Abstract: Energy use reductions can be achieved by minimising the energy demand by rational energy use and by recovering heat. The increased availability of reliable and efficient energy services stimulates the use of more green energies. The adoption of green or sustainable approaches to the way in which society is run is seen as an important strategy in finding a solution to the energy problem. The key factors to reducing and controlling CO₂ emissions to the atmospheric sink which is the major contributor to global warming are the use of alternative approaches to energy generation and the exploration of how these alternatives are used today and may be used in the future as green energy sources. This study discusses a comprehensive review of biomass energy sources, environment and sustainable development. This includes the biomass energy technologies, energy efficiency systems, energy conservation scenarios, energy savings and other measures necessary to reduce climate change.

INTRODUCTION

Energy is an essential factor in development since, it stimulates and supports economic growth and development. Fossil fuels, especially oil and natural gas are finite in extent and should be regarded as depleting assets and efforts are oriented to search for new sources of energy.

The clamour all over the world for the need to conserve energy and the environment has intensified as traditional energy resources continue to dwindle whilst the environment becomes increasingly degraded. Alternative energy sources can potentially help fulfil the acute energy demand and sustain economic growth in many regions of the world (Haripriye, 2000; The World Bank, 2001; DEFRA, 2002; EUO, 2000).

Energy security, economic growth and environment protection are the national energy policy drivers of any country of the world. As world populations grow, many faster than the average 2%, the need for more and more energy is exacerbated (Davenport et al., 2005). Enhanced lifestyle and energy demand rise together and the wealthy industrialised economics which contain 25% of the world’s population, consume 75% of the world’s energy supply (United Nations, 2001).

The world’s energy consumption today is estimated to 22 billion kWh year^-1 (UNECA, 2003a, b; UNECE, 2004). About 6.6 billion metric ton carbon equivalent of Greenhouse Gas (GHG) emission are released in the atmosphere to meet this energy demand (UNEP, 2003; World Bank, 2003a, b). Approximately, 80% is due to carbon emissions from the combustion of energy fuels (World Bank, 2003a, 2004). At the current rate of usage, taking into consideration population increases and higher consumption of energy by developing countries, oil resources, natural gas and uranium will be depleted within a few decades.

Bioenergy is beginning to gain importance in the global fight to prevent climate change (Omer, 2008a, b; IEA, 2008; Fowler, 2001). The scope for exploiting organic waste as a source of energy is not limited to direct incineration or burning refuse derived fuels.

Biogas, biofuels and woody biomass are other forms of energy sources that can be derived from organic waste materials. These biomass energy sources have significant potential in the fight against climate change. Technological progress has dramatically changed the world in a variety of ways. It has however, also led to developments, e.g., environmental problems which threaten man and nature.

Build-up of carbon dioxide and other GHGs is leading to global warming with unpredictable but potentially catastrophic consequences. When fossil fuels burn, they emit toxic pollutants that damage the environment and people’s health with >700,000 deaths resulting each year according to The World Bank (2001) and Huttrer (2001). At the current rate of usage, taking into consideration population increases and higher consumption of energy by developing countries, oil resources, natural gas and uranium will be depleted within a few decades (Roriz et al., 2001; Witte et al., 2002; Commission of the European Communities, 2000). The sources to alleviate the energy situation in the world are sufficient to supply all foreseeable needs (Trevor, 2007; IEA, 2007; Brain and Mark, 2007; Omer, 2005a, b, 2009a, b; Pernille, 2004). Conservation of energy and rationing in some form will however have to be practised by most countries to reduce oil imports and redress balance of payments positions.

Meanwhile, development and application of nuclear power and some of the traditional solar, wind, biomass and water energy alternatives must be set in hand to supplement what remains of the fossil fuels. The encouragement of greater energy use is an essential component of development.

In the short term, it requires mechanisms to enable the rapid increase in energy/capita and in the long term, we should be working towards a way of life which makes use of energy efficiency and clean environment without causing safety problems (IPCC, 2001; Lazzarin et al., 2002; David, 2003). Such a programme should as far as possible be based on renewable energy resources.

Large-scale, conventional, power plant such as hydropower has an important part to play in development. It does not however, provide a complete solution. There is an important complementary role for the greater use of small scale, rural based-power plants. Such plant can be used to assist development since it can be made locally using local resources, enabling a rapid built-up in total equipment to be made without a corresponding and unacceptably large demand on central funds. Renewable resources are particularly suitable for providing the energy for such equipment and its use is also compatible with the long-term aims. In compiling energy consumption data, one can categorise usage according to a number of different schemes:

•	Traditional sector-industrial, transportation, etc.
•	End-use-space heating, process steam, etc.
•	Final demand-total energy consumption related to automobiles to food, etc.
•	Energy source-oil, coal, etc.
•	Energy form at point of use-electric drive, low temperature heat, etc.

The scope for exploiting organic waste as a source of energy is not limited to direct incineration or burning refuse-derived fuels. Biogas, biofuels and woody biomass are other forms of energy sources that can be derived from organic waste materials. These biomass energy sources have significant potential in the fight against climate change. Energy is a vital prime mover to the development whether in urban or rural areas. The rural energy needs are modest compared to urban. A shift to renewables would therefore help to solve some of these problems while also providing the population with higher quality energy which will in turn, improve living standards and help reduce poverty. For proper rural development, the following must be considered:

•	Analyse the key potentials and constraints of development of rural energy
•	Assess the socio-technical information needs for decision-makers and planners in rural development
•	Utilise number of techniques and models supporting planning rural energy
•	Design, import and interpret different types of surveys to collect relevant information and analyse them to be an input to planners

MATERIALS AND METHODS

Bio-wastes development: Waste is defined as an unwanted material that is being discarded. Waste includes items being taken for further use, recycling or reclamation. Waste produced at household, commercial and industrial premises are control waste and come under the waste regulations. Waste Incineration Directive (WID) emissions limit values will favour efficient, inherently cleaner technologies that do not rely heavily on abatement (Omer, 2000, 2005a, b). For existing plant, the requirements are likely to lead to improved control of:

•	NOx emissions by the adoption of infurnace combustion control and abatement techniques
•	Acid gases by the adoption of abatement techniques and optimisation of their control
•	Particulate control techniques and their optimisation, e.g., of bag filters and electrostatic precipitators

Bioenergy is biomass energy made available from agricultural materials (crops, trees, etc.) and animal residues/wastes (dung) derived from biological sources. In its most narrow sense, it is a synonym to biofuel which is fuel derived from biological sources. It is usually meant as fuel produced from organic crops, most of which are grown, specifically to be used as fuel.

Energy produced from renewable biomass (plant derived organic matter) resources can yield electricity, liquid, solid and gaseous fuels, heat, chemicals and other materials.

Bioenergy is energy from the sun stored in materials of biological origin (Aroyeun et al., 2009; Vilinac, 2008; United Nations, 2004). This includes plant matter and animal waste known as biomass. Plants store solar energy through photosynthesis in cellulose and lignin whereas animals store energy as fats.

When burned, these sugars break down and release energy exothermically, releasing carbon dioxide, heat and steam. The by-products of this reaction can be captured and manipulated to create power, commonly called bioenergy (United Nations, 2002a, b).

Biomass is considered renewable because the carbon is taken out of the atmosphere and replenished more quickly than the millions of years required for fossil fuels to form.

The use of biofuels to replace fossil fuels contributes to a reduction in the overall release of carbon dioxide into the atmosphere and hence, helps to tackle global warming (Brain and Mark, 2007; Crisp et al., 1988; Dieng and Wang, 2001; UNEP, 2003). The range of waste treatment technologies that are tailored to produce bioenergy is growing. There are a number of key areas of bioenergy from wastes including (but not limited to) biogas, biofuels and bioheat.

When considering using bioenergy, it is important to take into account the overall emission of carbon in the process of electricity production. The biomass energy resources are particularly suited for the provision of rural power supplies and a major advantage is that equipment such as flat plate solar driers, wind machines, etc. can be constructed using local resources and without the high capital cost of more conventional equipment. Further advantage results from the feasibility of local maintenance and the general encouragement such local manufacture gives to the build up of small scale rural based industry. Table 1 shows the energy sources available for poor people.

Currently, the non-commercial fuels wood, crop residues and animal dung are used in large amounts in the rural areas of developing countries, principally for heating and cooking; the method of use is highly inefficient. Table 2 shows some renewable applications.

Table 3 shows the most important of energy needs (Omer, 2006, 2007c-e) for household. Considerations when selecting power plant include the following:

•	Power level whether continuous or discontinuous
•	Cost-initial cost, total running cost including fuel, maintenance and capital amortised over life
•	Complexity of operation
•	Maintenance and availability of spares
•	Life
•	Suitability for local manufacture

Table 1:	Sources of energy for poor people (Zuatori, 2005; Omer, 2004, 2008f-h; Lund et al., 2005)

Table 2:	Energy applications (Omer, 2007a, b, 2008a, b)

Table 3:	Energy needs in rural areas (Omer, 2008c)

The internal combustion engine is a major contributor to rising CO₂ emissions worldwide and some pretty dramatic new thinking is needed if the planet is to counter the effects. With its use increasing in developing world economies, there is something to be said for the argument that the vehicles we use to help keep the inner-city environments free from waste, litter and grime should be at the forefront of developments in low-emissions technology.

Materials handled by waste management companies are becoming increasingly valuable. Those responsible for the security of facilities that treat waste or manage scrap will testify to the precautions needed to fight an ongoing battle against unauthorised access by criminals and crucially to prevent the damage they can cause through theft, vandalism or even arson. Of particular concern is the escalating level of metal theft, driven by various factors including the demand for metal in rapidly developing economies such as India and China.

Fig. 1:	Biomass utilistation concept

Table 4:	Methods of energy conversion (Omer, 2008d-f)

Table 4 showed methods of energy conversion. There is a need for greater attention to be devoted to this field in the development of new designs, the dissemination of information and the encouragement of its use.

International and government bodies and independent organisations all have a role to play in biomass energy technologies.

Environment has no prcise limits because it is in fact a part of everything. Indeed, environment is as anyone probably already knows not only flowers blossoming or birds singing in the spring or a lake surrounded by beautiful mountains.

It is also human settlements, the places where people live, work, rest, the quality of the food they eat, the noise or silence of the street they live in. Environment is not only the fact that the cars consume a good deal of energy and pollute the air but also that we often need them to go to work and for hoildays.

Obviously man uses energy just as plants, bactria, mishrooms, bees, fish and rats do (Fig. 1). Man largely uses solar energy-food, hydropower, wood and thus participates harmoniously in the natural flow of energy through the environment. But man also uses oil, gas, coal and nuclear power. By using such sources of energy, man is thus, modifying his environment. Economic importance of environmental issue is increasing and new technologies are expected to reduce pollution derived both from productive processes and products with costs that are still unknown.

This is due to market uncertainty, weak appropriability regime, lack of a dominant design and difficulties in reconfiguring organisational routines. The degradation of the global environment is one of the most serious energy issues. Various options are proposed and investigated to mitigate climate change, acid rain or other environmental problems.

RESULTS AND DISCUSSION

Energy use and the environment: Energy use is one of several essential components for developing countries:

•	The overall situation and the implications of increased energy use in the future
•	The problem of the provision of power in rural areas including the consideration of energy resources and energy conversion

In addition to the drain on resources such an increase in consumption consequences together with the increased hazards of pollution and the safety problems associated with a large nuclear fission programmes.

This is a disturbing prospect. It would be equally unacceptable to suggest that the difference in energy between the developed and developing countries and prudent for the developed countries to move towards a way of life which whilst maintaining or even increasing quality of life, reduce significantly the energy consumption per capita. Such savings can be achieved in a number of ways:

•	Improved efficiency of energy use for example better thermal insulation, energy recovery and total energy

Conservation of energy resources by design for long life and recycling rather than the short life throwaway product and systematic replanning of the way of life for example in the field of transport. The aim of any modern biomass energy systems must be:

•	To maximise yields with minimum inputs
•	Utilisation and selection of adequate plant materials and processes
•	Optimum use of land, water and fertiliser
•	Create an adequate infrastructure and strong R and D base

Furthermore, investigating the potential to make use of more and more of its waste. Household waste, vegetable market waste and waste from the cotton stalks, leather and pulp and paper industries can be used to produce useful energy either by direct incineration, gasification, digestion (biogas production), fermentation or cogeneration. Therefore, effort has to be made to reduce fossil energy use and to promote green energies, particularly in the building sector.

Energy use reductions can be achieved by minimising the energy demand by rational energy use by recovering heat and the use of more green energies. Energy ratio is defined as the ratio of: energy content of the food product/energy input to produce the food.

Combined Heat and Power (CHP): The atmospheric emissions of fossil fuelled installations are mostly aldehydes, carbon monoxide, nitrogen oxides, sulpher oxides and particles (i.e., ash) as well as carbon dioxide. Table 5 shows estimates include not only the releases occurring at the power plant itself but also cover fuel extraction and treatment as well as the storage of wastes and the area of land required for operation (Table 6).

A review of the potential range of recyclables is shown in Table 7. Combined Heat and Power (CHP) installations are quite common in greenhouses which grow high-energy, input crops (e.g., salad vegetables, pot plants, etc.).

Scientific assumptions for a short-term energy strategy suggest that the most economically efficient way to replace the thermal plants is to modernise existing power plants to increase their energy efficiency and to improve their environmental performance. However, utilisation of wind power and the conversion of gas-fired CHP plants to biomass would significantly reduce the dependence on imported fossil fuels.

Although, a lack of generating capacity is forecast in the long-term, utilisation of the existing renewable energy potential and the huge possibilities for increasing energy efficiency are sufficient to meet future energy demands in the short-term.

A total shift towards a sustainable energy system is a complex and long process but is one that can be achieved within a period of about 20 years.

Implementation will require initial investment, long term national strategies and action plans. However, the changes will have a number of benefits including: a more stable energy supply than at present and major improvement in the environmental performance of the energy sector and certain social benefits (Fig. 2). A vision used a methodology and calculations based on computer modelling that utilised:

•	Data from existing governmental programmes
•	Potential renewable energy sources and energy efficiency improvements
•	Assumptions for future economy growth
•	Information from studies and surveys on the recent situation in the energy sector

The main advantages are related to energy, agriculture and environment problems are foreseeable both at national level and at worldwide level and can be summarised as follows:

•	Reduction of dependence on import of energy and related products
•	Reduction of environmental impact of energy production (greenhouse effect, air pollution, waste degradation)
•	Substitution of food crops and reduction of food surpluses and of related economic burdens
•	Utilisation of marginal lands and of set aside lands and reduction of related socio-economic and environmental problems (soil erosion, urbanisation, landscape deterioration, etc.)
•	Development of new know-how and production of technological innovation

Table 5:	Annual GHG emissions from different sources of power plants (Omer, 2008e)

Table 6:	Energy consumption per population (Omer, 2008f)

Fig. 2:	Schematic process flowsheet

Table 7:	Summary of material recycling practices in the construction sector (Robinson, 2007)

In Some countries, a wide range of economic incentives and other measures are already helping to protect the environment. These include:

•	Taxes and user charges that reflect the costs of using the environment, e.g., pollution taxes and waste disposal charges
•	Subsidies, credits and grants that encourage environmental protection
•	Deposit-refund systems that prevent pollution on resource misuse and promote product reuse or recycling
•	Financial enforcement incentives, e.g., fines for non-compliance with environmental regulations
•	Tradable permits for activities that harm the environment

District Heating (DH) also known as community heating can be a key factor to achieve energy savings, reduce CO₂ emissions and at the same time provide consumers with a high quality heat supply at a competitive price. DH should generally only be considered for areas where the heat density is sufficiently high to make DH economical.

In countries, like Denmark DH may today be economical even to new developments with lower density areas due to the high level of taxation on oil and gas fuels combined with the efficient production of DH (Sims, 2007). To improve the opportunity for DH local councils can adapt the following plan:

•	Analyse the options for heat supply during local planning stage
•	In areas where DH is the least cost solution, it should be made part of the infrastructure just like for instance water and sewage connecting all existing and new buildings
•	Where possible all public buildings should be connected to DH
•	The government provides low interest loans or funding to minimise conversion costs for its citizens
•	Use other powers for instance national legislation to ensure the most economical development of the heat supply and enable an obligation to connect buildings to a DH scheme

Denmark has broadly seen three scales of CHP which where largely implemented in the following chronological order (Omer and Fadalla, 2003):

•	Large scale CHP in cities (>50 MWe)
•	Small (5 kWe–5 MWe) and medium scale (5-50 MWe)
•	Industrial and small scale CHP

Most of the heat is produced by large CHP plants (gas-fired combined cycle plants using natural gas, biomass, waste or biogas). DH is energy efficient because of the way the heat is produced and the required temperature level is an important factor. Buildings can be heated to temperature of 21°C and Domestic Hot Water (DHW) can be supplied with a temperature of 55°C using energy sources that are most efficient when producing low temperature levels (<95°C) for the DH water. Most of these heat sources are CO₂ neutral or emit low levels. Only a few of these sources are available to small individual systems at a reasonably cost whereas DH schemes because of the plant’s size and location can have access to most of the heat sources and at a low cost. Low temperature DH with return temperatures of around 30-40°C can utilise the following heat sources:

•	Efficient use of CHP by extracting heat at low Calorific Value (CV)
•	Efficient use of biomass or gas boilers by condensing heat in economisers (Table 8)
•	Efficient utilisation of geothermal energy
•	Direct utilisation of excess low temperature heat from industrial processes
•	Efficient use of large-scale solar heating plants

Heat tariffs may include a number of components such as: a connection charge, a fixed charge and a variable energy charge. Also, consumers may be incentivised to lower the return temperature. Hence, it is difficult to generalise but the heat practice for any DH company no matter what the ownership structure can be highlighted as follows:

•	To develop and maintain a development plan for the connection of new consumers
•	To evaluate the options for least cost production of heat
•	To implement the most competitive solutions by signing agreements with other companies or by implementing own investment projects
•	To monitor all internal costs and with the help of benchmarking, improve the efficiency of the company
•	To maintain a good relationship with the consumer and deliver heat supply services at a sufficient quality

Installing DH should be pursued to meet the objectives for improving the environment through the improvement of energy efficiency in the heating sector. At the same time, DH can serve the consumer with a reasonable quality of heat at the lowest possible cost. The variety of possible solutions combined with the collaboration between individual companies, the district heating association, the suppliers and consultants can as it has been in Denmark be the way forward for developing DH in the United Kingdom.

Biomass utilisation and development of conversion technologies: Sustainable energy is energy that in its production or consumption has minimal negative impacts on human health and the healthy functioning of vital ecological systems including the global environment.

It is an accepted fact that renewable energy is a sustainable form of energy which has attracted more attention during recent years. A great amount of renewable energy potential, environmental interest as well as economic consideration of fossil fuel consumption and high emphasis of sustainable development for the future will be needed.

Explanations for the use of inefficient agricultural environmental polices include: the high cost of information required to measure benefits on a site specific basis, information asymmetries between government agencies and farm decision makers that result in high implementation costs, distribution effects and political considerations (Omer, 2007a).

Table 8:	Final energy projections including biomass (Mtoe) (Omer, 2007a)

Achieving the aim of agric environment schemes through:

•	Sustain the beauty and diversity of the landscape
•	Improve and extend wildlife habitats
•	Conserve archaeological sites and historic features
•	Improve opportunities for countryside enjoyment
•	Restore neglected land or features
•	Create new habitats and landscapes

Efficient bio-energy use and improvement: The data required to perform the trade-off analysis simulation can be classified according to the divisions shown in Table 9, the overall system or individual plants and the existing situation or future development. The effective economic utilisations of these resources are shown in Table 10 but their use is hindered by many problems such as those related to harvesting, collection and transportation besides the photo sanitary control regulations.

Biomass energy is experiencing a surge in interest stemming from a combination of factors, e.g., greater recognition of its current role and future potential contribution as a modern fuel, global environmental benefits, its development and entrepreneurial opportunities, etc.

Possible routes of biomass energy development are shown in Table 11. The key to successful future appears to lie with successful marketing of the treatment by products.

There is also potential for using solid residue in the construction industry as a filling agent for concrete. Research suggests that the composition of the residue locks metals within the material thus, preventing their escape and any subsequent negative effect on the environment. The use of biomass through direct combustion has long been and still is the most common mode of biomass utilisation as shown in Table 9-11.

Table 9:	Classifications of data requirements

Examples for dry (thermo-chemical) conversion processes are charcoal making from wood (slow pyrolysis), gasification of forest and agricultural residues (fast pyrolysis this is still in demonstration phase) and of course, direct combustion in stoves, furnaces, etc. Wet processes require substantial amount of water to be mixed with the biomass. Biomass technologies include:

•	Briquetting
•	Improved stoves
•	Biogas
•	Improved charcoal
•	Carbonisation
•	Gasification

The increased demand for gas and petroleum, food crops, fish and large sources of vegetative matter mean that the global harvesting of carbon has in turn intensified. It could be said that mankind is mining nearly everything except its waste piles. It is simply a matter of time until the significant carbon stream present in municipal solid waste is fully captured.

Table 10:	Effective biomass resource utilisation (Omer, 2009b)

Table 11:	Agricultural residues routes for development

In the meantime, the waste industry needs to continue on the pathway to increased awareness and better optimised biowaste resources.

Optimisation of waste carbon may require widespread regulatory drivers (including strict limits on the landfilling of organic materials), public acceptance of the benefits of waste carbon products for soil improvements/crop enhancements and more investment in capital facilities. In short, a significant effort will be required in order to capture a greater portion of the carbon stream and put it to beneficial use.

From the standpoint of waste practitioners, further research and pilot programmes are necessary before the available carbon in the waste stream can be extracted in sufficient quality and quantities to create the desired end products. Other details need to be ironed out too including measurement methods, diversion calculations, sequestration values and determination of acceptance contamination thresholds.

Briquette: Charcoal stoves are very familiar to African society. As for the stove technology, the present charcoal stove can be used and can be improved upon for better efficiency. This energy term will be of particular interest to both urban and rural households and all the income groups due to the simplicity, convenience and lower air polluting characteristics.

However, the market price of the fuel together with that of its end-use technology may not enhance its early high market penetration especially in the urban low income and rural households.

Briquetting is the formation of a char (an energy-dense solid fuel source) from otherwise wasted agricultural and forestry residues. One of the disadvantages of wood fuel is that it is bulky with a low energy density and is therefore enquire to transport. Briquette formation allows for a more energy-dense fuel to be delivered thus, reducing the transportation cost and making the resource more competitive. It also adds some uniformity which makes the fuel more compatible with systems that are sensitive to the specific fuel input.

Improved cook stoves: Traditional wood stoves can be classified into four types: three stone, metal cylindrical shaped, metal tripod and clay type.

Another area in which rural energy availability could be secured where woody fuels have become scarce are the improvements of traditional cookers and ovens to raise the efficiency of fuel saving. Also by planting fast growing trees to provide a constant fuel supply. The rural development is essential and economically important since, it will eventually lead to better standards of living, people’s settlement and self sufficient in the following:

•	Food and water supplies
•	Better services in education and health care
•	Good communication modes

Biogas: Biogas technology can not only provide fuel but is also important for comprehensive utilisation of biomass forestry, animal husbandry, fishery, agricultural economy, protecting the environment, realising agricultural recycling as well as improving the sanitary conditions in rural areas.

The introduction of biogas technology on wide scale has implications for macro planning such as the allocation of government investment and effects on the balance of payments. Factors that determine the rate of acceptance of biogas plants such as credit facilities and technical backup services are likely to have to be planned as part of general macro-policy as do the allocation of research and development funds (Omer, 2007b).

Bacteria form biogas during anaerobic fermentation of organic matters. The degradation is very complex process and requires certain environmental conditions as well as different bacteria population. The complete anaerobic fermentation process is briefly described blew as shown in Table 12 and Fig. 3. Biogas is a relatively high-value fuel that is formed during anaerobic degradation of organic matter.

The process has been known and put to work in a number of different applications during the past 30 years for rural needs such as in (Pernille, 2004) food security, water supply, health cares, education and communications. Biogas is a generic term for gases generated from the decomposition of organic material.

As the material breaks down, methane (CH₄) is produced as shown in Fig. 3. Sources that generate biogas are numerous and varied. These include landfill sites, wastewater treatment plants and anaerobic digesters. Landfills and wastewater treatment plants emit biogas from decaying waste.

To date, the waste industry has focused on controlling these emissions to the environment and in some cases, tapping this potential source of fuel to power gas turbines thus, generating electricity. The primary components of landfill gas are methane (CH₄), carbon dioxide (CO₂) and nitrogen (N₂). The average concentration of methane is ~45%, CO₂ is ~36% and nitrogen is ~18%.

Table 12:	Anaerobic degradation of organic matter (Bacaoui et al., 1998)

Fig. 3:	Biomass production process

Other components in the gas are oxygen (O₂), water vapour and trace amounts of a wide range of Non Methane Organic Compounds (NMOCs).

For hot water and heating, renewables contributions come from biomass power and heat, geothermal direct heat, ground source heat pumps and rooftop solar hot water and space heating systems. Solar assisted cooling makes a very small but growing contribution. When it comes to the installation of large amounts of PV, the cities have several important factors in common. These factors include:

•	A strong local political commitment to the environment and sustainability
•	The presence of municipal departments or offices dedicated to the environment, sustainability or renewable energy
•	Information provision about the possibilities of renewables
•	Obligations that some or all buildings include renewable energy

During the last decades thousands of biogas units were built all over the world in different areas, producing methane CH₄ for cooking, water pumping and electricity generation. In order not to repeat successes in depth on local conditions and conscientious planning urged (D’Apote, 1998). The goals should be achieved through:

•	Review and exchange of information on computer models and manuals useful for economic evaluation of biogas from biomass energy
•	Exchange and compile information on methodologies for economic analysis and results from type causes
•	Investigation of the constraints on the implementation of the commercial supply of biogas energy
•	Investigation of the relations between supplies and demand for the feedstock from different industries
•	Documentation of the methods and principles for evaluation of indirect consequences as effects on growth, silvicultural treatment and employment

Biogas is a mixture containing predominantly methane (50-65% by volume) and carbon dioxide and in a natural setting, it is formed in swamps and anaerobic sediments, etc., due to its high methane concentration, biogas is a valuable fuel. Wet (40-95%) organic materials with low lignin and cellulose content are generally suitable for anaerobic digestion. A key concern is that treatment of sludge tends to concentrate heavy metals, poorly biodegradable trace organic compounds and potentially pathogenic organisms (viruses, bacteria and the like) present in wastewaters.

These materials can pose a serious threat to the environment. When deposited in soils, heavy metals are passed through the food chain, first entering crops and then animals that feed on the crops and eventually human beings to whom they appear to be highly toxic. In addition, they also leach from soils, getting into groundwater and further spreading contamination in an uncontrolled manner.

European and American markets aiming to transform various organic wastes (animal farm wastes, industrial and municipal wastes) into 2 main by-products:

•	A solution of humic substances (a liquid oxidate)
•	A solid residue

In the past two decades, the world has become increasingly aware of the depletion of fossil fuel reserves and the indications of climatic changes based on carbon dioxide emissions.

Therefore, extending the use of renewable resources, efficient energy production and the reduction of energy consumption are the main goals to reach a sustainable energy supply. Renewable energy sources include water and wind power, solar and geothermal energy as well as energy from biomass.

The technical achievability and the actual usage of these energy sources are different around Europe but biomass is seen to have a great potential in many of them. An efficient method for the conversion of biomass to energy is the production of biogas by microbial degradation of organic matter under the absence of oxygen (anaerobic digestion). It is now possible to produce biogas at rural installation, upgrade it to bio-methane, feed it into the gas grid use it in a heat demand-controlled CHP and to receive revenues.

Improved forest and tree management: Dry cell batteries are a practical but expensive form of mobile fuel that is used by rural people when moving around at night and for powering radios and other small appliances. The high cost of dry cell batteries is financially constraining for rural households but their popularity gives a good indication of how valuable a versatile fuel like electricity is in rural area. Dry cell batteries can constitute an environmental hazard unless they are recycled in a proper fashion. Direct burning of fuel-wood and crop residues constitute the main usage of biomass as is the case with many developing countries.

However, the direct burning of biomass in an inefficient manner causes economic loss and adversely affects human health.

In order to address, the problem of inefficiency, research centres around the world have investigated the viability of converting the resource to a more useful form, namely solid briquettes and fuel gas (Fig. 4). Biomass resources play a significant role in energy supply in all developing countries.

Biomass resources should be divided into residues or dedicated resources, the latter including firewood and charcoal can also be produced from forest residues (Table 13).

Gasification: Gasification is based on the formation of a fuel gas (mostly CO and H₂) by partially oxidising raw solid fuel at high temperatures in the presence of steam or air. The technology can use wood chips, groundnut shells, sugar cane bagasse and other similar fuels to generate capacities from 3-100 kW. Three types of gasifier designs have been developed to make use of the diversity of fuel inputs and to meet the requirements of the product gas output (degree of cleanliness, composition, heating value, etc.).

The requirements of gas for various purposes and a comparison between biogas and various commercial fuels in terms of calorific value and thermal efficiency are shown in Table 14.

Sewage sludge is rich in nutrients such as nitrogen and phosphorous. It also contains valuable organic matter, useful for remediation of depleted or eroded soils. This is why untreated sludge has been used for many years as a soil fertiliser and for enhancing the organic matter of soil.

A key concern is that treatment of sludge tends to concentrate heavy metals, poorly biodegradable trace organic compounds and potentially pathogenic organisms (viruses, bacteria and the like) present in wastewaters.

These materials can pose a serious threat to the environment. When deposited in soils, heavy metals are passed through the food chain, first entering crops and then animals that feed on the crops and eventually human beings to whom they appear to be highly toxic.

In addition, they also leach from soils, getting into groundwater and further spreading contamination in an uncontrolled manner. Biomass is a raw material that has been utilised for a wide variety of tasks since, the dawn of civilisation.

Table 13:	Biomass residues and current use

Table 14:	Comparison of various fuels (Bacaoui et al., 1998)

Fig. 4:	Biomass resources from several sources are converted into a range of products for use by transport, industry and building secorts (Pernille, 2004)

Important as a supply of fuel in the third world, biomass was also the first raw material in the production of textiles.

The gasification of the carbon char with steam can make a large difference to the surface area of the carbon. The corresponding stream gasification reactions are endothermic and demonstrate how the steam reacts with the carbon char (D’ Apote, 1998):

(1)

(2)

(3)

Agricultural wastes are abundantly available globally and can be converted to energy and useful chemicals by a number of microorganisms.

The organic matter was biodegradable to produce biogas and the variation show a normal methanogene bacteria activity and good working biological process as shown in Fig. 5 and 6.

The success of promoting any technology depends on careful planning, management, implementation, training and monitoring. Main features of gasification project are:

•	Networking and institutional development/ strengthening
•	Promotion and extension
•	Construction of demonstration projects
•	Research and development, training and monitoring

Fig. 5:	Organic matters before and after treatment in digester

An easier situation can be found when looking at the ecological effects of different biogas utilisation pathways. The key assumptions for the comparison of different biogas utilisation processes are:

•	Biogas utilisation in heat demand controlled gas engine supplied out of the natural gas grid with 500 kWeelectrical efficiency of 37.5%, thermal efficiency of 42.5% and a methane loss of 0.01
•	Biogas utilisation in a local gas engine, installed at the biogas plant with 500 kWe electrical efficiency of 37.5%, thermal efficiency of 42.5% and a methane loss of 0.5
•	Biogas production based on maize silage using a biogas plant with covered storage tank-methane losses were 1% of the biogas produced
•	Biogas upgrading with a power consumption 0.3 kWhe m-3 biogas-methane losses of 0.5

Fig. 6:	pH sludge before and after treatment in the digester

Energy and environmental problems: Technological progress has dramatically changed the world in a variety of ways. It has however, also led to developments of environmental problems which threaten man and nature.

During the past two decades, the risk and reality of environmental degradation have become more apparent. Growing evidence of environmental problems is due to a combination of several factors since the environmental impact of human activities has grown dramatically because of the sheer increase of world population, consumption, industrial activity, etc., throughout the 1970s most environmental analysis and legal control instruments concentrated on conventional effluent gas pollutants such as SO₂, NO_x, CO₂, particulates and CO (Table 15).

Recently, environmental concerns has extended to the control of micro or hazardous air pollutants which are usually toxic chemical substances and harmful in small doses as well to that of globally significant pollutants such as CO₂. Aside from advances in environmental science, developments in industrial processes and structures have led to new environmental problems.

Table 15:	EU criteria pollutant standards in the ambient air environment (Omer, 2009b)

Table 16:	Significant EU environmental directives in water, air and land environments (Omer, 2009c)

For example in the energy sector, major shifts to the road transport of industrial goods and to individual travel by cars has led to an increase in road traffic and hence a shift in attention paid to the effects and sources of NO_x and Volatile Organic Compound (VOC) emissions. Environmental problems span a continuously growing range of pollutants, hazards and ecosystem degradation over wider areas. The main areas of environmental problems are: major environmental accidents, water pollution, maritime pollution, land use and sitting impact, radiation and radioactivity, solid waste disposal, hazardous air pollutants, ambient air quality, acid rain, stratospheric ozone depletion and global warming (greenhouse effect, global climatic change) (Table 16).

Table 15 EU criteria pollutant standards in the ambient air. The four more important types of harm from man’s activities are global warming gases, ozone destroying gases, gaseous pollutants and microbiological hazards (Table 17). The earth is some 30°C warmer due to the presence of gases but the global temperature is rising.

Fig. 7:	Global mean temperature changes over the period of 1990-2100 and 1990-2030

Table 17:	The external environment (Omer, 2009d-f)

This could lead to the sea level rising at the rate of 60 mm each decade with the growing risk of flooding in low-lying areas (Fig. 7). At the United Nations Earth Summit at Rio in June 1992, some 153 countries agreed to pursue sustainable development (D’ Apote, 1998). A main aim was to reduce emission of carbon dioxide and other GHGs. Reduction of energy use in buildings is a major role in achieving this. Carbon dioxide targets are proposed to encourage designers to look at low energy designs and energy sources.

Problems with energy supply and use are related not only to global warming that is taking place due to effluent gas emission mainly CO₂ but also to such environmental concerns as air pollution, acid precipitation, ozone depletion, forest destruction and emission of radioactive substances. These issues must be taken into consideration simultaneously if humanity is to achieve a bright energy future with minimal environmental impacts. Much evidence exists which suggests that the future will be negatively impacted if humans keep degrading the environment (Table18).

During the past century, global surface temperature have increased at a rate near 0.6°C/century and the average temperature of the Atlantic, Pacific and Indian oceans (covering 72% of the earth surface) have risen by 0.06°C since 1995.

Fig. 8:	Comprison of thermal biomass usage options, CHP displacing natural gas as a heat source

Table 18:	Global emissions of the top fourteen nations by total CO2 volume (billion of ton)

Global temperatures in 2001 were 0.52°C above the long-term 1880-2000 average (the 1880-2000 annually averaged combined land and ocean temperature is 13.9°C).

Also, according to the USA Department of Energy, world emissions of carbon are expected to increase by 54% above 1990 levels by 2015 making the earth likely to warm 1.7-4.9°C over the period 1990-2100 as shown in Fig. 8. Such observation and others demonstrate that interests will likely increase regarding energy related environment concerns and that energy is one of the main factors that must be considered in discussions of sustainable development.

•	Large Steam Power (LSP)
•	Small Steam Power (SSP)
•	Brayton Cycle Power (BCP)
•	Bio-oil Conversion Power (B-CP)
•	Gasification Power (GP)
•	Small Steam CHP (SSCHP)
•	Turboden Cycle CHP (TCCHP)
•	Entropic Cycle CHP (ECCHP)

Lifecycle analysis of several ethanol feedstocks shows the emission displacement per ton of feedstock is highest for corn stover and switchgrass (about 0.65 ton of CO₂ ton^-1 of feedstock) and lowest for corn (about 0.5 ton). Emissions due to cultivation and harvesting of corn and wheat are higher than those for lignocellulosics and although, the latter have a far higher process energy requirement (Fig. 8). GHG emissions are lower because this energy is produced from biomass residue which is carbon neutral.

Sulphur in fuels and its environmental consequences: Coal is formed from the deposition of plant material according to the peat to anthracite series:

Vegetation → peat
→ Lignite (brown coal)
→ Sub-bituminous coal
→ Bituminous coal → anthracite

Organic sulphur is bonded within the organic structure of the coal in the same way that sulphur is bonded in simple thio-organics, e.g., thiols. Sulphur contents of coals vary widely and Table 19 shows some examples.

Control of SO₂ emissions: Emissions will also of course, occur from petroleum-based or shale-based fuels and in heavy consumption such as in steam raising. There will frequently be a need to control SO₂ emissions. There are broadly speaking, three ways of achieving such control:

•	Pre-combustion control involves carrying out a degree of desulphurisation of the fuel
•	Combustion control incorporating into the combustion system something capable of trapping SO2
•	Post-combustion control removing SO2 from the flue gases before they are discharged into the atmosphere

Table 20 shows brief details of an example of each.

The control of NO_x release by combustion processes: Emission of nitrogen oxides is a major topic in fuel technology. It has to be considered even in the total absence of fuel nitrogen if the temperature is high enough for thermal No_x as it is in very many industrial applications. The burnt gas from the flame is recirculated in two ways:

•	Internally by baffling and restricting flow of the burnt gas away from the burner, resulting in flame re-entry of part of it
•	Externally by diverting >10% of the flue gas back into the flame

Table 19:	Representative sulphur contents of coals (Omer, 2009e)

Table 20:	Examples of SO2 control procedures

Some of the available control procedures for particles are shown in Table 21. Several definitions of sustainable development have been put forth including the following common one: development that meets the needs of the present without compromising the ability of future generations to meet their own needs. A recent World Energy Council (WEC) study found that without any change in our current practice, the world energy demand in 2020 would be 50-80% >1990 levels. According to a recent USA Department of Energy (DoE) report, annual energy demand will increase from a current capacity of 363-750 million kW by 2020.

The world’s energy consumption today is estimated to 22 billion kWh year^-1, 53 billion kWh by 2020. Such ever-increasing demand could place significant strain on the current energy infrastructure and potentially damage world environmental health by CO, CO₂, SO₂, NO_x effluent gas emissions and global warming.

Achieving solutions to environmental problems that we face today requires long-term potential actions for sustainable development. In this regards, renewable energy resources appear to be the one of the most efficient and effective solutions since, the intimate relationship between renewable energy and sustainable development. More rational use of energy is an important bridge to help transition from today’s fossil fuel dominated world to a world powered by non-polluting fuels and advanced technologies such as Photovoltaic (PV) and Fuel Cells (FC).

Growing concerns about social and environmental sustainability have led to increased interest in planning for the energy utility sector because of its large resource requirements and production of emissions. A number of conflicting trends combine to make the energy sector a major concern, even though a clear definition of how to measure progress toward sustainability is lacking.

Table 21:	Particle control techniques

These trends include imminent competition in the electricity industry, global climate change, expected long-term growth in population and pressure to balance living standards (including per capital energy consumption). Designing and implementing a sustainable energy sector will be a key element of defining and creating a sustainable society.

In the electricity industry, the question of strategic planning for sustainability seems to conflict with the shorter time horizons associated with market forces as deregulation replaces vertical integration. Sustainable low-carbon energy scenarios for the new century emphasise the untapped potential of renewable resources. Rural areas can benefit from this transition.

The increased availability of reliable and efficient energy services stimulates new development alternatives. It is concluded that renewable environmentally friendly energy must be encouraged, promoted, implemented and demonstrated by full-scale plant especially for use in remote rural areas. This is the step in a long journey to encourage a progressive economy which continues to provide us with high living standards but at the same time helps reduce pollution, waste mountains, other environmental degradation and environmental rationale for future policy-making and intervention to improve market mechanisms. This vision will be accomplished by: decoupling economic growth and environmental degradation.

The basket of indicators illustrated shows the progress being made. Decoupling air and water pollution from growth, making good headway with CO₂ emissions from energy and transport.

The environmental impact of the own individual behaviour is more closely linked to consumption expenditure than the economy as a whole. Focusing policy on the most important environmental impacts associated with the use of particular resources, rather than on the total level of all resource use. Increasing the productivity of material and energy use that are economically efficient by encouraging patterns of supply and demand which are more efficient in the use of natural resources.

The aim is to promote innovation and competitiveness. Investment in areas like energy efficiency, water efficiency and waste minimisation. Encouraging and enabling active and informed individual and corporate consumers.

Wastes: Waste is defined as an unwanted material that is being discarded. Waste includes items being taken for further use, recycling or reclamation. Waste produced at household, commercial and industrial premises are control waste and come under the waste regulations.

Waste Incineration Directive (WID) emissions limit values will favour efficient, inherently cleaner technologies that do not rely heavily on abatement. For existing plant, the requirements are likely to lead to improved control of:

•	NOx emissions by the adoption of infurnace combustion control and abatement techniques
•	Acid gases by the adoption of abatement techniques and optimisation of their control
•	Particulate control techniques and their optimisation, e.g., of bag filters and electrostatic precipitators

The waste and resources action programme has been working hard to reduce demand for virgin aggregates and market uptake of recycled and secondary alternatives. The programme targets are:

•	To deliver training and information on the role of recycling and secondary aggregates in sustainable construction for influences in the supply chain and
•	To develop a promotional programme to highlight the new information on websites

CONCLUSION

The adoption of green or sustainable approaches to the way in which society is run is seen as an important strategy in finding a solution to the energy problem. The key factors to reducing and controlling CO₂ which is the major contributor to global warming are the use of alternative approaches to energy generation and the exploration of how these alternatives are used today and may be used in the future as green energy sources. Even with modest assumptions about the availability of land, comprehensive fuel-wood farming programmes offer significant energy, economic and environmental benefits.

These benefits would be dispersed in rural areas where they are greatly needed and can serve as linkages for further rural economic development. The nations as a whole would benefit from savings in foreign exchange, improved energy security and socio-economic improvements. With a nine-fold increase in forest plantation cover, a nation’s resource base would be greatly improved.

The international community would benefit from pollution reduction, climate mitigation and the increased trading opportunities that arise from new income sources. The non-technical issues which have recently gained attention include.

Environmental and ecological factors e.g., carbon sequestration, reforestation and revegetation. Renewables as a CO₂ neutral replacement for fossil fuels. Greater recognition of the importance of renewable energy, particularly modern biomass energy carriers at the policy and planning levels. Greater recognition of the difficulties of gathering good and reliable renewable energy data and efforts to improve it. Studies on the detrimental health efforts of biomass energy particularly from traditional energy users.

Biogas technology can not only provide fuel but also important for comprehensive utilisation of biomass forestry, animal husbandry, fishery, evoluting the agricultural economy, protecting the environment, realizing agricultural recycling as well as improving the sanitary conditions in rural areas. The biomass energy, one of the important options which might gradually replace the oil in facing the increased demand for oil and may be an advanced period in this century. Any county can depend on the biomass energy to satisfy part of local consumption.

Development of biogas technology is a vital component of alternative rural energy programme whose potential is yet to be exploited. A concerted effect is required by all if this has to realise. The technology will find ready use in domestic, farming and small-scale industrial applications.

Support biomass research and exchange experiences with countries that are advanced in this field. In the meantime, the biomass energy can help to save exhausting the oil wealth.