Eyes on Nigeria: Gas Flaring
Ongoing conflict in the Niger Delta region of Nigeria has overlapping ethnic, economic and environmental causes, including environmental concerns arising from the activities of the oil industry. The ongoing practice of gas flaring, in which the natural gas associated with petroleum extraction is burned off in the atmosphere rather than being removed by alternative means such as subterranean re-injection or confinement to storage tanks for eventual sale, is particularly controversial. Gas flaring is often performed for economic reasons, as alternative disposal methods are more costly than the immediate elimination of the gas, which is a less profitable and potentially hazardous byproduct of the industry. Gas flaring introduces toxic pollutants such as sulfur dioxide into the atmosphere, which can lead to environmental problems such as acid rain, as well as the generation of greenhouse gases which contribute to global climate change (Obanijesu et al. 20091, Osuji and Avwiri 20052). When the burning of natural gas occurs in close proximity to wildlife or inhabited areas, the effects raise potential environmental and health concerns. In order to better understand the impact of gas flaring on the human population, which often lives in close proximity to these activities, the AAAS Geospatial Technologies and Human Rights Project, in partnership with AI-USA, undertook a survey of the Niger Delta region using space borne infrared hotspot detections from 2000 to 2010, supplemented by high-resolution visible-band satellite imagery.
II. Methods and Technologies
Thermal infrared wavelengths, which can be detected using orbiting satellites, possess unique properties which are ideally suited for the detection of gas flaring. At these wavelengths, the intense blackbody radiation of man-made heat sources throughout the Niger Delta contrasts starkly with that emitted by comparatively cooler surfaces of the surrounding land. Even phenomena such as forest fires and large-scale agricultural burning are spectrally distinct from the powerful infrared glow of a methane gas flare, the fireballs of which can reach tens of meters in diameter. The Moderate Resolution Imaging Spectroradiometer (MODIS), a twinned pair of instruments on NASA’s Terra and Aqua Earth-Observing Satellites, provides near real-time global coverage in the visible and infrared wavelengths at spatial resolutions ranging from 250 meters to 1 kilometer per pixel. MODIS has a mature data use community3, including volcanologists from the University of Hawaii who have developed MODVOLC, a hotspot detection algorithm which monitors incoming MODIS data for all pixels that exhibit the distinct infrared signature of abnormally high temperatures. These hotspots, which are reported regardless of volcanic origin, are stored in a publically available database which is updated daily. The archives of this database now span over a decade- a feature that is ideal for monitoring the long-term effects of gas flaring. AAAS obtained all MODVOLC detections from February 24, 2000 to December 31, 2010 for the study area. Over long time periods, the continuous presence of abnormally high temperatures in an area will result in a cluster of individual detections which strongly suggests the presence of gas flaring.
While MODIS thermal emission measurements alone are well suited for establishing the temperature of a flare’s fireball itself, they cannot directly detect parameters such as air temperature. When taken in conjunction with ground-based data, however, orbital observations can yield far more meaningful results. In 2005, researchers from the University of Benin collected air temperature data around a gas flare near the town of Ovade (Odjugo and Osemwenkhae 20094). The measurements occurred at multiple distances from the fireball, and enabled the authors to determine the magnitude of the excess air temperature resulting from the flare as a function of distance. By observing the relationship between the Ovade flare’s power output as measured by MODIS and the data recorded by Odjugo and Osemwenkhae, it was possible to scale those air temperature measurements to other flares throughout the Niger Delta.
Once the locations of the flares and their physical properties were estimated using MODIS data, the possible impacts on nearby communities were examined. High-resolution visible-band imagery was used, allowing for the precise characterization of the flares’ sizes and locations, though the extent of the study area made it impractical for large-scale mapping of every flare at high-resolution. In addition, high-resolution imagery permitted a detailed examination of the numerous small towns and villages that dot the region, many of which are often not found on existing maps of the region.
Of the 57,788 MODVOLC daily hotspot detections in the study area, 14,059 were identified as probable land-based gas flares based on their spectral properties and occurrence in discrete clusters. Inspection of these clusters using high-resolution satellite imagery subsequently confirmed the presence of gas flares at 74 sites on land (an additional 19,326 detections appear to be related to offshore gas flares at 22 sites, and 3867 to natural fires on land; the remaining detections could not be immediately attributed to a specific natural or artificial source). A summary of these detections is presented in Figure 1, below:
Figure 4.1: Hotspot Detections in the Niger Delta, 2000-2010
Analysis revealed that of the 74 gas flares active in the delta during the study period, 48 were located such that their outer thermal radii (temperature +4.3ºC / 7.7ºF) encompassed areas of human habitation or agriculture (see Figure 2). Within that outer isotherm (radius of constant temperature), the proximity of the flare to local communities varies considerably, ranging from the very edge of the 2 kilometer search area to under 100 meters. While the number of active flares has decreased since the government moratorium on gas flaring went into effect in 2008, 41 flares were active in 2010. These flares are represented in Figure 4.2 by solid black circles. A chart of active flares by year is shown in Figure 4.3. Some examples of the placement of gas flares with respect to local communities are shown in Figures 4.4 to 4.7. In these examples alone, dozens of individual homes are exposed year-round to temperatures elevated by twelve degrees Celsius (22 degrees Fahrenheit) above the already-sweltering ambient tropical heat.
Figure 4.2: Flares in Proximity to Human Habitation
Figure 4.3: Active Gas Flares by Year
Figure 4.4: Gas Flares Shown Using High-Resolution Imagery
Two gas flares in close proximity to a village. Estimated air temperatures are at least 11.6 degrees Celsius above ambient. Lat: 5.655 N, Long: 5.148 E.
Figure 4.5: Human Habitation in Proximity to a Gas Flare
Two gas flares in close proximity to a village. Estimated air temperatures are approximately ten degrees Celsius above ambient. While not flaring at the moment this picture was taken, this site was detected to have been active every year from 2000 to 2010. Lat: 5.654 N, Long: 5.148 E.
Figure 4.6: Two Gas Flares Flanking Human Habitation
Two gas flares located on opposite sides of a village. Estimated air temperatures are approximately ten degrees Celsius above ambient. Additionally, many agricultural fields are located near the flares. Lat: 5.441 N, Long: 5.881 E.
Figure 4.7: Further Evidence of the Proximity of the Population to Gas Flaring
Multiple gas flares located near a village. Estimated air temperatures are approximately nine to twelve degrees Celsius above ambient. As before, many agricultural fields are located in proximity to the flares. Lat: 5.459 N, Long: 6.694 E.
Despite a government moratorium on gas flaring that went into effect in 2008, the analysis detailed in this report indicates that the practice remains widespread throughout the Niger Delta, including in areas in close proximity to the local population. Thousands of individuals currently live within areas where estimated ambient temperatures are significantly elevated above the already considerable tropical heat. In addition to the health, safety, and quality of life issues arising from this situation, peer-reviewed research shows that these higher temperatures are associated with reduced crop yields, potentially in conjunction with other environmental factors such as acidified rain from SO2 pollution.5
1. E. Obanijesu, F. Adebiyi, J. Sonibare, and O. Okelana. 2009. Air-borne SO2 Pollution Monitoring in the Upstream Petroleum Operation Areas of the Niger Delta, Nigeria. Energy Sources, Part A (31):223-231. Available here.
2. L. Osuji and G. Avwiri. 2005. Flared Gases and Other Pollutants Associated with Air Quality in Industrial Areas of Nigeria: An Overview. Chemistry & Biodiversity (2):1277-1289. Available here.
3. Applications of the MODIS instrument are diverse, ranging from wide-area vegetation monitoring to detecting violence during the ongoing conflict in Darfur.
4. P. Odjugo, and E. Osemwenkhae, 2009. Natural gas flaring affects microclimate and reduces maize (Zea mays) yield. International Journal of Agricultural Biology (11): 408-412. Available here.
A PDF of Eyes on Nigeria: Technical Report is available here.