Techno-economic evaluation of sago biomass-based combined heat and power (CHP) system

Sago biomass (barks and fibres) generated from sago starch extraction process can be converted into various products and bioenergy (heat and power). However, in current industrial practice, such biomass are deposited around the factory and washed off into nearby streams without proper treatment. These practices caused severe pollution issues to environment (river and air pollutions). Reduction of these environmental pollutants by sustainable conversion of biomass into clean bioenergy is of paramount interest. Barks and fibres consist of solid lignin structures, thus such biomass are suitable for combustion to generate bioenergy via combined heat and power (CHP) system with market-ready biomass boiler. Such CHP system is typically much simpler in design, implementation and maintenance, giving electricity at the mains voltage level for transfer of the net electricity output to the national grid. In this work, techno-economic performance of CHP system with biomass boiler is evaluated via a commercial simulation software (Aspen Plus) and spreadsheet-based yield model. Given the boiler efficiency of 80%, a total of 2,672 kW of heat and power can be generated from the dry sago barks and fibres (16.7 t/d). In this system, 0.91 kg/s of superheated steam at 50 bars is produced in boiler. Part of the generated steam is supplied to existing extraction process; while the remaining steam is further converted into 612 kW of electricity via back pressure and condensate turbines. Based on the generated bioenergy, 10,997 kg CO2/day of carbon dioxide can be reduced. A sensitivity analysis on payback period of CHP system is conducted and noted that payback period is highly depended on labour and feedstock cost.