A techno-economic assessment of biomethane and bioethanol production from crude glycerol through integrated hydrothermal gasification, syngas fermentation and biomethanation

Abstract

Bioethanol is widely perceived as a clean fuel that can be used directly as automobile fuel or blended with petrol without engine modification. Similarly, biomethane can be used as an environmentally friendly substitute to natural gas for diverse applications such as transportation, heating, and electricity generation. Recently, there has been a growing interest in the cost-effective and sustainable production of both these biofuels. The present study reveals a conceptual design for biomethane and bioethanol production from crude glycerol obtained from the biodiesel industry. The techno-economic feasibility of three different scenarios was assessed. Scenario 1 is based on bioethanol production by coupling hydrothermal gasification and syngas fermentation. Scenario 2 consists of hydrothermal gasification, syngas fermentation, and CO2 capture unit. In scenario 3, biomethanation and electrolytic unit were added to scenario 2 to convert CO2 to biomethane. The energy efficiency of the scenarios examined ranges from 30.2% to 35.1%. Scenario 3 had the highest energy efficiency of 35.1%. Moreover, the minimum selling price of bioethanol declined in the following order: scenario 2 (USD $1.4 per liter) > scenario 1 (USD $1.32 per liter) > scenario 3 (USD $0.31 per liter). The discounted cash flow analysis results indicated that scenario 3 is the most profitable because of its non-discounted net present value of USD $34.9 million compared to the other case studies. Sensitivity analysis reveals that electricity and glycerol cost had the most effect on the minimum selling price of bioethanol.

Keywords

• Biodiesel
• Biomethane
• Bioethanol
• Glycerol
• Process simulation
• Techno-economic analysis