Energy production is by far the most important single use made of the world’s annual wood harvest. In 1999 total world wood harvest was an estimated 3,591 million m3, of which 48.1 percent was classified as woodfuel2. No other single product category comes close to this as a percentage of the total harvest. Even so, the 1999 figure for woodfuel as a proportion of the harvest mix was the lowest recorded for some time. For most of the last decade, woodfuel accounted for more than 50 percent of the world wood harvest (e.g. Solberg, 1996). Only in the last two years of the 20th century (figures for both of which may be subject to revision) has woodfuel production fallen to less than 50 percent of the total harvest.
Although woodfuel production as a percentage of total products may have declined a little in the last few years, the interest in wood as a fuel has increased due to concern over greenhouse gases and global warming. Moreover, fuel usage of wood is somewhat greater than indicated by figures based on a simple classification of harvest into either industrial or fuelwood. A distinguishing feature of the industrial wood sector is that in most countries it supplies a significant proportion of its own net process energy needs (typically of the order of 30 to 40 percent). It does this by burning biomass sourced from in-house manufacturing operations. At an international level, the dominant internal contributor to the industrial wood energy supply mix is the energy recovered from the burning of black liquor during the chemical regeneration cycle of chemical pulping. However, in some jurisdictions bark, slabwood and sawdust from other processes applied to the industrial component of the wood harvest are also a significant source of energy - particularly for the sawmilling industry itself.
If the energy component of the industrial wood harvest is recognized and accounted for as such, then by volume at least 14 percent of wood classified as ‘industrial’, and possibly as much as 20 to 25 percent of this harvest, eventually finds its way into fuel uses. When this component is added to the woodfuel component of the harvest it means that currently at 60 to 65 percent of all wood harvested is used as fuel.
In addition to the issue of ‘industrial’ woodfuel, there is also a need to recognize the existence of significant uncertainties surrounding the accuracy of published data concerning woodfuel production and consumption. Because of the site-specific and dispersed nature of much of the production and consumption of woodfuels (a significant portion of which takes place outside of the money economy), systematic collection of reliable data on woodfuel supply and demand is both expensive and time consuming. Despite the obvious importance of woodfuel as a forest product and as an energy source for some groups, published international data on woodfuel consumption are largely based on estimates. These estimates are in many cases derived from survey produced baseline estimates. In some cases the surveys on which the estimates are based are now at least 40 years old. For at least one group of countries, the RWEDP countries3, the Food and Agriculture Organization of the United Nations (FAO, 1997) reports that these baseline estimates have been updated annually under the assumption that the population elasticity of consumption is exactly united. FAO also notes that in the energy balances published by national sources, data on the supply of woodfuels are usually worked back from stated consumption figures. As a result, most supply figures do not provide independent confirmation of the consumption estimates. Changes in reported consumption of woodfuel over time (and FAO data indicates a 53 percent increase in the period from 1970 to 1999) is therefore in many cases simply a reflection of population increase rather than measured changes in woodfuel consumption.
Projections of future woodfuel consumption in most models (e.g. FAO, 1995; Apsey and Reed, 1995) are essentially based on a continuation of trends recorded in the historical data estimated and reported by FAO. However, current consumption may be considerably higher than that reported by agencies such as FAO. Sharma et al (1992) suggests higher consumption levels than the official figures, while Nilsson (1996) reports a number of different sources that suggest a significant portion of woodfuel consumption may go unreported. FAO itself (ibid.) has reported that some surveys carried out in the early 1990s by the World Bank revealed discrepancies of more than 100 percent with the FAO data.
As well as uncertainty in supply/consumption estimates, there is also uncertainty in the relative importance of different sources of supply of woodfuel. In some countries, both developed and developing, much of the woodfuel consumed is not produced as a result of direct harvesting of the forests that are the source of industrial wood. Instead, woodfuel is gathered from a variety of sources and types of vegetation, some of which are not classified as forest. In the 1970s and 1980s it was generally assumed that all woodfuels originated from public forestlands. However, data from seven RWEDP member-countries indicate that only about one-third of these countries’ woodfuels originate from such lands (FAO, 1996).
Even considering these various caveats about the reliability of basic data, it is clear that fuel is the major use of wood. However, despite the obviously vital importance of wood as a fuel to some groups and to some countries, woodfuels currently account for no more than around 7 percent of total world energy supply4.
The complexity of the systems, actors, dynamics, and relationships between forest and energy sectors, is outlined in some detail by Trossero et al., (1998). There are clear inter-country differences in the split between woodfuel and industrial wood, and in the precise uses made of woodfuels. Many of these differences simply relate to country location and forest endowment. However, as a generalization the most striking differences in terms of the role and importance of woodfuels in the national primary energy mix, and in the ways in which wood is used to provide energy, are the differences between countries based on their classification as either developed or developing.
In 1999, developing countries produced 1,562.95 million m3 of woodfuel and 392 million m3 of industrial roundwood5. In fact, the woodfuel produced by developing countries represented 90.4 percent of global woodfuel production. As a group, roundwood production by developing countries is dominated by woodfuel production. In the last five years, the percentage of the world’s woodfuel produced by developing countries has fluctuated between 88 and 91 percent. Woodfuel makes up around 75 to 80 percent of total wood harvest in developing countries. As a result, woodfuels account for something like 15 percent of total primary energy consumption in developing countries.
In contrast, developed countries produce only 9.5 to 12 percent of all the wood classified as fuel. In 1999 (according to FAO figures), developed countries harvested some 164.7 million m3 of woodfuel. In the same year this group of countries harvested 1,470.6 million m3 of industrial wood. As might be expected from these figures, the relative contribution of energy recovered from the processing of industrial wood compared to what is actually classified as woodfuel is somewhat greater in developed countries than in developing countries. The 1995 contribution of woodfuels and the mix of woodfuel, charcoal and black liquor in the total consumption of woodfuels by developed and developing countries, is reported in Table 1.
Table 1: Woodfuels Consumption and Share in Total Energy Use 1995
Region |
(millions of m3 equivalents) |
Woodfuel’s share in total energy use (%) | ||
Woodfuel |
Charcoal* |
Black liquor |
||
1533 |
131 |
34 |
15 | |
Africa |
445 |
72 |
3 |
35 |
Asia – developing |
859 |
25 |
12 |
12 |
Oceania – developing |
6 |
0 |
0 |
52 |
Latin America and the Caribbean |
223 |
34 |
19 |
12 |
187 |
6 |
228 |
2 | |
Europe, Israel and Turkey |
56 |
2 |
51 |
3 |
Former USSR |
32 |
0 |
8 |
1 |
Canada and United States |
96 |
4 |
146 |
3 |
Australia, New Zealand & Japan |
3 |
0 |
23 |
1 |
1720 |
137 |
262 |
7 | |
Source (FAO, 1999)
* Figures for charcoal are rather conservative since most charcoal production is not recorded, even when traded.
Based on the conversion ratios implicit in Table 1 and the estimated wood harvest and forest production estimates for 1999, global production of charcoal and black liquor would have accounted for (in that year, and in roundwood terms) some 142 and 268 m3 (respectively) of estimated woodfuels consumption. The split between developed and developing countries for this consumption (in millions of m3 of roundwood equivalent) in 1999 would have been (approximately) 5 to 136 for charcoal and 232 to 36 for black liquor. This means that for the developed countries, with a 1999 harvest of 1,635 million m3, approximately 25 percent (in roundwood equivalent terms) of all production ended up being used for energy. However, of this wood energy usage by developed countries, nearly 60 percent of the estimated total is in the form of energy recovered as part of an industrial wood processing operation, with only 40 percent coming in the form of material harvested as woodfuel.
This is in sharp contrast to the result for developing countries. This grouping’s 1999 harvest was some 1,955 million m3, of which almost 80 percent was classified as woodfuel. Energy recovered from the industrial harvest, in the form of heat recovered from black liquor, would have accounted for approximately 9 percent of this grouping’s industrial wood harvest. This means that for developing countries as a whole, nearly 84 percent of total wood production (compared to 25 percent in developed countries) ended up as fuel. The main reason for the difference, it should be noted, is because the percentage of total production classified as woodfuel (as opposed to industrial wood) is substantially higher for developing countries than for developed countries. However, while it is not so critical to the difference the relative importance of energy recovered from that wood classified as industrial also differs between the two groups. For the developed countries, some 15.8 percent of industrial wood ends up being used as fuel. For the developing countries though the figure is only 9 percent.
For developing countries, woodfuels are a vitally important component of primary energy supply (Eckholm et al, 1984), principally for cooking and home space heating, and also cottage industries e.g. ceramics, building material, tobacco curing, etc. As a result, a large portion of the woodfuels research effort in these countries over the last 20 years has understandably been focused on improving the efficiency of stoves, efficiency of fuel production, and with the provision of non-industrial plantations, to help meet fuelwood needs.
In contrast, for the developed countries, oil (40 percent share of total energy supply), natural gas (22 percent), coal (26 percent) and nuclear (7 percent) are the dominant fuels for primary energy supply (IEA, 2000). Also in contrast, industry, electricity generation and transportation are the main end uses for the energy produced. Wood typically supplies something in the range of 1 to 15 percent of national energy needs in developed countries. As a result of the differences in the fuel mix between developed and developing countries, the energy concerns of the two groups of countries are quite different.
The oil shocks of 1973/74 and 1979/80 triggered within a number of countries an increased interest in the potential of biomass as a renewable, indigenous fuel source, as a way of lessening dependency on fuel imports. This interest has stimulated research on all aspects of the fuel cycle, ranging from the production of raw input to consumer reaction to changes to the fuel used in particular applications. New Zealand (with its research on liquid fuels from biomass, and in particular liquid woodfuels research - refer Appendix 1) and Brazil (with its agrofuels ethanol-from-sugar cane program - refer Appendix 2) provide good examples of the concerns of the period and of the response within both the developed and developing world.
The New Zealand research program on woodfuels also demonstrates the major issues and changes in concerns of most energy research in developed countries in recent decades. Initially the concern was very much focused on transport fuels and in particular the imported oil used by the nation’s road transport sector, the focus then shifted to be less specific and more concerned with efficiency while latterly it has been somewhat more concentrated on the environmental aspects of energy use. For New Zealand, as for many other nations, the last 15 years of the 20th century also produced a move away from formal sectoral policies and planning in energy towards a greater reliance on competitive markets and market signals to determine both the sources to be used in various sectors and to ensure adequate provision of energy to meet local needs. Reforms to the energy sector have been generally aimed to both create and sustain competitive markets (e.g., by increasing the penalties for anti-competitive behavior). This change in manner of operation has had, and will continue to have, implications for renewable energy resources and their exploitation.
Appreciation of the importance of costs and benefits other than just those directly associated with growing and processing of fuel crops, and in particular woodfuel crops, grew during the 1980s and has, if anything, increased since. If cheap alternative energy sources imply that purpose grown fuel crops are unable to be justified simply on the basis of the direct cost of the energy from these crops, then externalities (particularly ones relating to the natural environment), sustainability, employment and regional development are seen as possibly sufficient to tip the balance in favor of bioenergy and fuel crops in general. However, increased concern about possible failure to fully account for all externalities associated with energy use, and in particular negative externalities relating to fossil fuel use, has in a number of cases been coupled with a move away from formal government plans and targets, and towards a more deregulated market oriented way of dealing with energy problems.
It is somewhat debatable whether a major change in perceptions of the full cost of fossil fuel use will occur (or if it does, whether it will occur at a sufficient rate) to cause a significant increase in the role of bioenergy in the world’s primary energy supply in the next 20 years. There are, of course, many other scenarios that include biomass energy as a significant source of energy e.g. IPCC, Shell International, World Energy Council, etc, ranging from 67 EJ to 450 EJ for the period 2025-2050 (see Hall et al., 2000). However, for a number of reasons, for the purpose of this analysis the IEA scenario has been utilized. The reference scenario for the International Energy Agency’s world energy outlook, (IEA, 2000), covering the period 2000 to 2020, renewable energy projects (including biofuel) are the fastest growing primary energy source. However, the scenario also projects the contribution of renewables to world primary energy supply will still remain at less than 10 percent of the total energy supply by 2020. This is despite the fact that the IEA reference scenario takes into account those greenhouse gas policies that have already been adopted or announced by OECD countries in the period up to mid-2000.
While over the next 20 years renewable energy are the fastest growing primary energy source in the IEA reference scenario, a large part of the increase is attributable to hydropower (particularly due to increased projected usage in developing countries). Increases in all other renewable energy sources (including geothermal, solar, wind, tide, wave, waste, and biomass) is still only sufficient to take these renewables from 2 percent of the current primary energy supply to 3 percent. It should be noted that the IEA reference scenario excludes a lot of traditional woodfuel usage and as a result woodfuels currently account for less than 2 percent of world primary energy supply in this particular analysis compared to 7 percent in FAO estimates.
The IEA scenario also does not include the impacts of possible future initiatives relating to greenhouse gases and climate change. In that regard and in particular it does not include any effects arising from implementation of the 1997 Kyoto Protocol. This protocol arose out of the 1992 United Nations-adopted Framework Convention on Climate Change (FCCC). It divides countries into developed (Annex 1) and developing (Annex 2) and calls for reduction, by Annex 1 countries, in emissions of greenhouse gases that are not already controlled by the Montreal Protocol, for the period 2008-2012. Specifically the protocol:
• makes provision for emission trading as a means of minimizing the costs of abatement;
• acknowledges the contribution of sinks (specifically the contribution of carbon absorption from afforestation and other land use changes since the 1990 base year);
• sets differentiated emission reduction targets for the Annex 1 nations; and
• covers six greenhouse gases, not just carbon dioxide.
The overall emission reduction by the Annex 1 countries required by the Kyoto Protocol is 5.2 percent of the 1990 levels for the period 2008-2012. Much public discussion of the Kyoto Protocol treats it (and its implications) as a fait accompli. However, before it can come into force it must be ratified, approved, accepted or acceded to by “not less than 55 Parties to the Convention, …which accounted in total for at least 55 per cent of the total carbon dioxide emissions for 1990 of the Parties included in Annex 1”.6 Given that the Kyoto Protocol has been ratified by only 22 of 84 original signatories to the protocol (as of 13 January 2000) – none of whom would be required to reduce their emissions under the terms of the treaty – it is not difficult to see why a scenario such as the IEA reference one (in which effectively the Kyoto Protocol does not come into force) should be considered at least as being a real possibility7. However, it does mean that should this, or for that matter any other protocol on climate change, be implemented it would imply somewhat different base conditions than those applying in the IEA reference scenario.
Figure 1 shows the projected world energy supply by source up to 2020. In the light of these projections, the focus of much of the current analysis should clearly be on woodfuel as a substitute for oil, gas and coal. As a result the technologies to be examined in the remainder of this paper are primarily ones that allow woodfuels to substitute for these fossil fuels either directly or alternatively that are ones which may be used to provide a product (e.g., electricity) which is currently supplied by these fuels.
Traditional firewood/woodfuel use for cooking, home heating, and cottage industries, despite the fact that it is currently the major energy use of wood, does not fit with this focus and is not dealt with in any detail in the remainder of this paper. Options that this paper will attempt to cover are:
• direct combustion for heat for direct use and/or electricity production;
• gasification to provide a fuel for combustion, both for heat or for use in an engine or turbine for electricity generation;
• fast/flash pyrolysis to provide a liquid fuel that can substitute for fuel oil in any static heating or electricity generation application. The liquid can also be used to produce a range of specialty and commodity chemicals; and
• fuel ethanol production.
Source: IEA, 2000
2 FAO data base www.fao.org
3 RWEDP is a grouping of 16 developing
countries in Asia; namely Bangladesh, Bhutan, Cambodia, China, India, Indonesia,
Laos, Malaysia, Maldives, Myanmar, Nepal, Pakistan, Philippines, Sri Lanka,
Thailand and Vietnam.
4 This figure is sourced from the FAO’s data base and from the “Importance of Forest Energy” (see www.fao.org/forestry/FOP/FOPW/ENERGY/IMPORT-e.stm).
Others, such as the International Energy Agency (2000) suggest that wood
provides a lower percentage (of the order of 2 to 3 percent) of world primary
energy supply.
5 FAO
data base.
6 From the first paragraph of Article
25 of the Kyoto Protocol.
7 A
view that may be reinforced by the US decision not to sign up to the Protocol –
a decision that was announced after this section had been written.