Estimation of the CO2 Level due to Gas Flaring in the Niger Delta
The level and distribution of CO2 and other associated potential contaminants at some flare sites in the Niger Delta were investigated to evaluate possible environmental characteristics. Two flowstations, Agbada 1 and 2 of Shell Petroleum Development Corporation were monitored while Eneka village with no history of gas flaring was introduced as control for comparison for a period of three months. At the Department of Petroleum Resources (DPR) recommended distance of 200 m away from flare stack, concentrations of contaminants were for CO 55 μg m-3, CO2 59.25 μg m-3, Ammonia 1 ppm, Particulates 0.8 μg m-3, sulphur dioxide 7.45 μg m-3 and nitrogen dioxide 16.3 μg m-3; Carbon monoxide 11.2 μg m-3, Carbon dioxide 69.05 μg m-3, Ammonia 1 ppm, Particulates 0.85 μg m-3, sulphur dioxide 24.2 μg m-3 and nitrogen dioxide 37.3 μg m-3; and Carbon monoxide 5.71 μg m-3, Carbon dioxide 5.54 μg m-3, Ammonia 1 ppm, Particulates 1.26 μg m-3, sulphur dioxide <0.01 μg m-3 and nitrogen dioxide <0.01 μg m-3 for Agbada 1 flowstation, Agbada 2 flowstation and Eneka village, respectively. The rainwater characteristics of the monitoring zones were also evaluated as core component of air quality and results gave acidic pH and significant bicarbonate levels showing CO2 emission activities. DPR and Federal Ministry of Environment set limits were also employed at assessment of flaring activities alongside the control study area. The findings suggest that the flaring activities at Agbada 1 and 2 flowstations significantly impacted on the environment via emissions and thus require mitigation measures to avert inherent biomagnifications with time.
Received: February 25, 2011;
Accepted: March 19, 2011;
Published: May 27, 2011
As the international community is debating issues related to climate change,
clean energy and sustainable development, how important is it to address gas
flaring reduction around the world (400 MT CO2 Eq year-1).
In the World Energy Outlook 2006, CO2 emissions (Jacob,
1999; Le Treut et al., 2007; Gholizadeh
and Darand, 2009) will increase from 26 billion tonnes a year in 2004 to
40 billion tonnes in 2030. Even including policies only under consideration,
not committed to, only lowers CO2 emissions 16% (Muis
et al., 2010; Narayanan and Natarajan, 2006)
below the Baseline level in 2030. This need not be the outcome and it is not
expected that it will be the outcome but, at present, it is the current path.
Most of the known matter that is destroying the earths ozone (Chevron,
2010) layer and contributing to global warming is derived from manmade compounds
and chemicals with high Global Warming Potential (GWP) and commonly known as
Greenhouse Gases (GHGs). Greenhouse gases are gases in an atmosphere that absorb
and emit radiation within the thermal infrared range. This process is the fundamental
cause of the greenhouse effect (OPEC, 2004; Masarie
and Tans, 1995). Gas flaring is the process of burning off unwanted hydrocarbons
during various production operations such as when oil wells are tested and prepared
for production and this produces toxic gases (Archer, 2005;
Canadell et al., 2007), such as soot, acid rain
and noise. This is done through the aid of gas flaring stack. However, in many
fields in Nigeria, routine gas flaring continues even during production life
of the field. The foremost move to stop gas flaring from the routine oil production
operations dates back to the earliest laws regulating the oil industry in Nigeria.
The petroleum Act of 1969 (regulations) section 42 came into being and with
no serious progress made towards extinguishing flare, the introduction of penalties
as disincentive for flaring gas began. These pollutants can involve a deterioration
(Beerling and Berner, 2005; Elaigwu
et al., 2007) of the quality of the air on the local plan but also
on the regional scales and international, particularly with certain hydrocarbons
which are at the origin of the photochemical oxidant formation when certain
weather conditions are joined together. A quantitative estimate of this pollution
can be realized by carrying out an inventory detailed on the level of the entire
Air pollution can be defined as the emission into the atmosphere of a waste
gas stream containing one or more pollutants such as dust, gases and fumes in
concentrations sufficient to be injurious to humans, plants or animals
health or to affect property values adversely. Of course, a pollutant is a substance
present in greater than natural concentration as a result of human activity
and which has a net detrimental effect upon its environment or upon something
of value in that environment. Particulate matter is a perpetrator of human diseases
(Pope and Dockery, 2006; USEPA, 2004).
Exposure to air pollution and automobile traffic has been shown to trigger myocardial
ischaemia (Pekkanen et al., 2002; Gold
et al., 2005).
Emissions can be divided into two main classes- particulates and gases. For
the purposes of this project, gaseous pollutants, particularly the carbon monoxide
and carbon dioxide will be of major concern.Therefore, basic objective of this
study is gives as:
||To monitor the proportion of CO2 released into the atmosphere
from flared gas as well as associated contaminants due to flaring
||To investigate compliance of CO2, CO and associated contaminants
with the Department of Petroleum Resources Environmental Guidelines and
Standards for the petroleum industry and other relevant standards
MATERIALS AND METHODS
Sampling/monitoring points: This was carried out at the following designated
||About 60 m from the flare tip along the flare gas pipe prior to the tip
||Two hundred meters away from the flare point along the direction of the
Air quality sampling: Air quality samples were taken in the windward
direction of the project locations for in-situ determination of the CO2,
NOx, SOx, NH3, CO, H2S and VOC parameters of the ambient
air characteristics using hand-held (environmental sensor meters) air quality
monitoring equipment while SPM was determined using high volume sampler. They
are digital meters which read parameters at a time-weighted average. Rain water
monitoring is a composite measurement to air quality monitoring hence the sampling.
Meteorology: Hand held SKYWACH GEOS high precision weather station was used for data collection. Heat radiation was measured with a pyranometer produced and supplied by Kipp and Zonen B. V of Rontgenweg in Holland. The sensor of the instrument was focused on the flare for five minutes to record radiation at one minute interval. The mean reading taken over the exposure time was recorded as the heat radiation. The relative smoke density was measured by using a Ringlemann smoke chart prescribed by The British Standard Institute (BS 2742: 1969). It involves visual comparison of the density of the smoke as it leaves the flare tip with the charts standard shades of grey to black on a scale of 0-4. The wind direction and speed were determined using Kestrel 4000 combined wind vane and anemometer. The anemometer reads wind speed in meters per second (m sec-1). The wind vane measured wind direction in compass directions as North, East, West and South and various combinations of directions. The ambient air temperature, pressure and relative humidity were measured at the designated point using the Kestrel 4000 equipment. The temperature was read in °F and converted to °C, pressure in mm Hg-1 and relative humidity in percent. A combination of wind direction and wind speed at each station was brought into a scale of atmospheric turbulence in a vertical plane and quantified in terms of dispersion equations. These were categorized into a range of weather series ranging from A to F, where A represents unstable atmospheric conditions (storms) and F represents stable atmospheric conditions (calm weather). The readings of wind speeds and direction variations were used to compute the turbulence.
Sample collection, identification, measurement, transportation and storage:
Air samples were collected and determined in-situ using electronic equipment
for measurement of the various parameters. These were calibrated based on the
manufacturer's recommendation before and after each batch of sampling. Back-up
batteries powering electronic equipment were always at hand to give accurate
and reliable readings. Carbondioxide (CO2), Carbon monoxide (CO),
Nitrogen oxides (NOX), Sulphur oxides (SOx), Hydrogen
sulphide (H2S) and Ozone (O3) were determined using in-situ
specific meters produced and supplied by Environmental Sensors CO of Boca
Raton in England. The meters were switched on at each sampling point for a period
of thirty minutes and the mean values read and recorded. A Varian gas chromatograph
(Varian Aerograph series 3700) fitted with a Flame Ionization Detector (FID)
was used in the hydrocarbon analysis in line with ASTM methods. The method of
determination for suspended particulate matter is essentially a modification
of the United States Environmental Protection Agencys (USEPA) Hi-volume
Gravimetric method (1990) (Nwaichi, 2010). The glass fiber
used for the SPM calculations was digested and used for heavy metal determinations
on an AAS. The noise levels at various distances were measured using a pre-calibrated
Delta Ohm sound level meter model HD 8701. Analyses of samples were performed
in triplicates and mean values reported.
Rain water samples from receptacles were subjected to in-situ measurements for pH, TDS, conductivity and temperature. A complete chain of custody was maintained and samples were also properly labeled with all relevant information duly registered in the laboratory notebook on arrival in the laboratory. Rainwater samples were equally transported in sealed coolers with ice chests and on arrival at the laboratory; they were stored in the refrigerator until required for analysis. DPR guidelines on withholding time series for each parameter were strictly adhered to.
Monitoring areas: Agbada 1 and 2 flowstations are located within Oil Mining License (OML) 17 concession areas in Rivers State of Nigeria. The areas are essentially dry land with poor drainage and as a result subjected to occasional flooding during the wet season. According to PEAH-1 District HSE case (SPDC-2005-0056915) revision 10, mean ambient temperatures range between 23 and 35°C with mean annual rainfall of 3800 mm. The facilities are accessible either by land or air.
Project description: Agbada gas lift compressor station, commissioned February 1993, was designed to receive HP/LP gas from the adjacent Agbada 2 flowstation and compress a maximum of 19.63 MMscfd (555,888 sm3 d-1) of natural gas to provide high-pressure gas for gas lift of a cluster of oil wells in Agbada field in order to enhance their production. The gas is also treated to a hydrocarbon and water dew point of 15°C at 75.9 barg before routing to the oil well to be gas-lifted. There is also a provision for future sales gas line connection to the discharge line. Wet gas from the 8 HP/LP gas headers of the adjacent Agbada 2 flowstation is routed through two suction lines to the gas compression station. LP gas is routed through the 12 suction line while the HP gas is routed through the 8 suction line. The HP gas pressure is reduced via a pressure controller and passed with the LP gas into the LP inlet scrubber where the first level of scrubbing is done. The gas is then directed to each of the two parallel compressor modules where it is compressed to the required injection pressure for gas lift of the nominated oil wells in the Agbada field. The two flowstations are chosen for their varying discharge potential.
Eneka monitoring area is sited within the Chiroda acquired area at a location in the outskirts of Port Harcourt city along Igwuruta/Eneka road. It lies on Latitude 22°E and Longitude 12°N. The area is located on plain land rain forest belt of Nigeria. There are naturally occurring vegetations around the surroundings a part of which has given way to agricultural activities. Eneka community is slightly metropolitan although communal life of the people seems intact with commercial trading and farming as their major occupation. This was chosen for a control owing to non-flaring activities within this zone.
RESULTS AND DISCUSSION
Among the three most important requirements (Air, water and food) needed to
sustain life, air is the most important. Because of this important primary function
of air, the need for access of clean air cannot be over-emphasized. Clean air
volume consists of only gas molecules approximately 78.09% of Nitrogen, 20.94%
of Oxygen, 0.95% of Argon and 0.03% of CO2. Presence of other molecules,
therefore, constitute pollution. Carbon dioxide emissions from power plants
and stationary industrial sources account for more than 60% of global greenhouse
gas emissions. However, this CO2 can be captured and stored and if
injected into depleting oil reservoirs, can increase recovery through an "Enhanced
Oil Recovery" (EOR) process. Thus, CO2 capture and storage and EOR
present opportunities for the oil industry to participate in activities that
will substantially reduce emissions and in the case of EOR, increase the recovery
from oil fields. Gas flaring, another source of greenhouse gas emissions, can
be practically eliminated in oil field operations by utilization of the gas
for re-injection, as fuel for power generation (Canadell
et al., 2007) and/or for poverty reduction programmes that are focused
on bringing modern energy supplies to the least developed areas of the world,
consistent with the principles of sustainable development. Average value of
69.25 μg m-3 CO2 level observed for Agbada 1 did
not differ significantly with 69.05 μg m-3 for Agbada 2 but
gave a marked variation with 5.54 μg m-3 obtained for the Control
point (Fig. 1) and further supports the findings of Archer
(2005). Release of CO2 has potential to adversely affect the
health and well-being of nearby organisms. Potential release of CO2
is colorless and odorless unless present at concentrations in excess of 40%
which is lethal in a matter of minutes, is especially hazardous because CO2
is toxic (Jensen, 2007) to many mammals.
||Average levels of air quality parameters monitored. Data represent
Mean±SE at p≤0.05
Carbon-dioxide causes temporary hardness in water. The associated gas could
be used to provide the basis of a successful petrochemicals industry as reported
by Azar et al. (2006). Observed level of CO,
a criteria air pollutant exceeded the set limits of 10 and 11.4 μg m-3
by the DPR and FMEnv, respectively. CO interferes with the blood's ability to
carry oxygen to the body's tissues and results in numerous adverse health effects.
SOx and NOx levels averaged 8.45, 17.3, 26.3 and 27.6 μg m-3
at Agbada 1 and 2, respectively. An extensive vegetation structure overlap was
recorded at the various fields studied and this is in agreement with the findings
of Olaleye et al. (2005).The levels observed
for hydrocarbons fell below the detection limit of the analytical instrument
at the Control point. Comparable levels of particulates recorded among all monitoring
zones were well below set limits of 90 and 250 μg m-3 for DPR
and FMEnv, respectively. Ammonia levels (Fig. 1) gave 2.5,
4 and 1 μg m-3 for Agbada 1, 2 and Eneka, respectively. Ammonia
reacts with NOx to form ammonium nitrate a major PM 2.5 component in the Western
United States. Recorded noise levels exceeded set limits for DPR and FMEnv except
for the control (Fig. 1). The Agbada 1 and 2 flowstations
location experienced stable to moderate air turbulence (F-D) (Table
1). At Agbada 1, air temperature was warm (35.80°C 200 m from flare
to 38.3°C at the flare) whereas the relative humidity varied from 58.2%
in front of generators to 70.2% in front of pumps. The ratio of the amount of
water vapor in the air at a specific temperature to the maximum amount that
the air could hold at that temperature, expressed as a percentage refers to
relative humidity. Humans are sensitive to humid air because the human body
uses evaporative cooling as the primary mechanism to regulate temperature. Under
humid conditions, the rate at which perspiration evaporates on the skin is lower
than it would be under arid conditions. Because humans perceive the rate of
heat transfer from the body rather than temperature itself (Perry
and Green, 1997), we feel warmer when the relative humidity is high than
when it is low. High relative humidity, over 50%, encourages biological agents
such as bacteria and viruses, house dust mites and molds-to grow and be released
into the air. High humidity causes condensation on windows or windowsills and
obvious mold growth or a mildew odor. Windiness varies and an average value
for a given location does not alone indicate the amount of energy a wind turbine
could produce there. To assess the climatology of wind speeds at a particular
location, a probability distribution function is often fit to the observed data.
|| Meteorological data from study sites
|Values are average results, NA: Not applicable, NE: Northeast
Observed wind speed conformed to a two-parameter Weibull distribution modeled
and they were predominantly Northeast. Higher power generates higher wind speed
as evident in observed levels at the flowstations (Table 1).
Atmospheric pressure is the total weight of the air above unit area at the point
where the pressure is measured. Thus air pressure varies with location and time
because the amount of air above the Earth's surface varies and is altitude dependent
(States and Gardner, 2000). A range of 552.2 to 753.5
mmHg atmospheric pressure was maintained throughout the study period. The heat
radiation values were slightly higher near the flare site because of the heat
emanating from the flare. The solar radiation values ranged from 0.23-0.35 kW
m-2 and were uniform in all sampling locations throughout the study
period. The discharge temperatures from electric-power plants generally range
from 5 to 11°C (EPA, 1998) above ambient temperature.
Room temperature may otherwise be indicated by general human comfort, with the
common range of 20 (68 oF) to 29°C (84°F), though people
may become acclimatized to higher or lower temperatures. There was varied increased
in air temperature between Agbada 1 and 2 (Table 1). The increased
temperature accelerates chemical-biological processes and decreases the ability
of the water to hold dissolved oxygen. Turbulence is often caused by the quick
changes of pressure and air flow around a structure. Recorded values as indicated
in Table 1 gave stable weather.
The rise in global temperature caused by the green house gases such as CO2
could lead to the addition of heat to the surface waters which subsequently
increases the receiving water temperature; the implication of this is that the
numbers and kinds of species found in aquatic environment will change. It can
even result in a heat banner in a water way; that will prevent migration
of fish to their spawning grounds. Emission rate (The weight of a pollutant
emitted per unit of time (e.g., tons year-1) between the two facilities
were statistically insignificant. Rainwater characteristics (Fig.
2) for Agbada 1 and 2 FS gave acidic ranges of 6.35 to 6.48 as shown in
Fig. 2 and is in agreement with the findings of Le
Treut et al. (2007). These values are below regulatory limits for
DPR and FMEnv (6.50-9.20). Thesemay be formed by the combination ofnitrogen
and sulfur oxides with water vapor in the atmosphere. The concentrations of
heavy metals in the rain samples for all the facilities covered were less than
0.001 mg L-1 and fell below the detection limit of the analytical
instrument used. Most rainwater properties however, were within acceptable ranges.
||Average levels of rainwater quality parameters monitored.
Data represent Mean±SE at p≤0.05
The fight against this air pollution requires a rigorous program of maintenance
of the various installations and a monitoring of ambient pollution on the various
production sites, of treatment and storage of hydrocarbons to detect all excessive
From the reported study, CO2, CO and associated air pollutants gave significant and more or less worrisome concentrations at the choice sites evident in recorded values in comparison to the Control site and reference regulatory set standard. Further 200 m distance from flare stack did not show statistically significant difference in terms of emissions and risk of death from carbon dioxide poisoning could threaten if there are no interventions. Airborne pollutants, such as gases, chemicals, smoke particles and other substances, reduce the value of and ability to enjoy affected property and cause significant health and environmental problems. Mandatory carbon emissions reporting will definitely lower the greenhouse gas emissions in Nigeria. Hazard evaluation consisting in comparing measurements of exposure (or dose) with exposures (doses) known to be safe or known to be hazardous is therefore pertinent.
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