## 3 Performance Attributes and Scenarios  
### Performance Attributes  
The performance attributes can be classified into different main classifications, namely, technology performance, economic performance, environmental performance, and fuel requirements. Technology performance indicators include the specific gas production rate (GPR), the carbon conversion efficiency (CCE), the energy content of the syngas produced (EC), the cold gas efficiency (CGE), and the tar generation rate (TG). The specific gas production rate is calculated by the ratio of the syngas flow rate (Q\({}_{\text{SYN}}\)) to the fuel feeding rate (Q\({}_{\text{BM}}\)) into the gasifier as given by Equation (1). \[\text{GPR}=\frac{\text{Q}_{\text{SYN}}}{\text{Q}_{\text{BM}}}\frac{\text{Nm}^{ 3}}{\text{kg}} \tag{1}\]  
The gasification performance of updraft gasifiers was experimentally tested with palm starch waste and was found to produce about 2.5 Nm\({}^{3}\) of gas per kilogram of waste [26]. The carbon conversion efficiency (CCE) of the gasifier is the carbon leaving the gasifier in the form of syngas divided by the carbon available in the biomass fed into the gasifier. x\({}_{\text{jc}}\) is the part of the carbon in the different components of the product gas 1 to j. y\({}_{\text{c}}\) is the part of the carbon in the biomass supplied to the gasifier as given by Equation (2). \[\text{CCE}=\frac{\text{Q}_{\text{SYN}}\times\sum_{\text{j}=1}^{n}\text{x}_{ \text{jc}}}{\text{Q}_{\text{BM}}\times\text{y}_{\text{c}}} \tag{2}\]  
The energy content of the syngas is calculated from the combustible elements in the different components of the syngas measured using the gas calorimeter in KJ/Nm\({}^{3}\). Figure 3: (a) Bubbling fluidized bed gasifier and (b) dual fluidized bed gasifier. The term cold gas efficiency (CGE) is the chemical energy leaving the gasifier associated with the cold and tar-free syngas divided by the chemical energy entering the fuel or MSW supplied to the gasifier. Tar generation (TG) is one of the problems associated with gasifiers and has undesirable consequences when the syngas condenses downstream and results in clogging and blockages of burner holes when the syngas is burned directly or used in internal combustion engines. The economic performance is assessed using two parameters, which are the life cycle cost (LCC) and the payback period. The LCC is determined by the sum of the initial cost (IC), the operating cost (OC), and the maintenance cost (MC), which are the recurring costs brought down to present value calculated over a period (n) of 15 years with an interest rate of r. The salvage cost (SC) at the current rate is deducted finally to calculate the LCC as given by Equation (3). \[\text{LCC}=\text{IC}+\sum_{n=1}^{15}\frac{\left(\text{MC}+\text{OC}\right)}{ \left(1+\text{r}\right)^{n}}-\text{SC} \tag{3}\]  
The payback (PB) period represents the number of years needed to recouple the total cost invested in the project, and it is calculated by dividing the initial cash (IC) outlay by the annual or monthly cash inflow during the project as given by Equation (4). \[\text{PB}(\text{years})=\frac{\text{IC}}{\text{INFLOW}}\frac{\text{USD}}{ \frac{\text{USD}}{\text{year}}} \tag{4}\]  
The environmental performance attributes include the water, air, and soil pollution caused by the MSW gasification process. The air-polluting emissions such as greenhouse gases like CO\({}_{2}\) and CH\({}_{4}\), furans, dioxins, and particulate matter are considered in this analysis. Soil and water pollution happens due to the storage of MSW on open lands, and it causes an enhancement in the organic matter content of the soil as well as an increase in certain heavy metals like copper, zinc, cadmium, nickel, and chromium [27]. Fuel requirements are the cost incurred due to fuel preparation activities to feed the fuel into the gasifier like the fuel size and moisture content specifications, which require fuel grinding or drying.