Biomass energy has the potential to mitigate greenhouse warming through the provision of energy from a CO2-neutral feedstock. With good management and growth strategies other environmental and developmental benefits may result from integrated bioenergy programmes. These benefits may include land rehabilitation, soil stabilisation, water-shed protection, decreased SO2 and NOx emissions, and the development of permanent rural industries and employment. In assessing the future role of biomass energy and greenhouse abatement scenarios, a detailed understanding of both above and below-ground carbon flows, and energy output to input ratios, is needed for each intended biomass crop. Also required is an appreciation of the potential damage which may result from uncontrolled' development of biomass energy systems. Despite the potential benefits outlined above a significant biomass energy programme will not develop spontaneously due to a number institutional, technical and social constraints. Successful mechanisms to overcome these constraints need to be found. (see below)
A Future Role for Biomass Energy
Biomass could become a central part of future sustainable energy supplies. Both the economic and practical feasibility of such a developmental approach has been demonstrated by Johansson et al. {1993} in their Renewables Intensive Global Energy Scenario (RIGES). RIGES demonstrates that it is possible to provide energy for growth and development at no extra cost compared to conventional fossil-based systems. A reduction in global CO2 emissions would occur as a result of such an increase in renewables-based energy supply of which biomass would be a significant energy resource.
Two recent studies have recently emerged which provide independent support for such an important economic claim. Kulsum Ahmed of the World Bank {1993} has shown that biomass conversion technologies are capable of providing modern energy carriers at costs comparable with equivalent oil-based carriers if oil is priced at about US$ 20 per barrel. An important conclusion of this report is that there is a strong downward trend in the costs of biomass based technologies which is likely to continue. Secondly, a Shell Co. report has shown the promise of biomass based electricity generating units (BIG/GT) which could be produced at the same or lower capital costs to fossil based units ie. at about US$ 1,500 per MWe, if the anticipated results of an existing Global Environment Funded (GEF) project are achieved. {Elliott P., 1993}
To put the potential contribution of biomass in context, under RIGES by 2050, biomass would provide 17% of electrical power and 38% of direct fuel use. Altogether, "renewables" could supply 3/5 of electrical power production and 2/5 of direct fuel use by 2050 at the same or lower cost to future advanced fossil fuel-based systems. (see section 6)
Such a switch to modern bioenergy systems of the scale outlined above would have significant benefits to both developing and industrialised countries. In developing countries, the provision of affordable rural energy supplies will provide important improvements in both food and cash crop yields, mainly by enabling farmers to provide irrigation and agro-industrial energy at the various levels. Indeed, such rural biomass-based systems could provide the catalyst for self-sustaining indigenous rural development once constraints are removed (see below), also providing a sustainable energy source for urban centres. As such, modern biofuel technologies may actually aid developing country farmers to increase food crop yields at a faster rate than population growth. In so doing, indigenous biomass energy crops could help avoid the need to expand food production onto marginal land thus, negating potential food versus fuel arguments. {Williams, 1994}
A growing number of industrialised countries are beginning to view biomass-based energy systems as an important policy tool for addressing complex problems such as GHG emissions, rural development and energy security. Industrialised countries where biomass is providing a fast growing share of the energy sector include Austria, Denmark, Finland, France, Norway, Sweden and the USA. Sustainably grown biofuels are CO2-neutral and low acid rain polluters and need large quantities of land. This land use intensity is regarded as a benefit as it allows policy makers a novel use for the excess cropland areas which are now emerging due to rationalisation of agricultural policies in Europe and North America.
A major facet of modern bioenergy growth and conversion facilities is their modularity at relatively modest scales (1 to 100 MW). Modularity is an important concept as it allows energy planners to provide small incremental additions to the production capacity as opposed to the large-scale (500 to 1,000 MWe) fossil-based additions usually needed. For example, modern bioenergy conversion facilities are not prone to the economies of scale of existing fossil-based systems, thus, negating the necessity to add very large increments (500 to 1,000 MW) to the energy production capacity in order to benefit from those economies of scale. Thus, inaccurate supply and demand forecasting will not be as important with such biomass systems. In addition, the relatively large number of small biomass energy generating systems provides an inherent increase in supply security.
Constraints.
Why then have modern biomass energy technologies not been spontaneously and widely adopted and thereby obtaining a more significant share of the energy market?
The answer lies partly in the complexity and site specificity of the factors governing biomass growth and conversion. Whilst in developing countries traditional biomass use may already be highly important, present trends in its use are often unsustainable and of low efficiency. In industrialised countries, biomass use for energy up until the last few years has been restricted to niche markets where feedstock costs have been low or zero such as in sawmills, pulp and paper industries, etc.
Despite the site specificity of factors such as feedstock cost, proximity to market and likely market size, a number of general constraints to increased bioenergy use can be identified:
i) subsidies to competitors e.g. kerosine, or fossil fuel derived electricity, the so-called "uneven playing field."ii) scepticism over the reliability and economic feasibility of biomass energy projects due to a number of high profile biomass energy project failures. Often these failures were due to social incompatibilities or inflexibility of project aims and not necessarily concerned with the technology per se, however, the sentiment persists.
iii) a secure market must exist for biomass-energy products.
iv) traditional biomass conversion technologies are dogged by low conversion efficiencies and viewed more as a means of waste disposal than for energy production.
v) there is a lack of awareness by senior decision makers, potential users and financiers about the multiple benefits of bioenergy systems.
vi) bioenergy systems require co-operation between sectors which do not normally communicate. At the national level, the agriculture and forestry sectors must communicate effectively with the energy and land planning sectors. At the international level there needs to be an integrated approach between institutions such as the World Bank, the UN (including UNEP, UNDP, FAO) and multi-national companies which must also involve NGOs.
vii) at the local/village level there is a need for the strengthening or creation of a transparent organisational infrastructure so as to ensure technically sound biofuel systems provide effective and equitable returns to consumers and suppliers alike.
viii) the initial capital costs of conversion equipment may be higher than comparable fossil fuel systems, and potential financiers may be difficult to find despite the cheaper full life-cycle costs. There may also be little or no backup or operation and maintenance facilities due to the novelty of the technology.
Despite these constraints when full life-cycle costs and potential environmental and wider social benefits are accounted for biomass-based energy systems will, in many cases be the least-cost long-run option.
Environment & Management.
Besides potential greenhouse abatement benefits of biomass energy, its production can address many other "secondary" issues. {Ranney, 1992a} Such problematic areas which may benefit from large scale biomass energy are: soil erosion, raising habitat diversity, control of nitrogen run-off and the protection of watersheds. (see section 5)
Bioenergy is certainly no panacea for solving the world's energy problems since it is not without its difficulties. Indeed, the production of the biomass itself can be intensive in planning, management, labour and land. For sustainable growth, detailed planning will be required from local, to national, to regional levels. The inappropriate selection and site-matching of species or management strategies can have deleterious effects and lead to degradation and abandonment of land. However, the correct selection of plant species can allow the economic production of energy-crops in areas previously only capable of sustaining low plant productivities; simultaneously multiple benefits may accrue to the environment. Such selection strategies may allow synergistic increases in food-crop yields and decreased fertiliser applications whilst providing sustainable local sources of energy and employment.
Biomass Use for Large scale Energy Production.
The perception of biomass energy has changed recently in a number of industrialised countries. This has led to biomass gaining a growing and significant share of the primary energy sector in USA, Sweden and Austria (4%, 16% and 10% of primary energy respectively; see section 3). Biomass has previously been regarded as a low-grade, "poor man's" fuel, but is increasingly viewed as an environmentally and socially advantageous source of energy. In the newly industrialising countries, for example Brazil, biomass energy has always been an important traditional energy source, predominantly for the domestic sector. However, under the initiative of various programmes in a number of countries, such as for ethanol and electricity production, biomass energy has attained a significantly higher profile. With a better understanding of the negative aspects of biomass supply and methods for their mitigation, bioenergy is increasingly perceived by energy planners not as a problem, but as an opportunity for the sustainable provision of energy.
Global Warming.
The Intergovernmental Panel on Climate Change's 1992 Supplement (IPCC92) has found no evidence to markedly change their 1990 global warming predictions. They now state i.e. missions resulting from human activities are substantially increasing the atmospheric concentrations of greenhouse gases. ii) modelling studies indicate that the mean surface temperature sensitivity to doubling CO2 is unlikely to lie outside the range 1.5°C to 4.5°C, iii) the global mean surface temperature has increased by 0.3°C to 0.6°C over the past 100 years, and iv) the unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more. Furthermore, of the 6.0 ±0.5 GtC emitted in 1989/90 from the two primary atmospheric CO2 sources, mainly, the combustion of fossil-fuels and secondly, land-use changes, the latter change accounts for 1.6 ± 1.0 GtC. A substantial proportion of the carbon emissions from land-use changes are derived from the 17 Mha yr.-1 of tropical deforestation estimated to have occurred between 1981 and 1990, which is expected to continue {IPCC, 1992}.
However, the measured increase in the atmospheric concentration of CO2 is not consistent with the calculated level of emissions from fossil fuel use and land use changes. These measurements indicate that either the level of emissions is exaggerated, which seems unlikely, or that more CO2 is being reabsorbed, by an unknown mechanism, than estimated, i.e. there exists a "missing sink." The destination of the so-called "missing sink" carbon is still uncertain. It is thought that not all this "missing" CO2 has been absorbed into a large oceanic sink but that a terrestrial sink exists possibly resulting from a C02 fertilisation effect on vegetation growth. {Wigley 1992.} Even though there is some uncertainty over the extent of global warming the latest estimates only serve to make the arguments concerning "the precautionary principle" and the possible benefits from land rehabilitation of greater importance.
A Conflict for Resources?
Of greater certainty is that the global population will continue to increase. The IPCC92 revised estimates of population growth predict rises of between 1.27% and 2.28% per year or the equivalent of a gross increase of 44% to 80% by the year 2025 from 1990 levels. Population growth makes increasing both food and energy supplies of paramount importance. Potential conflicts between these resources must be assessed and planned for.
The perception that all development requires more energy per se, is not necessarily valid. Improvements in the efficiency with which energy is produced and used, have highlighted the importance of the services that energy can provide, as opposed to increasing total amounts of energy i.e. less energy can be made to do more. Future policies for indigenous biomass energy production should ensure that improvements in income generation, provision of modern energy services and trade benefits are returned in a significant fraction to the local populations. This implies that the rural incentives and the infrastructure necessary for the sustainable development and provision of such biomass energy services are developed at the local level. (see section 3, Hosahalli)
However, the provision of biomass-based energy services should not conflict with land requirements for food production. Research indicates that the problem is not the size of the land resource, but its efficient management for biomass production in all its forms- for food, fuel, fodder, etc. (see sections 2 and 3.) Research on wood energy activities over the last decade (after the 1981 Nairobi Plan of Action), has shown that contrary to popular belief, "factors other than the use of fuelwood and charcoal are the chief causes of deforestation; processes such as farming, forest fires and the industrial use of forests are the chief causes." {FAO, 1993} Small increases in energy inputs (especially where none previously existed) will provide significant returns in yield improvements, effectively increasing land availability rather than competing for it, hopefully reducing the pressures causing deforestation and land degradation. Modern, efficient industrial and domestic energy conversion technologies are also required if full advantage is to be taken of the potential environmental, economic and health facets of biomass energy. (see chapters 4 & 5).
Energy Balances.
The high yields presently achieved by intensive agriculture require significant energy inputs and mechanical methods of production. For many crops under intensive management the energy required for cultivation and processing may exceed the energy content of the food produced. However, the energy output to input ratio of woody and fibrous energy crops is very favourable (in excess of 10 times and about 6 to 7 times for ethanol from sugarcane); for these crops high energy inputs can be rewarded with net increases in energy output. {Ledig, 1981; Gladstone & Ledig, 1990} In general, cereal crops give a positive energy return even under intensive management e.g. maize contains 3.5 times the energy in the harvested grain alone than it requires to cultivate and process. However, some crops presently require more energy to produce than they return in the food produced e.g., energy output to input ratios are: apples 0.9, lettuce 0.2, tomatoes 0.6 and cabbage 0.8 {Pimentel, 1984}. Note that many of these calculations do not account for the energy content of the associated residues which are significant.
There are considerable opportunities to make farms and forests both net energy exporters and net carbon sequesterers2. This potential has been highlighted in a recent report by the USA Council for Agriculture, Science and Technology (CAST, 1992). It states that "a great opportunity for U.S. agriculture to help mitigate climate change lies (through the) stashing of carbon in soil and trees and displacing fossil fuel." CAST estimates that US agriculture could plausibly displace 8% of US energy with biomass fuels which would reduce total US CO2 emissions by 10%.
2 "Sequester" is defined as the net removal of CO2 from the atmosphere and subsequent storage in organic matter.
However, where fossil fuels are used in the production of biofuels some CO2 is inevitably emitted, even where this CO2 is effectively re-absorbed through increases in standing carbon or in fossil fuel substitution benefits. In the future these emissions could be eliminated through the use of biofuels or non-CO2-emitting renewables to supply the energy for growth and processing of the biofuels.
The Potential Biomass Energy Resource.
Given appropriate institutional and management policies biomass energy offers the opportunity for the provision of substantial amounts of energy. At the same time it can provide rural employment and environmental benefits. The adoption of biomass energy systems globally may, however, require changes in farming, forestry and energy-use practices. Initially, such energy systems would have to be based primarily on agricultural residues during the establishment and development of bioenergy plantations. The potential for sustainable energy supplies from such plantations is considerable. For example, energy plantations on only 3% of Brazil's land could theoretically provide much more than its current total primary energy consumption. It is now recognised that biomass presently plays an integral role in the energy provision of most developing countries. However, the future potential of biomass energy must be realistically assessed accounting for present (usually very inefficient) production and use, and the problems of future energy provision.
Prevailing climatic conditions in many developing countries lend themselves to high biomass yields if growth is not unduly limited by nutrient, water or pest and disease constraints. Many of these countries e.g. Brazil, Zaire and Thailand are also well endowed with large potential land areas for biomass growth and could thus become net energy exporters. The development of the rural energy industries required would provide significant levels of employment and income generation.
