Framework Documentation
The NOAA-TDC Dual-Flow ESG Asset Attribution Framework adapted for Australian oyster aquaculture in New South Wales.
The model operates across four tiers, each adding precision and context to the ecosystem service valuation. Tiers 3 and 4 are always active, while Tier 1 or Tier 2 is selected based on data availability.
| Tier | Name | When Active |
|---|---|---|
| 1 | Latent Potential | Default: area-based rates + regional environmental data |
| 2 | Realised Contribution | When harvest tonnage is available (Oceanfarmr data) |
| 3 | Spatial Apportionment | Always: NSW DPI estuary classification, seagrass, marine parks |
| 4 | Data Quality Adjustment | Always: DAF = ((REDQS/5)² + REDQS/5) / 2 |
The DAF discounts all ESV estimates based on the quality and proximity of supporting environmental data. It uses the Regional Environmental Data Quality Score (REDQS), scored 1-5:
DAF = ((REDQS / 5)² + REDQS / 5) / 2
| REDQS | DAF | Scenario |
|---|---|---|
| 1 | 0.100 | No local data; estuary-level fallback |
| 2 | 0.280 | BOM station >10 km; single-year data |
| 3 | 0.480 | BOM/DPI station within 10 km; multi-year average |
| 4 | 0.720 | Station within 5 km; verified farm data |
| 5 | 1.000 | On-farm sensors + verified Oceanfarmr records |
Oysters remove nitrogen from the water column through bioassimilation into tissue and shell. NSW-specific rates from NSW Farmers / Blueshift (2025):
Tier 1: N_removed = Area_ha × 13.8 kg/ha/yr × TN_adj × AF
Tier 2: N_removed = HarvestT × SpeciesRate × AF
Value: N_removed × A$100/kg × DAF
Sydney Rock Oyster
5.58 kg TN/t harvested
Pacific Oyster
4.46 kg TN/t harvested
Tier 2 only — requires harvest tonnage data. Phosphorus is removed through tissue bioassimilation.
P_removed = HarvestT × P_SpeciesRate × AF → Value = P_removed × A$100/kg × DAF
Sydney Rock Oyster
0.69 kg TP/t harvested
Pacific Oyster
0.55 kg TP/t harvested
Shell carbon is calculated using the IPCC (2006) lime proxy method. Shell composition is 92% CaCO₃ (de Roover 2024). Note: this method is scientifically contested — Pernet et al. (2024) argues harvesting CaCO₃ does not constitute a CO₂ sink.
ShellWeight = HarvestT × 1000 × ShellRatio
CO₂_seq = ShellWeight × 0.92 × 0.12 × 3.67 → ≈ 0.4 kg CO₂/kg shell
Value = CO₂_seq (tonnes) × A$34/t × DAF
SRO Shell Ratio
75.8%
PAC Shell Ratio
83.8%
Benefit transfer from Grabowski et al. (2012) and McLeod et al., adjusted for AUD. Split into commercial fisheries enhancement and recreational fishing value. Multiplied by seagrass density and marine park proximity factors.
Habitat_comm = Area_ha × A$1,200/ha × Seagrass_mult × MarinePark_mult × AF × DAF
Habitat_rec = Area_ha × A$600/ha × Seagrass_mult × MarinePark_mult × AF × DAF
Each oyster filters approximately 189 litres per day (~50 US gallons). This is reported as a co-benefit but excluded from the total ESV to avoid double-counting with nitrogen removal.
NSW Farmers / Blueshift (2025)
N/P removal rates, shell carbon, species-specific data
IPCC (2006)
Lime proxy emission factor for shell carbon
de Roover (2024)
Shell elemental analysis (92% CaCO₃)
Grabowski et al. (2012)
Habitat provision values for oyster reefs
FSANZ
Tissue composition data for SRO and PAC
| Standard | Application |
|---|---|
| TNFD LEAP | Locate (POAA polygon), Evaluate (DPI/BOM/FDT data), Assess (DAF confidence), Prepare (ESV report) |
| GRI 304 | Biodiversity: proximity to marine parks, seagrass meadows, essential fish habitat |
| SEEA EA | Ecosystem accounts: N/P removal and carbon as regulating service flows |
| EPBC Act | Matters of National Environmental Significance: marine species, wetlands |
| OISAS 2021 | NSW Oyster Industry Sustainable Aquaculture Strategy: POAA area classification |
High
Peer-reviewed rate, active area, FDT/BOM station within 5 km, REDQS ≥ 4
Medium
Benefit-transfer value, or estuary-level WQ data, REDQS 2-3
Low
Inactive/prohibited area, no local data, REDQS 1
Overall confidence = lowest confidence across all active service vectors.