18-Env-A6 Solid Waste Engineering and Management · May 2017
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Reference texts: Tchobanoglous, Theisen & Vigil, Integrated Solid Waste Management: Engineering Principles and Management Issues; Vesilind, Worrell & Reinhart, Solid Waste Engineering; Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); CCME, Guidance Document on Landfill Gas Management; ISO 14040/14044, Environmental Management — Life Cycle Assessment.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Advantages: (1) generally the lowest-cost disposal method per tonne where suitable land is available; (2) can accept a very wide range of waste types without the pre-processing or feedstock-quality requirements of composting or waste-to-energy; (3) technically proven and flexible — capacity can be phased in cell-by-cell as the facility develops; (4) generated landfill gas can be captured and used as an energy resource rather than simply flared; and (5) a completed, closed landfill can potentially support beneficial post-closure land use (parkland, solar facility) once settlement and gas generation have sufficiently declined.
Disadvantages: (1) leachate generation poses an ongoing groundwater/surface-water contamination risk requiring collection, treatment and long-term monitoring, even decades after closure; (2) landfill gas is a fire/explosion hazard and a disproportionately potent greenhouse gas if not adequately captured (see Q7); (3) land consumption and increasing site scarcity — suitable sites (geology, buffer distance, access) are progressively harder to find near growing urban areas; (4) strong community/siting opposition ("NIMBY" effect) makes approval of new capacity politically difficult regardless of the technical merits; and (5) irreversible loss of embodied material and energy value in the buried waste compared to recycling or energy-recovery alternatives, and long-term (post-closure) liability and monitoring cost that persists long after the site stops generating revenue.
Because the disadvantages are largely environmental/social and the advantages largely economic/operational, a municipality's actual choice between landfilling and an alternative (incineration, expanded diversion) usually turns less on a single "better/worse" verdict than on which category of risk — cost overrun versus environmental/social risk — the community and its regulator are least willing to accept, which is why the waste-management hierarchy treats landfilling as a necessary fallback rather than eliminating it as an option entirely.
