Kit Prins
KIT PRINS is an economist on the staff of the FAO/ECE Agriculture and Timber Division at the United Nations office in Geneva. The work on which this article is based was carried out in cooperation with Jim Cunningham, then on the stab of the EEG Energy Commission.
Man's first use for wood was as fuelwood, and this remains the major use for it in most of -the world. The change from a wood-energy economy to a coal-energy economy occurred first in Britain at the end of the sixteenth century, caused by the inability of wood supply to meet the rising demand for energy (mainly for iron-and glassworks and brick kilns) and the easy availability of coal as a substitute fuel. It may be of interest for today's energy forecasters to note that this radical change was accomplished in a relatively short time - perhaps thirty to fifty years -and with considerable economic and social disruption, including steep rises in the price of fuelwood (Dwyer, 1976).
Since this first shift away from a wood-based energy economy, fuel-wood's advantages -- renewability, simplicity of harvesting and combustion -have been outweighed by its disadvantages-low ratio of calorific value to volume, which increases handling costs, and leek of convenience for large-scale automated boilers. But the main disadvantage of wood is that the supply of fuelwood is not up to the world's growing demand for energy.
A rise in the relative prices of purchased energy as foreseen by many forecasters might have some of the following consequences for the forest industries:
· Higher production and a rise in the share of production costs taken by energy-such a change could take place fairly rapidly.· The implementation of further energy conservation measures, and greater importance given to energy conservation criteria in investment decisions.
· Reappraisal of the economics of using wood, including industrial wood residues, as a source of energy with possible effects on raw material availability for the manufacture of pulp, particle board and fibreboard.
· Modifications in the competitive position of different forest products and of alternative materials according to their energy intensity.
At the present stage of knowledge on energy consumption patterns of the forest industries, it is not possible to quantify with any degree of accuracy to what extent any of these consequences will occur or to attempt any forecasts.
We hope that further information will become available, thus affording a better analysis of an aspect of the forest industries which, until very recently, has been neglected at least in the mechanical wood-processing sector.
In order to provide a basis for planning and executing such measures, interested countries should strengthen considerably these data bases, notably by collecting comparable data for all sources of energy, including wood-based fuels, and by providing information for the forest industries at the individual product level.
This study aims to estimate the quantity of energy derived from wood at present; to find out how this energy is used; also, to examine the consequences for the forest industries of an increase in the use of wood as a source of energy and to identify some of the factors which might cause such an increase.
No attempt is made to examine the "unconventional" wood/energy systems which have recently been proposed (manufacture of liquid or gaseous fuels, energy plantations, etc.), which are being examined elsewhere in the United Nations Economic Commission for Europe (ECE). Readers are referred to reports on the situation and prospects for wood-derived energy in Finland, Norway and Switzerland by Messrs Hakkila, Gislerud and Semadeni (TIM/SEM.7/R.18, 4 and 6 respectively) and to the assessment by Mr. Zerbe of the technical and economic potential for wood-derived fuels (TIM/SEM.7/R.15).
Most roundwood harvested specifically for fuel is used domestically on the farms or in the forests where it is harvested, mainly for space and water heating in rural areas. Large quantities are used without ever entering commercial channels and are not recorded statistically. Therefore, accuracy of data on fuelwood consumption is probably very low and we should not rely too much on the volumes shown, although these recorded developments probably reflect real trends fairly adequately.
The steady decline in fuelwood consumption in the ECE region over the last 25 years is apparent from Table E Over this period the decline was most marked in North America (-75 percent) and least marked in the USSR (-24 percent). In Europe fuelwood consumption was halved.
Has the "energy crisis" of 1973-74 and the consequent increased attention to energy questions affected fuelwood consumption ? Table 2 shows that the decline in fuelwood consumption appears to have continued in Europe and the USSR, with temporary irregularities in 1975-76 for Europe and in 1974 for the USSR. In North America, however, consumption rose by 9 percent in 1976 and by 16 percent in 1977 (admittedly from a low base). Is this a passing trend or is it the first sign of a significant move back toward fuelwood in a region where many people are acutely aware of the ecological implications of their choice of fuel and where wood is easily available in rural areas ? The fuelwood stove is a part of the "alternative lifestyle:" but will this change - this increase in the use of fuelwood-at the national level have any measurable impact on the wood economy? And if so, will the trend spread to Europe, at least to areas where the presence of both suitable wood and conditions can encourage its use ? These questions cannot be answered after only two years of results and enthusiastic press reports. However, we must now give some considerations to these possibilities in any long-term assessment of prospects for the timber economy and for energy supplies.
The forest industries also derive part of their energy from solid wood residues and bark and from pulping liquors. For our study we assumed that half the residues not used as raw materials were used for energy. Conversion factors presented in an OECD study were used to estimate the amount of energy derived from pulping liquors. On the basis of the recorded statistics for fuelwood and the above assumptions, the quantity of energy derived from wood may be estimated as in Table 3.
Thus wood accounted for 1.4 percent of total energy consumption in Europe, 1.2 percent in North America and 2.6 percent in the USSR. This relatively small percentage is, however, not an adequate reflection of the importance of wood as a source of energy for rural communities and forest industries.
On the reasonable assumption that most fuelwood is used domestically or on farms and that all wood residues and pulping liquors provide energy for industrial purposes, we may make the following breakdown of the use of wood for energy (in percent of total energy derived from wood):
|
|
Domestic/rural Industrial | |
|
|
Percent | |
|
Europe |
56 |
44 |
|
North America |
17 |
83 |
|
USSR |
77 |
23 |
|
ECE region |
51 |
49 |
The contrast in the distribution of uses between the different regions is striking. In North America, wood derived energy is predominantly industrial: in fact over 70 percent is in the form of pulping liquors, and energy from fuelwood or solid wood residues has dwindled to negligible proportions (although these sources appear to be making a comeback). In the USSR on the other hand, more than three quarters of wood-derived energy came from fuelwood, an easily available energy source for human settlements in remote regions such as, for example, Siberia, where fossil fuels such as oil or coal are difficult and expensive to obtain. Furthermore, in relation to the total economy of the country, the chemical pulp industry in the USSR is relatively little developed. In Europe (excluding the USSR), about half of wood-derived energy is from fuelwood, used in remote areas (such as parts of Scandinavia and Finland, mountain valleys, parts of southern and eastern Europe) and half from wood residues and pulping liquors, consumed by the region's forest industries. The even distribution between rural/domestic and industrial uses at the level of the ECE region results from the combination of these trends.
Figure 1. ECE region: energy flows in the forest industries in the mid-1970s (106 TJ)
|
Energy may be measured in many ways including calories, kilowatt-hours, Btus (British Thermal Units), coal equivalent or oil equivalent. There is a trend, at least at the international level, for energy analysis to standardize on the Joule (symbol: J) and its multiples for general energy balances. The Joule is used throughout this study. A Terajoule (TJ) is a million million (1012) Joules. One Terajoule is equivalent to 0.2388 Teracalories, 277.7 thousand kilowatt-hours, 947.8 million Btus or 34.1 thousand million metric tons coal equivalent. A Gigajoule (GJ) equals one thousand million Joules or 1/1000 of a Terajoule. |
|
Net primary production on forest land "Net primary production" is the production of biomass over a given period net of photosynthesis. It is defined as the difference between total biomass at the beginning and at the end of the period plus those plants or parts of plants which have died and been shed and those plants or parts of plants which have been eaten by animals. |
Figure 1 shows, in energy terms, the flow of raw materials and energy in the forest industries sector of the ECE region in the mid-1970s (where possible the data are averages for 1974-76). From the net annual increment stage onward, the chart is based on ECE/FAO Agriculture and Timber Committee statistics and on the estimates of the two secretariat papers.
The sunlight and net primary production figures were calculated from values given in the current literature of quantitative ecology for the latitudes and major vegetational types represented by the forest lands of the ECE countries. For the sake of completeness, some flows have been calculated as residuals, and particular items missing for certain subregions have been estimated on the basis of partial or unofficial information. It has also been necessary to omit certain factors for lack of information (energy used in harvesting and transport, bark, natural losses, logging residues, energy contained in glues and other additives, etc.).
Table 1. ECE region: consumption of fuelwood 1949-51 to 1974-76
|
|
Volume consumed |
Annual average change |
|||||
|
1949-51 (av.) |
1959-61 (av.) |
1969-71 (av.) |
1974-76 (av.) |
1949-51 to 1959-61 |
1959-61 to 1969-71 |
1969-71 to 1974-76 |
|
|
Million m³ |
Percent |
||||||
|
Europe |
121.8 |
93.6 |
68.4 |
56.3 |
-2.6 |
-3.1 |
-3.8 |
|
North America |
69.9 |
50.9 |
20.7 |
17.9 |
-3.1 |
-8.6 |
-2.9 |
|
USSR |
111.6 |
111.1 |
86.9 |
84.8 |
- |
-2.4 |
-0.5 |
|
ECE region |
303.3 |
255.6 |
176.0 |
159.0 |
-1.7 |
-3.6 |
-2.1 |
Table 2. ECE region: consumption of fuelwood, 1973 to 1977
|
|
1969 71 (av.) |
1973 |
1974 |
1975 |
1976 |
1977 |
|
Million m³ | ||||||
|
Europe |
68.4 |
58.8 |
54.0 |
54.9 |
56.0 |
54.0 |
|
N. America |
20.7 |
17.6 |
17.6 |
17.2 |
18.8 |
21.7 |
|
USSR |
86.9 |
83.5 |
84.8 |
82.2 |
81.6 |
74.0 |
|
ECE region |
176.0 |
159.9 |
156.4 |
154.3 |
156.4 |
146.1 |
Table 3. ECE region: energy derived from wood compared to total energy consumption
|
|
Fuelwood |
Residues |
Pulping liquors |
Total |
Total energy consumption |
|
Thousand TJ | |||||
|
Europe |
505 |
110 |
280 |
895 |
61 761 |
|
N. America |
160 |
105 |
650 |
915 |
77 531 |
|
USSR |
765 |
¹135 |
90 |
990 |
38 656 |
|
ECE region |
1 430 |
350 |
1 020 |
2 800 |
177948 |
(¹Estimated that 15 percent of total available residues used as fuel.)
With reference to assessing potentials for solar power in general, and biomass in particular, we should note the great step down from incident solar radiation to net primary production (see Figure 1). Nevertheless, forests remain one of the most efficient means for capturing solar energy, and particularly for storing it semi-permanently. Increasingly widespread recognition of this fact is responsible for the current interest in the possibilities of "energy plantations" among national energy planners as well as foresters.
On the basis of the estimates made above, it is possible to make a summary evaluation of the place of wood as a source of energy.
On the national or regional level, wood is not an important direct source of energy. The three types of wood-derived energy mentioned in Table 3 accounted for about 1.5 percent of consumption of energy in the mid 1970s, both in Europe and the ECE region as a whole. The relative importance of the forest in energy terms would appear greater if substitution effects were taken into account by comparing net energy input for wood-derived products with net energy input to non-wood products performing the same function. In fact, biological synthesis of the wood itself is a (solar energy-intensive process, comparable in some ways to industrial synthesis of substitutes.
The size and nature of the resource will not permit wood to be a major annual source of energy on the scale of oil, coal or gas without changes of unprecedented magnitude or without severely depleting the resource. To take an extreme example, even ':he total net annual increment of stem-wood of about 2 275 million m³ with. bark in the ECE region is equivalent, in energy terms, to little more than 10 percent of its energy consumption. It is thus fair to say that, without really far-reaching measures such as the allocation of large areas of fertile land to "energy plantations" and with the possible exception of certain forest-rich areas, wood cannot be more than a supplementary source of energy :for the ECE region.
Although marginal in terms of annual fuel requirements, the forest is a renewable resource, which gives it some advantages over other, depletable resources in the longer term. Thus, if the composition and productivity of the forests in the ECE region were only to remain constant over the next 50 years (a period chosen as the generally agreed maximum endurance of reserves of oil and gas), the energy equivalent of the cumulative increment of stemwood would be slightly more than 1 t × 109 TJ (Terajoules-see chart): this is equivalent to almost half the region's recoverable reserves of oil and gas, estimated by the World Energy Conference (Istanbul, 1978), slightly modified for North America, at 2.2 t × 109 TJ, and about 15 percent of world reserves of these fuels, estimated a 7t × 109 TJ. This comparison does bring out the sometimes underestimated long-term potential of small flows from a renewable resource, compared with a supply from a large, non-renewable one.
The generation of energy remains, however, an important end use for wood. An unexpected fact which appears from the estimates in Table 3 is that about one quarter of all the wood removed from the ECE forests is ultimately used as a source of energy. In fact, the amount of wood which is burned appears to lie roughly equivalent to the volume of sawnwood produced in the region, slightly larger than the volume of fibre, including waste paper, contained in pulp and paper, and considerably larger than the wood in wood-based panels. Although it must be stressed that these proportions are based on estimates, notably as regards the importance of pulping liquors, they should lead those concerned with policies in the forest sector to examine more closely their importance as an end use for wood. The conclusion must be that even in the developed world, the use of wood for the generation of energy has not been small, although its importance has declined. Furthermore, indications are that as policy-makers devote increasing attention to energy supplies, looking for renewable sources to replace fossil fuels, this use for wood will grow in importance.
For the forest industries, however:, wood is an important source of energy. Waste liquors alone account for over 20 percent of energy input to the pulp and paper industries of the region and liquors and solid wood residues together for over 25 percent of energy input to the forest industries as a whole.
Without far-reaching measures such as allocation of large areas of fertile land to "energy plantations, and with the exception of certain forest-rich regions, wood cannot become more than a supplementary source of energy for Europe, the USSR and North America.
Some sectors of the forest industries are in theory self-sufficient or even net providers of energy. Increased use of wood as a source of energy could make the forest industries in general and sawmills in particular more self-sufficient in energy. Indeed the energy value of the residues created by sawmills, plywood mills, and veener mills, about 550 thousand GJ (Gigajoules -- see [Figure 1), is about 2.5 times as much as the energy consumption of the mechanical wood-processing sector, about 210 thousand GJ (which includes the manufacture of particle board and fibreboard, which do not generate solid wood residues in large quantities). However. this self-sufficiency is at present almost entirely theoretical: we saw that wood is at present a minor source of energy for the mechanical wood-processing sector. Also most of the residues "available" for use as energy are in those areas where the forest industries are less intensively developed, and where at present a large proportion of residues generated is probably lost. Species also plays an important role: hardwood residues which are less suitable for use as raw material are therefore more readily available as a source of energy. This is currently being demonstrated in the United States.
Those areas with large mechanical wood-processing sectors, which need important quantities of energy, are naturally those where the intensive use of residues for raw material is most highly developed, correspondingly reducing the availability of residues as a source of energy. Nevertheless, in purely quantitative terms, enough energy could be generated from the residues of sawsmills, plywood mills and veneer mills to satisfy the needs of the mechanical wood-processing sector. For some sectors, difficulties may arise from the fact that energy is frequently needed in the form of electricity which it may be impractical or uneconomic to generate from wood residues at the mill -particularly in small-scale operations.
The possibility and economic desirability of using more wood residues to produce energy in any one case depend on a wide range of factors, including the following:
· Type and quantity of energy required (high- or low-pressure steam, electricity, space heating, etc.).· Type, quantity and condition of residues available (moisture content, proportion of bark, sander dust, planer shavings, etc.).
· Energy equipment already installed and cost of different types of new equipment.
· Cost of non-wood energy and possible developments during the lifetime of equipment installed.
· Desirability of energy self-sufficiency for the plant (risk of interruption of external energy supplies).
· The costs and/or benefits of other possible destinations for residues (e.g., sale for use as raw material, in-plant transfer, disposal).
The combination of those factors will lead to different decisions in different circumstances although rising costs of energy will probably increase the proportion of residues being used for energy, with possible consequences for the raw material supply of the pulpwood-using industries.
A significant increase in the use of wood residues as a source of energy, caused by a rise in the relative price of energy, could have consequences for the whole of the forest and forest industries sector. The first consequence would be a further decline in the proportion of residues left unused, although, as mentioned earlier, the reserve of unused residues is already relatively limited in some parts of the region.
In a situation of continued expansion of demand for the products of pulpwood, that is, if final demand is not seriously affected by higher prices for energy, the following is envisaged:
Competition for the available residues between demand for raw material and demand for energy could raise their price and increase demand for alternative types of wood raw material. This in turn could increase the availability of wood raw material from sources currently less exploited for economic or technical reasons (whole tree logging, silvicultural thinnings, round pulpwood in areas where harvesting costs have so far discouraged exploitation). Higher prices for pulpwood could also divert some wood from the sawnwood to the pulpwood sector, either by pulping of small sawlogs or by reducing yields of sawnwood. The recovery of waste paper could also be encouraged.
In these circumstances, overall raw material costs for the pulpwood-using industries would increase. The interrelationship of the factors concerned is, however, very complex and varies widely between different areas and industries. Further analysis, in both qualitative and quantitative terms, is therefore necessary before the full implications of a rise in energy prices for the forest and forest industries sector are fully understood.
It has been suggested that the following potential sources of wood energy be developed as part of an effort to increase the share of renewable sources of energy and thus reduce pressure on reserves of depletable fuels: silvicultural thinnings; logging residues (including branches, tops, etc., harvested as part of full-tree or full-stem logging); "energy plantations" of quick-growing trees or shrubs, cultivated exclusively as a source of biomass energy.
Several countries have been examining the technical and economic feasibility of developing these sources of energy, either by direct combustion or for the manufacture of liquid or gaseous fuels, as well as the implications of such development on the forest sector. For example, they are looking into the possibility of catching up on thinning regimes which have fallen behind what is silviculturally desirable; competition for logging residues between the energy sector and the pulpwood-using sector; need for more mechanized harvesting systems and different silvicultural practices, including the choice of different species.
This study has attempted to describe briefly the present situation, and past trends, regarding energy consumption by the forest industries and energy derived from wood, and to explore possible energy conservation measures and consequences of a rise in energy prices. To summarize, here are the main ways through which these industries can participate in energy conservation at the national or regional level:
· Technical improvement of production processes (using less energy to do the same job). The pulp and paper sector has a record of success in this field.· Ensuring that no combustible residues are unused or burned without recovery of the energy. In future, more favourable economies could encourage the industries even to burn those residues which are at present a source of raw material with consequences which are difficult to foresee.
· Encouragement of products that are less energy intensive. Little work has been done on this at present because of the complexity of the calculations involved. Not only should most energy used in manufacture be appraised, but also the characteristics of each product in use must be examined. Forest products appear less energy intensive than most other building products. It may be that energy conservation in construction could be encouraged by higher consumption of forest products, in place of other construction materials such as concrete or steel.
Unfortunately, however, the quality and quantity of the data on which this article is are founded leave much to be desired. The major conclusion to be drawn is all too familiar: the need for further investigation. Only then can a policy be formulated on a basis of sound knowledge and analysis.
DWYER, ALAN D. Wood and coal: a change of fuel. History Today, September, 1 976.
OECD. Energy profile and opportunities for savings in the pulp and paper industry. DSTI/IND/PP/7802.
See also HANNON et al. Energy and Labor in Construction Sector. Science, 24, November 1978.
