Calculator Inputs
Example Data Table
These values are sample engineering scenarios for quick reference. They are illustrative and should not replace measured laboratory yield data.
| Scenario | Feedstock (kg/day) | TS (%) | VS of TS (%) | Yield (m³/kg VS) | Methane (%) | Captured Biogas (m³/day) | Net Electricity (kWh/day) |
|---|---|---|---|---|---|---|---|
| Cattle Slurry | 1200 | 12 | 78 | 0.42 | 56 | 166.8 | 272.4 |
| Food Waste Blend | 850 | 24 | 88 | 0.78 | 60 | 354.5 | 621.1 |
| Poultry Litter Mix | 700 | 30 | 70 | 0.50 | 54 | 206.0 | 313.2 |
Formula Used
1) Solids and Organic Matter
Dry Solids (kg/day) = Feedstock Mass × Total Solids
Volatile Solids (kg/day) = Dry Solids × Volatile Solids Fraction
2) Biogas Production
VS Destroyed (kg/day) = Volatile Solids × VS Destruction
Gross Biogas (m³/day) = VS Destroyed × Specific Biogas Yield
Captured Biogas (m³/day) = Gross Biogas × Capture Efficiency
3) Methane and Energy
Methane Volume (m³/day) = Captured Biogas × Methane Content
Methane Energy (kWh/day) = Methane Volume × Methane Lower Heating Value
Gross Electricity (kWh/day) = Methane Energy × Electrical Efficiency
Net Electricity (kWh/day) = Gross Electricity × (1 − Parasitic Load)
4) Heat Recovery and Digester Size
Recoverable Heat (kWh/day) = Methane Energy × Thermal Efficiency
Daily Slurry Volume (m³/day) = (Feedstock Mass + Added Water) ÷ Slurry Density
Digester Volume (m³) = Daily Slurry Volume × Hydraulic Retention Time
5) Annual Effective Output
Annual Effective Value = Daily Value × 365 × System Uptime
How to Use This Calculator
- Enter the daily wet feedstock quantity delivered to the digester.
- Add laboratory or estimated solids values for total solids and volatile solids.
- Set the expected VS destruction and specific biogas yield.
- Enter methane content, gas capture efficiency, and annual uptime.
- Provide dilution, slurry density, and retention time for size estimation.
- Set electrical, thermal, and parasitic assumptions for energy recovery.
- Press the calculate button to display daily and annual performance above the form.
- Use the CSV or PDF buttons to save the results for reporting.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates captured biogas, methane output, energy content, net electricity, recoverable heat, slurry flow, and recommended digester working volume from engineering input assumptions.
2) Why is volatile solids important?
Volatile solids represent the biodegradable organic portion of the feedstock. Biogas potential depends more on volatile solids than on total wet mass alone.
3) Should I use gross biogas or captured biogas?
Captured biogas is more practical for design and economics because it accounts for collection losses, minor leaks, and operational handling inefficiencies.
4) Does the calculator size the whole plant?
No. It provides a recommended digester working volume from slurry flow and retention time. Full plant sizing still needs mixing, heating, storage, and safety design checks.
5) What methane heating value should I use?
A common engineering value is about 9.97 kWh per cubic meter of methane. Adjust it if your project uses another standard basis.
6) Why is uptime applied to annual output?
Daily results show nominal operating performance. Annual effective output applies uptime so maintenance, outages, and seasonal interruptions are reflected in yearly totals.
7) Can I use this for co-digestion projects?
Yes. Use weighted average inputs for mixed feedstocks, or pre-calculate combined solids, methane fraction, and yield values from your blend proportions.
8) Is this suitable for financial decisions?
It is useful for screening and feasibility work. Final investment decisions should use pilot data, lab assays, detailed process design, and project-specific economics.