Optimizing life cycle sustainability based on municipal solid waste streams and treatment potentials.

This study applies multicriteria mathematical modeling to optimize municipal solid waste (MSW) management across a three bottom-line (BL) framework: environmental, social and economic. The interrelationships and the ripple secondary impacts among the three BLs are examined systematically using an augmented simplex lattice mixture (ASLM) method. Detailed waste and waste treatments, including pyrolysis (PY), anaerobic digestion (AD), animal feed (AF), composting (CP), recycling (RE), incineration (INC) and landfilling (LF), are constructed based on waste stream fractions and treatment allowable limits. The environmental BL is assessed using life cycle assessment (LCA). The economic BL is determined by calculating the per ton capital recovery with return, and the social bottom line is assessed using the analytic hierarchy process (AHP). The three bottom lines are optimized through a mathematical model using CPLEX solver. The results indicate that CP abates 973 kgCO₂eq/t compared to 61.8 kgCO₂eq/t from AD and 28.3 kgCO₂eq/t from AF. CP generates $23.5/t despite its low social desirability. Plastic waste PY credits ethylene by 364 kg/t, however, it costs $226.7/t despite the subtraction of credited energy and recovered byproducts. Metal RE carbon and water footprints are −236 kgCO₂eq/t and 268 m³/t, respectively. AF is the second-best economic scenario after metal RE as it generates up to $122.6/t in profit. AF production scores are second highest within the social BL after plastic PY; however, the supporting legislation sub-indicator is low. The ASLM support policy that assigns 66% to the environmental BL and 16.7% to the economic and social BL to achieve carbon neutrality within the MSW sector. [ABSTRACT FROM AUTHOR]