4.1 Air

4.1.1 Sources of Air Pollution

In order to put air pollution issues into perspective, sources are referred to as:
(i) stationary sources, that is, energy generation, industries, and public services; and,
(ii) on mobile sources, such as motor vehicles, trains, aeroplanes, among others.

4.1.1.1 Stationary Sources

The major sources of gaseous emissions in this category are energy generation and industries.

Energy Use

Energy sources are grouped as biomass (wood, animal waste, agricultural residue etc), fossil fuels (natural gas,
petroleum), electricity generation, nuclear and solar energies. The latter two are not important as far as air
pollution is concerned.

(i) Biomass Burning

Approximately 96% of the total quantity of energy consumed in Kenya is provided by the woody biomass (mostly
fuelwood). It is used for household heating, cooking, and lighting. In many cases it is used for commercial and
industrial energy requirements and charcoal production. The current wood requirements (1995) are 7,992.9m 3 as
firewood and 5,087.7m 3 used for charcoal giving a total of 13,080.6m 3 . The average consumption is 0.5 x 10 3 m 3 of wood per person per year. This figure is set to double by the year 2020, although the per capita consumption may not change. This is expected since over 75% of total consumption is for household purposes and should closely
follow the rate of increase of the rural population. Over the period 1981 to 1992 (inclusive) household consumption of fuelwood represented the largest use
category at 75% followed by commercial consumption (10.5%) then charcoal 60%.

This estimate is an underestimated since most of the supply comes from outside scheduled areas where no are records kept. In normal cases it has been discovered that a home of 5 people on average uses 39.64m 3 of fuelwood per year or 7.92m 3 per person. This would represent 20kg of
firewood per day and 2.5 kg of charcoal for cooking meals. C

Emissions Related to Biomass Burning
The importance of wood to air pollution cannot be underestimated. For the case of households, dispersion of combustion gases is not controlled. People are exposed to these gases. In general, indirect fuel boilers, as in industrial
activities and institutions, have separate stacks for the gaseous by-products of combustion such as oxides of
nitrogen.

Technology of Wood Burning

Wood fuels for ovens, grills, barbecues may release particulate matter. The amount of oxides of nitrogen
produced depends on the combustion temperature, the higher the temperature, the more oxides of nitrogen. In households, the main combustion is through open fire
wood stoves, charcoal-stoves and ovens. Besides wood, the same facilities may burn bio-waste, and in very limited
cases, biogas. These are not discussed in detail here. In many cases, boilers and furnaces are used to generate
energy.

Emissions Related to Wood Burning

The technology applied is important in determining whether the carbon content will leave as the "harmless "carbon
dioxide or as carbon monoxide, particulate and soot. In most cases boilers are used.

(ii) Electricity Generation

Electricity is often referred to as clean energy. Its generation, however, sometimes does not warrant this tag. The main modes of generating electricity in Kenya are hydro-electric
power plants, thermal, gas turbines and geothermal. Many premises also have diesel fuelled generators used only when there is a power failure or when there is a voltage drop. Generators, unless continuously used, do not generate serious pollution problems except at a local level. In this report, only the bigger generation of electricity is considered.

(iii) Petroleum Products

Fossil fuels are imported into Kenya either as crude oil or refined products. Refined petroleum products are
converted through combustion to various gases. Crude oil normally is 3% sulphur which is converted to SO 2 at the
refinery and emitted into the atmosphere. Refined products
emanating from crude oil refinery is emitted in the environs of the Kenya Oil Refinery at Mombasa.

(iv) Selecting Priority Pollutants from the Energy Sector

Power generation uses 41.5 thousand tonnes of petroleum products while industrial, commercial, and other uses
account for 407.9 thousand tonnes or ten times as power generation.

Hence, electricity generation and industries are the major stationary sources of air pollutants. It can be assumed that the oil in industries is used in the boilers described earlier.
Residue fuel oil produces nitrogen oxides, particulate, and sulphur oxides as the main pollutants, in that order. In this regard the priority pollutants are NO x , and to a lesser extent, carbon monoxide.

Some of the industries that use energy extensively are:

- inorganic chemical factories such as those of sulphuric acid and sulphonic acid;
- Iron and steel foundries and galvanising plants;
- paper mills;
- tea factories; and,
- cement production factories.

4.1.1.2 Industries

Industries are major sources of air pollutants due to their intensive use of fuels. In this section, focus is on pollutants other than those associated with energy generation mainly from industries.

(i) Chemical Industries

Chemical industries are essential for the formation of a strong and sustainable industrial base. They are also vital
in forging the necessary linkages between industry and the agricultural, transport and communication sectors. Those that are likely to have significant gaseous emissions are as
listed below:

- Metallurgical industries relted to iron and steel production which provide a wide range of materials required by the engineering industry. This industry is
important in recycling metal chemical containers which release highly volatile compounds.
- Chemical and bio-technological industries that provide fertilizers, pesticides, industrial process
chemicals and packaging materials relevant especially to agriculture and food production. The industries
release persistent organic products in gaseous form.
- Pharmaceutical industries for the production of medicinal drugs and vaccines which release complex
chemical formulations.
- Agro-industries such as power alcohol generation.

(ii) Rubber and Plastics Industry

Rubber and plastics industries are major sources of VOCs. There are about 100 manufacturers of plastic products in
the country. Almost all the raw materials are imported; however, there are also two plants that recycle plastic wastes. These generate many organo-chlorine compounds such as vinyl chloride which are carcinogenic.

The top ten chemicals released by the rubber and miscellaneous plastic industries are 1,1,1 trichloromethane; acetone; carbon disulphide; dichloromethane; methanol; methylethylketone; styrene
and xylene. They are suspect in areas where chemicals are heated to vaporisation temperature during operations or during open air burning.
(iii) Paper Mills Industry

Pulp mills processes emit gaseous wastes as part of the manufacturing process. The typical odour of Kraft pulp mill is due to the presence of sulphur in the boiling liquor which is responsible for the production of hydrogen sulphide,
methyl mercaptan, methyl disulphide, and sulphur dioxide gases. In some mills, other additional emission types may come from auxiliary operations. At the Pan Paper Mills in Webuye, for example, chlorine is released from chlorine washer tower as well as from the caustic soda/chlorine generation plant. The sources of these gases are as follows:
- blow tank vents of the batch digester plant;
- seal tank vents of brown stock washing plant;
- recovery boiler and lime mud reburning kiln stack;
- smelt dissolving tank vent stack;
- vent from hot well (foul condensate tank) in evaporation plant;
- vent from bleach plant (washers and bleach towers); and,
- leakages from caustic soda/chlorine plant.

Apart from the odorous gases, the particulate matter are emitted from the stacks of bark boiler, recovery boiler, and lime-mud reburning plant. Dust carry-over in the flue gas from the recovery boiler is collected in three electrostatic precipitations and back to the system. Similarly, the dust carry-over from the kiln is scrubbed in a venturi scrubber with mill water and fed to clarifiers for the separation of
sludge which is fed into the system. It, therefore, becomes difficult to pinpoint, in the factory, the actual stack that is
emitting fugitive gases.

The pulp and paper industry releases 87% of its total toxic emissions into the atmosphere; approximately 10% to
water, and 2% is transferred to site or disposed of on land.

Air releases can be traced to a variety of sources. Approximately 50% are methanol, a by-product of the pulp making process. The other major toxic chemicals emitted include chlorinated
compounds, sulphuric acid and the chelator methylethylketone, originating from the bleaching stage.

The priority pollutants are particulate matter, total reduced sulphur (TRS) and NMVOC.

(iv) Cement and Excavations

There are three cement plants in Kenya whose combined production capacity is 1.55 million tonnes per year while
actual production is about 1.4 million tonnes per year. Domestic consumption of cement is 1.1 million tonnes per
year leaving a surplus of 0.3 million tonnes for export. The main raw materials for cement production are limestone, pozzuolana, and gypsum and are available in adequate quantities in various parts of the country. The main
pollutants are dust particulates, grit and dust.

(v) Ceramic Tiles

There are three ceramic plants producing crockery, wall tiles, and sanitary ware. The basic raw materials such as silica sand, kaolin, Kisii soapstone, quartz, among others,
are locally available. The main pollutants are dust
particulates, grit and dust.

(vi) Glass Factories
There are three glass container manufacturing plants in the country. The country imports the larger containers. The basic raw materials for glass manufacture such as soda ash, silica sand, sodium sulphate, and fluorspar are locally available.

The Central Glass Industries in Ruaraka is the largest container glass industry in Kenya, which is located in a heavily residential area and currently a major concern to residents in as far as air pollution is concerned. The main
pollutants are sulphur oxides, NMVOC, carbon monoxide, dust and particulates.

Working with the raw materials of the above industries exposes one to respiratory diseases, digestive disorders, skin diseases, rheumatic and nervous conditions, hearing, and vision disorders.

(vii) Excavations

The building and construction industry including harvestingand transport of building materials is a major source of
particulate releases to the atmosphere.

Typical activities in this area include sand harvesting, transport and storage; stone crushing and dressing, quarry
blasting and construction. Sand harvesting presents a peculiar source of pollutants since it depends on where the sand is mined. The sand
from the coastal and Machakos areas has heavy grains which are not easily airborne .Volcanic sand used in the
central region of Kenya and mined around Mt. Longonot, however, has got finer grains which are easily air-borne
with possible negative impacts to the environment.

Particulate matter is emitted from sand and gravel operations and is made up principally of inert crystal material, for example, soil and rock particles. Dust
emissions in the form of fugitive dust occur during removal of over burden, sand and gravel from the deposit, wind-
blown dust from storage piles, from transport, during material dumping from trucks, front and leaders, and conveyors from screening. The amount of moisture affects the amount of dust emissions that occur. In Kenya the deposit is dry and the material have high silt content and usually dust emissions are significant.

This is an area where standards are difficult to formulate. Emissions can be reduced by various technological
innovations. They include: - using water sprays to keep materials wet;

- limiting drop heights of materials;
- covering lorries;
- using enclosures or holding materials at transfer and handling points; and,
- exhausting air from these points to air pollution control systems.

The priority pollutants are dust and particulate, carbon monoxide, and hydrogen sulphides.

(viii) Tanneries and Leather Industry

Leather tanning industry uses many types of chemicals which, when they react together, emit hazardous and
offensive smells such as hydrogen sulphide in addition to generating other toxic chemicals and hazardous wastes.
The Government has put in place a number of programmes aimed at reducing chemical risks, strengthening
management of hazardous wastes, and maximising environmentally sound waste re-use and recycling. Special
incentives were given in the national budget speech of 1994, to encourage tanneries to set up effective effluent disposal plants to overcome the present pollution problems. The Kenya Industrial Research and Development Institute is
carrying out research in treatment of tannery waste which would reduce air pollution associated with tanneries.

4.1.1.3 Mobile Sources

Under this category fall the following emission sources:

- marine and inland water transport (ships plying Lake Victoria) ;
- rail transport;
- Road transport; and,
- Air Transport.