*2.2. Itemized Cost Estimation*

To investigate the economic feasibility of each MP system, itemized cost estimation proposed by Turton et al. [55] was conducted considering various parameters of reaction temperature, types of fuel combusted and its ratio, and the ratio of reactant for gasifier. In this method, the unit H2 production cost (USD kgH2 <sup>−</sup>1) is obtained from the sum of the total cost (USD y<sup>−</sup>1) divided by the total amount of H2 produced (kg y<sup>−</sup>1). In this study, the total cost is defined as annualized capital cost (USD y<sup>−</sup>1), which is estimated from original capital cost (USD) by applying capital recovery factor (CRF) as shown in Equation (4), and operating cost (USD y<sup>−</sup>1). Table 2 shows the list of these.

$$\text{CRF} = \frac{i(1+i)^N}{(1+i)^N - 1} \tag{4}$$

where *i* is a discount rate and *N* is an economic analysis period.

In addition, to properly estimate each capital cost, the six-tenth rule (Equation (5)) and concept of chemical engineering plant cost index (CEPCI) (Equation (6)) are applied to consider economics of scale and effects of inflation.

$$C\_2 = C\_1 \left(\frac{S\_2}{S\_1}\right)^{0.6} \tag{5}$$

where *C* is an equipment cost (USD) and *S* is a scale of the certain chemical process.

$$C\_2 = C\_1 \left(\frac{I\_2}{I\_1}\right) \tag{6}$$

where *C* is an equipment cost (USD) and *I* is a CEPCI.

**Table 2.** List of economic parameters and assumptions used in itemized cost estimation.


#### *2.3. Sensitivity and Scenario Analysis*

Key economic parameters of each system of MP and future unit H2 production cost with varied C selling price, which can be advantages for economic feasibility, were quantitatively investigated by sensitivity and scenario analysis, respectively. For sensitivity analysis, with varied capital and operating cost in a range of ±20% with other parameters fixed, the degree of variation in unit H2 production cost for each MP system was investigated. In addition, trends of unit H2 production cost for each scenario according to different H2 production scales and C selling prices were obtained and compared to conventional H2 production methods of SMR and SMR with CCS.

#### **3. Results and Discussion**
