Proposal of a biogas upgrading process for a novel eco-friendly trigeneration model, producing power, methanol, and desalinated water

Non-renewability and difficult access to fossil fuels can be replaced with renewable fuels, such as biogas. Due to the close structure of biogas to fossil fuels, it has become a powerful fuel for energy systems, especially when it enters the upgrading process. With this in mind, the proposed system proposes a novel trigeneration model integrated into a biogas upgrading unit, producing electricity, desalinated water, and methanol. This process is proposed for the first time, which is able to increase the thermodynamic, economic, and environmental performances compared to previous studies. Negative CO2 emission is its main feature that is available using a methanol synthesis unit. Thermal desalination and ammonia Rankine cycles are other equipment used in the proposed structure. The whole system is simulated in the Aspen HYSYS software and is investigated from the 4E aspect, namely energy, exergy, economics, and environment. Also, a sensitivity study is conducted. The overall energy and exergy efficiencies equal 51.54% and 87.39%, respectively. These criteria are improved between 4.54% and 15.64%-points and 32.29–74.70%-point compared to the existing literature review, respectively. In addition, the net CO₂ emission intensity equals −0.54 kg_CO2/kg_MeOH, which is considerably lower than other relevant technologies (between 1.78 and 10.68 times). Moreover, the unit cost of methanol in the proposed process equals 0.21 $/kg, which is 63.54–85.61% lower than other methods available in the literature review.