An. 3. Enc. Energ. Meio Rural 2003
The role of biomass energy in rural development
Kings College London, Division of Life Sciences, Waterloo Campus (FWB), London SE1 8WA, Tel. + (44-02) 7848 40 84
Bioenergy is often the main source of energy in many developing countries. It currently represents about 14% of the world's energy supply (e.g.55EJ) and potentially as much as 450EJ by mid 21st Century. Changes in the energy supply matrix present many opportunities and challenges for bioenergy production and use. A major challenge is to provide people with what they want e.g. clean, cheap and efficient energy such as electricity, in an environmentally acceptable manner.
Bioenergy and rural development are intrinsically intertwined. By providing energy at local level, bioenergy can make a significant contribution to social and economic development in rural areas. Farmers have demonstrated that they can produce far more food (and energy) if they are given the opportunity. To achieve that, they need clear market incentives, availability of capital, energy, skills, credit, etc. The increased use of bioenergy will also bring many environmental benefits. However, bioenergy should not be regarded as the panacea for solving agricultural and energy problems in the rural areas, but as an activity that can play a significant role in improving agricultural productivity, energy supply, the environment and sustainability.
Keywords: biomass energy, rural development, food production, sustainability, CO2 abatement.
Bioenergy production and use is an important agricultural activity, particularly in many rural areas of developing countries (DLG), in addition of being often the largest source of energy. Currently biomass energy provides about 55EJ (equivalent to 25 million of barrels oil/day), or about 14% of the world's energy. In DLG as a whole bioenergy represents about 34% of the total energy, both in its traditional and modern forms, but in some countries it provides over 90% of total energy consumption. Modern bioenergy applications are increasing, particularly in industrial countries where in some cases it provides about 20% of the primary energy. Much of this energy originates from various types of agricultural and forest residues, although in the future various types of dedicated forestry/energy crops plantations are expected to provide a much larger proportion.
A major challenge facing the production and utilization of bioenergy will be to modernise to be able to provide the sort of energy people want e.g. electricity, heating, liquid biofuels, etc, in an environmental acceptable manner. The foreseeing increase in biomass energy could have important repercussions for rural development e.g. by creating many new commercial opportunities, employment, etc. The availability of modern biomass energy carriers will stimulate social and economic development while at the same time making a significant positive contribution to the environment and sustainability.
2. OVERVIEW OF BIOMASS ENERGY
Biomass was the main source of energy until the early 20th century. It was only during the past few decades, the so-called "oil era" when biomass energy was relegated and largely ignored by policy makers and energy planners alike. Current trends indicate that the amount of bioenergy use remains stable in DLG (or even growing due to population growth), and a real increase in industrial uses particularly in the industrial countries e.g. EU and USA, mainly for environmental rather than purely energy reasons.
Biomass currently supplies about a third of the DLG' energy - varying from about 90% in countries like Nepal, Rwanda, Tanzania and Uganda, to 45% in India and 28% in China; examples in industrial countries are about 14% in Austria, 20% in Finland and 18% in Sweden. On a global basis, biomass contributes about 14% of the world's energy (55EJ or 25 M boe), offsetting 1.1 PgC of net CO2 emissions annually). The crucial questions are whether the two billion or more people who are now dependent on biomass for energy will actually decrease in numbers in the next century and what are the continuing consequences to development and environment (local and global) from this dependence if energy efficiency is not increased significantly(1).
Bioresources are potentially the world's largest and sustainable source of fuel and chemicals- a renewable resource comprising 220 billion oven dry tonnes (about 4,500 EJ) of annual primary production. The energy content of biomass on the earth's surface is the equivalent to about 36 x 1021 J. (2). However, the average coefficient of utilization of the incident photosynthesis active radiation by the entire flora of the earth is only about 0.27%.
Since the early 1990s the increasing interest in biomass for energy has been manifested in most energy scenarios showing biomass as a potentially major source of energy in the 21st century. Hoogwijk et al (3) have analyzed 17 of such scenarios which they classified into two categories: i) Research Focus (RF) and ii) Demand Driven (DD). The estimated potential of the RF varies from 67 EJ and 450 EJ for the period 2025-2050, and that of the DD from 28 EJ and 220 EJ during the same period. As share of the total final energy demand this lies between 7 and 27%. Residues are currently the main sources of bioenergy and this will continue to be the case in the short to medium term. In the long term, dedicated crops will play much greater role. This expected increase of biomass energy could have a significant impact for agriculture and rural development.
2.1 TRADITIONAL APPLICATIONS OF BIOENERGY.
Currently the main use of bioenergy in DLG is in its traditional forms. This is where the main problem lies because of the low combustion efficiency. Energy efficiency varies considerably e.g. from about 2% to 20%, compared to 65 to 80% (or even 90%) in industrial countries. Secondly, is the enormous waste of resources as a result of this low efficiency, and also the potentially serious environmental problems. These problems will have to be tackled head on from environmental, energy, sustainability and economic perspectives. Thus, the clear message is that bioenergy production and use must be modernised. Thirdly, is the inability of traditional bioenergy to provide the type of energy that most people want e.g. clean, cheap and efficient energy such as electricity, ethanol fuel, etc.
2.2 Modern applications of bioenergy.
Thus for biomass energy to have a future, it must be able to provide people with things they wants e.g. lighting, electricity, etc. In addition, there are enormous pressures on resource utilization, environment, etc, for better use of scarce resources which can only be best met by more efficient combustion technologies. Modern applications simply mean clean, convenient, efficient, reliable, economically, environmentally and sustainable sound applications. There exist already many mature technologies that can meet such criteria, which are not necessarily more expensive that fossil fuels if all costs are internalised.
A clear indication is the growing modern applications of biomass energy in the EU and USA. The EU has recently unveiled its proposals for renewable energy (RE). The draw law aims to double the proportion of RE from 6% to 12% of the primary energy supply by increasing the share of RE generated electricity from 14% to 22% by 2010. This new law represents a turning point. See Tables 1 & 2. (4).
For example, Austria had at the end of 1997, 359 biomass plants with an output of 483 MWe and currently nearly 0.6 million homes are heated by biomass energy. A program of research has permitted increase combustion efficiencies from 60% to almost 90% in the past decade alone.
In 1986 the Danish government embarked in a program of RE aiming at providing 35% of the country's primary energy by 2030. Today the country has 150 heating plants operating on woody biomass with about 450 MWe; there are about 80,000 wood-based and straw-based boilers in the country, plus a further 200 MWe of CHP. Denmark is a world's leader in large-scale biogas technology. It has 20 large centralized plants which in 1998 treated nearly 1.4 M tonnes of waste and produced over 50 M m3 of biogas, equivalent to 1166 TJ. Waste disposal is a major aim of biogas production in Denmark (5).
In 1998 Finland's energy consumption was 31 Mtoe of which about 25% was RE, mostly biomass. Finland's 1999 Action Plan for RE foresees an increased of at least 50% by 2010. Spain's new energy plan foresees a tenfold increased in the energy generated from biomass from the current 1,139 GWh to 13949 GWh by 2012.
In the USA about 4% of the primary energy comes from biomass; there are about 7000 MWe of biomass-based installed capacity, and 12% of the fuel market is supplied by ethanol from corn. These are just a few examples.
2.3 UTILIZATION OF RESIDUES.
Residues are a large and under-exploited potential energy resource, and represent many opportunities for better utilization, and thus deserves particular attention. However, there are a number of important factors which need to be addressed when considering the use of residues for energy. Firstly, there are many other alternative uses e.g. animal feed, erosion control, use as animal bedding; use as fertilisers (dung), etc. Secondly, there is the problem of agreeing on a common methodology for determining what is and what is not a recoverable residue e.g. estimates often vary by a factor of five. This is due, among other things, to variation in the amount of residue assumed necessary for maintaining soil organic, soil erosion control, efficiency in harvesting, losses, non- energy uses, etc.
2.3.1 AGRICULTURAL RESIDUES.
For the reasons explained above, it is necessary to remain cautious when dealing with agricultural residues, despite the many attempts carried out to estimate their energy potential. For example, Smil (6) has calculated that in the mid 1990s the amount of crop residues was between 3.5 to 4 Gt annually, with an energy content representing 65 EJ, or 1.5 Gt oil equivalent. On the other hand, Hall et al (7) estimated that using the world's major crops only (e.g. wheat, rice, maize, barley, and sugarcane), a 25% residue recovery rate could generate 38 EJ and offset between 350 to 460 Tg C/yr. There is no doubt that a large part of the residues are wasted, handled inappropriately, causing undesirable effects from an environmental, ecological and food production viewpoint. For example, Andreae (8) has estimated that over 2 Gt of agricultural residues are burned annually world-wide, while Smil (6) estimates are between 1.0 and 1.4 Gt, producing 1.1 and 1.7 Gt/yr of CO2. Paustian et al, (9) have estimated that crops residues could offset 220 to 320 Tg C based on assumptions for energy conversion and degree of substitution for fossil carbon.
2.3.2 FORESTRY RESIDUES.
Forestry residues obtained from sound forest management do not deplete the resource base, on the contrary, it can enhance and increase future productivity of forests. One of the difficulties is to estimate, with some degree of accuracy, the potential of residues that can be available for energy use on a national or regional basis, without more data on total standing biomass, plantation density, thinning and pruning practices, current use of residues, MAI, etc. Recoverable residues from forests have been estimated to have an energy potential of about 35 EJ/yr (10). A considerable advantage of these residues is that large part are generated by the pulp and paper and saw mill industries and thus could be readily available. Currently, a large proportion of such residues is used to generate energy in these industries, but there is no question that the potential is much greater.
2.3.3. LIVESTOCK RESIDUES.
The potential of energy from dung alone has been estimated at about 20 EJ worldwide (10). However, the variations are so large that figures are often meaningless. These variations can be attributed to a lack of a common methodology which is the consequence of variations in livestock type, location, feeding conditions, etc. In addition, it is questionable whether animal manure should be used as an energy source on a large scale, except in specific circumstances. This is because: i) its greater potential value for non-energy purposes e.g. it use as fertiliser may bring greater benefits to the farmer, ii) it is a poor fuel and people tend to shift to other better quality biofuels whenever possible, iii) the use of manure may be more acceptable when there are other environmental benefits e.g. the production of biogas in Denmark, because there are large surpluses of manure which, if applied in large quantities to the soil, represent a danger for agriculture and the environment, iv) environmental and health hazards which are much higher than other biofuels.
2.4 ENERGY CROPS.
It is difficult to predict at this stage what will be the future role of specifically grown biomass for energy purposes. This is, in many ways, a new concept for the farmer which has got to be fully accepted if large scale energy crops are to form an integral part of farming practices. Hall et al (7) estimated that as much 267 EJ/yr could be produced from biomass plantations alone
Currently there are in the world over 100 Mha of plantations. During the past decade over 40 Mha have been planted in developing countries, two-thirds in community woodlots, farms and small holdings, to provide industrial wood, environmental protection and energy. In the USA some 50,000 ha of agricultural land has been converted to woody plantations and in Sweden about 18,000 ha of willows for energy purposes. But little experience still exists with large-scale energy plantations. Exemptions are eucalyptus for charcoal production and ethanol from sugarcane in Brazil and with willows for heat and power generation in Sweden which, in any case, tend to follow traditional agricultural and forestry practices. (1)
The growing concern with the potential negative effects of large scale dedicated energy forestry/crops plantations has led to a considerable amount of effort to address these concerns which has resulted in the development of some "good practice guidelines" for the production and use of biomass for energy e.g. Austria, Sweden, UK and USA. These guidelines recognize the central importance of site-specific factors, and the breadth of social and environmental issues which should be taken into consideration.
3. BIOMASS ENERGY AND RURAL DEVELOPMENT.
The role of agriculture in energy production is lost in history. From early hunter-gathering to annual agriculture, plant products provided human food, fuel, fodder, building material, etc. The diverse use of biomass utilization is well represented in the so-called six Fs: "food, fuel, feed, feedstock, fibre, and fertiliser". Biomass was the main source of energy up to the early 20th century. Biomass energy has played and continues to play a major role in rural development. Indeed, in many rural areas of DLG bioenergy constitutes almost the sole source of energy. This role has gone, until recently, largely unrecognised in many parts of the world by politicians and energy planners alike.
Thus, what could be the implications of an enhanced role of bioenergy in the future for rural development, if current energy scenarios projections are correct?. The world is facing a future in which no single energy source is going to have a monopoly of supply, and in which energy efficiency and renewable energies should play a major role. The availability of modern biomass energy carriers could have major implications for modernising agriculture in many DLG which could be reflected in a sustainable increase in food production and economic growth and social development. Already the modernisation of bioenergy e.g. cogeneration of electricity from sugarcane bagasse in Brazil and India, production of biogas in Denmark, and improved stoves and biogas in China, is producing very positive effects.
Living conditions in rural areas are greatly affected by the amount and quality of available energy, which is currently a major limitation in many DLG. Increased energy use can be of any benefit only if it provides essential services e.g. cooking, lighting, heating, water pumping, transport, industrial uses, etc. Considering that about 2.5 billion people live in rural areas, this is a problem that cannot be ignored.
Bioenergy could play a significant role in a flexible and sustainable system where the supply of food, energy, feed, etc, is integrated. For example, in China there are over 3.4 million households using integrated technology to produce biogas, digested sludge, fertilizer and effluent utilization. A "bioenergy village concept" is based in the idea that bioenergy (in its modern forms) should be available to provide all the essential needs of its population e.g. sustainable production of food, animal feed, energy, etc. It must be highly integrated to minimize waste, and to allow the application of the best techniques, practices and locally available skills. However, the "bioenergy village concept" cannot be the panacea to solve the food-energy problem, but it may be able to make a significant contribution to rural development. Modern and advance processing of feed, food, and energy together with marketing and distribution systems, need to be adopted to preserve the whole dynamic structure. Maximizing economic growth is not the best way for social development if it does not trickled down to the most needy.
Adequate food supplies and reasonable quality of life require energy both in commercial and non-commercial forms; in DLG the latter is the most important, particularly in rural areas. The economy of many developing countries relies on agriculture where most of the work is often done using primitive tools and working practices that have seen little change for decades. Food can be produced in primitive ways with very little or no fossil fuel energy, e.g. using slash-and-burn agriculture. For example, FAO statistics show that human effort provides over 70% of the energy required for crop production in many poor countries. However, population, environmental, economic and social pressures makes this option unrealistic for the future. These agricultural practices, as with traditional bioenergy, need to be modernised.
3.1 BIOENERGY AND EMPLOYMENT
Employment opportunities have long been recognised as being a major advantage of biomass energy because of the many multiplying effects which help to generate more economic activity and help strengthen the local economy, particularly in rural areas. Bioenergy is a significant source of employment and income generation for many poor people in developing countries, particularly for the landless and jobless who otherwise would have few or no means of livelihood. Evidence seems to indicate that bioenergy is very often closely and intricately interwoven with local economic and employment conditions, and hence with local, regional and even national prosperity and growth. This has also major implications for the agricultural sector of many countries.
Agriculture and forestry, together with bioenergy related activities, are the most intensive and largest source of employment according to FAO. A rough estimate of employment in the forestry sector suggests that annually about 60 million man/years are employed in the forestry sector globally i.e. 48 million in DLG and 12 million in industrial countries. Some 20-25 million man/years annually are calculated to depend just on fuelwood collection and charcoal production in developing countries (11).
For example, in the Philippines in 1992 it was estimated that some 830,000 households (530,00 gatherers, 158,000 charcoal makers and sellers, 40,000 rural traders, and 100,000 urban traders) were involved in the woodfuel trade, from gathering to retailing, covering 10% of all rural households and about 40% of their cash income. (12). In Brazil, the sugarcane ethanol-based industry employs about 800,000 people and the production and use of charcoal production generated about 120,000 direct jobs in 1996. Another important factor is the cost of employment creation, which is quite cheap in comparison to other industrial activities. For example, in Brazil to create a job in the sugarcane-ethanol industry in the mid 1990s required an investment of about US$ 11,000, compared to US$220,000 in the oil sector, US$91,000 in the automobile industry, US$419,400 in the metallurgical industry, $12,980 in the agricultural sectors, $11,180 in livestock, and $7,260 in afforestation activities. (13). Much of this work represents a secondary activity of farmers. In the future agro-energy employment could be even a larger source of employment.
The World Bank (14) conducted a study that confirm the central role of bioenergy in generating employment. (See Table 3). However, these estimates apply only to large-scale operations, and for the small rural producer, the amount of employment generated could be ten times higher.
In the industrial countries bioenergy is also an important source of employment e.g. Scrase (15) found that in the EU the labour required to produce biomass fuels is approximately 4 to 10 times much greater than that needed for fossil fuels, and total direct employment (including power generation) is 3 to 4 times greater than for fossil fuel systems. Compared with nuclear energy, biomass for electricity requires approximately 15 times as much labour. These figures only consider direct employment, while many indirect jobs would be created or destroyed by a change in the energy mix.
However, estimation of the employment impacts of bioenergy is a complex issue because the many uncertainties involved. There are two major issues that need to be addressed: i) intensity of employment e.g. could such labour intensive activity hamper economic development?. It is clear that this has major implications and that more studies are needed to establish more clearly this relationship; ii) quality of employment. Most of the jobs generated by traditional bioenergy (as is the case with many other agricultural and rural activities) are unskilled and of poor quality. The same cannot be said of modern bioenergy applications which involves highly qualified jobs.
3.2 THE FOOD VERSUS FUEL ARGUMENT
This has always been a controversial topic because of the many misconceptions surrounding land availability, particularly at a time of rapid population growth. To better understand this issue it is necessary to understand the intertwined nature of food and energy production. There is plenty of land available but the issues are complex from political, socio-economic, cultural, and managerial points of view.
Land availability is perceived as a constraint to large scale production of biomass but only from a perspective of current agricultural practices which often comprises mismanagement, waste, unsustainable practices, etc. Many studies have shown that land availability is not the main problem, but many other issues unrelated to the earth's carrying capacity. For example, FAO (11), after studying the potential cropland resources in over 90 developing countries concluded that as a whole, the DLG will only be using 40% of their potential cropland in 2025, although there are wide regional variations.
Large areas of surplus agricultural land in USA and EU could also become significant biomass producing areas. In the USA, farmers are paid not to farm about 10% of their land, and over 30 Mha of cropland were set aside to reduce production or conserve land; a further 43Mha of croplands have high erosion rates and a further 43Mha have a wetness problems, which could be eased with a shift to various perennial energy crops. In the EU, up to 15% of arable farmland can be "set-aside" although the percentage has varied over the last 5 years (16). But in these countries there is a lot of capital, skills, etc, and low population growth, which is not the case in DLG.
Thirty five years ago about half the population (one billion people) of DLG were undernourished - today it is under 20% (about 800 million people). During this period cereal yields, total cereal production and total food production in developing countries more than doubled while the population grew by 75%. As a result average daily calorie supply increased by a quarter from under 2,000 calories per person per day in the early 1960s to almost 2,500 calories in the mid 1980s, of which 1500 calories was provided by cereals. This trend has continued into the mid 1990s so that the last 30 year period has seen a world wide 19% per capita increase in food for direct human consumption with a 32% increase for developing countries as a whole. Today only 10% of the world population lives in countries with a very low per capita food supplies (under 2200 calories) down from 56% in 1969-1971 (17).
However, these gains have been very unequal e.g. Sub-Saharan Africa countries appear no better and often worse off today than 20 years ago; India has increased its food grain production four fold from 50 to 200 Mt, while population has increased three fold from 330 to one billion.
It is understandable that there should great deal of concern when land is suggested to be converted to energy purposes while there are so many people undernourished around the world. Food production is a complex socio-economic, political, and cultural issue that goes beyond the earth's carrying capacity to produce food. If farmers are given the opportunity e.g. capital, economic incentives, land tenure rights, abundant energy supply, they will be able to produce more food that it has been the is case so far.
Thus it is important that all these complex issues are recognised as part of solving the problem e.g. some failures of the Green Revolution, mismanagement of resources, the role of women in food supply, the role of staple food in developing countries, the food-energy nexus, etc. For example, an aspect of agriculture which is often ignored is that 60-80% of the staple food production in DLG is produced to a large extent by women. Unfortunately, in the past the role of women in local food production has not received much recognition so that their inputs were not targeted by yield-enhancing techniques.
By the year 2030 as many as 8 billion people may be on the planet. Can all of them be adequately fed?. The answer may be not if present practices do not change considerably. To feed a growing population satisfactorily we need more than increased agricultural production, it is about political changes that prioritise agricultural R&D, about changing people attitudes, improving the quality of life of many, and providing incentives and motivation. It is also a precondition to have abundant and accessible sources of energy if this is to be achieved. And this is where bioenergy could play a major role.
These represent major changes, but they are possible as illustrated by the Cuban case. The break up of the Soviet Bloc in 1989 plunged Cuba into the worst economic crisis of its history. Its agriculture was highly dependent on imported pesticides, fertilisers, and farming equipment, and without these inputs, domestic production, led to an estimated 30 percent reduction in calorie intake in the early 1990s.
Cuba was faced with a dual challenge of doubling food production with half the previous inputs, but responded to the crisis with a national call to increase food production by restructuring agriculture. This transformation was based on conversion from a conventional, large scale, high input, mono-crop agricultural system to a smaller scale, organic and semi-organic farming system. It focussed on utilising local low cost and environmentally safe inputs, and relocating production closer to consumers in order to cut down on transportation costs. Urban agriculture has been a key part of this effort. By 1994 urban residents joined a planned government strategy to create over 8,000 ha and 2,500 city farms in Havana alone. The success of these gardens has significantly contributed to the easing of Cuba's food crisis, and in 1998 an estimated 541,000 tons of food were produced in Havana alone for local consumption, and some neighbourhoods are producing as much as 30% of their own subsistence needs. Food quality has also improved as citizens now have access to a greater variety of fresh fruits and vegetables. The opening of farmers markets and the legalisation of direct sales from farmers to consumers greatly increased production incentives for urbanites. (18).
Cuba is not the only case. Urban agriculture has a role to play in many parts of the world e.g. it is estimated that 800 m people worldwide harvest 15% of the world's food supply by growing vegetables and livestock in cities. Hong Kong, one of the most densely populated cities in the world, produces two-thirds of its poultry and almost 50% of its vegetables. Many other experiments are being tried e.g. Argentina, Brazil, Peru, etc.
3.4. POLICY APPROACHES TO AGRICULTURE AND ENERGY.
Agricultural development has been very unequal around the world, which is expected given the differing level of development, resource endowment, climatic conditions, policies, etc. In many developing countries a major reason has been lack of political support to farmers for infrastructure, markets, R&D, extension, etc, despite the fact that agriculture is often the main source of livelihood for the majority of the population. Agriculture has been considered by many governments as a secondary activity for far too long; industrialisation was a higher priority despite the fact that agriculture has been the main source of income and employment. A number of important policy changes have been taken place in the past decade that mark an important shift e.g. an enhanced role for market forces and less government interference, more consultation with the farming community, greater political recognition that traditional farming knowledge has a role to play, that modernisation of agriculture needs good technical skills, the role of women in food production, etc. There is also greater recognition of the potential role of bioenergy in socio-economic development and in food production e.g. bioenergy can be a large (be it secondary) source of employment and income for many farmers in remote rural areas.
Changes in the energy sector are leading to a new paradigm with major implications for agriculture and energy. Up to the late 1980s, the cold war played a major role in determining our energy thinking. With the end of the cold war various major trends began to emerge: i) privatisation and decentralisation of the energy sector e.g. energy production and delivery increasingly passing to the private sector which is gradually replacing state monopolies; ii) greater awareness of the environmental impacts of energy production and use, and a greater willingness to address such problems e.g. climate change and environmental sustainability. The concern with energy availability has been replaced by the concern as how to provide energy without endangering the environment and the stability of the global climate; and iii) greater global co-operation to alleviate the most pressing needs and problems e.g. poverty, equity, and affordable energy(1).
It is evident that the world is presently undergoing important changes which are leading to a new political and economic order, affecting the way we produce and use energy. This decentralised model could bring increasing opportunities for many individuals involved in bioenergy. These developments provide valuable new insights to prepare new strategies and policies for the coming century for biomass energy.
Energy is central to this new paradigm and a challenge to the aim of sustainability. The new scenario requires that social and environmental costs and benefits of energy production, delivery and use to be included in decision making along with market and investment factors e.g. that all costs are internalised.
Scientific and technical advances, no doubt, will have to play a major role but in the end it is possible that the most difficult obstacle may have more to do with economics, sociology and politics. The energy consumption patterns and monitoring of their impacts in an integrated framework needs to be studied in detail so that policy makers can use them to frame energy and environmental policies. Much of this information is not yet available.
3.5. BIODIVERSITY IMPLICATIONS
Agricultural development and the preservation of biodiversity are often perceived as an obstacle to modernisation. Often such conflicts do not exist and, on the contrary, it can be very beneficial. As Thrupp (19) puts it "evidence shows that integrating biodiversity and agriculture is beneficial for food production, ecosystem health, and for economically and ecologically sustainable growth". However, the conservation of biodiversity has a cost and thus it is difficult to convince farmers and decision-makers to spend money on any proposed measure if we are not capable of quantitatively expressing the values of biodiversity in such a way that they can be compared, which currently is not possible.
The developing countries modernisation drive should not necessarily be at the expense of the environment, sustainability and biodiversity. They should try to find sound alternatives and combine modernisation with local solutions while learning from the mistakes of intensive agricultural practices in both the industrial and DLG. Bioenergy production, as function of agriculture, can be optimised so as to reduce to the minimum the impact on the biodiversity function; it can also, in areas of high density of population, enhance the employment function.
The role of agriculture in food and energy production needs to be re-evaluated. Population growth and environmental pressures require a new paradigm to ensure sustainability. Global agricultural practices vary enormously ranging from very high inputs (energy intensive, machinery, capital, chemical fertilisers, etc) in the industrial countries, to almost primitive forms in many rural areas of DLG. These differences must be recognised.
4. BIOMASS ENERGY, AGRICULTURE AND CLIMATE CHANGE
Human civilisation, as we know it, would be impossible without considerable additional use of energy beyond the work capacity of humans. Current agricultural production would have been impossible without this additional energy e.g. machinery, fertiliser, water pumping, plowing, etc. all of which require modern use of energy. This additional energy is driving our modern society. It is important to bear in mind the potential of biomass, particularly in its modern forms, to provide multiple local, regional and global benefits, in addition to sustainable energy. It is a long term entrepreneurial opportunity for improved land management based on optimal productivity using minimum inputs of resources while producing environmental and social benefits.
Of the various strategies put forward for CO2 abatement the use of biomass energy as a direct substitute for fossil fuels offers the greater potential. This strategy can be achieved in various ways: i) by increasing the land area dedicated to bioenergy production either from existing or abandoned agricultural land; ii) better use of agro-forestry residues; iii) increased efficiency of biomass-based conversion processes, and iv) integrated food-energy production.
The experience with energy crops is still very limited and most of what it is known owes more to traditional agricultural techniques that anything else. Nonetheless the use of dedicated energy forestry/crops is increasing rapidly e.g. Brazil's ethanol from sugarcane program and charcoal from plantations, USA's ethanol from maize, and Sweden's willow plantations. Some studies have indicated that the potential for replacing fossil fuel by energy crops in the tropics alone can be as high as 150 to 510 Tg (150-510 Mt) C/yr; in the temperate zones C offsets could potentially reached 80 to 490 Tg C/yr. Agroforestry systems, where trees are grown in managed combinations with food or feed, could offset 10 to 50 Tg C/yr and between 50 to 200 Tg C/yr in tropical regions. (20; 9).
Estimating biomass energy potential and its implications for agriculture is rather complicated because of the many variables involved ranging over crop productivity, land availability, harvesting and transportation, conversion efficiencies, fuel substitution factors, etc. Paustian et al (9) have tried to estimate the primary energy that could be substituted over the next few decades as a result of agricultural biomass production. Overall, they estimated that energy forestry/crops and crop residues have the potential to substitute for 0.5 to 1.6 Pg fossil fuel C/yr, or about 8-27% of the current global consumption of fossil fuels. Bauen & Karltschmitt (21) have estimated that biomass energy has a potential to avoid between 17 and 36% of the current fossil energy consumption and between 12 and 44% of the CO2 of 1998.
There are significant opportunities for mitigating CO2 in agriculture through changes in the use and management of agriculture with the potential of converting agriculture into a net C sink, which has not been fully explored, and merit particular attention. These fall into two broad categories: i) changes in terrestrial C stocks, primarily C stored in vegetation and soils; e.g. decreases in these stocks results in a net flux of CO2 while increasing the standing stocks of organic C in soils and biomass removes CO2 from the atmosphere; ii) reduction of fossil fuel consumption either or energy of other industrial uses. Agriculture consumes fossil fuel energy in various ways e.g. production and use of machinery, crop drying, transportation, manufacture of fertilisers, etc. Thus a reduction/improvement in these activities will lead to various mitigation opportunities.
Historically, agriculture has been a major source of anthropogenic GHG, at least until the 1920s . In the 1990s agriculture was responsible for about 20% of total anthropogenic CO2, about 1.6 GtC, mainly caused by rapid land changes such as deforestation in the tropics. The current stock of C contained in the world vegetation is estimated at 550-700 Pg while soil organic C (to 1 m depth) amounts to 1400-1600 Pg. The estimated current C stock in cultivated land is 168 Pg C, excluding 54 Pg C of historical losses. The global potential for C sequestration in agricultural soils over the next 50-100 years has been estimated to be in the order of 20-30 Pg C. (9).
Climate change and the potential implications for agriculture, and hence for bioenergy, poses many questions but there are still very few answers. Simply not enough is known to make meaningful predictions. The intricacies of land availability, food and fuel competition are being addressed more seriously, and it is now more widely accepted that land availability is not at the core of the problem but agricultural mismanagement, waste, land tenure, policy interference, etc, are more crucial problems. The potential role of bioenergy is being addressed more seriously since the early 1990s when important changes began to take place e.g. environmental pressures, privatisation of the energy sector, concern with sustainability.
Farmers have demonstrated their capacity for change and innovation if they see clear opportunities. With proper support (e.g. availability of modern energy, extension services, infrastructure, financial, etc) farmers will be able to produce far more food and energy, provided that the necessary changes are put in place. Weather this is a realistic assumption for DLG is another matter. It is important to remember that production of food and energy in agriculture is mutually interrelated and complementary. Bioenergy programmes which couple with agroforestry and integrated farming can improve food production by making energy and income available, where it is needed, in a more environmentally and sustainable manner.
5. ENVIRONMENTAL AND HEALTH HAZARDS
The environmental benefits of biomass energy are widely known and hence would not be discussed in this paper, instead we will discuss briefly health hazards. It is now well known that traditional uses of biomass energy in DLG households can have two major negative health impacts: i) acute respiratory infections (ARI), particularly in children, and ii) chronic obstructive lung disease (COLD) in adults. However, these are more a direct consequence of complex socio-cultural factors and underdevelopment than the nature of the fuel themselves These factors have not, perhaps, received as much attention as they should have in the past, which can only be addressed in the longer term. In the shorter term, there two main technical steps which could reduce the health effects significantly: i) improve combustion and energy efficiency of cooking stoves; ii) substitution of fuel e.g. dung for wood, or kerosene, and the introduction of solar cookers. Other factors include changing cooking practices, improve housing e.g. increase ventilation, installing chimneys, windows, etc. (see e.g. 14).
Biomass energy provides about 14% of the world's energy (55EJ) and potentially as much as 450EJ by mid 21st century, an 8-fold increase. The implications are potentially very large, in particular for rural areas. A major challenge is to modernise to provide what people want e.g. clean, cheap and convenient energy such as electricity, and ethanol fuel, in an environmentally sound manner. The implications for rural development could be far reaching if bioenergy can supply a significant proportion of this modern energy requirements. Many commercial possibilities could be created with many social and economic benefits. In addition, there is a considerable potential for improving the environment.
However, bioenergy production is a complex issue that depends of many and varying factors. Bioenergy should not be regarded as the panacea for solving agricultural and energy problems in the rural areas, but as an activity that can play a significant role in improving agricultural productivity, energy supply, the environment and sustainability. Its final contribution will depend on a combination of social, economic, environmental, energy and technological factors. The potential role in bioenergy production should receive greater recognition, together with the need for positive political encouragement, and socio-cultural adaptations.
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