Where a survey has objectives limited to only a few variables, it is possible to make do with partial analyses. Examples: analysis of fuel consumption by an industrial sector or branch; comparison of specific consumption and costs associated with different means of burning fuel; appraisal of actual and potential supply in a given area.
In these cases the investigation must concentrate on obtaining answers to certain specific questions, in particular those posed by the interest groups (see box).
Where the survey sets out to analyse the whole wood energy situation in a given context, an integral analysis is called for. For this, all important aspects of demand, supply and provision must be considered, with a description of physical and economic flows of woodfuels and examination of the balance of supply and demand.
This element of the analysis concerns the physical magnitudes (volume or weight, distance) of woodfuel transfer from source to end user. Its representation takes the form of a network or system. It is important for identifying the principal sources and their share of supply, indicating areas or types of source where demand is high, quantifying labour involved in provision, and facilitating analysis of transport costs and their share in the final prices of energy in the system.
The physical flows of self-provision and commercial supply must be reported separately in graph form (with a map or diagram of flow), and numerically (with a flow table). Where the physical flow of certain types of woodfuel is important and can be differentiated, these too must be disaggregated. For example: pasture clearings, 15 000 t/yr; sawmill waste 2 500 t/yr; pine firewood 800 t/yr; charcoal 1 300 t/yr.
Generally, the scale used for analysing this variable is local or micro-regional since woodfuels are not usually transported over great distances. There are, however, some notable exceptions such as charcoal for industrial and residential uses in countries like Argentina, Brazil, Ghana and Sudan, where heavy charcoal flows of 500, 800 and even 1 200 km have been reported.
In order to construct the physical flows of woodfuels, we need to:
(a) identify the principal places of origin or production (geographic location, kinds of resources used, and quantities involved);
(b) describe the producers, processors, stockpilers and distributors of woodfuels within each area;
(c) specify the routes and means of transport used and quantities transported;
(d) estimate the quantities from each source consumed by respective sectors or branches of end users.
If the flows are constructed from data obtained from consumption surveys conducted by sampling, the sources will be known for only a fraction of the fuels consumed, i.e. that corresponding to the consumers included in the sample, and it will not be possible to extrapolate its distribution to the rest of the stratum or population in question (see Annex X). In this case, the flow is partial and it will not be much more representative than the fraction sampled. This is not a serious limitation where the survey does not have a wide coverage, for example a municipality, a district or a micro-region where demand is concentrated and the flow in “funnel” form. This difficulty could even be overcome with supplementary data from specific questionnaires to producers, traders, transport operators, control bodies, etc., which will give a better picture of aspects not fully reported by consumers.
As a general rule, it is cheaper and easier to conduct flow studies from areas where demand is concentrated. There, samples of consumers and surveys of other sources will help identify areas of origin and main patterns of procurement. With this preliminary characterization, the information search then proceeds “upstream” along the chain of distributors, stockpilers, transport operators, producers to the point where the main or most representative part of the total flow is covered.
A further possibility is to conduct a “downstream” survey in cases where there is an area of major or concentrated production, or a source of particular interest (e.g. a charcoal district, an area of mangroves or oak woods). What we are dealing with here are partial flows that are worth surveying because of their high importance or economic or social impact.
Where supply and demand are scattered or where the area exceeds normal transport ranges, there is no point in attempting to characterize complete physical flows.
This element of the analysis describes the economic magnitude of the commercial physical flows. It is represented as a network or system that reflects the commercial network of each case, and is important for understanding of the economic and social importance of the commercial woodfuel supply systems and the distribution of added value within these systems.
Just as with physical flows, economic flows can only be analysed at the local or micro-regional level, subject to the above-mentioned caveats.
To construct economic flows, it is first necessary to know the physical flows, the marketing network and the prices of woodfuels at each link of the chain. The marketing network will take shape as the physical flow is constructed. For final or consumer prices, the best sources of information are the consumer samples but, for intermediate prices, specific surveys must be conducted among producers, stockpilers, transport operators and wholesalers. If, as frequently occurs, the prices do not vary greatly, these surveys need not cover a large number of cases.
Once the price chain is known, it is possible to estimate the value added at each stage, the proportion accruing to each group of players (producers, stockpilers, transport operators, wholesalers and retailers), and their contribution to final prices. This information is important in deciding tax measures, social policy and incentives for technological improvement.
An understanding of economic flows helps gauge and interpret the importance of woodfuels in the regional or national economy, their contribution to job creation and income generation, their potential for the creation of fiscal revenue and the impact of substitution of energy sources. This is very important for defining energy, social and natural resource management policy.
The balance of supply and demand is the final and most integrative part of the woodfuel analysis. It represents the relationship between consumption and availability, and offers pointers to possible deficits or surpluses.
Two basic kinds of balance can be constructed:
(e) static or time-specific balances that relate to annual consumption of total stocks, effective availability or productivity at a given moment and for a given area;
(f) dynamic or serial balances that bring together projected demand and potential or actual supply in respect of diverse sources of woodfuel over a time span.
Static balances are useful in analysing the structure of demand in relation to actual supply, particularly if constructed by disaggregating the contributions of the different sources and their incidence in satisfying the requirements of different sectors and branches of demand (see Annex VIII). This helps identify most important sectors and branches in absolute and relative terms, specific relations between sectors of demand and sources of supply, and many other relations that detail and enrich understanding of the environmental, economic and social impact of woodfuel use within a given geographical environment and for a given moment in time.
Dynamic or serial balances enable, analyse and compare the evolution of supply-demand relations over time, and evaluate the result of present and potential trends in demand as against future variations in supply. For example, an analysis can be made of the impact of increased consumption of charcoal resulting from development of the steel industry on supply to users, fuelwood stocks, land use, creation of plantations, substitution in other consumer sectors, and rural employment and income in a given region; or the possible impact on logging resulting from a reduction in specific fuelwood consumption due to the dissemination of more efficient stoves or an increased penetration of LPG.
To construct static balances, it is necessary to have data: on demand - at least the specific consumption for each fuel and user type (exclusive and multiple) and the number of users per type of fuel, sector and branch; on supply - at least the area, unit stocks and productivity of primary sources, and annual production from secondary sources and recoveries. For dynamic balances, we also need data or firm hypotheses on increases or reductions in consumer populations, technical ratios and rates of fuel substitution, rates of change in land use and possible changes in resource productivity.