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Chapter one: Preface and objectives of the review
There is an increased recognition, in both developing and industrial countries, of the need for technical and economic efficiency in the allocation and exploitation of resources. Systems for the recovery and utilization of household and community wastes are gaining a more prominent place in the world community. Today, a new environmental agenda is emerging, which is now forcing itself on the attention of policy-makers and the public at large. Its concerns are both practical and urgent: they address the survival of human, animal and plant populations over vast sections of our globe.
Today's issues arise from the spread of deserts, the loss of forests, the erosion of soils, the growth of human populations and industrialized animal husbandry, the destruction of ecological balances, and the accumulation of wastes. As a result, the politics needed to meet present and future challenges require a new vision and new diplomacy, new leadership and new policies. In a world that is daily more complex and economically interdependent, the economic and security interests of the Developing Countries must be understood in a broader, global context.
These acute, relatively new problems of the world stem from either poverty and excessive population growth, in the Developing Countries, or from the careless and excessive use of natural resources in the Developed Countries; with more cumulative impact on the poor countries than on the rich. While many of these problems have been recognized for some time, they demand a new policy agenda for the world. The emergence of such a new approach has been accompanied by the growing realization that the goals of environmental conservation and economic growth in both developing and industrial countries are more complementary than often depicted. A.W. Clausen, President of the World Bank, has stressed these relationships: "There is increasing awareness that environmental precautions are essential for continued economic development over the long run. Conservation, in its broad sense, is not a luxury for people rich enough to vacation in scenic parks. Rather, the goal of economic growth itself dictates a serious and abiding concern for resource management".
Necessary goals are to achieve economic and environmental benefits through sustainable projects for resource recovery and utilization, and programs for Developing Countries. The use of anaerobic digestion in an integrated resource recovery system in Developing Countries is important to solve both ecological and economic problems.
Sustainability in waste management systems depends upon the interrelationship of policy, technique and economy. This interrelationship is particularly important in integrated resource recovery systems. This review aims to provide governments, development agencies, consultants and others with information necessary for the development and implementation of policy on waste management. It summarizes the latest developments in anaerobic digestion applicable to Developing Countries, as reported in English-language publications up to the year 1990. The review is prepared in an attempt to answer the questions of officials in Developing Countries about anaerobic digestion facilities throughout the world to provide health and economic benefits by digesting (fermenting) animal wastes, residues from harvesting, night soil and, in a number of cases, also from septage and sludges. The review summarizes the main issues of anaerobic digestion and its fundamentals in both the microbiological and practical aspects, discusses the various products of the process and their uses, alone or in integrated resource recovery systems, in different parts of the world, provides a brief review of the economic aspect of both household and commercial plants, and gives some information on biogas programs in several Developing Countries, their advantages and drawbacks. The review also includes some technological information and a bibliography of additional sources of information, as well as a list of companies and groups in different parts of the world involved in biogas technology.
It may be asked why a new review is called for.
1. When oil prices began dropping in 1986, oil users everywhere sighed with relief, but the energy crisis did not end, in fact. More than half the world's people cook and heat with firewood, dung and field residues. For most of these people, cheap oil is little cause for celebration, while bioenergy development, on the other hand, is a realistic proposition for a better social and economic life. The new developments and technologies in this field must be distributed and incorporated into the existing infrastructure of Developing Countries.
2. Today, anaerobic digestion is widely accepted as a sound technology for many waste treatment applications, and novel reactor designs are being applied on a commercial scale. In spite of this acceptance, advances are still being made, and technological developments are concentrating on applications in Developing Countries.
3. New and already developed approaches and processes for upgrading the quality and use of the effluent from anaerobic digestion are the reason for more economical uses of bioenergy processes.
4. Effective biodegradation of organic wastes into methane requires the coordinated metabolic activities of different microbial populations. Recent results of physiological and biochemical experiments are presented, in order to explain the fundamentals of mixed culture metabolism, which influence the rate of organic degradation.
5. The enormous development of computer technology and use makes simulation and model projections of the anaerobic digestion processes possible, on the one hand, and facilitates the use of developed control systems in the processes, on the other.
6. Last, but not least, the ecological aspect: the concern for the environment has come to the consciousness of the world, and we now understand better that our environmental heritage must be protected, for the sake of the quality of our lives and those of our children. This attitude is now beginning to govern our behaviour in waste management, and is encouraged increasingly by governments in both Developed and Developing Countries.
This review is therefore intended to up-date students, practitioners and consultants concerned with Biogas technologies, and to contribute to bringing biogas systems to a more advanced stage, and thereby to achieve a palpable impact in Developing Countries.
Probably the most serious source of conservation problems faced by Developing Countries is the backwardness of rural development. In the struggle for food and fuel, large areas of vegetation, trees and shrubs, are felled and stripped for firewood, cultivation and fodder. The consequence is the impairment of ecological processes in these countries, and the permanent destruction of normally renewable resources. There is an urgent need for rural development that combines short term measures for survival with long-term measures to safeguard the resource base and improve the quality of life, while ensuring the future. Unfortunately, many rural communities are so poor that they lack the economic flexibility that would enable them to defer the consumption of resources in need of restoration. Conservation measures are needed that will, at the least, maintain the standard of living of these communities, or improve it, while taking into account their own knowledge of the ecosystem, and finding effective ways to ensure that these resources are used sustainably.
According to the World Conservation Strategy towards sustainable development (as set out by IUCN, UNEP, WWF, FAO and UNESCO), which recognizes the need for international action to implement it, and to stimulate and support national action, an integrated approach to many of the problems involved is necessary. Cooperation between nations and organizations can facilitate the deployment of the limited means available, and thereby enhance the prospects for conservation and for sustainable development. Joint international action can do a great deal towards restoring the environment, tackling environmentally induced poverty, and enabling countries to make the best use of their resources, provided that the projects so supported are environmentally sound and assessed with due consideration for the local ecology. The first objective of the World Conservation Strategy is to maintain essential ecological processes, such as soil regeneration and protection, recycling of nutrients, and the cleansing of water, on which human survival depend. Part of this objective can be achieved, as a matter of urgency, by procedures for the rational use of organic matter, in Developing Countries, to help rural communities conserve their basic living resources, the essential springboard for development of energy and land.
One of these procedures is the production of biogas from organic agricultural wastes. These materials are destructible without proper conservation methods, but otherwise can yield a great sustainable benefit, at farm level. In order to achieve the World Conservation Strategy in this particular field, an increase in the number of trained personnel, and much wider awareness, are needed, as well as research-oriented management with the necessary basic information. Conservation and sustainable development, in rural communities whose only fuel is wood, dung and crop wastes, is all that stands between them and destruction. Biogas production combines the short-term economic needs of such communities with conservation and the end of ecological degradation.