Siting a composting facility with odour and flood constraints
A council of 18,000 residents must site a composting facility for separately collected organic waste. Generation is 0.55 kg per person per day, of which 34% is organic. Two sites are shortlisted. Site A is a disused quarry 200 m from 45 homes, with a clay liner and good road access. Site B is in an industrial estate 1.2 km from housing but on a floodplain that flooded twice in ten years. Composting would use open windrows turned weekly; leachate and odour are the main concerns. The national recycling target requires the facility within 18 months, and the council has a capital budget of €2.8 million. Residents near Site A have collected 1,200 signatures against it; the industrial estate has offered land at no cost but requires flood mitigation.
1. Estimate the daily and annual organic waste tonnage. Does the scale of the facility affect how the two sites should be judged?
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Calculation
Total waste = 18,000 × 0.55 = 9,900 kg/day. Organic fraction = 9,900 × 0.34 = 3,366 kg/day ≈ 3.4 t/day. Annual = 3,366 × 365 ≈ 1,229 t/year.
Interpretation
This is a modest facility, but 3.4 t/day of open windrows is enough to generate significant odour and leachate if poorly managed. Scale affects siting in two ways:
- A smaller facility can be enclosed or covered more affordably, which weakens the argument that odour forces it far from homes.
- The tonnage is large enough that flood risk at Site B is not trivial: if the site floods, leachate can escape and the facility can be out of action for weeks, while waste continues to arrive.
So scale does not decide the site, but it makes management design and flood resilience central criteria rather than afterthoughts.
2. Evaluate Sites A and B against environmental, social and economic criteria, and recommend a site with conditions.
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Criteria
- Environmental: Site A has a clay liner and is 200 m from homes; odour and bioaerosols are credible. Site B is 1.2 km away but on a floodplain - leachate containment during floods is the dominant risk.
- Social: Site A faces 1,200 signatures and likely delay or legal challenge. Site B has fewer nearby residents but shifts risk to an industrial area that may still flood.
- Economic: Site B has free land but needs flood mitigation; Site A may need odour control and legal/consultation costs. Budget €2.8m and 18 months are tight.
Recommendation
Site B is preferable only if flood mitigation is designed and costed first: raised platform above the 1-in-100-year plus climate allowance, perimeter bund, sealed leachate tank, flood warning and shutdown plan. If that exceeds the budget or cannot be permitted in time, Site A should be used with enclosed composting and a biofilter, not open windrows.
The judgement is conditional because neither site is cleanly best. The recommendation should state which condition triggers the fallback.
3. What monitoring and complaint-response arrangements should the council require?
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Monitoring should cover the pathways that caused concern:
- Odour: daily site checks, weekly olfactometry or field panel near receptors, and a logged complaints line with response times.
- Leachate: volume, pH, BOD/COD, ammonia and metals; groundwater monitoring boreholes up/down-gradient.
- Bioaerosols: periodic sampling at the boundary if windrows are open.
- Flood: water level, rainfall forecast trigger, and proof that the leachate tank is isolated during flood.
- Process: incoming tonnage, contamination rate, temperature, compost quality and maturity.
A community liaison group with published monthly data is important because trust, not just technical performance, determines whether the facility survives. If complaints exceed an agreed threshold or leachate is detected in groundwater, the council should have an enforceable trigger to cover or relocate operations.