Chapter 6 Differences in Consumption Rates and Patterns between Firewood
6.3. Materials and Methods
6.3.1. Household survey
We selected 16 villages along the roads for the household survey to cover villages with different levels of accessibility to the forest, as shown in Figure 6.1. For each village, households were selected randomly, resulting in a total of 181 households comprising 147 firewood users and 34 charcoal users. The surveys were conducted twice; the first in February in 2014 for 40 firewood users and the second in December 2014 for the other users.
These households used only either firewood or charcoal. This sampling intensity covered approximately 10 % of the total number of households in the 16 surveyed villages. The interviews were based on semi-structured questionnaires focusing on household sector energy uses only. The questionnaires were linked to a family member, income, woodfuel consumption, stove types, and cooking frequency, which can influence the amount of woodfuel consumption. Additional variables, such as the species and sizes of trees used for firewood, whether dead or green wood was collected for firewood, and the sources of firewood, were included in the questionnaires. Among the 147 firewood users, the 40 users during the first survey were not interviewed for income, species and sizes, because the first survey was conducted just under the narrower scope. The 2 users among the rest 107 users had no idea about the sizes. The firewood sources were classified into four categories (natural forest, private plantation, agricultural farm and buying) and the respondents (n = 107) answered the fraction of each of the four categories they sourced from. For each source except for buying, the fraction of dead or green wood was also asked. These respondents also listed species that they used for firewood. The firewood sizes were classified into four classes (≤ 5.0 cm, 5.1-10.0 cm, 10.1-20.0 cm, 20.1-30.0 cm and 30.1-35.0 cm) and the respondents (n = 105) answered the fraction of consumption among the size classes. It was difficult for the the respondents to answer a specific range of size, and so we showed actual wood samples with different size classes to them during the interviews.
Five additional respondents who produce charcoal for income were interviewed in December 2014. Emphasis was given to the sizes and species of trees used in charcoal
production, the sources of wood, and the method of charcoal production. A group discussion was also conducted in December 2015 to classify species into four grades in terms of charcoal production: grade 1 is the best quality species for charcoal, followed by grades 2 and 3, while grade 4 comprises species that are not used for charcoal production.
To estimate the amount of woodfuel consumption, two different measurements were used: measuring the user-stated amount and the actual amount for daily consumption. To measure the user-stated amount, the main cooks were requested to show how much woodfuel they thought would be consumed daily, and then the interviewer weighed and recorded the woodfuel used for all 181 households. Measurements of actual consumption for one day were conducted using a weight survey method (Bhatt et al., 1994; Fox, 1984) in 100 households that were selected from the 147 firewood users and 34 charcoal users. During the course of the interviews, the interviewer weighed some woodfuel, which was the amount more than the main cook’s answer about their daily consumption, and requested the cook to use the woodfuel for one day’s cooking. The following day, the interviewer visited those households again, measured the remaining woodfuel, and calculated the actual daily consumption. Then, the daily consumption was converted into annual consumption.
Woodfuel weights (in kg) were recorded under air-dried conditions when the available firewood in the household was ready for use.
Additionally, to determine the solid wood volume of the consumed woodfuel, we measured the stacked volume and weight of firewood in 43 randomly selected households.
Then, we converted the stacked volume into the solid volume (m³) using a conversion factor applied by the Forest Department of Myanmar (1.0 m³ stacked volume = 0.66 solid m³).
These measurements and the conversion factor resulted in 710 ± 34 kg (mean ± standard error) of air-dried firewood per 1.0 m3 of solid wood. This value is very close to the 700 to 720 kg m-3 ofsolid volume that was estimated by the United Nations Food and Agriculture Organization (FAO, 1983) as average values for tropical species. The conversion factor for charcoal weight and the solid wood volume needed for charcoal production was 167 kg m-3 (FAO, 2016), which was used in this study.
6.3.2. Forest inventory
Forest inventory was carried out in March 2013 by the project on “Capacity Building for Developing REDD+ Activities in the Context of Sustainable Forest Management (2012-2015)” by ITTO (International Tropical Timber Organization) and the Forest Department of
Myanmar. Systematic sampling with equal distance of 2 km between the plots was applied to cover forests in Yedashe Township, resulting in a total of 384 sample plots. The nested plot design was applied; in the 50 m x 50 m plot, all trees ≥ 20 cm DBH were recorded, and in the subplot B (25 m x 25 m small plot), trees with DBH ≥ 10 cm and < 20 cm were enumerated. The total area of the plots was 81.75 ha and its sampling intensity was 0.06 %.
The measured parameters were DBH (Diameter at Breast Height (1.3 m)) and species.
Species identification was carried out by the assistance of local Forest Department’s staff and villagers.
In order to evaluate potential impacts of woodfuel consumption on forests nearby the villages, only 243 plots located within the area of 5 km distance from a total of 301 villages in the rural area were used among the total 327 plots distributed over the whole township (Figure 6.1). This 5 km threshold of distance was commonly used in the other studies (Luoga et al., 2000; Top et al., 2006). The village locations were digitized in ArcMap 10.1 using 2014 population data from Department of population, Yedashe Township Myanmar, and 1:50000 Universal Transverse Mercator Projection (UTM, 2004 edition) map from Forest Department, Myanmar.
6.3.3. Data analysis
To calculate basic statistics, we used data from the user-stated consumption to estimate per capita consumption for firewood (n = 147) and charcoal (n = 34). This is because we analyzed differences between user-stated consumption and actual consumption, confirming that there were no significant differences for either firewood or charcoal (paired t-test, p = 0.87 for firewood and p = 0.25 for charcoal). In this study, per capita consumption was calculated by dividing the total consumption by the number of family members who ate together in each household.
We applied generalized linear model (GLM) with a Gaussian link to examine factors affecting firewood and charcoal consumption rates. The dependent variable was per capita annual consumption rates, and the independent variables included household size, annual income, cooking frequency, stove types (fuel-efficient, three-stone and three-iron), and forest accessibility (easy or moderate). Among the 16 surveyed villages, we defined “easy” forest accessibility for 7 villages located in the western part of the township and “moderate” for the rest located relatively near the highway road (Figure 6.1). R software (R Core Team 2014) was used for all statistical analyses. For the GLM analysis, we used data for the measured
consumption of firewood (n = 100) and charcoal (n = 34), as we did not have such data for 47 firewood users, 40 of which were also lacking income data.
To evaluate potential impacts of firewood and charcoal use on natural forests, we estimated forest area needed to meet the demand for forest-originated green wood as sources of firewood and charcoal;
Ft = Fc×Nr (1)
Fc = Dc / Bw (2)
where Ft and Fc are forest areas needed to meet the demand by the total number of firewood users or charcoal users in the Yedashe Township (Nr) and the demand on per capita basis, respectively, Dc is per capita demand for forest-originated green wood ≥10cm diameter and Bw is forest biomass density that can be used as woodfuel production in terms of size and species. We assumed that wood with smaller size of <10 cm diameter would mostly come from branches rather than the main trunks, and so the demand for such small wood can be negligible to evaluate the impacts on standing trees. Nr for each of firewood or charcoal users at the township scale was estimated based on the township population (213,593) and the ratio of firewood users (147 households) and charcoal users (34 households) obtained from our random sampling. Dc and Bw were calculated as;
Dc = Ccw × Pg × P10 (3)
Bw = Ba × Psi × Psp (4)
where Ccw, Pg and P10 are per capita consumption on a solid wood basis, the fraction of green wood and the fraction of trees ≥ 10cm in the consumption, respectively. Ba, Psi and Psp are forest biomass density and the fraction of tree size and species that can be used for producing firewood and charcoal.