18-Env-B6 Agricultural Waste Management · December 2019
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams, December 2019 — 18-Env-B6, Agricultural Waste Management (3 hours, open book, all 15 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); Environment and Climate Change Canada / Canada–Ontario Lake Erie Action Plan.
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.
Land-applied manure is the largest single odour-complaint source on Ontario livestock farms, and the engineering response is almost entirely about cutting the exposed surface area and the time that area stays exposed. Five independent, complementary steps are described below; a well-designed nutrient management plan typically combines several rather than relying on one.
1. Incorporate or inject immediately. Tillage incorporation within a few hours (ideally same-day) or direct soil injection buries the manure below the surface boundary layer where volatile compounds would otherwise escape freely to the atmosphere; injection alone can cut odour intensity by roughly 50–80% compared to unincorporated surface broadcast.
2. Use low-trajectory / low-disturbance application equipment. Drag-hose, drop-hose (sleighfoot) or band application place manure in narrow bands at the soil surface instead of broadcasting it through the air with a splash-plate, minimizing aerosolization and the surface area exposed per unit volume applied.
3. Apply under favourable weather and timing. Spreading during cool, calm, overcast conditions (rather than hot, sunny, still afternoons) slows volatilization; scheduling around weekends, holidays and prevailing wind direction toward neighbours reduces the number of people affected by any given application.
4. Maintain setbacks and vegetative buffers from sensitive receptors. Keeping application away from property lines, dwellings and watercourses, and using a vegetative buffer strip, gives odour plumes distance and time to dilute before reaching a receptor; many Ontario Nutrient Management Strategies (NMS) set minimum distance separation for exactly this reason.
5. Treat the manure before land application. Anaerobic digestion (Question 5) or composting destroys the labile organic compounds responsible for most characteristic odour, so digestate or finished compost is noticeably less odorous in the field than raw manure — treatment addresses the odour source itself rather than only managing the application event.
