A COMPARATIVE STUDY OF THE PERFORMANCE AND EXHAUST  EMISSIONS OF A SPARK IGNITION ENGINE FUELLED BY NATURAL GAS AND GASOLINE

Abstract

The purpose of this study was to obtain a detailed comparison of engine performance and exhaust emissions from natural gas and gasoline fuelled spark ignition engines. Each fuel was tested at both wide-open throttle and two part-load operating conditions over a wide range of air—fuel ratios. The results show that the power output of the engine at a given throttle position was reduced by about 12 per cent when fuelled by natural gas due to displacement of air by the gas. The emission levels for natural gas were lower by from 5 to 50 per cent, depending on the pollutant, compared to gasoline. On an energy basis, both fuels exhibited nearly equal thermal efficiency, except that at very lean air—fuel ratios natural gas showed increased efficiency due to an extension of the lean limit of combustion. 

CHAPTER ONE

INTRODUCTION

Background to the Study

Exhaust emissions are emissions of gases or vapors from pressurized equipment due to leaks and other unintended or irregular releases of gases, spark ignition engine fuelled by natural gas and gasoline mostly from industrial activities. As well as the economic cost of lost commodities, exhaust emissions contribute to air pollution.

Warming of the climate system is an undisputable fact of the 21st century (Intergovernmental Panel on Climate Change, IPCC, 2001). This average increase in global temperature is unequivocal, as it is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level (IPCC, 2007). Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decades since 1850, and the period from 1983 to 2012 was likely the warmest 30- year period of the last 1400 years in the Northern Hemisphere (IPCC, 2014). The globally averaged combined land and ocean surface temperature data as calculated by a linear trend show a warming of 0.85 (0.65 to 1.06) °C over the period 1880 to 2012 (IPCC, 2014).

This observed increase in global average temperatures and the associated climate change has been attributed with a very high level of confidence and strong scientific consensus to the increase in anthropogenic greenhouse gases (GHGs) concentrations which is largely due to fossil fuel combustion and to a smaller extent due to changes in land use and deforestation (United Nations, 2013). These gases have been proven to be capable of absorbing infrared radiation as it is reflected from the earth’s surface, therefore acting like a blanket, trapping heat, and keeping the earth warm, a process known as the greenhouse effect (World Resource Institute, WRI, 2006).The Kyoto protocol identified six of these gases that affect the energy balance of the global atmosphere and needs to be urgently addressed, they include, carbon dioxide (CO₂) the most prevalent, followed by methane (CH₄), nitrous oxide (N₂O), perfluorocarbons (PFCs), hydrofluorocarbons (HFCs) and Sulphur hexafluoride (SF₆) in a decreasing order of prevalence (WRI, 2006).

Anthropogenic emissions of CO₂ constitute by far, the largest part of the emissions of greenhouse gases and of these CO₂ emissions, those that are produced from fuel combustion make up the great majority and almost all may be directly estimated from combustion activities (Simmons, 2010). Since the beginning of the Industrial revolution, the levels of GHGs in the atmosphere have been observed to have grown rapidly as a result of human activities, particularly due to the burning of fossil fuels like coal, oil, and natural gas as an energy source (WRI, 2006). IPCC (2014) reported that between 1750 and 2011, the cumulative anthropogenic CO₂ emissions to the atmosphere were 2040 ± 310 GtCO₂ which by far exceeded the natural range over the last 650,000 years and of which half of this emissions occurred in the last 40 years. They revealed that total anthropogenic GHG emissions continuously increase from 1970 to 2010 with larger absolute increases between 2000 and 2010.

In Nigeria, according to the second national communication of the country greenhouse gas inventory to the united nation framework convention on climate change in 2014 by the Federal Ministry of Environment, Nigeria contributed about 214.21 million tones of CO₂ to the atmosphere in the year 2000 and as expected, the energy sector (fuel combustion and fugitive emissions) contributed the largest proportion (53.6%) of these emissions (Federal Ministry of Environment, 2015). Within this sector, combustion of fossil for powering industrial processes was identified as a major contributor to the atmospheric CO₂.

Globally, the industrial sector is the third largest source of man-made CO₂ emissions after electricity/heat and transportation sector (International Energy Agency IEA, 2012). This sector produced 20% of fossil fuel related CO₂ emissions in 2010. The industrial sector consists of manufacturing, construction, mining, and agriculture. Manufacturing is the largest of the 4 and can be broken down into 5 main categories: paper, food, petroleum refineries, chemicals, and metal/mineral products. These categories account for the vast majority of the fossil fuel use and CO₂ emissions by this sector. Manufacturing and industrial processes all combine to produce large amounts of each type of greenhouse gas but specifically large amounts of CO₂. This is because many manufacturing facilities directly use fossil fuels to create heat and steam needed at various stages of production. For example factories in the cement industry, have to heat up limestone to 1450°C to turn it into cement, which is done by burning fossil fuels to create the required heat (IEA, 2012). In Nigeria, an industrial activity is a cause of a substantial amount of CO₂ emission. According to the latest national GHG inventory communication to the United Nation Convention on Climate Change (UNFCCC) by the Federal Ministry of Environment in 2014, energy-related activities have the dominant share of GHG emissions in Nigeria and industrial activities has been identified has a major contributor of these emissions (Federal Ministry of Environment, 2014).

Statement of the Research Problem

The review of the global greenhouse gas emission in the last three decades by IPCC (2007) as reported in their fourth assessment report showed that there is a continuous and rapid increase in atmospheric concentrations of the long-lived GHG gases especially CO₂ and that the predominant source of the increase is from the combustion of fossil fuels. It has also been established that the sustained increase in CO₂ emission is interfering and will continue to interfere with the natural climate system thereby increasing the risk of permanent environmental damage and grave socio-economic consequences.

Unfortunately, Nigeria contributes a significant amount of these gases to the atmosphere and energy-related activities have the dominant share of the emission of these gases. Within the energy sector, industrial activities especially manufacturing have been identified as a major

     Justification of the Study

Industrial sector is a major focus towards sustainable management of future GHG emissions in Nigeria. As a result, there is need for detailed, systematic and regular assessment of CO₂ emission in this sector of the economy, so that the best emission reduction opportunities can be identified. There is also need for implementation of effective emission management strategies in this sector so that the sector will develop in a clean and climate friendly manner.

However, in light of prior reviews of literatures concerning CO₂ emission and management practices observed in the manufacturing sector, there are a lot of gaps that are needed to be filled and to the best of the researcher’s knowledge, no empirical studies exist on the assessment of CO₂ emission and management in the Nigerian manufacturing sector with a view of discerning the nature and management strategies of CO₂ emission in the sector. The closest related literatures include the work of Edeoja and Edeoja (2015) who evaluated the management of

carbon emissions in the Nigerian construction industry by measuring the amount of CO₂ being emitted from constructional activities within some selected organizations, the work of Anomohanra (2011) who investigated the amount of CO₂ emission released from the consumption of petroleum product in Nigeria between 1999 and 2009, the work of Nwaichi and Uzazobona (2011) who delve into exploring the level and distribution of CO₂ and other associated potential contaminants in the Niger Delta and the work of Okhimamhe and Okelola (2013) in a study of the assessment of the levels of atmospheric carbon dioxide emission at road junctions in three major cities in the southeast of Niger State in Nigeria. The idea thereof of this study is to fill this gap in research. This study therefore seeks to contribute to the efforts directed to managing GHG emission by assessing the CO₂ emissions and management strategies observed in the Nigerian manufacturing sector by means of some selected industries at Agbara industrial estate, Ogun state.

Consequently, the information derived from the result of the study will first and foremost enable the likes of the selected manufacturing industries to identify opportunities to reduce emissions and draw up a long-term plan to manage their company’s impact on climate change. This study will also provides information that will be useful in monitoring and managing emissions of manufacturing industries in the study area and elsewhere in the country by the relevant agencies (National Environmental Standards and Regulation Enforcement Agency, NESREA, Department of Petroleum Resources, DPR, Federal and States Ministries of Environment e.t.c.). The result of the study will also be useful in the development of emission abatement policies aimed at accelerating energy efficiency improvement in the industrial sector in Nigeria. Also the information derived from the study will provide an intelligent basis for accounting for the emissions due to manufacturing industries activity in the country. The study will also reveal the provisions that are put in place and currently observed for CO₂ emission monitoring and

management in the Nigeria manufacturing industry which will allow for its scrutiny as to how adequate and effective it is. This study will therefore, ultimately contribute to the global efforts directed at managing GHG emissions.

This study then seeks to answer the following questions.

1. What are the sources of CO₂ emission of the selected industries in the study area?

1. What are the activity data of the identified emission sources?

1. What is the amount of CO₂ emitted from the identified emission sources?

1. How close is each selected industry to CO₂ management best practices?

Aim and Objectives

The aim of this study is to assess the methods of analyzing exhaust  emissionsin the Niger delta region

while the specific objectives are to:

1. identify CO₂ emission sources of the selected industries in the study area.
2. identify the activity data of the identified emission sources.

1. determine the amount of CO₂ emitted from the identified emission sources.
2. compare the management practices of each selected industry to CO₂ management best practices.

Scope of the Study

The study covered CO₂ emissions from five carefully selected industries in the study area. The study focused on direct/scope 1 emission that are from stationary combustion that is, combustion of fossil fuels in stationary equipment such as boilers, furnaces, generators, burners, turbines, heaters, incinerators, engines, flares, etc. and the emission estimation covered a period of 12 months (June 2015-May 2016).

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