Converting wet organic waste such as sewage sludge, food waste, and animal manure into bioenergy presents a significant opportunity to support U.S. biofuel goals while addressing challenges associated with traditional waste management practices like landfilling and incineration. Hydrothermal liquefaction (HTL) and anaerobic digestion (AD) technology are two promising technologies to address the above issue. HTL is a thermochemical process capable of converting high-moisture organic waste into biofuels without requiring energy-intensive drying. Operating at moderate temperatures (approximately 350°C) and pressures (around 35 bar), HTL efficiently transforms wet waste into valuable bioenergy products. In contrast, AD is a well-established biological process that decomposes organic matter in the absence of oxygen, producing biogas and digestate as outputs. Despite the proven efficacy of both methods, there are notable research gaps in directly comparing HTL and AD processes. This work addresses these gaps by developing detailed process models for both technologies in Aspen Plus, using identical feedstock for consistency. These models allow for detailed mass and energy balance analyses, supporting a multi-indicator evaluation of efficiency, economics, and environmental impacts. The presentation will cover conceptual process designs, model development, and comprehensive evaluations of both HTL and AD pathways, offering valuable insights into their respective advantages and potential applications in waste management and bioenergy production.
