions from the dairy industry and wastewater sector to date. The collected data doubles the number of facilities with published emissions data. This was enabled by our state-of-the-art and lightweight laser spectrometers. Overall, in addition to finding that current inventories underestimate measured emissions, we also found that emissions had very high variability both temporally and between different facilities. This implies that continuous measurements at the facility scale are necessary for adequately monitoring and mitigating emissions. Our results can be used to better understand the variability in emissions and guide future studies.

Guest info :

Nathan Li is in the final year of a master’s and doctorate (PhD) program in Civil and Environmental Engineering at Princeton University in the United States

Contact : Juliette Lathiere