Excel reconciliation
The engine is compared against both source workbooks and against metered 2025 production. Divergence is reported and explained — never quietly reconciled.
Lines within 2%
3/16
Divergent lines
8
More than 10% away from the workbook figure
Open conflicts
3
Engine version
1.0.0
Engine versus workbook
Each line names its source sheet and explains why the engine differs where it does.
| Metric | Workbook | Engine | Delta | Status | Explanation |
|---|---|---|---|---|---|
Grid injection target (NEA limit) Nm3/h · Yorks Process Flow v1 (07/08/26, Merged Models) — Levers!B6 | 853 | 853 | +0% | match | The backward engine starts from the same NEA ceiling as the workbook's NEA-Backward Model. |
Biomethane required (pre-propane) Nm3/h · Yorks Process Flow v1 (07/08/26, Merged Models) — NEA-Backward Model | 813.18 | 813.18 | -0% | match | Grid target divided by (1 + propane uplift). A delta means the GCV levers have been amended. |
Biogas required Nm3/h · Yorks Process Flow v1 (07/08/26, Merged Models) — NEA-Backward Model | 1,349.15 | 1,376.68 | +2% | close | Biomethane requirement divided by the derived CH4 fraction and BUU recovery. |
Grid injection achievable Nm3/h · Yorks Process Flow v1 (07/08/26, Merged Models) — NEA-Backward Model | 665.68 | 322.32 | -51.6% | divergent | The workbook binds on feedstock availability. The engine additionally applies biological derates, so it can sit lower. |
Hydrolysis retention time days · Yorks Process Flow v1 (07/08/26, Merged Models) — Bio Hydrolysis!B13 | 6.35 | 6.68 | +5.1% | close | Same first-order kinetics; the engine adds a pH factor the sheet omits. |
Biogas yield per m3 of feed Nm3/m3 · Yorks Process Flow v1 (07/08/26, Merged Models) — Bio Levers!C42 | 144.13 | 105.93 | -26.5% | divergent | COD chemistry yield. The engine applies the biological efficiency multiplier on top of it. |
Hydrolysis retention time (historic) days · Bio Processing Model v1.3 (Cleaned 05/08/26) | 6.35 | 6.68 | +5.1% | close | The engine reproduces the workbook's first-order kinetics; any delta comes from the pH factor, which the workbook omits. |
Hydrolysis capacity m3/day · Bio Processing Model v1.3 (Cleaned 05/08/26) | 346.24 | 329.36 | -4.9% | close | The engine additionally derates hydrolysis for measured downtime, so it should sit below the workbook figure. |
Pasteurisation capacity m3/day · Bio Processing Model v1.3 (Cleaned 05/08/26) | 624 | 608.61 | -2.5% | close | The workbook uses hold + fill/empty only. The engine splits fill, heat, transfer and empty and applies the compliance gate. |
Digestion capacity m3/day · Bio Processing Model v1.3 (Cleaned 05/08/26) | 237.5 | 154.65 | -34.9% | divergent | The workbook applies the DS-load rule alone. The engine takes the minimum of HRT, VS/COD loading, DS load and the volumetric push rate. |
Biogas yield per m3 of feed Nm3/m3 · Bio Processing Model v1.3 (Cleaned 05/08/26) vs Yorks Process BUU Back v2.2 (14/07/26) | 144.78 | 105.93 | -26.8% | divergent | The two workbooks disagree on the yield basis (COD-kinetic vs fixed 140 Nm3/m3). The engine applies the biological efficiency multiplier on top. |
Biogas production Nm3/day · Bio Processing Model v1.3 (Cleaned 05/08/26) | 34,386.04 | 12,484.85 | -63.7% | divergent | Difference is the combined effect of downtime and the methanogenic temperature / pH / solids derate. |
Propane enrichment ratio Nm3 per Nm3 biomethane · Yorks Process BUU Back v2.2 (14/07/26) | 0.05 | 0.05 | -0% | match | Both derive propane from the GCV energy balance; a delta means the site GCV levers have been amended. |
Feedstock digested t/yr · Yorks Process BUU Back v2.2 (14/07/26) 2025 Actuals | 69,872.32 | 43,017.86 | -38.4% | divergent | Actual digested tonnage is the strongest calibration point; a large gap means capacity levers do not reflect how the plant was run. |
Biogas produced Nm3/yr · Yorks Process BUU Back v2.2 (14/07/26) 2025 Actuals | 9,349,506.7 | 4,556,969.45 | -51.3% | divergent | Compares the modelled gas against metered production for the same site. |
Average grid injection Nm3/h · Yorks Process BUU Back v2.2 (14/07/26) 2025 Actuals | 693.6 | 322.32 | -53.5% | divergent | Metered average injection over the year, including downtime. The engine already nets downtime off, so these should be close. |
Workbook conflict register
Where the two spreadsheets disagree with each other. The engine exposes both readings and applies the one recorded in the variable register.
| Topic | Bio Processing Model v1.3 | Yorks Process BUU Back v2.2 | Impact if unresolved | Resolution in the merged workbook |
|---|---|---|---|---|
| Site operating days | 360 (Bio Processing Model v1.3) | 365 (BUU Back v2.2) | 1.4% difference in annual output. | resolved — merged workbook Levers!B31 = 365 |
| Hydrolysis pump hours | 12 h/day | 24 h/day | Doubles or halves pump-limited hydrolysis capacity. | resolved — merged workbook Levers!B54 = 24 h/day |
| Digester DS loading limit | 4.75 kg DS/m3/day | 5.0 kg DS/m3/day | 5% difference in the digestion ceiling. | resolved — merged workbook Bio Levers!C17 = 5.0 |
| Methane content of biogas | Flat 60% assumption | Flat 60% assumption | Changes biogas volume for the same methane mass. | resolved — merged workbook Bio Levers!C20 derives CH4% from BOD:COD |
| Biogas yield basis | COD-kinetic yield | Fixed 140 Nm3/m3 | Changes gas output and every downstream capacity check. | resolved — merged workbook Bio Levers!C42 = 144.1 Nm3/m3 from COD chemistry |
| Feedstock available | n/a | 2025 actual tonnages (117,689 t/yr) | Sets the modelled feed rate. | resolved — merged workbook Levers!B24 = 117,480 t/yr forward looking availability; 2025 actuals are a benchmark only |
| Pasteuriser heat recovery | 85% | n/a | Changes boiler fuel demand. | resolved — merged workbook Levers!B113 = 94.4% |
| Tanker cycle interpretation | n/a | Sequential vs parallel not stated | Changes loads per shift and transport capacity. | open — merged workbook Levers!D45 raises the same question |
| REL/HOL downtime allocation | n/a | Hydrolysis and pasteurisation not split by site | Misattributes lost production between sites. | open — merged workbook leaves HOL hydrolysis/pasteurisation blank |
| Sm3 vs Nm3 | Nm3 throughout | GCV values quoted per Sm3 | 5.5% volume difference; must be converted explicitly. | open — merged workbook Levers!B81 B83 gives both bases |