## 3 Prediction of Biochemical Methane Potential  
The theoretical amount of biogas and biomethane production is referred to as biochemical methane potential (BMP). It is an important parameter used in evaluating the productivity of organic materials (feedstock) in producing biogas and CH\({}_{4}\). There are  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Crude and Oil** & **Natural Gas** & **Wind** & **Solar** & **Bioenergy** &
\begin{tabular}{c} **Total** \\ **Renewables** \\ \end{tabular} \\ \hline
2014 & 221,872 & 369,389 & 3 & 374 & 121 & 497 \\
2015 & 241,053 & 398,121 & 3 & 379 & 121 & 503 \\
2016 & 208,611 & 443,796 & 1 & 455 & 121 & 577 \\
2017 & 189,219 & 486,088 & 24 & 1626 & 121 & 1078 \\
2018 & 175,439 & 509,615 & 24 & 1610 & 121 & 1770 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Electrical power generation in the GCC region by energy type (GWh). Data source (GCC-STAT, 2021).  
numerous methods to estimate the BMP of feedstocks. [PERSON] and [PERSON] [29] classified all current BMP estimation methods into experimental and theoretical methods, and reviewed the advantages and disadvantages of both groups. Most experimental techniques consist of laboratory-scale batch assays that utilize manometric, volumetric, and gas chromatography methods to measure CH\({}_{4}\) production.  
Experimental BMP methodologies mimic AD conditions on a practical level and such estimates are valid and reliable. However, the main drawbacks of such methodologies include relatively high costs and the length of time required for obtaining results [29]. Conversely, theoretical methodologies are employed for predicting BMP from readily available feedstock parameters, such as elemental/chemical compositions and chemical oxygen demand (COD). The utility elemental composition (C, H, O, S, N) of a substrate as a predictor of BMP is based upon [PERSON]'s stoichiometric formula [30], which assumes that organic matter is completely biodegraded to CH\({}_{4}\) and CO\({}_{2}\). In contrast, [PERSON] [31] proposed a modified bioenergetics and stoichiometry approach which takes into account the fraction of substrate used for cellular synthesis and energy production (CH\({}_{4}\)). Furthermore, in cases where elemental composition of the substrate is unknown, the chemical composition (mainly carbohydrates, proteins and lipids) can alternatively be used to determine BMP. [PERSON] et al. [32] demonstrated the reliability of chemical composition as a predictor of BMP using statistical models, though the accuracy of such a prediction is sensitive to the model structure. The biogas yield of substrates varies, depending on the elemental and chemical composition, total and volatile solids, organic content, oxygen demand, carbon to nitrogen (C/N) ratio, and level of inhibitory substances [29]. Typically, fats and proteins generate increased CH\({}_{4}\) levels than carbohydrates, with compounds such as lignin not being degradable under anaerobic conditions [33]. Biological oxygen demand (BOD) and COD are additional indicators of organic content in feedstocks and are both employed for predicting biogas production [4,34,35,36]. The optimal range of C/N ratio for gas production is 20-35:1 [36]. A low ratio indicates elevated proteomic content, resulting in exacerbated ammonia levels and eventual methanogenic inhibition, while high ratios lead to reduced gas production due to nitrogen depletion [37].