ANALYSIS OF EXHAUST EMISSIONS FROM ENGINES FUELED WITH PETROL, DIESEL AND THEIR BLENDS WITH BIODIESEL PRODUCED FROM WASTE COOKING OIL

CHAPTER ONE

INTRODUCTION

1.1 Introduction

In the last century, the level of carbon dioxide in the atmosphere has increased by more than 30% as a result of human activities. The effects of climate change are becoming more pronounced and they include droughts, floods, heat waves and changes in the weather patterns. Global temperatures have increased by almost 0.8°C over the past 150 years. Without any global action, it is expected that temperatures will increase further by 1.8 – 4 °C by 2100 (IPCC, 1996). It is anticipated that this rise will result in sea level increment of 15 to 95 centimeters. While the transportation sector is crucial to a nation’s economy and personal mobility, it is also a significant source of GHGs. Nearly 50% of global CO, HCs, and NOx emissions from fossil fuel combustion come from internal combustion engines (ICE). The contribution of the transport sector to total CO₂ emissions in developed nations is forecast to increase from 20% in 1997 to 30% in 2020 (Ken et al., 2004). The transport sector accounts for almost all the oil demand growth around the world (Ming et al., 2009). The world transportation oil demand has continuously risen with increasing GDP. World forecasts show that transport oil demand in developing nations will increase three times more than in developed nations. Increasing income will cause a tremendous increase in car ownership in developing countries, where the vehicle stock is expected to triple (IEA, 2006). Developing countries account for about 10% of the global automobile population and a little over 20% of the global transport energy consumption. In comparison, the United States alone consumes about 35% of the World’s transport energy (Shiva, 2006).

Road vehicles are among the main consumers of world energy and they dominate global oil utilization, consuming up to 80% of transport energy. The transport sector’s share of oil consumption has been increasing steadily at around 0.6% per year. Current policies are not sufficient to control road vehicle energy use. Even if governments implement all the measures that are currently being considered, projections by the International Energy Agency (IEA) show that road vehicle energy use would still rise between now and 2030 at 1.4% per annum respectively(IEA, 2006). In developing nations, it is envisaged that with rising income and the rapidly rising mobility that accompanies it, the increase in automobile emissions will be even greater than the developed nations. Steady growth in vehicular populations has put environmental stress on urban centers in various forms particularly causing poor air quality. There is growing evidence that links vehicle pollutants to human ill health. Motor vehicles are major emission sources for several air pollutants, including nitrogen oxides (NOx) and carbon monoxide (CO) (Suresh et al., 2009). These pollutants have significant adverse effects on human beings and the environment. Vehicle emissions cause both short and long term problems associated with health effects. For example, HCs and NOx are the precursors of ozone gas, which has effects ranging from short term consequences such as chest pain, decreased lung function, and increased susceptibility to respiratory infection, to possible long-term consequences, such as premature lung aging and chronic respiratory illnesses (WHO, 2005).

The most affected group is the urban inhabitants especially the traffic policemen who are exposed to the fumes for a long period of time. Children attending a school located near a busy way in Utrecht, Netherlands were compared with children attending a school located in the middle of a green area in a suburban area. It was discovered that respiratory diseases were more pronounced in the urban than suburban children (Suresh et al., 2009). The severity of the problem increases when traffic flow is interrupted and the delays and start-stops occur frequently. These phenomena are regularly observed at traffic intersections, junctions and at signalized roadways. Emission rates depend on the characteristics of traffic, vehicles and type of road intersections. The age of a vehicle and maintenance levels also contribute to the emissions of all classes of vehicles. Further, the fuel quality has a direct effect on the vehicular exhaust emissions (Perry and Gee, 1995).

In most developing countries of the world vehicular growth has not been checked properly by environmental regulating authorities leading to increased levels of pollution (Han et al, 2006). Traffic emissions contribute about 50-80% of NO₂ and CO concentration in developing countries (Fu, 2001; Goyal, 2006). This situation is alarming and is predicated on the poor economic disposition of developing countries. Poor vehicle maintenance culture and importation of old vehicles, which culminates in an automobile fleet dominated by a class of vehicles known as ‘’super emitters’’ with high emission of harmful pollutants, has raised this figure of emission concentration(Ibrahim, 2009). The increase in this traffic-related pollution is not based on the aforementioned factor only, but also on low quality fuel, poor traffic regulation and lack of air quality implementation force. These are clear indices to high levels of traffic-related pollution in developing countries.

In Nigeria as well as in other developing countries, which are not yet fully industrialized, majority of the air pollution problems result from automobile exhaust. In the major towns of some developing countries, because of tropical nature of the climatic conditions, many activities are performed outdoors. People stay along the busy roads every day either to do their work or to sell their wares. Therefore, the ill effects on health due to air pollution resulting from automobile exhaust emission must be very serious indeed (Ayodeleand Bayero, 2009).

Enugu State in the absence of a reliable public transport system, has had air pollution worsened because of an increased number of old second-hand cars, taximotorbikes (popularly called okada), substandard petrol and other products imported into the country. There is presently no available data on emission and impact of air pollution in Enugu state, but it is anticipated that air pollution will become a major health problem if adequate mitigation measures are not taken (Nwadiogbu et al., 2013). In Nigeria much attention is given to general industrial pollution and pollution in oil industries, with little reference to damage or pollution caused by mobile transportation sources of air pollution (Faboya, 1997; Iyoha, 2002; Magbagbeola, 2001). Pollution from mobile transportation is on the rise due to increase in per capital vehicle ownership, thus resulting in high congestion on Nigeria city roads and increase in the concentration of pollutants in the air, consequently, increasing health risks for human population. In addition compared with the large volume and varieties of studies carried out in the developed world, exposure studies carried in Nigeria are relatively scarce. So as a vital step in focusing attention on these problems, it is necessary to know the types of air pollutants present along with the level of each pollutant.

1.2       Transport and Climate change

According to the IPCC guidelines, the direct greenhouse gases are carbon dioxide, methane, hydro-fluorocarbons, per-fluoro-carbons (PFCs), sulphurhexafluoride (SF₆) and nitrous oxides. The indirect greenhouse gases include nitrogen oxides (NO_X), carbon monoxides (CO), non-methane volatile organic compound (NMVOC), hydro fluorocarbons (HFCs) and sulphurdioxide (SO₂). Some GHGs such as CO₂ occur naturally and are emitted to the atmosphere through natural processes and human activities. Other GHGs (e.g., fluorinated gases) are created by human activities. Current vehicle fleets emit significant amounts of carbon monoxide (CO), nitrogen oxides (NOx), total organic gases (TOGs) or reactive organic gases (ROGs) more commonly known as volatile organic compounds, VOCs), particulate matter (PM) and carbon dioxide (CO₂). The VOC and NOx are precursors to secondary ozone formation and aerosols and more importantly, particulate matter and ozone are the two critical pollutants of greatest concern causing human health deterioration and leading to a social cost (Guihaet al., 2009). The direct greenhouse gases have different effectiveness in radiative forcing. This can be determined by comparing their Global Warming Potential (GWP). GWP is a means of providing a simple measure of the relative radiative effects of the emissions of the various gases. The index is defined as the cumulative radiative forcing between the present and a future time horizon expressed relative to that of CO₂. It is necessary to define a time horizon because the gases have different lifetimes in the atmosphere. Methane and Nitrous oxide have a greater GWP than carbon dioxide as shown Table 1.1.

 Table 1.1: Global Warming Potential defined on a 100-year horizon.

Source: IPCC, 1996

The main sectors contributing to emission levels include energy, Industrial processes, solvents, agriculture, land use change and forestry and waste. The power generation sector currently accounts for 24% of the CO₂ emission. Many forms of transportation create GHG (including CO₂) emissions, both direct and indirect. Transport is one of the major contributors to air pollution problems at the local, region and global levels contributing 14% of the global carbon dioxide emissions. It relies on fossil fuel burning, primarily oil, and is now the fastest-growing source of greenhouse gas emissions, particularly in developing countries. Transportation accounts for 27% of total global energy consumption. Greenhouse-gas emissions (CO₂ and CFCs) from motor vehicles in developing countries contribute less than 3% to the global greenhouse effect, compared to a 9 to 12°% contribution from motor vehicles inOrganisation for Economic Co-operation and Development(OECD) countries and Eastern Europe (Asif, 1993).

There is growing number of motorcycles being used for fast transportation in cities and towns across Nigeria. This has contributed to a large percentage of the automobiles in Nsukka town. An analysis of motor cycle emissions is of great importance given their growing numbers. Motor cycles are preferred to mini buses for public transport because of their mobility and convenience. According to the Taiwan Environmental Protection Administration (TEPA), motorcycles contribute 38% of the total CO, 64% of HC and 3% of NO emitted from automobiles (Lin et al., 2008). This implies that motor cycles have a potential of producing high amounts of emissions if not checked.

Figure 1.1: Global Share of CO₂ emission by Sector.
Source: Stern, 2006

According to the IPCC (1996), the world’s temperature is expected to increase over the next hundred years by up to 5.8°C. This is much faster than anything experienced so far in human history. The goal of climate change policy should be to keep the global mean temperature rise to less than 2°C above pre-industrial levels. At 2°C and above, damage to ecosystems and disruption to the climate system increases dramatically. This means that global emissions will have to peak and start to decline by the end of the next decade at the latest. Given that personal mobility is a pre-requisite of economic and modern life, the question arises on how to meet the mobility needs of a contemporary lifestyle and yet reduce direct and indirect emissions of GHGs. This is shown in Figure 1.2. Figure 1.2: Projected growth in CO₂ emission levels in the world
Source:Stern,2006.     
From Figure1.2, assuming a business as usual scenario, the largest source of transport emissions is the OECD North America producing 37% of the total emissions. This is confirmed by the world highest car ownership of 0.6 vehicles per person in North America (Stern, 2006).Africa has the lowest projected CO₂ emission growths followed closely by Asia. This is as a result of the low industrialization levels in these regions. However, the need to develop will see a twist in the future as the developing countries push for more industrialization to match the OECD.

1.3       Impact of different emission types

Although automobiles contribute to the degradation of air quality, there is no simple means of measuring the precise impact. The impact will vary from city to city, depending upon such factors as vehicle density, the split between petrol and diesel vehicles, the type of vehicles on the road and their average age, the traffic management systems in place and atmospheric conditions. The pollutants from motor vehicles have significant adverse effects on human beings and the environment.

1.3.1    Carbon monoxide