Proposal and comprehensive study of an integrated polygeneration process relying on landfill gas, renewable hydrogen, and binary geothermal cycle

Abstract

Landfill gas (LFG) is an accessible, inexpensive, and carbon-rich source, and due to its methane content, it can also be used as a fuel. In this paper, a novel polygeneration structure is presented that uses LFG as the input fuel as well as geothermal energy to produce valuable products, including electricity, methanol, freshwater, heating, and cooling. The configuration is made of biogas combustion unit, binary geothermal power plant, cooling water production unit, Kalina power cycle, desalination unit, water electrolysis unit, and methanol synthesis and purification unit. The methanol synthesis unit is modified using a scrubbing column, resulting in recovery of methanol without loss. Aspen HYSYS application is used to model this procedure, and it is examined from a 4E (energy, exergy, economic, and environmental) standpoint. The findings show that a total of55.46% of energyand 77.29% of exergy efficienciesare reached. From the environmental standpoint, it is found that the proposed structure has negative emissions, and its carbon dioxide (CO2) footprint is equal to −0.161 kgCO2/kgprod. In addition, the total CO2 emission of 46,780 kg/h is calculated. Concerning the economic aspect, the cost rate of produced methanol, heating, cooling, and freshwater are found at 0.268 $/kgMeOH, 1.01 $/kgLPS, 0.26 $/kgCW, and 0.7 $/kgFW, respectively. Besides, it is concluded that the methanol production cost rate of this model is comparatively lower than the methods such as power-to-methanol and coke oven gas-to-methanol.