Question 14 of 16: Ground-Up Drywall as Bedding

Question 14: Ground-Up Drywall as Bedding (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.

Ground gypsum drywall is a real and sometimes-used bedding/manure amendment, but several discussions should happen before adopting it. Source and contamination: confirm the material is genuinely NEW/unused (never mold-resistant, painted, or demolition drywall), since demolition sources risk paint, joint-compound additives, and possibly asbestos or other contaminants that have no place in bedding or land-applied manure. Sulphur (gypsum) content and manure gas risk: gypsum is calcium sulphate, and elevated sulphate in stored manure promotes microbial sulphate reduction to hydrogen sulphide — this compounds exactly the H₂S hazard already discussed in Questions 11 and 13, so ventilation and gas-testing precautions may need to be more conservative where gypsum bedding is used. Regulatory classification: if the drywall is sourced off-farm (which it typically is), it is a Non-Agricultural Source Material (NASM) under Ontario's Nutrient Management Act, requiring the appropriate NASM plan/approval and testing before it can be brought on-farm and eventually land-applied with the manure. Particle size and absorbency: grind size affects both bedding comfort/dustiness for livestock and how well the material absorbs moisture, which changes the moisture content assumptions used elsewhere in the farm's nutrient management calculations (e.g., Question 2's Table A.1 approach). Equipment wear and soil impact: gypsum is abrasive to pumps and spreading equipment, and adds sulphur/calcium/sodium loading to the receiving fields that should be tracked in the nutrient management plan alongside N-P-K.