The methods described below are designed to easily determine the methane productivity of a specific substrate from its COD characterization, elemental composition or organic fraction composition in order to obtain reliable results quickly and get an economic advantage. These methods are applied considering that all the organic material is degraded; therefore a proper adjustment of this value is necessary, using the biodegradability

obtained from the experimental BMP tests. The methane potential is expressed as AZD5363 mw mlCH4 at standard temperature and pressure conditions per amount of organic material added (VS). The maximum methane potential can be calculated from the amount of material and the COD concentration of the test using Eq. (2), assuming that this equation is valid for any substance or product [35]. This equation gives the theoretical value of methane at laboratory conditions: find more equation(2) BMPthCOD=nCH4RTpVSaddedwhere BMPthCOD is the theoretical production at laboratory conditions, R   is the gas constant (R   = 0.082 atm L/mol K), T   is the temperature of the glass bottle(308 K), p   is the atmospheric pressure (1 atm), VSadded (g) are the volatile solids

of the substrate and nCH4nCH4 is the amount of molecular methane (mol) determined from Eq. (3) equation(3) nCH4=COD64(g/mol) The stoichiometric equation based on the atomic composition of the waste material (BMPthAtC), is also

used to calculate the theoretical methane composition by taking into account the elements C, O, H and N (Table 3). The presence of proteins and ammonia are considered in Boylés Eq. (4) ([32]): CnHaObNc+(n−a4−b2+3c4)H2O→(n2+a8−b4−3c8)CH4+(n2−a8+b4+3c8)CO2+cNH3 Galeterone equation(4) BMPthAtC=22.4(n/2+a/8−b/4−3c/8)12n+a+16b+14c The determination of the elemental composition is relatively fast for all the compounds, although this equation does not differentiate between biodegradable and non-biodegradable matter, and part of the biodegradable organic matter used by the bacteria to grow does not contribute to the BMP theoretical value [27]. The use of the organic fraction composition to calculate the theoretical production (BMPthOFC) is a good method in which the easily biodegradable compounds such as carbohydrates, lipids and proteins and the poorly biodegradable compounds as fiber are taken into account. Bushwell’s formula indicates the amount of methane provided by the different compounds which follow the next general Eq. (5)[27]: equation(5) BMPthOFC=415×%carbohydrates+496×%proteins+1014×%lipidsBMPthOFC=415×%carbohydrates+496×%proteins+1014×%lipids Even though this method can predict the ultimate methane yield, the chemical composition is obtained using chemical methods, taking less time than a full BMP test but still being time-consuming, requiring anything from several hours to several days.