Sustainable energy pathways for land transport in Nigeria

We used a bottom-up optimisation model to explore the energy system implications of five alternative policy pathways for the Nigerian transport sector. Our study considered fuel switching, improved fuel economy, modal shifting, improved logistics, and carbon tax for the period 2010–2050. Results show that the alternative pathways will reduce energy demand and CO₂ emissions significantly. Particularly, we found that improved vehicle fuel economy and a carbon tax can lower Nigeria's CO₂ emissions by 42.8% and 26.9% respectively, in 2050 when compared with the reference case. Additionally, low-carbon pathways will enhance air quality, energy security, and the productive use of energy.     

Testing the environmental Kuznets curve hypothesis: an empirical study for East African countries

ABSTRACT

The green economy aims to achieve economic growth and development without an adverse effect on the environment. The environmental Kuznets curve (EKC) hypothesis explains the relationship between economic activity and environmental degradation. Using the EKC hypothesis as a theoretical framework, this study tested the EKC hypothesis for 12 East African countries using the Pooled Mean Group (PMG) approach for the period from 1990 to 2013. The result shows that the relationship between per capita income and CO₂ emissions (a proxy for environmental degradation) is bell shaped and thus is an extended version of the original inverted U-shaped curve relationship between economic activities and environmental degradation. Hence, one can conclude that the economic activities in East African countries do not lead to CO₂ emissions. Therefore, environmental conservation policies, technological advancement and modern industrial policies are required to make the economic growth of East African countries effective in reducing CO₂ emissions.     

An economic input-output life cycle assessment of food transportation in Thailand

This study applies an economic input-output life cycle assessment (EIO-LCA) approach for 180 industrial sectors of the Thai economy. The approach is used to evaluate energy consumption and CO₂ emissions of the agricultural sector for the entire supply chain and particularly focusing on transportation. Transportation emits the second largest amount of CO₂ by sector in Thailand. Road transportation is the dominant form of cargo transport, accounting for 80% of all modes. The results show that transportation emissions from all modes of cargo transport account for 1–6% of total supply chain emissions. The vegetable sector shares highest CO₂ emissions in transportation. By changing the transportation mode from road freight to rail, emissions could be expected to decline. If 50% of road transportation was shifted to rail, CO₂ emissions would drop by 30%.     

Interventions for large-scale carbon emission reductions in future UK offices

Previous work by the authors has shown the effect that changing climate and small power/lighting equipment can have on heating and cooling loads of typical existing UK offices, for a 2005 baseline. This follow-on study uses an improved office, with reduced cooling loads, and performs retrofit fabric and HVAC measures to further reduce the energy and CO₂ emissions associated. The effect of heat recovery on the proposed “2030 office” is then quantified, showing that such an office can tend towards being “passively heated”. With adaptive comfort also applied, the office CO₂ emissions are estimated for various UK locations. The measures suggest CO₂ emissions relating to heating, cooling and ventilation (HVAC) can be reduced by 61% for the specific office-type studied. The proposed measures are carried out while allowing for a change in activity between 2005 and 2030. When all factors leading to changes in energy use are accounted for, namely small power, lighting, HVAC and climate change, total CO₂ savings of 65% are estimated when compared to the 2005 baseline. In achieving these theoretical savings, the relationship between internal activity and HVAC is studied, and identified as being a crucial area if challenging CO₂ emission targets are to be reached.     

Optimum configuration and design of a photovoltaic–diesel–battery hybrid energy system for a facility in University of Port Harcourt,Nigeria

Optimum configuration, using a hybrid optimisation model for electric renewable software, and design of a photovoltaic (PV)–diesel–battery hybrid energy system has been proposed to power a facility in the University of Port Harcourt, which is located in the suburb of Port Harcourt city, Nigeria. The configuration of the optimum hybrid system is selected based on top-ranked system configuration, according to the net present cost. An optimal system design delivers the best components alongside appropriate operating strategies to provide the most efficient, reliable cost-effective system possible. The system investigated reduces CO₂ emissions by 36.3%/year. This will reduce costs imposed on CO₂ emissions by future environmental legislation. The system has a better potential for providing the energy needs of the facility considered in this paper compared with a stand-alone PV–battery system as capital costs are reduced by 55%. Reliability was improved as the diesel generator can provide power as and when it is needed.     

Sustainable water-energy nexus in the optimization of the BBC golf-course using renewable energies

ABSTRACT

Water distribution networks and irrigation systems consume high energy quantities that need to be recovered if the water managers want to meet sustainable systems. A sustainability optimization is proposed in this research in order to replace the energy consumption in a golf-course system by renewable solutions joining energy recovery, sustainable urban drainage systems and hybrid solutions (solar panels and wind turbine). Different sustainable approaches were considered in which energy (using PATs), economic and environmental factors were analysed. Both scenarios and analyses showed interesting values related to economic indicators and environmental reductions of CO₂ emissions. The possibility to supply the daily electric consumption in the pumping stations was checked using only renewable systems. Net present value was calculated in different solutions, obtaining positive values as well as the payback period was lower than 6 years. The CO₂ emissions were reduced from 257,000 to 11,500 kgCO₂/year in the most unfavourable scenario.     

Impact of economic,financial, and institutional factors on CO2 emissions: Evidence from Sub-Saharan Africa economies

Given the acceleration of economic changes in Sub-Saharan Africa economies (SSA), a better understanding of the relationship between economic growth and pollution is essential for policy makers. The purpose of this study is to investigate the impact of economic, financial and institutional developments on CO₂ emissions for 25 SSA countries over the period 1996–2010. We use the reduced form modeling to control unobserved heterogeneity specific to countries and the GMM dynamic panel method to control endogeneity. We found no -evidence in our investigation for the Environmental Kuznets Curve (EKC) hypothesis. Indeed, a monotonically increasing relationship with GDP is found more appropriate for CO₂ emissions. The results confirm that political stability, government effectiveness, democracy, and control of corruption influence negatively CO₂ emissions. On the contrary, regulatory quality and rule of law have a positive effect on CO₂ emissions. The results confirm the importance of institutional frameworks in reducing carbon dioxide emissions since institutional quality not only affects carbon dioxide emissions directly, but also indirectly via economic growth and trade openness.     

Emission characteristics of neat rapeseed oil fuel in diesel engine

Studies show that the combustion of fossil fuel is the main cause of increasing global atmospheric carbon dioxide (CO₂) levels, which is the cause of the greenhouse effect. This has promoted increased research world-wide in a bid to source a greener alternative fuel substitute for conventional fossil fuel. Biofuel appears to be an alternative energy source for diesel engines. Although the combustion of biofuels produces CO₂, the same quantity is absorbed by plants during photosynthesis, hence CO₂ levels are kept in balance. The sulphur content of plant fuels is also low and less than 0.01% by weight compared to 0.05% by weight for diesel fuel. The effect of acid rain is therefore reduced or ameliorated. High viscosity is one of the major problems relating to the direct use of neat vegetable oils as fuels. One method of reducing viscosity is by blending with a low viscosity and volatile fuel. This paper investigates the emission characteristics of neat rapeseed oil and its blend with diesel fuel in a single cylinder unmodified diesel engine. Tests were also conducted on pure diesel fuel so that a comparative assessment could be made. Test results showed reduced hydrocarbon (HC) emissions when running on biofuels. The CO production was higher when running on biofuel at high engine speed and was significantly reduced at low speed operations. The CO₂ emissions were similar for all fuels. The analyses of lubrication oil after the runs on plant fuels showed a net reduction in viscosity.     

The environmental impact of optimum insulation thickness for external walls of buildings

The city of Denizli is in the 3rd climatic region in Turkey and there is a heating requirement for a period of approximately five months. During this period, thermal insulation of buildings is very important in minimizing the energy usage and reducing emission. In this study, environmental impact of optimum insulation thickness in external walls has been investigated for the case of Denizli, Turkey. In the calculations, coal was used as the fuel source and the expanded polystyrene as the insulation material. The results proved that when the optimum insulation thickness was used, energy consumption was decreased by 46.6% and the emissions of CO₂ and SO₂ were reduced by 41.53%.     

Examining the effects of the neighborhood built environment on CO2 emissions from different residential trip purposes: A case study in Guangzhou,China

This study developed structural equation models (SEMs) to examine the effects of the neighborhood built environment on CO₂ emissions from different trip purposes. CO₂ emissions were calculated using the Travel O-D Point Intelligent Query System (TIQS) and a 2015 travel survey in Guangzhou. The results showed that there were several differences in the influence mechanism of the neighborhood built environment on CO₂ emissions for different trip purposes. Most of the built environment elements tested in this study had significant effects on CO₂ emissions. Certain effects were direct effects, while others were indirect effects that influenced mediating variables, such as car ownership, mode choice or trip distance. In terms of total effect, the distance to city public centers had a positive effect on CO₂ emissions from commuting trips but had a negative effect on that from recreational and daily shopping trips. In contrast, residential density had a negative effect on CO₂ emissions from commuting trips but had a positive effect on that from social, recreational and daily shopping trips. Bus stop density was positively correlated with CO₂ emissions from commuting trips, a counterintuitive but not implausible outcome. Additionally, bus stop density had a significant negative correlation with CO₂ emissions from social and daily shopping trips. In addition, land-use mix had a negative effect on CO₂ emissions from commuting, social and daily shopping trips, while metro station density and road network density had significant negative effects on CO₂ emissions for all trip purposes. These results suggest that it is necessary to design targeted interventions in the built environment to encourage residents to change their travel behavior, reduce CO₂ emissions, and achieve low-carbon development.     

Gaseous elemental mercury emissions and CO2 respiration rates in terrestrial soils under controlled aerobic and anaerobic laboratory conditions

Mercury (Hg) levels in terrestrial soils are linked to the presence of organic carbon (C). Carbon pools are highly dynamic and subject to mineralization processes, but little is known about the fate of Hg during decomposition. This study evaluated relationships between gaseous Hg emissions from soils and carbon dioxide (CO₂) respiration under controlled laboratory conditions to assess potential losses of Hg to the atmosphere during C mineralization. Results showed a linear correlation (r² = 0.49) between Hg and CO₂ emissions in 41 soil samples, an effect unlikely to be caused by temperature, radiation, different Hg contents, or soil moisture. Stoichiometric comparisons of Hg/C ratios of emissions and underlying soil substrates suggest that 3% of soil Hg was subject to evasion. Even minute emissions of Hg upon mineralization, however, may be important on a global scale given the large Hg pools sequestered in terrestrial soils and C stocks.We induced changes in CO₂ respiration rates and observed Hg flux responses, including inducement of anaerobic conditions by changing chamber air supply from N₂/O₂ (80% and 20%, respectively) to pure N₂. Unexpectedly, Hg emissions almost quadrupled after O₂ deprivation while oxidative mineralization (i.e., CO₂ emissions) was greatly reduced. This Hg flux response to anaerobic conditions was lacking when repeated with sterilized soils, possibly due to involvement of microbial reduction of Hg²⁺ by anaerobes or indirect abiotic effects such as alterations in soil redox conditions. This study provides experimental evidence that Hg volatilization, and possibly Hg²⁺ reduction, is related to O₂ availability in soils from two Sierra Nevada forests. If this result is confirmed in soils from other areas, the implication is that Hg volatilization from terrestrial soils is partially controlled by soil aeration and that low soil O₂ levels and possibly low soil redox potentials lead to increased Hg volatilization from soils.     

Embodied and operational carbon dioxide emissions from housing: A case study on the effects of thermal mass and climate change

A 100-year lifecycle carbon dioxide (CO₂) emissions analysis is reported for a two-bedroom, 65 m² floor area, semi-detached house in south-east England. How the balance between the embodied (ECO₂) and operational CO₂ emissions of the building are affected by the inclusion of thermal mass and the impacts of climate change is quantified. Four ‘weights’ of thermal mass were considered, ranging from lightweight timber frame to very heavyweight concrete construction. For each case, total ECO₂ quantities were calculated and predictions for operational CO₂ emissions obtained from a 100-year dynamic thermal modelling simulation under a medium-high emissions climate change scenario for south-east England. At the start of the lifecycle, the dwellings were passively cooled in summer, but air conditioning was installed when overheating reached a certain threshold. The inclusion of thermal mass delayed the year in the lifecycle when this occurred, due to the better passive control of summertime overheating. Operational heating and cooling energy needs were also found to decrease with increasing thermal mass due to the beneficial effects of fabric energy storage. The calculated initial ECO₂ was higher in the heavier weight cases, by up to 15% (4.93 t) of the lightweight case value, but these difference were offset early in the lifecycle due to the savings in operational CO₂ emissions, with total savings of up to 17% (35.7 t) in lifecycle CO₂ found for the heaviest weight case.     

Experimental investigation on spark ignition engine using blends of bio-ethanol produced from citrus peel wastes

The performance and pollutant emissions of a four stroke spark ignition engine operating on gasoline and bio-ethanol blends were investigated experimentally. The citrus peel wastes were grinded and subjected to simple distillation to remove d-limonene and then the remains were kept in an autoclave at a temperature of 120°C for 15 min. Finally, by doing simple distillation, bio-ethanol was extracted. From the experiments, the specific fuel consumption (SFC) was slightly increased and the brake thermal efficiency was slightly decreased. Exhaust gas emissions were measured and analysed for hydrocarbons (HC), carbon dioxide (CO₂), carbon monoxide (CO) and oxides of nitrogen (NO_x) at an engine speed of 2500?rpm. The concentration of CO and HC emissions in the exhaust pipe was found to be decreased when bio-ethanol blends were used. The concentration of CO₂ was found to be slightly increased and NO_x was reduced when ethanol blends were used.     

Life cycle emissions analysis of two nZEB concepts

The net-zero emissions building (nZEB) performance is investigated for building operation (EO) and embodied emissions in materials (EE) for Norway's cold climate. nZEB concepts for new residential and office buildings are conceived in order to understand the balance and implications between operational and embodied emissions over the building's life. The main drivers for the CO₂ equivalent (CO₂e) emissions are revealed for both building concepts through a detailed emissions calculation. The influence of the CO₂e factor for electricity is emphasized and it is shown to have significant impact on the temporal evolution of the overall CO₂e emissions balance. The results show that the criterion for zero emissions in operation is easily reached for both nZEB concepts (independent of the CO₂e factor considered). Embodied emissions are significant compared to operational emissions. It was found that an overall emissions balance including both operational and embodied energy is difficult to reach and would be unobtainable in a scenario of low carbon electricity from the grid. In this particular scenario, the net balance of emissions alone is nonetheless not a sufficient performance indicator for nZEB.     

The corruption-emissions nexus: Do information and communication technologies make a difference?

The study investigates the effect of information and communication technology (ICT) and corruption on carbon dioxide (CO₂) emissions in the context of the Environmental Kuznets curve (EKC) hypothesis. Panel data representing 33 Asian countries for the period 2000–2015 is analyzed. The econometric analysis employed allows cross-sectional dependency and can handle the endogeneity, autocorrelation, and heterogeneity issues in the data. The results suggest that ICT increases CO₂ emissions and that corruption also contributes to environmental pollution. Furthermore, EKC is relevant to the significance of ICT and corruption in Asian countries. The study also provides insight into the role of ICT in combating corruption to meet environmental challenges. The introduction of e-governance could be an effective tool to reduce corruption that would be beneficial to improve environmental quality in the region.     

Assessment of the decrease of CO2 emissions in the construction field through the selection of materials: Practical case study of three houses of low environmental impact

A great quantity of CO₂ is emitted to the atmosphere through the different phases of a building life cycle: in the production of materials and products, in the construction of the building itself, in the setting on site, in the exploitation, the renovations, the later rehabilitations, up to the final demolition. The present paper shows the possibility of reducing the CO₂ emissions up to 30% in the construction phase, through a careful selection of low environmental impact materials. The purpose of this study is to quantify the total amount of CO₂ emissions saved by the method presented in the particular phase of material selection within the life cycle of a building. This material selection, as well as the bioclimatic characteristics, must be defined from the early design project phase.     

Life-cycle assessment of post-disaster temporary housing

The estimation of energy consumption and related CO₂ emissions from buildings is increasingly important in life-cycle assessment (LCA) studies that have been applied in the design of more energy-efficient building construction systems and materials. This study undertakes a life-cycle energy analysis (LCEA) and life-cycle CO₂ emissions analysis (LCCO₂A) of two common types of post-disaster temporary houses constructed in Turkey. The proposed model includes building construction, operation and demolition phases to estimate total energy use and CO₂ emissions over 15- and 25-year lifespans for container houses (CH) and prefabricated houses (PH) respectively. Energy efficiency and emission parameters are defined per?m² and on a per capita basis. It is found that the operation phase is dominant in both PH and CH and contributes 86–88% of the primary energy requirements and 95–96% of CO₂ emissions. The embodied energy (EE) of the constructions accounts for 12–14% of the overall life-cycle energy consumption. The results show that life-cycle energy and emissions intensity in CH are higher than those for PH. However, this pattern is reversed when energy requirements are expressed on a per capita basis.     

Life cycle primary energy use and carbon emission of an eight-storey wood-framed apartment building

In this study the life cycle primary energy use and carbon dioxide (CO₂) emission of an eight-storey wood-framed apartment building are analyzed. All life cycle phases are included, including acquisition and processing of materials, on-site construction, building operation, demolition and materials disposal. The calculated primary energy use includes the entire energy system chains, and carbon flows are tracked including fossil fuel emissions, process emissions, carbon stocks in building materials, and avoided fossil emissions due to biofuel substitution. The results show that building operation uses the largest share of life cycle energy use, becoming increasingly dominant as the life span of the building increases. The type of heating system strongly influences the primary energy use and CO₂ emission; a biomass-based system with cogeneration of district heat and electricity achieves low primary energy use and very low CO₂ emissions. Using biomass residues from the wood products chain to substitute for fossil fuels significantly reduces net CO₂ emission. Excluding household tap water and electricity, a negative life cycle net CO₂ emission can be achieved due to the wood-based construction materials and biomass-based energy supply system. This study shows the importance of using a life cycle perspective when evaluating primary energy and climatic impacts of buildings.     

Impact of process design on greenhouse gas (GHG) generation by wastewater treatment plants

The overall on-site and off-site greenhouse gas emissions by wastewater treatment plants (WWTPs) of food processing industry were estimated by using an elaborate mathematical model. Three different types of treatment processes including aerobic, anaerobic and hybrid anaerobic/aerobic processes were examined in this study. The overall on-site emissions were 1952, 1992, and 2435 kg CO₂e/d while the off-site emissions were 1313, 4631, and 5205 kg CO₂e/d for the aerobic, anaerobic and hybrid treatment systems, respectively, when treating a wastewater at 2000 kg BOD/d. The on-site biological processes made the highest contribution to GHG emissions in the aerobic treatment system while the highest emissions in anaerobic and hybrid treatment systems were obtained by off-site GHG emissions, mainly due to on-site material usage. Biogas recovery and reuse as fuel cover the total energy needs of the treatment plants for aeration, heating and electricity for all three types of operations, and considerably reduce GHG emissions by 512, 673, and 988 kg CO₂e/d from a total of 3265, 6625, and 7640 kg CO₂e/d for aerobic, anaerobic, and hybrid treatment systems, respectively. Considering the off-site GHG emissions, aerobic treatment is the least GHG producing type of treatment contrary to what has been reported in the literature.     

Multiple effects and uncertainties of emission control policies in China: Implications for public health, soil acidification, and global temperature

Policies to control emissions of criteria pollutants in China may have conflicting impacts on public health, soil acidification, and climate. Two scenarios for 2020, a base case without anticipated control measures and a more realistic case including such controls, are evaluated to quantify the effects of the policies on emissions and resulting environmental outcomes. Large benefits to public health can be expected from the controls, attributed mainly to reduced emissions of primary PM and gaseous PM precursors, and thus lower ambient concentrations of PM_2.5. Approximately 4% of all-cause mortality in the country can be avoided (95% confidence interval: 1-7%), particularly in eastern and north-central China, regions with large population densities and high levels of PM_2.5. Surface ozone levels, however, are estimated to increase in parts of those regions, despite NO_X reductions. This implies VOC-limited conditions. Even with significant reduction of SO₂ and NO_X emissions, the controls will not significantly mitigate risks of soil acidification, judged by the exceedance levels of critical load (CL). This is due to the decrease in primary PM emissions, with the consequent reduction in deposition of alkaline base cations. Compared to 2005, even larger CL exceedances are found for both scenarios in 2020, implying that PM control may negate any recovery from soil acidification due to SO₂ reductions. Noting large uncertainties, current polices to control emissions of criteria pollutants in China will not reduce climate warming, since controlling SO₂ emissions also reduces reflective secondary aerosols. Black carbon emission is an important source of uncertainty concerning the effects of Chinese control policies on global temperature change. Given these conflicts, greater consideration should be paid to reconciling varied environmental objectives, and emission control strategies should target not only criteria pollutants but also species such as VOCs and CO₂.