18-Env-A6 Solid Waste Engineering and Management · December 2013
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; Freeze & Cherry, Groundwater (Darcy's Law, vadose zone); CCME, Guidance Document on Landfill Gas Management; EGBC/Engineers Canada 04-Env-A6/18-Env-A6 examination syllabus.
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.
(1) Moisture content of the refuse — microbial (anaerobic) activity requires water, so gas generation rate rises with moisture content up to a point, which is also why the leachate/moisture-balance analysis in Q15 matters directly to gas production, not just to leachate quantity. (2) Waste composition — specifically the biodegradable organic fraction (food waste, yard waste, paper); readily biodegradable material generates gas faster and in greater ultimate quantity than slowly-degrading or inert material (plastics, metal, glass contribute essentially none). (3) Temperature within the landfill — anaerobic microbial activity (methanogenesis) proceeds fastest in the mesophilic (≈30–35 °C) to thermophilic range typical of the interior of a large landfill mass, and slows sharply at lower temperatures, so climate and landfill depth/insulation both influence the internal temperature and hence the gas generation rate.
