THE STATUS OF AIR POLLUTION IN ZIMBABWE Barnabas Chipindu, Dept of Physics, University of Zimbabwe.

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1 THE STATUS OF AIR POLLUTION IN ZIMBABWE Barnabas Chipindu, Dept of Physics, University of Zimbabwe. INTRODUCTION Air Pollution is the introduction of substances or surplus energy as waste products of human activities into the atmosphere which directly or indirectly adversely alter or destroy the quality of the environment or cause undesirable effects on man, animals, vegetation or materials. The wastes may be gaseous or particulate emissions. In recent years Zimbabwe has experienced a rapid expansion in the national vehicle population, increased investment in the manufacturing sector and higher energy demand. These have resulted in high emission rates of major air pollutants resulting in a deterioration of the ambient air quality especially in the major cities of Harare, Bulawayo, Gweru, Mutare and Kwekwe. SOURCES AND TYPES OF POLLUTANTS There are natural as well as anthropogenic (i.e. human-induced) sources. The major human activities that generate the bulk of air pollutants are transportation, industrial processes, industrial and non-industrial fugitive processes, the energy production, waste management and agricultural activities. Transportation Transportation is a major source of air pollutants. Vehicles are probably the largest single source of pollutants such as hydrocarbons, nitrogen dioxide and carbon monoxide. Other harmful emissions include as lead, benzene, arsenic, aldehydes, sulphates, particulate matter and the secondary creation of ozone. The lead content of petrol is 4 g/l which is higher than the permitted levels in other parts of the world. The national vehicle population has significantly increased in recent years. For example, in 1994 there were vehicles and the number had increased to by July 1999 (Table 2.1). In Harare the number of registered vehicles increased from in 1994 to and by August 1999 showing that the increase in the number of vehicles is mostly in the cities. These numbers exclude government, security, diplomatic and other unregistered vehicles. The main problem associated with this rapid growth in vehicle population in the major cities is increase concentration of line and area emission sources due to road congestion at peak times. The stock of vehicles is quite old and they lack emission control equipment. High import tariffs on vehicles and the absence of emission standards means that the country will continue to be flooded with imports of low cost second-hand vehicles that do not meet strict emission standards of the counties of their origin. 1

2 Table 1: National vehicle population from June 1994 to July 1999 YEAR TOTAL JUNE DECEMBER DECEMBER DECEMBER DECEMBER DECEMBER JULY GOVT, SEC, DIP et al Est of outstanding applications 5537 allowed 5% GRAND TOTAL Source: Central vehicle registry (1999) Although vehicles are a major source of pollutants, currently the re is no data on emissions from vehicles. Research is needed to quantify the contribution of vehicles to the air pollution problem. Industrial Processes Zimbabwean industries are located in the large cities namely Harare, Bulawayo, Gweru, Mutare and Kwekwe. Typical examples of industrial emissions include sulphur dioxide (SO 2 ), nitrogen oxides (NO x ), carbon monoxide (CO), methane (CH 4 ), and volatile organic compounds (VOC) and particulate matter. Most of emissions originate from industrial processes such as metallurgical plants and smelters, chemical plants and petroleum refineries, cement production, fertilizer and synthetic rubber manufacturing, pulp and paper milling. Heavy metals (lead, mercury, cadmium, etc.) are emitted from smelters, brass works and secondary lead plants and coal combustion. A summary of the emissions of nitrogen oxides (NO x ), carbon monoxide (CO), methane (CH 4 ) from the industrial sector in 1994 is shown in Table 2. The area of concern is the location of the industries in many cities. Many industries are situated between residential areas and any pollutants emitted by the industries are dispersed and eventually deposited in the residential areas resulting in serious impacts on the health of the residents. For example the heavy industries in Harare are situated to the east of the densely populated areas of the city. The wind blows from east to west during most the year and so the pollutants are carried and eventually deposit in the main residential areas. The same situation exists in Gweru and Kwekwe where the large smelters are very close to the residential areas. Industrial and non-industrial fugitive processes Process fugitive particles are not emitted from a definable point such as a stack. Industrial fugitive dust emissions result from wind erosion of storage piles and unpaved roads. Fugitive emissions result from industry-related operations such as materials handling, 2

3 loading and transfer operations. The mining, handling, transportation and storage of coal results in fugitive emission of pollutants, mainly methane. Volatile hydrocarbons vaporize when fuels such as gasoline and natural gas escape from storage tanks or are being transferred from one tank to another. Non-industrial fugitive emissions are caused by traffic entrainment of dust from public paved and unpaved roads, agricultural operations, construction and fires. The impact of fugitive dust emission is limited because the emissions are mostly large particles that settle a short distance from the source and fugitive dust sources are mostly in rural areas. The Energy Production In Zimbabwe most of the energy is derived from burning carbon-based fuels such as coal, petroleum products and wood. Wood fuel is the main energy source for over 90% of the rural population. The productive sector accounts for about 31% of energy use, the residential sector about 52% and the transport sector about 11% (Figure 1) Power Generation Indusry Transport Agriculture Commercial & Others Mining Residential Source: Zimbabwe s Initial National Communication Under the United Nations Framework Convention on Climate Change Figure 1: Sectoral distribution of greenhouse gas emissions from commercial fuels The burning of coal in thermal power plants is the greatest contributors to the sulphur dioxide pollution. For example in 1994 the total annual sulphur dioxide (SO 2 ) emission from the thermal power stations was tonnes. The burning of fossil fuels and wood is the major source of pollutants such as carbon monoxide, oxides of nitrogen, and particulate matter. The emissions from the energy sector in 1994 is shown in Table 2. 3

4 Table 2: Summary of the national emissions of methane, oxides of nitrogen and carbon monoxide for 1994 (Gg) CH4 NOx CO 1. All Energy (Fuel Combustion + Fugitive) A: Fuel Combustion i. Power Generation 0.01 ii. Residential 0.00 iii. Transport 0.98 iv. Agriculture 0.04 v. Mining 0.01 vi. Industry 0.05 vii. Commercial & Others 0.17 viii. Biomass burned for energy B: Fugitive Fuel Emissions i. Coal Mining ii. Post coal mining : Industrial Processes A: Metallurgical & Mineral Processing B: Fertilizer Manufacture : Agriculture A: Agricultural Waste B: Enteric Fermentation C: Manure Management 7.09 D: Savanna Burning E: Forest & Grassland Conversion :Waste A: Landfills B: Wastewater 0.84 TOTAL Source: Zimbabwe s Initial National Communication Under the United Nations Framework Convention on Climate Change Waste Management The treatment of noxious wastes is a major source of air pollution. Dump burning is done to reduce waste volume and to destroy harmful organic materials but it can result in emissions of large quantities of particulate matter, of which consists of unburned garbage and offensive odours. Damp burning may also put significant amounts of harmful chemicals into the atmosphere, especially if the dump contains tyres, petroleum-based wastes and industrial chemicals. In addition, highly toxic emissions of particulate matter such as dioxins, hydrochloric acid and heavy metals can result during poorly managed incineration of domestic, hospital and industrial waste. Waste burning in residential areas also contributes to the emissions. 4

5 Agricultural activities Agriculture is a key sector of the economy of Zimbabwe and missions of pollutants occur from several sources. Burning of crop residue, is a major source of hydrocarbons and particulate matter (Table 2.2). Livestock emit methane and ammonia. Savanna burning emits large amounts of carbon monoxide (CO) and substantial amounts of nitrogen oxides (NO x ) and methane (CH 4 ). Manure management and enteric fermentation emit methane. The spraying of the fields with pesticides, use of herbicides and dusting also contribute small amounts of pollutants Mitigating Options Air pollution is derived from a variety of sources stated earlier. Nationally the major source of emissions is power generation but country s main thermal power stations are situated in rural areas. The emission from biomass burning in rural areas is too small to cause a serious problem. In urban areas the major sources of air pollution is vehicles. The problem is that the current Atmospheric Pollution Prevention Act (1971) does not require vehicles to be fitted with emission control equipment. Most of the vehicles use leaded fuel resulting in emission of the dangerous lead particulate matter in the urban areas. There is therefore an urgent need to design and implement air pollution control measures in the urban areas of the country. Industry should be encouraged to adopt cleaner production technologies. The Government could introduce tax incentives to encourage industry to adopt air pollution control measures. Because a large proportion of air pollution stems from the combustion process, air pollution control measures should be centred on the combustion process. The control should be in three phases namely: pre-combustion, measures, modifications of the combustion process, and post-combustion cleaning. Pre-combustion controls involve changes in refining, storing and transporting fuels. Combustion control measures include the use of catalytic converters in vehicles. Post-combustion controls are attempts to cleanse the exhaust system, sometimes with some recycling or at reclaiming some of the chemicals involved. CONCLUDING REMARKS Air pollution has recently received wide publicity in the print and electronic media resulting in increased public awareness in Zimbabwe. There is growing concern about the health impacts of air pollution. The Government of Zimbabwe is currently enacting laws to address environmental pollution of all types. The National Air Quality Standards are also being drafted and should be implemented soon. Research should be carried out to quantify the ambient levels of air pollution in the country as well as the impacts of air pollution on the ecosystem. The urban local authorities are enacting bylaws to control emission from vehicles. 5