Field Measurements of Black Carbon Yields from Gas Flaring

Association between spill-related exposure to fine particulate matter and peripheral motor and sensory nerve function among oil spill response and cleanup workers following the Deepwater Horizon oil spill

BACKGROUND

Burning/flaring of oil/gas during the Deepwater Horizon oil spill response and cleanup (OSRC) generated high concentrations of fine particulate matter (PM2.5). Personnel working on the water during these activities may have inhaled combustion products. Neurologic effects of PM2.5 have been reported previously but few studies have examined lasting effects following disaster exposures. The association of brief, high exposures and adverse effects on sensory and motor nerve function in the years following exposure have not been examined for OSRC workers.

OBJECTIVES

We assessed the relationship between exposure to burning/flaring-related PM2.5 and measures of sensory and motor nerve function among OSRC workers.

METHODS

PM2.5 concentrations were estimated from Gaussian plume dispersion models and linked to self-reported work histories. Quantitative measures of sensory and motor nerve function were obtained 4-6 years after the disaster during a clinical exam restricted to those living close to two clinics in Mobile, AL or New Orleans, LA (n = 3401). We obtained covariate data from a baseline enrollment survey and a home visit, both in 2011-2013. The analytic sample included 1186 participants.

RESULTS

We did not find strong evidence of associations between exposure to PM2.5 and sensory or motor nerve function, although there was a suggestion of impairment based on single leg stance among individuals with high exposure to PM2.5. Results were generally consistent whether we examined average or cumulative maximum exposures or removed individuals with the highest crude oil exposures to account for co-pollutant confounding. There was no evidence of exposure-response trends.

IMPACT STATEMENT

Remediating environmental disasters is essential for long-term human and environmental health. During the Deepwater Horizon oil spill disaster, burning and flaring of oil and gas were used to remove these pollutants from the environment, but led to potentially high fine particulate matter exposures for spill response workers working on the water. We investigate the potential adverse effects of these exposures on peripheral nerve function; understanding the potential health harm of remediation tactics is necessary to inform future clean up approaches and protect human health.

Fence-Line Spectroscopic Measurements Suggest Carry-Over of Salt-Laden Aerosols into Flare Systems Is Common

Pollutant emissions from gas flares in the upstream oil and gas (UOG) industry can be exacerbated by aerosols of coproduced liquid hydrocarbons and formation water that survive separation and enter the flare. Of noteworthy concern is the potential impact of salt-laden aerosols, since the associated chlorine may adversely affect combustion and emissions. Here, we use a novel approach to remotely detect carry-over of salt-laden aerosols into field-operational flares via flame emission spectroscopy targeting two of the most abundant species in produced water samples, sodium and potassium. Ninety-five UOG flares were examined during field campaigns in the Bakken (U.S.A. and Canada) and Amazon (Ecuador) basins. For the first time, carry-over of salt species into flares is definitively detected and further found to be concerningly common, with 74% of studied flares having detectable sodium and/or potassium signatures. Additional analysis reveals that carry-over strongly correlates with reported flared gas volume (positive) and well age (negative), but carry-over was also observed in flares linked to older wells and those flaring relatively little gas. Given the scale of global UOG flaring and the risk of salt-laden aerosols affecting emissions, these findings emphasize the need to review separation standards and re-evaluate pollutant emissions from flares experiencing carry-over.

Black Carbon Emissions and Associated Health Impacts of Gas Flaring in the United States

Gas flaring from oil and gas fields is a significant source of black carbon (BC) emissions, a component of particulate matter that damages health and warms the climate. Observations from the Visible Infrared Imaging Radiometer Suite (VIIRS) satellite instrument indicate that approximately 17.2 billion cubic meters (bcm) of gas was flared from upstream oil and gas operations in the United States in 2019. Based on an emissions factor equation that accounts for the higher heating value of the gas, that corresponded to nearly 16,000 tons of BC emitted, though estimates vary widely across published emissions factors. In this study, we used three reduced-form air quality and health effect models to estimate the health impacts from the flaring-emitted BC particulate matter in the United States. The three models—EASIUR, AP3, and InMAP—predict 26, 48, and 53 premature deaths, respectively, in 2019. The mortality range expands from 5 to 360 deaths annually if alternative emission factors are used. This study shows that reduced-form models can be useful to estimate the impacts of numerous dispersed emissions sources such as flares, and that further research is needed to better quantify BC emissions factors from flares.

Source apportionment of circum-Arctic atmospheric black carbon from isotopes and modeling

Black carbon (BC) contributes to Arctic climate warming, yet source attributions are inaccurate due to lacking observational constraints and uncertainties in emission inventories. Year-round, isotope-constrained observations reveal strong seasonal variations in BC sources with a consistent and synchronous pattern at all Arctic sites. These sources were dominated by emissions from fossil fuel combustion in the winter and by biomass burning in the summer. The annual mean source of BC to the circum-Arctic was 39 ± 10% from biomass burning. Comparison of transport-model predictions with the observations showed good agreement for BC concentrations, with larger discrepancies for (fossil/biomass burning) sources. The accuracy of simulated BC concentration, but not of origin, points to misallocations of emissions in the emission inventories. The consistency in seasonal source contributions of BC throughout the Arctic provides strong justification for targeted emission reductions to limit the impact of BC on climate warming in the Arctic and beyond.

A Techno-Economic Analysis of Methane Mitigation Potential from Reported Venting at Oil Production Sites in Alberta

The technical and economic potential for reducing methane emissions from reported venting and flaring volumes in 2015 at 9422 upstream oil production sites in Alberta, Canada was evaluated in a comprehensive site-by-site analysis. For each site, up to six different technologies for mitigation were considered, based on conserving gas into pipelines, combusting gas on site, or using gas for on-site fuel. Economic viability of mitigation was calculated using current economic parameters and gas price projections on a net present cost basis. Monte Carlo simulations suggest that a 45% reduction in methane emissions (consistent with current federal and provincial targets) from reported flaring and venting is technically and economically feasible at overall average costs ranging from $-2.98 CAD/tCO₂e (i.e., a profit) to $2.51 CAD/tCO₂e with no one site paying more than $11.02 CAD/tCO₂e. If the reported baseline emissions are augmented to reflect results of recent airborne measurements, overall economics of mitigation generally improve due to larger available gas volumes at many sites. Considering federal carbon price targets of $50 CAD/tCO₂e by 2022, there are relevant economic opportunities for mitigating methane from reported venting and flaring volumes well beyond a 45% reduction. This could partially offset the challenge in addressing the additional methane emissions from fugitive and unreported venting sources.

Building a consumer market for ethanol-methanol cooking fuel in Lagos, Nigeria

A recently completed randomized controlled study in Nigeria that transitioned pregnant women from traditional fuels to ethanol in their cook stoves demonstrated improved pregnancy outcomes in mothers and children. We subsequently conducted a pilot study of 30 households in Lagos, Nigeria, to determine the acceptability of blended ethanol/methanol as cooking fuel and willingness to pay for the Clean Cook stove. A third of the pilot participants expressed a willingness to purchase the stove for the minimum price of 42 USD or more. Fuel sales data suggest sustained, but non-exclusive, use of the CleanCook stove. These results will influence the final design and implementation of a planned 2500 stove commercial pilot that is scheduled to start in Nigeria in August 2018.

Persistent Hot Spot Detection and Characterisation Using SLSTR

Gas flaring is a disposal process widely used in the oil extraction and processing industry. It consists in the burning of unwanted gas at the tip of a stack and due to its thermal characteristic and the thermal emission it is possible to observe and to quantify it from space. Spaceborne observations allows us to collect information across regions and hence to provide a base for estimation of emissions on global scale. We have successfully adapted the Visible Infrared Imaging Radiometer Suite (VIIRS) Nightfire algorithm for the detection and characterisation of persistent hot spots, including gas flares, to the Sea and Land Surface Temperature Radiometer (SLSTR) observations on-board the Sentinel-3 satellites. A hot event at temperatures typical of a gas flare will produce a local maximum in the night-time readings of the shortwave and mid-infrared (SWIR and MIR) channels of SLSTR. The SWIR band centered at 1.61 μm is closest to the expected spectral radiance maximum and serves as the primary detection band. The hot source is characterised in terms of temperature and area by fitting the sum of two Planck curves, one for the hot source and another for the background, to the radiances from all the available SWIR, MIR and thermal infra-red channels of SLSTR. The flaring radiative power is calculated from the gas flare temperature and area. Our algorithm differs from the original VIIRS Nightfire algorithm in three key aspects: (1) It uses a granule-based contextual thresholding to detect hot pixels, being independent of the number of hot sources present and their intensity. (2) It analyses entire clusters of hot source detections instead of individual pixels. This is arguably a more comprehensive use of the available information. (3) The co-registration errors between hot source clusters in the different spectral bands are calculated and corrected. This also contributes to the SLSTR instrument validation. Cross-comparisons of the new gas flare characterisation with temporally close observations by the higher resolution German FireBIRD TET-1 small satellite and with the Nightfire product based on VIIRS on-board the Suomi-NPP satellite show general agreement for an individual flaring site in Siberia and for several flaring regions around the world. Small systematic differences to VIIRS Nightfire are nevertheless apparent. Based on the hot spot characterisation, gas flares can be identified and flared gas volumes and pollutant emissions can be calculated with previously published methods.