## Materials and Methods
### Above Ground Biomass Potentials Estimation  
Estimating a yearly biomass increment is a regular reporting requisite in the Inter-Governmental Panel on Climate Change (IPCC) recommendations, implying that above-ground biomass can be estimated conventionally with remote sensing techniques and ecosystem modeling procedures [23]. Remote sensing-based estimation of terrestrial primary production has come along away within a few decades ago presenting datasets relating to biomass at regional, continental, and global scales. In addition to remote sensing-based assessments, it is possible to combine these methods with the ones using models. Moreover, satellite-based estimations have been complemented with calculated models to quantify the carbon fluxes globally [24].  
In this work, it is assumed that all para rubber plantations across Songkhla province are at least 25 years old since rubber trees have a 20-30-year economic existence [5; 14; 25]. The trees usually have an asset life of 25 years [26], this is long enough for significant carbon sequestration from the atmosphere. The above ground biomass (AGB) potentials were derived from NPP through a generic model approach proposed by [27]. Conventionally, NPP comprises both above-ground and below-ground production and it is quantified as the quantity of carbon per unit area (kgC/m\({}^{2}\)). However, only the above-ground biomass is mostly considered relevant for energy production, therefore conversion is required to find the aboveground NPP value from the overall volume. The entire process of assessing the above-ground biomass from para rubber is schematically presented in a flow chart (Figure 2), the figure provides an overview of the framework methodology employed in this work.  
Figure 2: A Flowchart of procedures and data variables used in para rubber biomass estimation. Moderate Resolution Imaging Spectroradiometer (MODIS) MODIS (MOD), fluxes network (FLUXNET), Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), and Net Primary Productivity (NPP).  
The following equation was used to translate NPP from MODIS/Terra product data to dry theoretical biomass.  
\[T=NPP\times\frac{\alpha}{\beta} \tag{2}\]  
where \(T\) is theoretical AGB, \(\alpha\) is the share of above-ground biomass in the aggregate biomass, and \(\beta\) is carbon concentration in dry biomass. For cultivated crops and grass, \(\alpha\) is 0.8 and \(\beta\) is 0.45 [27], while for forest and other woody vegetation, \(\alpha\) is 0.235 and \(\beta\) is 0.47 [28].  
Worthy of note is that: not all theoretical biomass can be used for energy production due to restraints, such as soil carbon maintenance, pulping, and other economic purposes. Therefore, energy usable biomass parameter is introduced to reveal the part of naturally obtainable biomass that is used for energy generation, and this is calculated thus.  
\[E=T\times r\times(1\text{--}e\text{--}l) \tag{3}\]  
where \(E\) is energy usable biomass; \(T\) is biological biomass; \(r\) is the portion of T that is not primarily produced. For crops, only the residues like straw and stems are used for energy production. However, for fast-growing grasses or trees that are dedicated to energy production, r can be equal to or approximately 1 [29]. \(e\) is the portion of omitting the biomass used for other economic purposes other than energy production. \(l\) represents the loss during the entire procedure, for instance, the loss taking place through the harvest. For forest biomass, \(l\) is 0.05 [27]. Other uses biomass share were computed from the difference between the theoretical AGB and energy AGB potentials.