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.
Odour from land-applied manure is generated at the manure–air interface and carried off-site by convection and diffusion; nearly every effective countermeasure works by shrinking that interface, shortening how long it stays exposed, or moving the plume away from receptors before it disperses. Four distinct, complementary steps:
1. Incorporate or inject the manure promptly. Tillage incorporation within hours (same-day is best) or direct soil injection buries the manure below the surface boundary layer, cutting the exposed interface almost to zero; injection typically reduces odour intensity by 50–80% relative to unincorporated surface broadcast.
2. Use low-trajectory, low-disturbance application equipment. Drag-hose, drop-hose (sleighfoot) or band applicators lay manure in narrow bands at the soil surface rather than flinging it through the air with a splash-plate, which minimizes aerosolization and the exposed surface area per unit volume spread.
3. Time the application to weather and calendar. Spreading during cool, calm, overcast conditions slows volatilization compared with hot, sunny, still afternoons; scheduling around weekends, holidays, and the prevailing wind direction relative to neighbours reduces how many people are affected by any single event.
4. Maintain setbacks and vegetative buffers from sensitive receptors. Keeping application away from property lines, dwellings and watercourses — and leaving a buffer strip — gives the odour plume distance and time to dilute; Ontario Nutrient Management Strategies (NMS) commonly set a minimum distance separation for exactly this purpose.
A fifth, often-overlooked lever is treating the manure before it ever reaches the field: anaerobic digestion (Question 5) destroys most of the labile organic compounds responsible for characteristic manure odour, so digestate is noticeably less odorous even before incorporation.
