Sara Pace, PhD Candidate, Biological Systems Engineering, UC Davis
Life Cycle Assessment Based Modeling of Organic Waste Residue Using Anaerobic Digestion and Composting
Organic waste is the largest component of municipal waste and comprises approximately 28% of the waste
stream. Composting is one of the more common methods to treat organic waste and reduce the amount disposed
in landfills. However, composting requires energy for aeration and water for evaporative cooling to maintain
important biological activity. The additional water required for composting is often limited in arid climates.
Anaerobic digestion followed by composting is one possible approach to reduce the need for water and external
energy for aeration. Decision‐making models are needed to determine best management practices for treating
organic residue based on organic matter composition. A life cycle assessment (LCA) model was developed to
elucidate the impact of conversion scenarios to sustainably treat organic residues and minimize environmental
impacts. These scenarios included combining anaerobic digestion and composting to treat organic residue and
produce soil amendment. The total environmental impacts of a combined organic residue management system
using anaerobic digestion and composting to produce soil amendment was evaluated using a process‐based LCA.
The LCA incorporated new water use impact assessment methods and energy and mass balance models to track
important energy and mass inputs and outputs. Anaerobic digestion residence time and organic waste content
were varied in the model to evaluate potential environmental impacts of the system. The results of this work will
help waste management specialists, policy makers, and city planners design, implement, and maintain sustainable
communities in resource limited environments.
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