Figure 1: World Primary Energy Use by Fuel Type (Source: Ref 1)

The role of biomass is of particular significance. Biomass use is unevenly distributed around the world. It represents 3% of energy use in industrialized countries and an average of 33% in developing countries, with large differences between regions. Biomass covered over 60% of final energy use in Africa, 34% in Asia and 25% in Latin America. Other renewable energy sources, such as small-scale hydropower, geothermal, wind, and solar energy, do not feature as significant energy inputs. Worldwide the aggregated energy supply from these renewable sources amounts to less than 1% of the total. The data also indicate that the proportions of different fuel types changed little in developing countries. (Ref 2)
In Nigeria Households and communities in rural areas typically rely on diverse sources of energy using one fuel for heating, another for cooking or lighting and others for agricultural and other productive activities. Most biomass is consumed in traditional ways in the household sector, and is simply collected rather than purchased. Such fuels are locally ‘free’ in cash terms, but have a cost of much time and physical effort often by children and women. In some rural and urban areas, charcoal has become a cash crop contributing to a monetised economy, and in some urban areas, there are active markets in local wood fuels.

Figure 2: Total Final Energy Use in Africa (source: Ref 2)

Because biomass remains such an important fuel around the world, energy policies for developing countries need to be as concerned with the supply and use of biomass, whether in its traditional role or used in modern technology, as they are about fossil fuels or other renewable sources of energy.

SECTORAL IMPORTANCE OF ENERGY TO THE NIGERIAN ECONOMY
THE UNITED STATES OF AMERICA AND THE NIGERIAN CASE STUDY
The U.S. ranks seventh in energy consumption per-capita (Ref 7). The U.S. Department of Energy tracks national energy consumption in four broad sectors:
• industrial,
• transportation,
• residential, and
• commercial.
The industrial sector has long been the country’s largest energy user, currently representing about 33% of the total. Next in importance is the transportation sector, followed by the residential and commercial sectors. (Ref 7)
Sector Summary: (Source: Ref 7)
Sector Name Description Major uses
Industrial Facilities and equipment used for producing and processing goods.

22%chemical production
16% petroleum refining
14% metal smelting/refining

Transportation Vehicles which transport people/goods on ground, air or water. 61% gasoline fuel
21% diesel fuel
12% aviation

1. Agriculture Sector as a User and Supplier of Energy
The dual role of agriculture as a user and supplier of energy is a major factor to put into consideration. Agriculture is itself an energy conversion process, namely the conversion of solar energy through photosynthesis to food energy for humans and feed for animals. Primitive agriculture involved little more than scattering seeds on the land and accepting the scanty yields that resulted. Modern agriculture requires an energy input at all stages of agricultural production such as direct use of energy in farm machinery, water management, irrigation, cultivation and harvesting. Post-harvest energy use includes energy for food processing, storage and in transport to markets. In addition, there are many indirect or sequestered energy inputs used in agriculture in the form of mineral fertilizers and chemical pesticides, insecticides and herbicides.
Agriculture accounts for only a relatively small proportion of total final energy demand in both industrialized and developing countries. In Nigeria, estimates are more difficult to find.
Agricultural energy demand can be divided into direct and indirect energy needs. The direct energy needs include energy required for land preparation, cultivation, irrigation, harvesting, post-harvest processing, food production, storage and the transport of agricultural inputs and outputs. Indirect energy needs are in the form of sequestered energy in fertilizers, herbicides, pesticides, and insecticides.
The data for energy use in agriculture also exclude the energy required for food processing and transport by agro-industries. Estimates of these activities range up to twice the energy reported solely in agriculture. Definitive data do not exist for many of these stages, and this is a particular problem in analysing Nigeria’s energy statistics. In addition, the data conceal how effective these energy inputs are in improving agricultural productivity. It is the relationships between the amounts and quality of the direct energy inputs to agriculture and the resulting productive output that are of most interest.
In a nut shell, all agricultural production has to become commercial to enable long-term food security as one of the prime inputs to agriculture.
2. Transportation Sector
Energy use in the transportation sector includes the energy consumed in moving people and goods by road, rail, air, water, and pipeline. The road transport component includes light-duty vehicles, such as automobiles, sport utility vehicles, small trucks, and motorbikes, as well as heavy-duty vehicles, such as large trucks used for moving freight and buses used for passenger travel. Consequently, transportation sector energy demand hinges on growth rates for both economic activity and the driving-age population. Economic growth spurs increases in industrial output, which requires the movement of raw materials to manufacturing sites, as well as the movement of manufactured goods to end users.
Almost 20 percent of the world’s total delivered energy is used in the transportation sector, where liquid fuels are the dominant source. Transportation alone accounts for more than 50 percent of world consumption of liquid fuels, and its share increases over the projection period. The transportation share of total liquid fuels consumption may rise to 61 percent in 2035, as their share declines in the other end-use sectors. Because liquids play a key role in the world transportation sector, understanding how the sector is likely to evolve could be the most important factor in assessing the future of liquid fuel markets. From 2007 to 2035, growth in transportation energy use may account for 87 percent of the total increase in world liquids consumption. (Ref 4)
According to the earth trends publication 2009, the Energy Consumption by the transport sector in Nigeria (in thousand metric tons of oil equivalent) is put at 5,867.
See details about the United States statistics above. Also, the people in the United States have always had a ‘love affair’ with the automobile. In 1973, there were 102 million cars on the road, driving an average of 9,600 miles a year. Today, there are more than 137 million cars, driving 12,000 miles a year. (Ref 9) Even with the scares of the oil embargoes, more cars are driven in the U.S and more miles though it is done more efficiently and cleanly. In the United States, there is also a push to develop vehicles that run on fuels other than petroleum products or on blended fuels. Today, there are vehicles that run on electricity, natural gas, propane, biodiesel, ethanol, and hydrogen. In 1973, there were only a few vehicles that ran on alternative fuels. Today, there are more than 775,000 in the United States, and that figure is increasing by about nine percent a year.

3. Industrial Sector
The United States is a highly industrialized society. Industry consumed 29.8 percent of the energy in 2009. Since 1973, the industrial sector has grown by more than 60 percent, but it has required only about 15 percent more energy. Advanced technologies have allowed industry to do more with less. Industry has also been a leader in developing cogeneration technology. Cogenerators produce electricity and use the waste heat for manufacturing, increasing overall energy efficiency by 50 percent.
Every industry both in Nigeria and in the United States uses energy, but there are six energy-intensive industries that use the majority of the energy consumed by the industrial sector.
• Petroleum Refining
• Steel Manufacturing
• Chemical Manufacturing
• Cement Manufacturing
• Aluminum Manufacturing
• Paper Manufacturing
In Nigeria, in addition to the above, the small and medium scale businesses also constitute a considerable consumption ratio. In my candid opinion, the industry sector utilizes more than 30% of total energy consumption in Nigeria. According to the earth trends publication 2009, the Energy Consumption by the Industry sector in Nigeria (in thousand metric tons of oil equivalent) is put at 9,035.

THE CURRENT ENERGY CHALLENGE
The current patterns of energy production and use, which have shaped the development process in the past, are unsustainable. The energy challenge now faced by countries around the world is to provide energy services that allow all people to achieve a decent standard of living, consistent with sustainable human development. This link between energy and development remains a key factor in development policy. It will be shaped by current trends of globalization, markets and popular participation in decision-making processes, the changing roles of government and energy utilities, and the mix of sources of external funding.
The World Energy Council has suggested (WEC, 2000b) that addressing the three goals of energy accessibility, availability and acceptability is fundamental to political stability world-wide, to stimulating new energy business strategies for the new century and to achieving a sustainable future for the world. Following the work done in establishing Agenda 21, UNDP has also identified (UNDP, 1997, and UNDP/EC, 1999) the need for a focused examination of the role of energy in achieving sustainable socio-economic development and has identified a series of actions required to increase the adoption of sustainable energy options. More recently, the World Bank has proposed a greater focus on rural energy in its lending for the energy sector, and is planning to bring renewable energy considerations more prominently into non-power sector lending, such as in the agriculture sector (World Bank, 1999). (Ref 4)
FAO has had significant experience with the energy needs of the agricultural sector. Bio energy issues and bio fuels have been on the organization’s agenda for decades. Over the last 10-15 years FAO has supported many rural energy projects in developing countries. These activities aim to assist developing countries to meet their energy requirements in agriculture, forestry and fisheries as a means of achieving sustainable development. A transition from the present energy supply of mainly wood fuel and animal and human work, to a more diversified base and a better use of modern energy technologies, is seen as key to improving the living conditions of rural populations (WEC/FAO, 1999).
Agriculture is an important, but not dominant, user of energy in developing countries. Nevertheless, improving energy services for rural people should include increasing the energy input to agriculture so that gains in productivity, enhanced food security and rural economic development can be made. Even a small amount of additional energy, normally insignificant at the level of national energy balances, can make an important contribution to a local rural economy. Due to its capacity for production of biomass, agriculture is also a potential source of renewable energy supply.
Together with the challenges faced by the international community in responding to the local and global environmental impacts of energy use, there is now a major opportunity for agriculture to play important extra role in sustainable energy development.
CLIMATE CHANGE
An issue of much relevance to future energy policy is mitigation of the effects of global climate change. Industrialized countries are responsible for at least 80% of the build-up of greenhouse gases in the atmosphere, and consumption of fossil-fuel derived energy accounts for the largest share of anthropogenic emissions of greenhouse gases. Through the UN Framework Convention on Climate Change and Agenda 21 (UNCED, 1992), the international community has agreed to work together to meet the problems of climate change, and industrialized countries are taking steps to reduce or stabilize their emissions of CO2 and other greenhouse gases.
The implementation of the Kyoto Protocol, once in force, or of any other agreement, which might develop from the Protocol, will greatly influence energy policy, investment decisions and the development and deployment of energy technologies. The Protocol assigns legally binding emission reduction targets and through Joint Implementation and the Clean Development Mechanism, industrialized countries can meet part of these targets by financing initiatives to reduce greenhouse gas emissions in other countries. This process may help to lever new financial support for sustainable energy development projects by providing additional benefits to investors (UNDP, 1998). Dealing with climate change will require global efforts to control greenhouse gas emissions. Emissions from developing countries e.g Nigeria are increasing, and will eventually naturally exceed those of industrialized countries. The means by which economic growth and increased energy demand can be reconciled with protection of the local and global environment is central for future sustainable energy development.
Agriculture has been shown to produce significant effects on climate change, primarily through the production and release of green house gases by the energy consumption and also by altering the earth land cover which can change its ability to absorb or reflect heat and light. Land use change e.g deforestation and desertification together with the use of fossil fuel are the major anthropogenic sources of carbon dioxide. Agriculture itself is the major contributor to increasing methane and nitrous oxide concentration in earths atmosphere.
Transportation is the fastest growing United States source of greenhouse gas emissions counting for 47% of the net increase in total U.S emissions since 1990 and is the largest end use source of carbon dioxide which is the most prevalent green house gas. (Ref 16)

FUTURE DIRECTIONS
With the above analysis of current situation in energy demand and supply by the Transportation, Agriculture and Industry critical sectors, it is envisaged that this situation might change in the future as a result of insufficient supply, climate change and resultant effects already being felt most especially in the developing economies e. g Nigeria. It is envisage that diversity of energy sources will take on the trend.
In simple terms, the concept of diversity of supply means not placing too much reliance on any single fuel, technology or other factor. Ensuring that there is diversity of fuel supply has long been a central theme within energy policy – both for primary fuel supplies and for sources of supply for derived electricity. Diversity has been of particular importance at times of oil price volatility and as one theme of the nuclear energy debate. One way of considering the benefits of diversity is to assess the variety, balance and disparity of fuel supply.
Variety of fuel supply considers the number of options available, including different technologies as well as fuel sources. The balance of supply must take into account how much the mix relies on any one of the available options while any disparity of supply assesses any qualitative differences between them. The central concept of diversity is responding to uncertainty and this underpins energy security – in turn this helps deliver economic performance and improves quality of life. Any failure to supply energy results in lost output and costs to industry, commerce and domestic users.
Diversity should, therefore, be seen as a means of providing greater strength in guarding against unforeseen events. It offers a kind of risk management which reduces the potential adverse impacts resulting from interruptions in supply, or excessive price rises in any single supply sector. It also provides additional options for substitution or replacement of supplies on which a country or region has become over-reliant. Diversity confers some insurance in the face of ignorance about the short and long term availability or price of any single energy source.
Indeed, history has shown that supply ‘shocks’ and extreme price volatility can have major economic and social impacts through national economies. The effects seem to be particularly sensitive when there is undue reliance on imported fuel oils. The oil price rises in 1973-74 led to major government initiatives in renewable energy, energy efficiency (conservation) and nuclear power development with a view to mitigating the risk associated with heavy use of oil. Today, although fossil fuel reserves seem sufficient, global concerns for the environmental implications of fossil-fuels for electricity and heat generation and their use in transport have changed perceptions about choices of fuels and opened a wider debate about the most appropriate global energy development pathway.
Renewable energy sources have the potential to meet an increasing proportion of the world’s energy needs over the coming decades. The basic reason for this is that modern renewable energy systems can make positive contributions against a number of underlying economic and social drivers – the drivers that determine the development and deployment of new energy technologies.
Hence, renewable energy systems are seen to offer benefits in terms of reducing the local environmental impact of energy production. They can provide both employment opportunities and economic benefits in rural areas due to their inherent localised nature. Renewable energy sources are an important means of providing increased diversity and security of supply, and they also offer another set of energy supply options that can mitigate the impact of climate change by substituting for fossil fuels. Overall, therefore, an increasing role for renewable energy is considered important to achieve a more sustainable energy future in both industrialized and developing countries alike (Nigeria).

References
1. http://www.fao.org/docrep/003/X8054E/x8054e04.htm#P191_23440
2. http://earthtrends.wri.org/pdf_library/country_profiles
3. EarthTrends 2003 publications
4. http://205.254.135.24/oiaf/ieo/transportation.html
5. http://earthtrends.wri.org/
6. United Nations Environmental Programme Publication 2010
7. http://en.wikipedia.org/wiki/Energy_in_the_United_States
8. http://www.eia.doe.gov/pub/international/iealf/tablee1c.xls
9. http://www.need.org/needpdf/infobook_activities/SecInfo/ConsS.pdf
10. UNDP, 1997 Publications
11. “Energizing the food production chain for the attainment of food security”, G Best, International Conference on Sustainable Agriculture for Food, Energy and Industry, Braunschweig, Germany, June, 1997.
12. UNDP/EC, 1999 Publication
13. United Nations Environmental Programme Publication 2008
14. FAO Environment and Natural Resources Working Paper 2009
15. CRS Report for Congress Energy Use in Agriculture: Background and Issues 2004
16. United States Environmental Protection Agency (transport and climate change report 1999)