GLOBAL WARMING AND ENVIRONMENTAL CHANGE PROBLEMS: RENEWABLE ENERGY AND CLEANER FOSSIL FUELS TECHNOLOGY AS SOLUTION K.R. Ajao1, H.A. Ajimotokan1 & W.O Raji2 1
Department of Mechanical Engineering, University of Ilorin, Ilorin, Nigeria Department of Geology, University of Ilorin, Ilorin, Nigeria E-mail:
[email protected]
2
REFERENCE NO Ref # 7-25
Keywords: Fossil fuel, ecosystems, biodiversity, renewable energy, green house gases
ABSTRACT Fossil fuel is a dominant player in the supply of energy as the global energy demand rises exponentially. The effect of climate and ocean acidification arising from greenhouse gasses emitted during consumption of fossil fuel worsens and the world is hard-pressed to find technologies to curb carbon dioxide emissions. Carbon Capture Storage (CCS) is a cleaner fossil fuel technology which isolates, captures, transports and stores carbon dioxide at great depths below the earth surface. Given the fact that fossil fuel are “finish-able” limited natural resources with bad environmental consequences, and issue of affordability and accessibility of CCS technology by underdeveloped and developing countries, this literature also presents renewable energy as a useful compliment and gradual replacement for fossil fuel. Unlike fossil fuel, renewable energy sources such as solar, geothermal, hydro and wind do not directly emit greenhouse gasses to the atmosphere. Renewable energy sources are cheap and “ever- present”. Increased use of cleaner fossil fuel and renewable energy technologies will reduce environmental harm arising from global warming and lower the average Green House Gases (GHG) emitted into the atmosphere.
1. INTRODUCTION Globalization is currently radically reshaping our economies and environmental policies and the world’s major emerging markets are increasingly steering global developments. Current patterns of resource use and consumption can easily cancel out the progress made through technological improvements and environmental policies. Plant and animal species are being lost in record numbers. The climate is changing, bringing threats such as rising sea levels and worsening droughts, storms and floods [1]. Fossil fuels, with its consequences of producing CO2 and other gases emissions will probably remain the main source of supply of primary energy until at least the middle of this century. Crude oil in particular will continue to fuel socio-economic development of all regions of the world. Technologies that capture carbon dioxide and store it are considered a vital means to reduce or limit carbon dioxide emissions. They may also provide a powerful indication of actions that could result in dual benefits of reducing carbon dioxide emissions into the atmosphere while enhancing oil recovery. There are a variety of strategies for reducing the climate change impacts of fossil fuel combustion. One of the most important near-term strategies for reducing CO2 emissions from fossilfired power generation is to maximize the efficiency of new and existing plants. The most important near-to-long-term strategy is carbon dioxide capture and storage (CCS). These strategies can and should be implemented simultaneously; as when new fossil plants are designed and operated at the highest efficiency [2]. 10th International Conference on Clean Energy (ICCE-2010) Famagusta, N. Cyprus, September 15-17, 2010
While coal-burning plants supply some of our stationary energy and as petroleum products help meet our transportation and domestic energy needs, we must continue to find ways to both reduce our reliance on fossil fuels and make their consumption less harmful to the environment. There is much to be gained by investing in cleaner fossil fuel and renewable energy technologies. Among the obvious benefits are the reduced environmental harm, lower average Green House Gases (GHG) intensity per unit of activity and the improved air quality. Green House Gases (mainly CO2, NO2, CH4, HFCs) are essential for maintaining the temperature of the Earth, but an excess emission of these gases can raise the temperature of the planet to lethal level. Poor communities are the hardest hit by degraded ecosystems, erosion, loss of biodiversity, forest resources, etc.; and thus, associated declines in clean air and water, higher prevalence of disease, and increased vulnerability to natural disasters. Without alternatives, poor communities tend to over use or under employ natural resources that are important for the protection of beneficial goods and services for domestic use and commercial efforts. As economies grow, environmental quality tends to decline, with humans at fault for the bulk of environmental problems. Activities such as logging, mining, industrial development, the exploitation of plant and animal resources, and conversion of natural habitats into cultivated land lead to ecological degradation, species extinction, and pollution of the environment. Breaking this pattern requires a focus on more efficient resource use and environmental protection. Energy plays a key role in the management of natural resources and the transition to environmentally sound economic growth. The selection, use, and development of renewable energy sources have a direct effect on the environment, with related health, economic, and social benefits [3]. Table 1 depicts the extent and causes of global land degradation and Table 2 depicts a projection of global energy demand by 2030. Type
Deforestation
Overgrazing Fuel consumption
wood
Agricultural mismanagement
Industry urbanization
and
Table 1: Causes and Extent of Global Land Degradation (Source: [3]) Extent of Causes of Recent Losses Damage (millions of hectares) 580 • Vast reserves of forests have been degraded by large-scale logging and clearing for farm and urban use • More than 220 million hectares of tropical forests were destroyed during 1975-1990, mainly for food production. 680 • About 20% of the World’s pasture have been damaged • Recent losses have been most severe in Africa and Asia. 137 • About 1.730 millions m3 of fuel wood are harvested annually from forests and plantations • Fuel wood is the primary source of energy in many developing countries. 550 • Water erosion causes soil losses estimated at 25,000 million tons annually • Soil salinization and water logging affect about 40 million hectares of land globally. 195 • Urban growth, road construction, mining and industry are major contributors to land degradation • Valuable agricultural land is often lost.
Table 2: World Primary Energy Demand (Mtoe) (Source: [4]) Energy Type
1
2002
2010
2020
2030
1
2389
2763
3193
3601
2
3676
4308
5074
5766
8
2190
2703
3451
4130
2
629
778
776
764
1
224
276
321
365
6
1119
1264
1428
1605
4
55
101
162
256
5
10282
12193
14405
16487
971 Coal 407 Oil 413 Gas 92 Nuclear 9 Hydro 04 Biomass 87
Other Renewable Total 536
Mtoe: Million Tons of Oil Equivalent
2. CLEANER FOSSIL FUELS Coal, oil and gas will remain critical sources of energy for all countries of the world for many years to come. Against this background of increasing energy demand, there is a need to improve the efficiency and environmental performance of fossil fuel use as a mean to mitigate environmental challenges. Significant opportunities exist today to achieve efficiencies and performance improvements in the stationary use of coal, oil and gas. The development and deployment of lower emissions technologies will be a key factor in delivering clean development and climate outcomes associated with fossil fuel use. There is a range of key advanced coal, oil and gas technologies identified with the potential to significantly reduce greenhouse gas emission levels, air-borne pollutants and other environmental impacts. The use of carbon dioxide (CO2) capture and storage is important in achieving significant reduction in greenhouse gas emission arising from the use of fossil energy. These capture-enabling technologies include integrated coal gasification combined cycle (IGCC), oxy-fuel combustion, and post-combustion CO2 capture. Other technologies, such as ultra-supercritical pulverized fuel, coal upgrading, gas hydrates and hydrogen technologies, coal bed methane, coal and gas liquefaction including poly-generation, co-gasification of coal/pet coke/residues/biomass are also important elements that need to be considered in developing a cleaner fossil energy strategy and these technologies are at different stages of development at different countries of the world. Relatively new technologies, such as post-combustion capture of CO2 and oxy-fuel combustion, need to be trialed in pilot plants or small-scale demonstration plants. Other technologies, such as IGCC, are being demonstrated commercially in developed countries and now being planned by several utility companies on commercial scale. For gas-fired power generation and city gas uses, small incremental improvements in the technologies related to gas processing, handling and transportation are probably easy to achieve and may have significant benefit in reducing fugitive emissions [5].
2.1 Carbon Dioxide Capture and Storage (CCS) Carbon dioxide capture and storage (CCS) involves the capture of CO2 from large point sources such as fossil fuel power stations, and its geological storage in deep underground geological formations for decades. These geological formations include depleted oil and gas reservoirs, nonminable coal seams, deep seated saline water aquifers and deep ocean bottom. Regionally speaking, there is good correlation between major CO2 sources and sedimentary basins which may later serve as carbon dioxide natural storage facilities. Many fossil fuel sources lie either directly above, or within reasonable distances (less than 300 km) from areas with potential for geological storage [6]. Carbon Capture and Storage involves the use of technology to: (i) Capture and concentrate CO2 produced (ii) Transport it to a suitable storage location (iii) Store it away from the atmosphere for a long period of time
Fig. 1: Techniques used in CCS (Image courtesy of [7])
2.1.1 CO2 Capture Methods Some potential methods of capturing carbon dioxide are discussed below: i) Post combustion/gas scrubbing routes CO2 is scrubbed from the gas exiting the combustion or production process of power station boilers or heating furnaces. ii) Pre-combustion/Syngas approach Synthetic H2 and CO2 rich gas is produced from the fuel. This approach is used in integrated gasification combined cycle plants (IGCC). It is a clean coal technology under development with few already existing plants in Europe and the US, but with promising prospects as a large-scale technology. iii) Oxy-fuel routes Combustion process is fired with O2 rather than air to create a flue gas primarily comprising CO2 but this method is still in a research and development stage.
Other methods include biological capture and direct injection into ocean bottom. Although CO2 capture methods are already in use industrially, selection of the appropriate method is determined by several factors. Available literatures indicate that its is costlier to retrofit existing power plants with CO2 capture compare to providing for it at the onset. Capture and compression need approximately 10-40% more energy than an equivalent plant without capture [6]. 2.1.2 Transport of CO2 i. Pipelines: This is the most common method for transporting compressed CO2 (mature market technology). The important properties of a pipe suitable for carbon dioxide transport is corrosion resistant ii. Ships, road or rail tankers: CO2 is transported as a liquid in insulated tanks at temperature below ambient the range and at much lower pressures. 2.1.3 Potential Storage Methods for CO2 Compressed CO2 can be injected into porous rock formations below the Earth’s surface using many of the same methods already used by the oil and gas industry. Identified geological formations suitable for carbon dioxide storage include depleted oil and gas reservoirs, deep saline aquifers, and un-minable coal beds. CO2 can for instance be physically trapped under a well-sealed rock layer or in the pore spaces within the rock. It can also be chemically trapped by dissolving in saline water and reacting with the surrounding rocks. Such geological formations should have good history of no leakage revealed by thorough geophysical investigations for fault, conduits and must share boundaries with non- porous rock to provide the required trap system. The risk of leakage from these reservoirs is rather small. Storage in geological formations is the cheapest and most environmentally acceptable storage option for CO2 [8].
Fig. 2: Potential CO2 Storage Sites (Image courtesy of [8])
(a)
Injection into underground geological formations
Estimates for CO2 global geological storage potential range from 1,000 to over 10,000 GtCO2 in depleted oil and gas reservoirs, saline aquifers and unminable coal seams. (i) Oil and Gas Reservoirs: CO2 is injected in almost-depleted oil/gas fields in order to enhance oil or gas production in both on- and off-shore sedimentary rocks. (ii) Deep Saline Formations : Injection of CO2 into saline aquifers below 800m. It has the largest storage potential globally but it is the least explored and researched of the geological options. (iii) Unminable Coal Beds: Preferential adsorption of CO2 onto coal replacing gases such as methane. (b) Injection into the deep ocean Carbon dioxide can be injected into the ocean bottom at depth of 3000m which can keep CO2 away from being in contact with the atmosphere for about 200 years. At ocean levels between 800 and 3000m, a stream of liquid carbon dioxide is less dense than sea water and tends to rise slowly, mixing and dissolving in the surrounding sea water. Below 3000m, liquid carbon dioxide reacts with sea water to form clathrate, a solid ice-like substance that that is denser that the surrounding water. (c) Industrial fixation in inorganic carbonates This includes the use of fertilizers in nutrient-poor oceanic environments to help increase the uptake of CO2. Neutralization of CO2 in the form of carbonic acid to form carbonates or bicarbonates and replicates injecting CO2 into alkaline strata (MgO and CaO) in silicate rocks to form carbonates or bicarbonates, neutralization of carbonic acid with carbonates to form aqueous solution to be injected underground or deep sea and formation of insoluble carbonates for storage and confinement. Some industrial processes also might utilize and store small amounts of captured CO2 in manufactured products. This include beverage industries, breweries and in chemical and biological processes where CO2 is the reactant e.g. urea and methanol production.
3.
RENEWABLE ENERGY
With the cutting edge advance being witnessed in the modern science and technology sector, renewable energy is increasingly becoming a feasible alternative to fossil fuel, the conventional energy sources. Unlike fossil fuel, energy obtained from renewable sources like hydropower, geothermal, solar and wind does not directly emit greenhouse gases [9].
Fig. 3: A Typical Offshore Wind Farm (Source: [10])
Fig. 4: Roof mounted Solar Modules (Source: [11])
Bio-fuel unlike gasoline is nontoxic, safe to handle and eco-friendly as it quickly breaks down into harmless substances if spilled. It reduces carbon monoxide and other toxic pollution making the air cleaner. Its characteristics enable cleaner combustion and better engine performance, which contributes in reducing pollutant emissions, even when it is mixed with gasoline. In response to the heightened market demand resulting from fluctuating fossil fuel prices and concerns over environmental and energy security issues, bio-fuel production capacity is expanding rapidly. The use of renewable fuel is expected to continue to grow over the coming years despite the fact that non-renewable fuel is continuing to be prevalent in the world energy market to meet most of the energy needs. Owing to the mounting call for reducing reliance on expensive fossil energy and a boost in green energy output, the production and use of renewable fuels has also grown more quickly in recent years. New ways for renewable energy resources are being sought today to help meet the global energy needs. Many developing countries such as Nigeria have great potentials in this regard as they have adequate natural conditions including soil, water, solar radiation and land to expand sugarcane oriented energy production. Brazil is prominent with regard to sugarcane bio-ethanol program that has delivered remarkable results from the improvement and development of higher yielding sugarcane varieties to the manufacturing of engines that run on any gasoline and bio-ethanol blend. Jatropha an oil plant, drought resistant shrub tree which is found growing in Nigeria and other African countries also hold good promises as a bio-fuel resource. Hydrogen fuel cell is another area where research is presently intensified. Hydrogen, like electricity, is a universal energy carrier that can be produced as secondary energy from a wide variety of primary energy sources. Considering the whole energy chain from production to end-use, hydrogen, used in fuel cells to power transport and stationary applications, can provide significant benefits in terms of greenhouse gas emissions and local pollutants through increased efficiency and lower the rate of emission per end-use energy unit [12]. Reducing cost and improving durability are the two most significant challenges to fuel cell commercialization. Fuel cell systems must be cost-competitive with, and perform as well or better than, traditional power technologies over the life of the system. Ongoing research is focused on identifying and developing new materials that will reduce the cost and extend the life of fuel cell stack components. 4. CONCLUSION Falling water tables, rising temperatures, flooding, soil erosion and desertification are likely to result in increasing food prices and dislocate the eco-system. The way to stabilize climate is by cutting carbon emissions through reduced demand for energy. First, we could phase out all old-fashioned, inefficient incandescent light bulbs and replace them with compact fluorescent bulbs that use only a third as much electricity. And second is the increase usage of remarkable piece of automotive engineering breakthrough with gasoline-electric hybrid engine over the next decade that will raise the fuel efficiency and cut gasoline use. On the supply side, we have a number of renewable sources with a lot of potential: wind, solar, geothermal and, in some places, biomass. Advances in wind turbine technology enable turbines to convert wind into electricity more efficiently, and harvest a much larger amount of energy. Whereas the average wind turbine in 1991 was around 40 metres tall, the ones going in today are 100 metres.
Not only are they on a larger scale, but the wind is much stronger up there. Wind has an enormous potential, it is abundant, cheap, inexhaustible, widely distributed, clean and climate-benign. No other energy source has all those attributes. In recent years emphasis has been on the evolution of the hydrogen economy. Fuel cells are quite efficient, but the advantage of the system is that the electricity is used directly to power the automobile. Governments can use various incentives and legislation to promote action toward progress and support initiatives in the development, deployment and utilization of cleaner and renewable energy resources for economic and environmental benefits. 6. [1] [2] [3]
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