**3. Conclusion**

In calculating and analyzing economic feasibility in the simulation, the following assumptions are made[11]: (1) The disposal costs of sludge will increase by 5% per year; (2) electricity consumption costs will increase by 3% per year; (3) employee salary costs will increase by 10% per year; (4) fuel costs will increase by 10% per year; (5) maintenance costs will increase by 10% per year; (6) miscellaneous costs will increase by 10% per year; (7) inflation rate is 6%

**Table 3.** Benefit cost analysis of the proposed business model (Source: Hakiki et al. [11] with modification).

**Figure 7.** Existing business model (Source: Hakiki et al. [11] with modification).

**No Items US \$/month**

Sludge disposal cost saving (to PPLI) (55% dry solid) 2808.0 Green energy produced (expressed in US \$ 0.08/kwh) 932.4 Employment cost saving (2 people) 512.0 **Total revenue 4252.4**

Employment cost (4 people) 1024.0 Electricity consumption 38.5 Fuel for start up 80.0 Generator maintenance 400.0 Reactor maintenance 400.0 Miscellaneous expenses 160.0 Depreciation on investment 886.9 **Total cost 2989.4** 3 **Profit 1263.4** 4 **% Profit to revenue 30%**

1 Revenue

114 Renewable Resources and Biorefineries

2 COGS/expenses

Management of wastewater sludge originating from wastewater treatment facilities can be done in several ways, including physical process (compacted into briquettes), biochemical process (anaerobic digestion), thermochemical process (pyrolysis/gasification), and extraction-transesterification (sludge as an alternative feedstock to produce biodiesel). In addition to these management methods, the last option has been commonly used in disposal to secured landfill. The last option is still seen as the best choice in terms of practicality and ease of process. In this option, the producing party utilizes the services of third parties who already have permission to manage the sludge produced. Along with increasing awareness about the decreasing reserves of fossil fuels and the increasing popularity of global warming issues, the secured landfill option needs to be reviewed further, considering that organic sludge still has the potential as an alternative energy source if managed with the proper method. Simulations carried out on wastewater sludge from Jababeka's centralized wastewater treatment facilities showed that thermochemical processing methods were quite effective in reducing sludge mass. In addition, green energy produced can also be used to fulfill some needs in treatment facilities and can be a substitute for fossil fuels. Overall, based on the results of the feasibility study simulation, it can be concluded that the thermochemical processing method can be further considered to develop into the pilot scale.

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