Feedstock Security Analysis for Wood Pellet Production in Thailand

: Thailand is one of the upcoming wood pellet exporters in the Southeast Asia region. Wood pellet production has been gradually increasing in Thailand; however, the recent trend is more rapid. Therefore, the objective of this study is to analyze the feedstock security for wood pellet production in Thailand. The important issue of feedstock security analysis relates to availability and diversity of feedstock (Shannon index) to meet the increased demand for the wood pellets in the future. The results present that the feedstock supply (from waste wood and fast-growing tree wood) in Thailand is 5.32 million tonnes of wood pellets per year. However, increasing 25% of wood pellet export and 50% of wood pellet domestic use causes a deﬁcit in fast-growing tree wood because para-rubber waste wood is not distributed uniformly in all regions of the country. The present diversity of feedstock supply is quite low (Shannon index 0.17). Increasing the fast-growing tree plantation area in the wastelands could help increase diversity. Recommendations on policy from this study focus on encouragement for the increase in domestic use of wood pellets, cultivation of fast-growing trees in wasteland and optimized logistics management.


Introduction
The use of biomass as renewable energy is broadly accepted for substituting fossil fuels [1]. Wood pellets are solid fuels made from biomass, especially waste wood. The wood pellets are bio-based products utilized for heat and electricity production in several countries [2]. Future forecast of global wood pellet demand predicts a significant increase up to 54 million tonnes in 2024 (40% demand for the heating pellet market and 60% demand for the industrial pellet market) [3]. The wood pellet demand depends on policies, weather and the price of fossil fuels. In 2018, about 52.7 million tonnes of the wood pellets were produced, including 17.7 million tonnes from China [4]. The growth rate average of the global wood pellet market is 11.6% annually (in 2012-2018) [3]. In Asia, South Korea and Japan have a huge potential demand for the wood pellet industry. South Korea presented a wood pellet demand of around 2.88 million tonnes for electricity production in 2020 [5]. The wood pellet demand in Japan will increase to 5.8 million tonnes in 2030 because the Japanese government plans to partially substitute coal with industrial wood pellets [6]. The main supplier of Japan was Vietnam in 2019 (Canada in 2018) [3].
Thailand exported 172,441 tonnes of wood pellets in 2019. The major importers of wood pellets from Thailand are South Korea and Japan. The wood pellet production of Thailand is expected to rise

Materials and Methods
Important indicators for evaluating feedstock security are quantity and diversity of wood feedstocks that are sufficient to produce wood pellets to meet the demand.

Evaluation of Wood Pellet Production
Statistical data of wood pellet production in Thailand have not yet been compiled at an organized level. However, the quantity of production can be estimated considering wood pellet export and domestic use. The data of wood pellet export can be obtained from the website of the Thai customs (https://www.customs.go.th). Interviewing entrepreneurs revealed that they sell only 20% of the entire wood pellet production for domestic use. Hence, it is assumed that 80% of the wood pellet production is for export.

Sensitivity Analysis
Sensitivity analysis is a tool to analyze how the different values of an independent variable affect a specific dependent variable under certain exact assumptions. In general, its aims are to analyze the data for the decision problem and to create a necessary decision model. It is used in several fields, for example, economics, biology, geography and engineering [23,24]. In this study, sensitivity analysis is used for testing the assumptions related to the wood pellet production in Thailand. The quantity of wood pellet production can refer to the quantity of feedstock, which is one of the indicators of sustainable wood pellet production. Domestic use and exports govern the demand of wood pellet production. Hence, domestic use and export of wood pellets are important factors to evaluate the quantity of wood pellets per year. Sensitivity analyses help to calculate the minimum and maximum values of wood pellet production under demand from domestic use and export. The variation in wood pellet demand was evaluated by increasing (+10%) the export and domestic use (tonne). The maximum quantity of wood pellet production helped to evaluate the sufficiency of raw materials. However, the wood pellet demand was also evaluated based on the policy of importers and the Thai government. Two-way sensitivity analysis is identified as the interaction effect between the increase in wood pellet export and domestic use. The increases in wood pellet export and domestic use were determined with a maximum of +150% to present the quantity of feedstock.

Evaluating the Potential Amount and Proportion of Feedstocks
The potential amount of wood (main feedstock) was analyzed because it is important for increasing the wood pellet production. The potential amount of wood or waste wood in the past was considered to prepare and plan for an increase in wood pellet production in the future, which is forecast by sensitivity analysis. The potential amount of feedstock was converted from the product by a conversion factor which was subtracted from the total amount of feedstock. The net feedstock balance was calculated by subtracting the projected feedstock requirements in the future from the estimated available feedstock resource. The available feedstocks for wood pellet production were estimated from the following equation [14,25]: where PQ i is the potential amount of feedstock i for wood pellet production in the country (tonne/year), TQ i is the total amount of feedstock i in the country for a period (tonne/year), CF ij is the conversion factor to convert amount of feedstock i for producing product j, D Domestic i,j is the total demand of product j for domestic consumption (tonne/year), and D Export i,j is the total demand of product j for export (tonne/year). Quantity of wood and waste wood data were collected from the related organizations. The data of wood pellet production were surveyed by questionnaires from farmers and wood pellet manufactures. The average conversion factor was calculated from five wood pellet factories having different processes and raw materials (Table 1).

Shannon Index-The Diversity of Supply
The diversity of feedstock supply relating to the feedstock security was calculated by the Shannon-Wiener index [26]. This index, applied to evaluate the long term security of supply and the diverse distributions of energy flows in a system, can open up more possibilities and channels for cooperation and interdependency in energy utilization [27]. Moreover, the diversity of the demand side, which is critical for an energy system because increasing variance and balance of the energy consumers enhances efficiency and adaptability, can be calculated by the Shannon-Wiener index as follows [26]: where H is the feedstock supply security indicator, p i is the share of fuel i in the energy mix or the market share of supplier i and, i is the feedstock source index.

Wood Pellet Production in Thailand
Thailand has 44 wood pellet factories, most of them set in the south and central region [28]. The wood pellet factories in the south of Thailand use para-rubber waste wood as raw material and in the other regions use whichever waste wood is available. Quantity of wood pellet export from Thailand decreased in 2015-2016 (as shown in Figure 1) because the price of wood pellets was higher than that in Vietnam [29]. Since 2017, the quantity of wood pellet export continued to grow. South Korea and Japan are the major importers. Japan increased the import of wood pellets from Thailand in 2019 ( Figure 2). From interviewing entrepreneurs who produce the wood pellets, it was found that in 2018, 80% of the wood pellet production was exported, and only 20% was for domestic use. Hence, the production of wood pellets in Thailand can be estimated at 361,600 tonnes in 2018 and 215,600 tonnes in 2019.

Shannon Index-The Diversity of Supply
The diversity of feedstock supply relating to the feedstock security was calculated by the Shannon-Wiener index [26]. This index, applied to evaluate the long term security of supply and the diverse distributions of energy flows in a system, can open up more possibilities and channels for cooperation and interdependency in energy utilization [27]. Moreover, the diversity of the demand side, which is critical for an energy system because increasing variance and balance of the energy consumers enhances efficiency and adaptability, can be calculated by the Shannon-Wiener index as follows [26]: where H is the feedstock supply security indicator, pi is the share of fuel i in the energy mix or the market share of supplier i and, i is the feedstock source index.

Wood Pellet Production in Thailand
Thailand has 44 wood pellet factories, most of them set in the south and central region [28]. The wood pellet factories in the south of Thailand use para-rubber waste wood as raw material and in the other regions use whichever waste wood is available. Quantity of wood pellet export from Thailand decreased in 2015-2016 (as shown in Figure 1) because the price of wood pellets was higher than that in Vietnam [29]. Since 2017, the quantity of wood pellet export continued to grow. South Korea and Japan are the major importers. Japan increased the import of wood pellets from Thailand in 2019 ( Figure 2). From interviewing entrepreneurs who produce the wood pellets, it was found that in 2018, 80% of the wood pellet production was exported, and only 20% was for domestic use. Hence, the production of wood pellets in Thailand can be estimated at 361,600 tonnes in 2018 and 215,600 tonnes in 2019.

Evaluating of Wood Pellet Demand in Thailand
To evaluate the potential of feedstock for wood pellet production, sensitivity analysis is used for forecasting the wood pellet demand. The wood pellet demand in Thailand consists of demand from export and domestic use. Evaluating of wood pellet demand when export and domestic use increase is shown in Table 2. The results show that if the export increases by 100% of export in 2018 and domestic use increases by 100% of the domestic use in 2018, the wood pellet demand will become 723,000 tonnes. Although the wood pellet demand in Thailand fluctuates depending on several factors (policy for domestic use, the demand of importer and competition of other countries), it can be predicted to be within a range of 398,000 to 904,000 tonnes. However, the trend of wood pellet demand in Thailand can be estimated from exports in the

Evaluating of Wood Pellet Demand in Thailand
To evaluate the potential of feedstock for wood pellet production, sensitivity analysis is used for forecasting the wood pellet demand. The wood pellet demand in Thailand consists of demand from export and domestic use. Evaluating of wood pellet demand when export and domestic use increase is shown in Table 2. The results show that if the export increases by 100% of export in 2018 and domestic use increases by 100% of the domestic use in 2018, the wood pellet demand will become 723,000 tonnes. Although the wood pellet demand in Thailand fluctuates depending on several factors (policy for domestic use, the demand of importer and competition of other countries), it can be predicted to be within a range of 398,000 to 904,000 tonnes. However, the trend of wood pellet demand in Thailand can be estimated from exports in the future related to the industrial demand of the main importers, South Korea and Japan (99% of wood pellet export), as shown in Figure 2, and the domestic use in Thailand (Table 3). In 2022, the wood Energies 2020, 13, 5126 6 of 14 pellet demand in Japan will become higher than South Korea by about 200,000 tonnes owing to new power plants coming into operation. The domestic use in Thailand focuses on heat production because the Thai government supports using wood pellets only for heat. The results indicate that the wood pellet demand for Thailand in 2025 will surge to 582,000 tonnes.

Feedstock Supply for Wood Pellet Production
The main raw materials of wood pellets are waste wood from economic wood and para-rubber wood, including wood from FGTs. In 2017, economic and FGT wood production (for domestic use) in Thailand was about 506,350 tonnes (excluding para-rubber wood)-see in Table 4. Some wood was imported from other countries at 30,254 tonnes, that is, only 5.64% of domestic use. Economic wood is timber that can be processed to products, including both direct and indirect benefits for growers such as furniture wood, construction wood, firewood or wood for extracting essential substances. It is valuable and expensive wood and provides farmers with income. It is harvested from trees that grow over three years old, such as, Tectona grandis, Pterocarpus macrocarpus, Samanea saman, Dalbergia cochinchinensis, Dalbergia oliveri, Hopea odorata, Afzelia xylocarpa, Shorea obtuse, Shorea roxburghii, Swietenia macrophylla, Azadirachta indica, Michelia champaca and Anthocephalus chinensis. The waste from economic wood is at 45% of total wood (198,500 tonnes).
FGTs can grow well and are popular in Thailand, for instance, Eucalyptus globulus, Acacia spp., Leucaena leucocephala, Melaleuca cajuputi and Casuarina junghuhniana. FGT production in Thailand was about 84,000 tonnes; these were used for several industries, not only renewable energy. The calculation of feedstock from FGTs is different from economic wood; the trunks of FGTs are used, whereas for economic wood, only waste wood is used to produce the wood pellets. Hence, the total waste wood from economic wood and FGT wood available for producing wood pellets is about 305,000 tonnes.
The para-rubber trees are an economic crop of Thailand for natural rubber production. The para-rubber wood is harvested when the yield of para-rubber reduces (over 25 years old). Thailand had a para-rubber plantation area of about 3.62 million hectares in 2018 [31]. Most of the plantation area (60%) is in the south of Thailand (see in Figure 3). The yield of para-rubber wood per hectare is about 285 tonnes. Waste wood from the para-rubber wood industry is around 8,000,000 tonnes per year [7].   The feedstock supply of wood pellets in Thailand from para-rubber waste wood, economic waste wood and FGT wood is 8.31 million tonnes, which can produce 5.32 million tonnes of wood pellets (CF 1.56). However, the proportion of feedstock type can be calculated by weighting in terms of the number of wood pellet factories and the volume of wood in each region ( Table 5). The results show that the proportions of para-rubber waste wood, economic waste wood and FGT wood are 0.65, 0.15 and 0.20, respectively. The potential amount of feedstock (PQ) in 2018 (Table 6) remains enough for wood pellet production. Nevertheless, a lot of the para-rubber waste wood is concentrated in the south of Thailand; hence, the distribution of feedstocks is not suitable. The feedstock supply of wood pellets in Thailand from para-rubber waste wood, economic waste wood and FGT wood is 8.31 million tonnes, which can produce 5.32 million tonnes of wood pellets (CF 1.56). However, the proportion of feedstock type can be calculated by weighting in terms of the number of wood pellet factories and the volume of wood in each region ( Table 5). The results show that the proportions of para-rubber waste wood, economic waste wood and FGT wood are 0.65, 0.15 and 0.20, respectively. The potential amount of feedstock (PQ) in 2018 (Table 6) remains enough for wood pellet production. Nevertheless, a lot of the para-rubber waste wood is concentrated in the south of Thailand; hence, the distribution of feedstocks is not suitable.
The potential amount of feedstock relates to the wood pellet demand in Thailand in the future. The maximum wood pellet demand is about 904,000 tonnes (Table 2), whereas the overall potential amount of feedstock can produce 5.23 million tonnes of wood pellets. Therefore, Thailand has a substantial potential to produce wood pellets. However, the feedstock, especially para-rubber waste wood, is not distributed evenly in all regions of the country. If the Thai government supports using wood pellets in domestic use conscientiously, the cost of raw material transportation will increase. The results in Table 7 indicate that increasing 25% of wood pellet export and 50% of wood pellet domestic use will lead to a lack of FGT wood (PQ of fast-growing woods becomes −3480 tonnes).  8,305,000 -Para-rubber waste wood 5 8,000,000 -FGT woods 6 106,500 -Economic waste wood 7 198,500 Potential amount of feedstock; PQ (tonne) 7,741,000 -Para-rubber waste wood (65%) 7,633,300 -FGT wood (15%) 22,000 -Economic waste wood (20%) 85,700

Diversity of Feedstock Supply
The diversity of feedstock supply (in 2018) for wood pellet production is shown in Table 8. The result indicates that the types of feedstocks for wood pellet production is small (the Shannon-Wiener index is 0.17). In 2018, Leucaena wood production was 0.45% of FGTs, which is rather small. However, Leucaena can be harvested faster than others (in only 2 years) and continuously every year because of regeneration. Hence, to support wood pellet production in the area which does not have para-rubber trees, Leucaena should be planted in the wasteland (areas unsuitable for agriculture, without irrigation systems, not for housing, not conservation area and not government areas). In this study, the increase in FGT production is set at 15%, 25%, 50%, 75% and 100%, as shown in Table 9. Production of Eucalyptus wood was 89.3% of all FGTs, with most of the Eucalyptus wood being used in the paper industry. Even though the weather of tropical countries is highly suitable for the rapid growth of Acacia without requiring any major agricultural input [32], Acacia can be harvested only after 3-4 years. However, the Shannon-Wiener index can be increased by having a variety of feedstock with equal proportions. If the FGT plantation area in wasteland is increased, the Shannon index will increase ( Table 9). Evaluation of FGT production in wastelands is determined by assuming an average yield of Energies 2020, 13, 5126 9 of 14 FGTs at 3 tonnes per 0.16 ha per year and allowing for the harvest of only 25% of the plantation area annually [33].  Although wasteland is selected without an irrigation system, which is a main factor for plantation, this area was identified considering the suitability of soil (in term of texture, depth, electrical conductivity, pH and slope) and rainfall. These results presented that FGT can grow in wasteland [34]. However, agriculture in wasteland needs more investment than an abandoned area, while the yield may be less. If agriculture management is not suitable, problems in relation to disease and insects will occur and affect other crops. Therefore, the farmers should increase the diversity of genus and species of FGT.
Increasing the trend of domestic use and export of wood pellets in Thailand will enhance the value added of waste wood, especially para-rubber waste wood. Thailand will earn more income from wood pellet export. Moreover, the promotion of fast-growing trees plantation in wasteland will also contribute to the utilization of the wasteland and generate income for agriculture. The wood pellet production will support the security of energy production in Thailand because the feedstock is domestically available. Therefore, wood pellet production is essential to the economy and energy supply of Thailand.

Encouragement for Increasing the Domestic Use of Wood Pellets
Although the Thai government has encouraged using the wood pellets only for heat production, by supporting 30-50% of the fund to change to new burners, some factories joined this project. Thailand has 8005 units of boilers (526 coal boiler units, 4760 liquid fuel boiler units and 2719 gas boiler units which can be changed to renewable energy [35]). However, promotion of wood pellet use in Thailand should be performed urgently because Thailand has the potential to become a more important producer and consumer on wood pellet markets if effective policy encouragement and a suitable regulatory framework are formulated. Furthermore, the Thai government should have a plan to raise the confidence of entrepreneurs for the acquisition of wood pellets and support a subsidy to control the price of raw materials.

Encouraging Cultivation of Fast-Growing Trees in Wasteland
Even though the feedstock from para-rubber waste wood is enough to produce a lot of wood pellets, the results from Sections 3.2 and 3.3 indicate that the distribution and quantity of feedstock supply in other regions are less in comparison to the south of Thailand. Moreover, the wood pellet factories are also concentrated only in the south of Thailand ( Figure 4A) [35]. Meanwhile, there is about 702,000 ha of wasteland in Thailand which is suitable for the growth of FGTs, most of which is in the north-east (40%) ( Figure 4B) [36]. The Thai government, through the Forest Industry Organization, tried to support only 3100 ha FGT plantation in 39 provinces in 2019 [11]. Hence, an increase in FGTs in the wasteland can help in the expansion of wood pellet production and higher diversity of feedstock. However, two cases can be set for comparison in terms of job opportunity, GHG emissions and increase in wood pellet cost. Case 1: the para-rubber wood pellets produced in the south of Thailand are sent to other regions (distance for sending to user: 1600 km (south to north or north-east)). In this case, there is no cultivation of FGTs for wood pellet production. Transportation of wood pellets to the north or north-east is by trains or trucks. Case 2: FGTs are encouraged to be planted in the wasteland areas of the northern or north-eastern regions. The wood pellet factories are set in the same area to minimize transportation requirements (100 km around the fast-growing tree cultivation area). The results in Table 10 indicate that Case 2 creates job opportunity of 0.13 person-year per ha from FGT cultivation and 0.0019 person-year per tonne from FGT wood pellets [37], which is higher than for Case 1. However, the employment from para-rubber wood cultivation is excluded, as it is latex, not para-rubber wood, that is the main product of this. Thus, the employment from cultivation should be considered for latex (rubber) rather than wood pellet production.    The GHG emissions per tonne of para-rubber wood pellets (144 kg CO 2 eq) are higher than the FGT wood pellets (88.8-94.4 kg CO 2 eq) because of the use of chemical fertilizers [38]. The para-rubber cultivation consumed 220 kg of chemical fertilizers per ha per year, whereas FGTs cultivation used only 30 kg per ha per year [38]. Even though a higher proportion of environmental impacts from para-rubber cultivation were allocated to latex, which is the main product, the chemical fertilizers allocated to para-rubber wood were still higher than those for FGT cultivation. The FGTs can grow for 1-5 years before harvest and utilization. In terms of the environmental burdens, the FGTs are a suitable feedstock for wood pellet production, especially in the wasteland where economic crops cannot be grown. If the para-rubber wood pellets are sent to the north or north-east, GHG emissions from transportation by trains or trucks will increase by 62.2 kg CO 2 eq per tonne and 458.0 kg CO 2 eq per tonne, respectively. Furthermore, the cost of transportation to user by trains or trucks will increase by 660 THB/tonne/1600 km and 3150 THB/tonne/1600 km, respectively. Therefore, if there is encouragement for increasing the domestic use of wood pellets in Thailand, FGT cultivation in the wasteland is a solution of choice for distribution and quantity of feedstock supply, including lower GHG emissions and cost from transportation.
However, the FGTs which are planted in different regions should be selected properly considering the specific factors of each region, such as type of soil, quantity of rain, etc. The Thai government should consider offering a guaranteed price which can help stimulate immediate short-rotation coppice adoption [39]. Furthermore, importers still request a certificate for good forestry management due to concerns about the raw material being from natural forest or poor cultivation. Hence, to address the issue of good forestry management, the increase in FGT cultivation should be managed by good forest management or sustainable cultivation which is safe for farmers and environmentally friendly. Moreover, the research on breeding to increase their yield should be encouraged by the Thai government. +Train 1600 km +62.2 --+Truck 1600 km +458.0 --Increase in cost +Train 2 1600 km +660 THB/tonne --+Truck 3 1 km +2 THB/tonne --+Truck 4 1600 km +3150 THB/tonne --1 Job opportunity of para rubber cultivation is not considered because the main product is para-rubber. 2 The data are from the State Railway of Thailand. 3 The data are from the Bureau of Standards and Evaluation, Department of Highways, Thailand. 4 This value is for the 100 km transportation around the FGT cultivation area.

Logistics Management
Logistics management is a considerable issue which relates to transportation of raw materials and products. Transportation of feedstock and wood pellets consumes fossil fuel such as diesel, which has a significant impact on the environment. Hence, setting the locations of feedstock cultivation, wood pellet factories and wood pellet users should be optimized to reduce the time and use of fuel. If the Thai government encourages wood pellet production for domestic use, the wood pellet factories should be distributed in all regions of Thailand to respond to the demand of industry and power plants.
Although there are no factories in the north-east, this region has the most amount of wasteland suitable for cultivating FGTs (Figure 4). Therefore, if the wood pellet factories are set in the north-east or other areas which have high abundance of feedstocks and high demand of wood pellets, the environmental burdens are anticipated to reduce.

Conclusions
The trend of wood pellet demand, with export and domestic use increasing by 10-150% from the values in 2018, was forecast to be within a range of 398,000 to 904,000 tonnes. Evaluating the wood pellet demand following the requirements of the main importers and increasing 10% of domestic use as in 2018 showed that the wood pellet demand of Thailand in 2025 would surge to 582,000 tonnes. The feedstock supply of wood pellets in Thailand from para-rubber waste wood, economic waste wood and fast-growing tree wood is 8.31 million tonnes per year, which can produce 5.32 million tonnes per year of wood pellets. Therefore, Thailand has sufficient feedstock to produce the wood pellets following the forecasted wood pellet demand. However, increasing 25% of wood pellet export and 50% of wood pellet domestic use will result in a deficit of the fast-growing tree wood because para-rubber waste wood is not the distributed across all regions. The diversity of feedstock supply suggests that the type of feedstocks for wood pellet production is less (Shannon-Wiener index: 0.17) because it is predominated by para-rubber wood. By increasing the fast-growing tree plantation area in the wasteland, the Shannon-Wiener index will increase. GHG emissions from the para-rubber wood pellets are higher than those from the wood pellets of the fast-growing trees because of the higher use of chemical fertilizers. Recommendations for policy from this study focus on encouraging increasing domestic use of wood pellets, cultivation of fast-growing trees in wasteland and optimized logistics management.