Potential Impacts of Integrated Oil and Gas Plant on Ambient Air Quality

Abstract

The ISCST-3 model has been used to study the ground level concentrations of carbon monoxide (CO), oxides of nitrogen (NOX), particulate matter less than 10.0 microns in diameter (PM10) and sulphur dioxide (SO2). The purpose was to predict air quality effects from an integrated oil and gas project (IOGP) proposed for the Niger Delta, Nigeria. The emissions of 12 elevated point sources for criteria air pollutants were considered with eight different scenarios. Both natural gas-fired and diesel (AGO) fired equipment were considered for the identified emission sources. Five years of hourly meteorological observations were used in the prediction of the ground level concentration of the pollutants. The model outputs show a general maximum ground level concentration between 0.5 – 3.5 km, with easterly and north-easterly receptors having the greatest concentration. The pollutants emitted in the greatest concentration in their order of magnitude were CO, NOx and PM10. Maximum ground level concentration for 1, 8 and 24 – hr periods for CO were below regulatory standards (less than 10 %) for scenarios 1 – 4 when the fuel is natural gas. The 8 – hr ground level concentrations were about 1.3 folds of the World Bank Standard in scenarios 5 – 8 when the fuel sources are switched to AGO. However in these scenarios, the Nigerian environment and petroleum ministries' emission limits were not breached for all the averaging periods. Modelled NOX concentrations were significant in all the scenarios except 3 and 4. Though NOX concentrations were within the standards for all the averaging periods in scenarios 1 – 4, except the 1 – hr limit that was breached in scenarios 1 and 2, these concentrations were about 1.1 – 2.8 folds in all the averaging periods of all the standards in scenarios 5 – 8. The predicted PM10 and SO2 concentrations are all below the guideline limits. If the use of AGO is completely avoided in the entire life of the proposed IOGP, the air quality of its immediate vicinity can be protected. Furthermore, the declaration of a radius 1.75 km natural forest buffer around the plant and continuous monitoring of ground level concentrations of CO, NOX, PM10, and SO2 may further assist in guaranteeing the safety of people in terms of air quality. The study shows the need for policy formulation that will integrate comprehensive cumulative impacts assessment of air quality in the environmental laws regulating the gas development projects in Nigeria.