Question 6 of 16: Strategy to Reduce Greenhouse Gas Emissions from Solid Waste

Question 6: Strategy to Reduce Greenhouse Gas Emissions from Solid Waste (5 marks)

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.

A defensible strategy follows the waste-management hierarchy, attacking GHG emissions at their source before managing what remains: (1) waste reduction and diversion — source-separated organics (food/yard waste) collection removes the single largest methane-generating fraction from the landfill stream entirely, redirecting it to composting or anaerobic digestion where the biogas can be captured and beneficially used rather than escaping uncontrolled; (2) recycling of paper, metal and plastics — avoids both the decomposition emissions of landfilling and the upstream (embodied) emissions of virgin material production, giving a double GHG benefit per tonne diverted; (3) active landfill gas collection and flaring/utilization for waste that is still landfilled — converting fugitive methane (a GHG roughly 25–30× more potent than CO₂ over 100 years) to CO₂ via flaring, or better, capturing it for electricity/heat generation to displace fossil-fuel use; and (4) collection-fleet efficiency — route optimization and lower-emission vehicles reduce the (smaller but still real) transportation component of the SWM system's carbon footprint. Diverting organics and capturing landfill gas typically dominate the achievable reduction, since methane from anaerobic decomposition is the largest single GHG source in a conventional SWM system.