18-Env-B6 Agricultural Waste Management · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams, May 2018 — 04-Env-B6, Agricultural Waste Management (3 hours, open book, all 16 questions to be attempted, 100 marks total).
Reference texts: Rynk et al., On-Farm Composting Handbook (NRAES-54); OMAFRA, Nutrient Management Act, 2002 and O. Reg. 267/03 / Nutrient Management Protocol (NMAN); Metcalf & Eddy, Wastewater Engineering (anaerobic digestion chapter); ASABE Standards (manure storage, land application equipment); Ontario Environmental Protection Act and Ontario Water Resources Act; Canada–Ontario Lake Erie Action Plan / Great Lakes Water Quality Agreement Annex 4.
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. High capital cost and long payback period. A farm-scale digester, gas handling/upgrading equipment and a combined heat-and-power unit represent a large upfront investment relative to typical farm revenue; payback periods of a decade or more are common without a strong incentive program.
2. Uncertain or insufficient economic incentives. Revenue depends heavily on electricity feed-in tariffs, renewable natural gas pricing, or carbon-offset markets, all of which have shifted significantly in Canada over the past decade (e.g., the end of Ontario's FIT/microFIT programs); without a stable, adequate price for the biogas/electricity produced, the economics are marginal even where the technology works well.
3. Technical complexity and operating/maintenance burden. A digester is a biological process needing consistent feeding, temperature control (a real parasitic heating load through a Canadian winter), and a skilled operator to avoid upsets (souring, foaming, inhibition); many farms lack in-house expertise, and specialized service providers are scarce in rural areas.
Feedstock supply uncertainty and NASM approval/permitting time are sometimes cited as contributing factors, but the three above are the most consistently cited barriers in Canadian on-farm digester adoption studies.
