11-CS-3 Engineering Management · December 2015
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 2015 — 11-CS-3 Sustainability, Engineering and the Environment. Closed book; approved calculator permitted. Any four questions constitute a complete paper; all questions are of equal value (25 marks each).
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.
This principle says that how a product or waste stream will be separated and purified for recovery should be planned at the design stage, since separation is often the hardest and most energy-intensive step. Example: designing a product so that its different materials can be easily separated at end of life—e.g. using snap-fits and a single polymer instead of glued, painted, or composite assemblies—so that recycling does not require energy-intensive separation, preventing the waste that arises when mixed materials cannot be economically parted and are landfilled.
System components should use materials, energy, and time as efficiently as possible. Example: a combined heat and power (cogeneration) system that uses the same fuel input to produce both electricity and useful heat maximizes energy efficiency by capturing what would otherwise be waste heat; running processes continuously at optimum load (temporal efficiency) and recovering and reusing process materials (mass efficiency) similarly prevent the pollution associated with wasted energy and material.
This is the core pollution-prevention principle: it is cheaper and more effective to avoid creating waste than to treat it afterward. Example: reformulating a manufacturing process to use a non-toxic, water-based solvent (or eliminating the solvent) so that no hazardous waste stream is created—rather than installing costly treatment to neutralize toxic solvent waste after the fact. Preventing the waste avoids the treatment cost, the residual risk, and the disposal burden entirely.
No—population is not the only factor. The IPAT equation shows that environmental Impact = Population × Affluence (consumption per person) × Technology (impact per unit of consumption). So affluence (how much each person consumes) and technology (how cleanly goods are produced) are equally important; a small but wealthy, resource-intensive population can have a larger impact than a large, low-consumption one. Consumption patterns and the efficiency/cleanliness of technology are the other key determinants.
(i) Functional unit: providing the operating instructions to all users of the product over its market life (e.g. per product sold, or per user accessing the manual). (ii) Stages: for the paper booklet—raw materials (pulp/paper), printing/manufacturing, distribution (shipping with product), use, and end-of-life (recycling/landfill); for the online manual—server/data-centre infrastructure and hosting energy, the user's device and electricity to access it, and (shared) network energy. (iii) Higher-impact alternative by stage: in materials/manufacturing and distribution, the paper booklet is worse (paper, ink, and the weight/volume shipped with every unit); in the use phase, the online manual carries the (small, per-access) energy of servers, networks, and the user's device; at end-of-life, paper generates physical waste while the online manual generates none directly. (iv) Stage of greatest impact: for the paper booklet, the raw-material/printing (and distribution) stage; for the online manual, the ongoing use-phase energy of hosting and access. The online manual is generally lower-impact if accessed occasionally, but heavy, repeated access on energy-intensive infrastructure narrows the gap.
Design for disassembly: designing products to be easily taken apart for repair, reuse, or recycling. Reverse manufacturing: disassembling used products to recover components/materials. Ecological footprint: the biologically productive land and water area needed to supply a population's consumption and absorb its waste. Biological capacity (biocapacity): the capacity of an area's ecosystems to produce useful biological materials and absorb waste—the "supply" side compared against the footprint "demand." Natural capital: the stock of natural resources and ecosystems yielding a flow of valuable services. Cap and trade: an emissions-trading system with a fixed total emissions cap and tradable allowances. Externalities: costs/benefits borne by third parties and not reflected in market prices. Intangibles: real but hard-to-quantify costs/benefits such as reputation or quality of life.
