Professor David Hall

14 November 1935 - 22 August 1999

David Hall was Professor of Biology at King's College London, where he undertook research on biomass energy policy, environmental aspects, external costs, bioenergy in developing countries and the effects of climate change. He was internationally acclaimed for his expertise and experience in biomass. He was an adviser for the European Union and the United Nations, and travelled extensively in promoting the development of biomass technologies.

He was a leading contributor to two working groups of the Intergovernmental Panel on Climate Change and was Treasurer of the Scientific Committee on Problems of the Environment and Director of the International Solar Energy Society.

As humanity grapples with one of the biggest transitions in its history, away from fossil fuels and towards clean and renewable energy, biomass will surely come to take its place as a prominent source of energy, especially in the tropics. Hall's work will always be acknowledged as a pioneering endeavour with major import for all our energy futures. He has left us at the height of his professional powers but, fortunately, with a bequest that should eventually enhance the lives of communities far and wide.

David was a good friend of FAO. He helped us develop our notions and programmes on bioenergy and always had the time and interest to discuss new ideas. His sense of humour, his unparalleled unselfishness and his love of life will always be remembered by those who felt and feel great pride at having known and worked with David, in the UN and in FAO.

David's friends in FAO


Unified Wood Energy Terminology (UWET)

The approach being used by FAO's Wood Energy Programme for the classification and differentiation of the various types of woodfuel, as well as its users and supply sources, was explained in the last issue of Forest Energy Forum. In this issue, definitions of the most important terms used in our proposed Unified Wood Energy Terminology (UWET) are described.

[See also the graph on page 3 of Forest Energy Forum No. 3, reproduced below.]

The basic idea behind UWET is to create an adequate framework to identify the amount and type of wood energy flowing from different supply sources to the final users. The fuel or product used to transport energy, therefore, is the basic parameter to be accounted and properly classified. Either by commercial or non-commercial ways, these fuels should always be considered as goods or commodities, worthy and able to solve any effective demand. UWET intends to make it easier to exchange the information and statistical data now available from different organizations, at both national and international levels, involved in the collection, collation and presentation of wood energy figures.

It is important to bear in mind that these definitions have been elaborated taking into consideration all the relevant definitions used, for biofuels in general and woodfuels in particular, and already agreed upon and discussed by different international organizations over the past 20 years.

Basic definitions

In a broad sense, energy is the capacity to promote changes and action (heating, motion, etc.) and biomass is all kinds of material coming directly or indirectly from contemporary photosynthesis reactions, such as all vegetal matter and derivatives: woodfuel, charcoal, paper, dung and a great portion of urban refuse. Bioenergy is the word used for energy associated with biomass, and biofuel is the bioenergy carrier, transporting solar energy stored as chemical energy. Biofuel should be considered as a renewable source of energy as long as there is sustainable biomass production.

The following are the main definitions to be used in UWET:

Woodfuels include all types of biofuels derived directly and indirectly from trees and shrubs grown in forests and non-forest lands. In the past, in FAOSTAT, fuelwood and charcoal included only what was derived from forest lands. WETT is trying to solve this problem using UWET. The definition of "forest" used in the FAO Forest Resource Assessment 1990 (FAO Forestry Paper No. 124, p. 7) is rather broad and includes lands with a minimum crown cover of 20 percent in developed countries and 10 percent in developing countries. Woodfuels also include biomass derived from silvicultural activities (thinning, pruning, etc.) and harvesting and logging (tops, roots, branches, etc.), as well as industrial by-products derived from primary and secondary forest industries which are used as fuel. They also include woodfuels derived from ad hoc forest energy plantations.

Woodfuel sources. Woodfuels can be divided into three groups according to their origin: direct woodfuels , indirect woodfuels and recovered woodfuels, defined as follows:

Direct woodfuels consist of wood directly removed from: forests (natural forests and plantations; land with tree crown cover of more than 10 percent and area of more than 0.5 ha); other wooded lands (land either with a tree crown cover of 5 to 10 percent of trees able to reach a height of at least 5 m at maturity in situ; or crown cover of more than 10 percent of trees not able to reach a height of 5 m at maturity in situ, and shrub or bush cover); and other lands to supply energy demands and including both inventoried (recorded in official statistics) and non-inventoried woodfuels.

Indirect woodfuels usually consist of industrial by-products, derived from primary (sawmills, particle boards, pulp and paper mills) and secondary (joinery, carpentry) wood industries, such as: sawmill rejects, slabs, edgings and trimmings, sawdust, shavings and chips, bark, black liquor, etc.

Recovered woodfuels refer to woody biomass derived from all economic and social activities outside the forest sector, usually wastes from construction sites, demolition of buildings, pallets, wooden containers and boxes, etc.

Direct woodfuels, indirect woodfuels and recovered woodfuels can be directly burnt or converted into another fuel, such as charcoal, pyrolysis gases, pellets, ethanol and methanol.

Woodfuel types. As regards the commodities to be considered for wood energy accounting, woodfuels can be presented in four types of product, fuelwood, charcoal, black liquor and other, defined as follows:

Fuelwood (or firewood) includes "wood in the rough" in small pieces (fuelwood), chips, pellets and/or powder derived from forests and isolated trees, as well as wood by-products from the wood products industry and from recovered woody products. It essentially preserves the original structure of wood and can be used either directly or after some conversion to another woodfuel, as charcoal. When needed, fuelwood can be prepared (without major physicochemical transformations) into more convenient products such as chips and pellets.

Chips are wood that has been deliberately reduced to small pieces from wood in the rough, or residues suitable for energy purposes.

Wood pellets can be considered as a fuel derived from the auto-agglomeration of woody material as a result of the combined application of heat and high pressure in an extrusion machine.

Charcoal refers to a solid residue derived from the carbonization, distillation, pyrolysis and torrefaction of wood (from the trunks and branches of trees) and wood by-products, using continuous or batch systems (pit, brick and metal kilns). It also includes charcoal briquettes, made from wood-based charcoal which, after crushing and drying, is moulded (often under high pressure), generally with the admixture of binders, to form artefacts of even shapes.

Black liquor is the alkaline-spent liquor obtained from the digesters in the production of sulphate or soda pulp during the process of paper production, in which the energy content is mainly derived from the content of lignin removed from the wood in the pulping process.

Other woodfuels include a broad range of liquid and gaseous fuels derived from fuelwood and charcoal basically by pyrolitic or enzymatic processes, such as pyrolisis gases, ethanol, methanol, products which are of growing interest but so far not very important as energy commodities.

Woodfuel users. Traditionally woodfuels were assumed to be used mainly by households. However, in some geographical areas, the use of woodfuels by the industrial and commercial sectors is also very important. Therefore, wood energy systems are not completely understood if the consumption side is not properly disaggregated by main users and/or consumption sectors.

Moreover, with the growing demand for woodfuel by new users of industrial wood energy, particularly for industrial power and heat, it is important to understand who is using woodfuels, how much they are using and where. This information is vital for analysing and planning sustainable and cost-effective wood energy systems.

For this reason, in our Wood Energy Information System (WEIS) woodfuel consumption data are categorized within the following main areas:

For more information, please contact Miguel Trossero.

[Information on units and conversion factors will be given in future issues of Forest Energy Forum.]


Bioenergy - encouraging perspectives

The multifunctional character of agriculture and land: bioenergy

Agriculture is intrinsically multifunctional in character. Furthermore, all agricultural activity and related land use lead directly to other non-agricultural functions ranging over social, environmental, economic and cultural goods and services, which can result in significant benefits or costs. However, there is abundant evidence that, beyond food security, the multifunctional character of agriculture makes significant contributions to achieving rural development, energy and environmental sustainability at the local, national, regional and global levels. An improved and more systematic understanding of this "multifunctional character" can lead directly to even greater benefits. Its significance constitutes a major issue for contemporary policy-makers and practitioners alike. This document is an attempt to assess the energy function of agriculture.

The role of agriculture as an energy consumer related to the energy needs for irrigation, fertilization, transport, processing and conservation is quite well documented, even if it is still necessary to view the energy/food nexus more systematically.

The role of agriculture as a major energy producer is neither recognized nor mobilized. Recent considerations regarding global climate change and the realization of the potential of biomass energy as a motor for rural development have triggered new attention. This study draws from these new concerns and understanding.

Bioenergy production and use is an important agricultural activity, particularly in many rural areas of developing countries.

Currently biomass energy provides about 55 EJ (equivalent to 25 million barrels per day of oil, and providing 14 percent of total global energy while being number one [34 percent] in developing countries as a whole), both in its traditional and modern forms. It can represent more than 90 percent of total energy use in many developing countries, and as much as 20 percent in some industrial countries. Much of this energy originates from various types of agricultural and forestry residues, although in the future various types of energy crops and plantations are expected to provide the main source.

Biomass was the main source of energy until the early twentieth century. It was only during the past few decades, the so-called "oil era", that biomass energy was less recognized and largely ignored by policy-makers and energy planners alike. Current trends indicate that the amount of bioenergy used remains stable (or even growing), with an increased use in industrial countries, such as European Union members and the United States, mainly for environmental rather than purely energy reasons. Since the early 1990s, the increasing interest in biomass for energy has been manifested in most energy scenarios showing biomass as a potential major source of energy in the twenty-first century, ranging from 59 to 145 EJ by 2025. This expected increase in biomass energy could have a significant impact on agricultural development.

Despite the high energy intensity of agriculture in industrial countries, in global terms the agricultural sector consumes little energy in comparison with other industrial sectors. In fact, in many developing countries these inputs are very low. This means that: first, by adopting western patterns for modernization of agriculture higher amounts of energy would result; and, second, the potential of carbon mitigation in agriculture from decreased energy use is much smaller than in other sectors. The combined potential of agricultural systems for mitigating CO2 has been estimated at between 0.94 and 2.53 PgC/year compared with present global emissions of 7.0 PgC/year.

In the short to medium term, residues will continue to be major sources of bioenergy and thus would have less direct implications for agriculture than would be the case if large-scale energy crops and plantations were established on agricultural land. Thus, guidelines for residues use are urgently needed to determine what is and what is not renewable to ensure maximum environmental advantages, as has been done with energy forestry/crops/plantations. The large-scale use of animal manure for energy is questionable because the non-energy uses may have greater value, except in specific circumstances where surplus manure poses environmental problems for agriculture, such as in Denmark, where surplus manure is treated to produce biogas and also fertilizer as a by-product.

Energy technology has been improved over the past two centuries to meet certain economic and also environmental criteria but not for sequestering carbon. Large-scale use of bioenergy, when it reaches market maturity, offers the most effective alternative to carbon sequestration. The conventional view that use of biofuels was often a cause of land degradation, deforestation and health hazards is not supported by evidence. For example, health hazards of biofuels are a more direct consequence of cultural practices, underdevelopment and poverty than to the nature of biofuels themselves. Most of these negative impacts could be eliminated by improved socio-economic conditions (such as better housing) and improved technology (such as improved cooking stoves).

Agricultural development has been very unequal around the world, which is to be expected given the differing level of development, resource endowment, climatic conditions, policies, etc. In many developing countries a major reason has been the lack of political support to farmers for infrastructure, markets, R&D and extension, for example, despite the fact that agriculture is often the main source of livelihood for the majority of the population. Some of these shortcomings are now being addressed through more consultation with the farming community, greater recognition that traditional farming knowledge has a role to play, that modernization of agriculture needs good technical skills, and of 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. Bioenergy can be a large (if normally secondary) source of employment and income for many farmers in remote rural areas. The potential implications of large-scale production and use of bioenergy for the rural economy are significant and thus should not be overlooked.

Climate change and the potential implications for agriculture poses many questions for which there are still very few answers. Simply not enough is known to make any meaningful predictions. Much more long-term research is needed before any unequivocal recommendations can be made. 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 has been addressed more seriously since the early 1990s when global concerns about sustainability and environmental impacts of development were put high on the political agenda and privatization of the energy sector started to be a major issue.

Farmers have demonstrated their capacity for change and innovation if they see clear opportunities. With proper support (extension services, infrastructure, financial services, etc.), farmers will be able to produce far more food and energy, provided that the necessary changes are put in place. It is important to remember that production of food and energy in agriculture are 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.

However, bioenergy production is a complex issue that depends on 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 which 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 multifunctional character of agriculture and its potential role in bioenergy production should receive greater recognition, together with the need for positive political encouragement, and socio-cultural adaptations.

Policy recommendations

Policies and institutions should

Research, development and extension should

Projects and financing should

(Extracted from: the executive summary of Bioenergy, a paper prepared by David Hall and Frank Rosillo-Calle of King's College London and finalized under the supervision of Gustavo Best, FAO's Senior Energy Coordinator. This paper represents one of the background documents of the FAO/Netherlands Conference on the Multifunctional Character of Agriculture and Land [MFCAL], held in Maastricht, the Netherlands, 12-17 September 1999. The full paper is available for downloading at: www.fao.org/mfcal/pdf/bp_2_bio.pdf )

[See under Events for more information on the conference .]

Bioenergy is a means to achieve all of these objectives - to heat our homes, to fuel our vehicles and to power our factories while producing virtually no greenhouse gas pollution. To make the most of these opportunities, government and industry must work together, as partners. In "industry" I include agriculture and small and big business, government and everyone in the private sector who is involved in this. (Extracted from: President Clinton's speech at the Bioenergy Climate Change Event, United States Department of Agriculture, 12 August 1999.)

FAO, IEA and bioenergy

A draft Memorandum of Understanding between FAO's Forestry Department and the International Energy Agency (IEA) covering a programme of research, development and demonstration on bioenergy is under preparation.

A meeting with Mr J. Tustin, Secretary, IEA Bioenergy, was held at FAO in September 1999 when details were discussed about possible areas of cooperation to be established in the coming months. We expect that closer collaboration with IEA, and IEA Bioenergy in particular, will play a catalytic role in increasing the visibility of the use of biomass as an environmentally friendly source of energy.

For more information, please contact:Miguel Trossero.

[More information will be given in the next issue of Forest Energy Forum.]

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