MICROBIAL METHANE OXIDATION PROCESSES AND TECHNOLOGIES FOR MITIGATION OF LANDFILL GAS EMISSIONS
1.1 Background to the Study
Global warming is a phenomenon that has been of great concern to world leaders, climate scientists, biologists and conservationists for a long time because of its devastating effect on the global climate system. The emission of greenhouses gases (GHGs) from human activities has been identified as the main cause of this warming of the earth. Emission of GHGs from the operation of buildings and their effects on the climate is one of the issues that have dominated discussions on global climate change for some time now (Sun et al,
2014). The most recent of these discussions include the climate change conferences held at
Warsaw in 2013, Doha in 2012, Durban in 2011, Cancun in 2010 and Copenhagen in 2009 (Shah, 2013). Ramaswami et al (2010) observed that the main source of GHG emissions from buildings is energy consumption and they also identified energy use reduction in buildings especially residential buildings as one of the strategies for large scale GHG mitigation. Even though it is established that majority of the emissions in the past and currently originated from the industrialized nations of the world such as America, Canada, Russia and so on, it is projected that in the very near future the level of emissions from buildings in rapidly industrializing countries like China will surpass emission levels from buildings in developed countries (UNEP, 2009a).
Now that the population of cities worldwide is more than half of the global population, the inhabitants of cities must be made aware of the key role they have to play in the mitigation of GHG emissions (Satterthwaite, 2008 in Kennedy et al, 2010). In an attempt to brace up to this challenge of addressing climate change many cities such as Frankfurt, Paris, New York, Toronto, Chicago, Sydney, Colombo, London, Manchester, Cape Town and so on have established inventories of GHG emissions. The International Council for Local Environmental Initiatives, ICLEI, (2008) in Kennedy et al, (2010) posited that such inventories of urban GHG emissions serves as a benchmark for assessing action on climate change.
Levine et al (2007) asserted that in 2004, emissions due to on site combustion of different types of fuel to meet the energy needs of the building sector amount to 3 GtCO2, 0.4 GtCO2-eq CH4, 0.1 GtCO2-eq N2O and 1.5 GtCO2-eq halocarbons (including
chlorofluorocarbons and hydro-chlorofluorocarbons). Levine et al pointed out that since GHG mitigation in the building sector involves a lot of measures aimed at energy efficiency, it is useful to compare the mitigation potential with carbon dioxide emissions, including those through the use of electricity.
Moreover the International Energy Agency (IEA) has observed that the emission of GHGs from buildings is closely related with energy use and that the rural communities of many developing countries rely mostly on burning fuel wood and other forms of biomass such as sawdust, crop residues and animal dung to meet their energy needs. The IEA estimates that as many as 2.4 billion people worldwide use biomass for their domestic energy needs, and that there is a higher probability of this figure increasing in the future (IEA, 2002 in UNEP, 2009a). Many households in many countries use inefficient technologies to burn the fuel and this result in emission of large quantities of GHGs. Nevertheless it has been observed that the emission of GHGs in Nigeria is on the average low because of the low per capita energy and other resources consumption in the country but these are expected to rise in the future as a result of the high population growth rate, and corresponding increase in per capita energy and other resource consumption (Ministry of Environment of the Federal
Republic of Nigeria 2003; Chah and Igbokwe, 2012).
According to Environmental Protection Agency, EPA, (2013a) a greenhouse gas inventory is an accounting of GHGs emitted to or removed from the atmosphere over a period of time. Policy makers use inventories to establish a baseline or a reference for tracking emission trends, developing mitigation strategies and policies, and evaluating the effectiveness of the mitigation strategies. The development of an emissions inventory is usually the first step taken by entities that want to reduce their emission of GHGs. EPA (2013a) also stated that a complete and transparent national GHG inventory is an essential tool for understanding emissions and trends, projecting future emissions and identifying sectors for cost-effective emission reduction opportunities. However ICLEI (2007) has pointed out that all inventories are necessarily estimates based on the best available data and procedures and as such are subject to change with time especially when faults are detected in the data used for preparing them.
1.2 Statement of the Research Problem
The Intergovernmental Panel on Climate Change (IPCC) has proposed a reduction in global CO2 emissions by half by the year 2050 from the estimated present level of 380 parts per million (ppm). This advice originated from the need to avoid the worst impacts from climate change due to human interference. Hassol (2011) affirmed that absolution from the most severe consequences of climate change will require the total global average warming to be kept within 2oC relative to pre-industrial era levels. Tufts Climate Initiative (2002) and Gupta and Garrigan (2013) established that for communities to be capable of reducing their GHG emissions and also be able to assess the effectiveness of their GHG mitigation measures, they first need to know which activities are the highest emitters and how much they are emitting. When this is done opportunities for emission reduction can be identified and even the extent of possible emission reduction can be estimated. ICLEI (2007) is of the view that since each local community has unique characteristics (such as population, housing types, transportation networks, industries, electricity fuel mix) that can substantially differentiate its GHG inventory from those of other cities or counties, it is recommended that energy audit for emission assessment be conducted for each community to identify these peculiarities.
Levine et al (2007) reported a great literature and data dearth about GHG emissions and mitigation options in developing countries and Nigeria is no exception. They observed that although the situation is somewhat better in the industrialized nations, the same cannot be said of a larger percentage of countries because the relevant data is poorly collected and reported. Furthermore literatures on GHG mitigation in agricultural (Achike et al, 2012; Chah and Igbokwe, 2012) and manufacturing (Ibikunle, 2006; Federal Ministry of Environment and United Nations Development Programme, 2009) sub-sectors abound but studies that are specifically targeted at residential GHG mitigation in Nigeria are scanty.
This study is intended to bridge some of that gap.
GHG mitigation frameworks exist for most cities and regions of the industrialized nations but these are not suitable for use in the Nigerian context because of the wide differences in energy usage and behavioural patterns. Even adoption and adaption cannot be done without a detailed energy study of the community and development of an inventory of GHG emissions.
1.3 Justification for the Study
The building sector worldwide consumes up to 40% of all energy and is also accountable for about 30% of global annual GHG emissions (UNEP SBCI, 2009). It has been observed that with the high increase in the rate of new construction in transiting economies, and coupled with the inefficiencies of existing building stock worldwide, if no deliberate action is taken, GHG emissions from buildings have the potential to more than double in the next two decades. In the vast majority of countries the residential sector is responsible for the greatest consumption of total primary energy. Takaoka (2011) observed that there is the possibility of reducing energy consumption in both new and existing buildings by an estimated 30-50% by 2020.
UNEP (2009a) avowed that those in authority must be proactive in dealing with the issue of emission reduction from the building sector if targets for GHG emissions reduction to close to pre-industrial era levels of about 300ppm are to be met. Mitigation of GHG emissions from buildings must be pursued with urgency because the building sector offers the greatest prospect for delivering an enduring, significant and cost-effective reduction in GHG emissions (UNEP, 2009a).
UNEP (2009b) observed that reducing emissions from buildings will bring multiple benefits to both the economy and to the society in general. The construction, renovation, and maintenance of buildings contribute 10 to 40 percent of countries’ Gross Domestic Product (GDP), and represent on a global average 10 percent of country-level employment. UNEP (2009a) also posited that if GHG mitigation strategies for buildings are carefully planned, they can stimulate the growth of new businesses, jobs, and contribute to social development goals such as better housing and access to clean energy and water.
It is important that local inventories establish a clear emissions baseline that can be used to monitor future progress since they are not prepared as frequently as other types of inventories (EPA, 2013b). Also, because of the direct correlation between GHG emissions and energy consumption, attempts at cutting down on the level of emissions will also be promoting energy efficiency. This is of great importance especially in countries like Nigeria where the supply of electricity to the various sectors is insufficient. Furthermore the assessment of options to reduce future GHG emissions has been considered as an important contribution to the sustainable development of Nigeria by the Ministry of Environment of the Federal Republic of Nigeria (2003).
A justification of the choice of Kaduna for this study can be found in the assertion by Sun et al (2014) that cities which occupy less than 1% of the earth surface accommodates over 50% of the global population and emit about 80% of GHGs globally. Kaduna is a typical city in Nigeria. Also, since the effects of the emissions on the climate are not localized to the area from which they originate, it becomes very vital for all communities and entities to be able to determine how much they are emitting so that appropriate mitigation measures can be put in place. This is why it is important for even low emitters like Nigeria to put in place a framework for mitigation of GHGs. These highlighted concerns necessitate the development of an inventory for each community and justify a study of this nature.
1.4 Aim and Objectives
The study aims to develop a framework for residential carbon dioxide mitigation in Kaduna metropolis with a view to defining a road map towards the reduction of emission of carbon dioxide from domestic energy consumption activities.
The objectives of the study are to:
- Synthesize information about residential buildings in Kaduna metropolis.
- Generate data on energy consumption by the residential buildings.
- Estimate the direct and indirect emissions of CO2 for a base year and some forecast years.
- Investigate the behaviours of households as it relates to CO2
- Measure the indoor and outdoor concentrations of CO2 in and around selected households.
- Develop a framework for mitigation of CO2 emissions from residential buildings in Kaduna metropolis.
1.5 Research Questions and Hypotheses
1.5.1 Research Questions
The following questions were asked by the study hoping that the answers provided will contribute in directing towards mitigation of GHGs:
- What are the main sources of energy for domestic use in Kaduna metropolis? ii. What is the extent of residential energy consumption in Kaduna metropolis? iii. What are the baseline and forecast emissions of carbon dioxide (CO2)?
- Are there any substantial differences between the different scenarios of emissions?
- Are there discernible differences in the average global atmospheric
concentration of CO2 and that of the surveyed area?
- How can CO2 emissions from residential buildings be effectively reduced?
1.5.2 Research Hypotheses
The following hypotheses were developed to guide further investigations into the anthropogenic GHG emission problem:
- There is no difference in CO2 emissions from the different scenarios. This is called the Null hypotheses, H0.
H0: μ1 = μ2 = μ3… = μk
- The CO2 emissions from the different scenarios are different. This is the alternative hypothesis, H
HA: The means of emissions from the different scenarios are not the same.
1.6 Scope and Limitations
Many anthropogenic activities emit greenhouse gases. Examples of these activities are manufacturing, transportation (road, air, etc.), agriculture, energy generation and transmission and operation of buildings as well as waste generation and deforestation. The extent of emission from the different activities also differs. This work is limited in scope to energy related emissions in residential buildings in Kaduna metropolis only. While all stages of a building’s life-cycle including construction and demolition produce carbon emissions, the building’s operational phase accounts for 80-90% of emissions resulting from energy use mainly for heating, cooling, ventilation, lighting and appliances and it is this stage of the building’s life-cycle that is the focus of this study. The study also focused on the emission of carbon dioxide (CO2) only since it is accountable for over 98% of all energy related emissions from the operation of buildings. Emission of GHGs from residential solid waste generation has not been included in this study.
GHG emission reduction targets are intended at reducing emissions to close to preindustrial era levels of around 300ppm. To facilitate the achievement of this, the study also involves measurement of CO2 concentrations in and outside the buildings to know the present levels.
Government agencies in Nigeria are not reputed for keeping up to date information about their activities and other public concerns and non-governmental organizations (NGOs) that could bridge this gap also do not exist. Households or citizens do not also fare any better in this regard. In view of this access to good data about energy consumption and efficiency is one factor that posed serious challenge to the success of the research. The willingness of the stakeholders to give objective responses to the questions in the questionnaires administered to acquire information on buildings and energy use also posed some challenges to the study. Moreover the level of awareness of the buildings occupants and users about the energy performance requirements and indicators of the buildings they live in is also a limiting factor for this work.
Another limitation to the study concerns the generation of primary data on two of the mitigation measures proposed in the framework. Since completed and inhabited buildings were surveyed, the study could only collect data on the behaviours of the users and likely modifications to these behaviours. There is no way the study could have obtained the data on measures that could be taken at the building and services design stage than through theoretical means (literature). While the energy efficiency of the existing buildings can be improved through the behavioural changes and some alterations to the buildings and their systems, the mitigation measures on building and services design can be applied to new developments in the communities.