Energy mass balanceBiomass
Biogas Feedstock Mix & BMP Potential (CH4/CO2/Digestate) (fork)
Estimate annual biomethane potential from a mixed feedstock inlet using TS (MS), VS (MV), BMP and biogas CH4 content; outputs biogas, CH4, CO2 and digestate quantity.
Inputs
Used to scale processed tonnage (downtime, collection limits, commissioning ramp-up).
min 0 · max 100 · step 1 · %
Typical raw biogas CH4 is often ~50–65% vol. Used to split CH4 vs CO2 volumes.
min 1 · max 80 · step 1 · %
Annual wet mass delivered to the digester (before utilisation scaling).
Total solids as % of wet mass.
Volatile solids fraction of TS.
Biochemical methane potential per tonne of volatile solids.
Annual wet mass delivered to the digester (before utilisation scaling).
Total solids as % of wet mass.
Volatile solids fraction of TS.
BMP per tonne of volatile solids.
Annual wet mass delivered to the digester (before utilisation scaling).
Total solids as % of wet mass.
Volatile solids fraction of TS.
BMP per tonne of volatile solids.
Annual wet mass delivered to the digester (before utilisation scaling).
Total solids as % of wet mass.
Volatile solids fraction of TS.
BMP per tonne of volatile solids.
Annual wet mass delivered to the digester (before utilisation scaling).
Total solids as % of wet mass.
Volatile solids fraction of TS.
BMP per tonne of volatile solids.
Results
Total processed feedstock (wet)
After applying utilisation (capacity factor)
Total dry matter (TS/MS)
Annual total solids entering digestion
Total volatile solids (VS/MV)
Annual volatile solids available for biodegradation
Raw biogas produced
Derived from CH₄ and biogas methane content
Methane produced (CH₄)
From VS and BMP
Carbon dioxide produced (CO₂)
Biogas remainder after CH₄ (and trace gases, if enabled)
Energy in produced methane (LHV)
Chemical energy content of CH₄ only
Digestate quantity (wet, screening)
Feedstock wet mass minus biogas mass
About
Calculator context
About
Calculator context
Introduction
This calculator screens the methane potential of an anaerobic digestion feedstock blend (e.g., manure, slurry, CIVE/catch crops, biowaste, industrial effluents) using project-stage inputs typically available during early development. It follows a transparent mass/volume balance approach used in biogas feasibility pre-studies, consistent with common practice in IEA Bioenergy technical reporting and widely cited biogas engineering handbooks.
Methodology
The model computes volatile solids (VS) from wet tonnage and solids content, then converts VS to methane using BMP, and derives total biogas and CO₂ from an assumed/entered biogas methane content.
Key steps (annual basis):
- Operating fraction and load hours
- load_hours = hours_per_year * capacity_factor * 0.01
- load_penalty = clamp(1 + penalty_coeff * (1 - capacity_factor*0.01), 1, max_penalty)
- effective_consumption = specific_consumption * load_penalty
- Per-feedstock solids and methane
- TS_t = wet_t * TS_% * 0.01
- VS_t = TS_t * VS_%_of_TS * 0.01
- CH4_Nm3 = VS_t * BMP_(Nm3CH4/tVS)
- Mixture gas split
- CH4_vol_frac = CH4_% * 0.01
- biogas_Nm3 = CH4_Nm3 / max(CH4_vol_frac, eps)
- CO2_vol_frac = max(1 - CH4_vol_frac - trace_vol_frac, 0)
- CO2_Nm3 = biogas_Nm3 * CO2_vol_frac
- Digestate wet quantity (simple screening)
- biogas_mass_t = (CH4_Nm3rho_CH4 + CO2_Nm3rho_CO2)/1000
- digestate_wet_t = max(feedstock_wet_t - biogas_mass_t, 0)
Default physical properties (gas densities, LHV) are drawn from standard gas data references (e.g., ISO 6976 conventions and NIST-type property tables). BMP remains user-provided because it is highly substrate- and test-dependent.
Applications
- Project developer: compare alternative feedstock mixes to decide whether to proceed to lab BMP testing or supplier MoUs.
- Engineering consultant: build a first-pass annual gas yield and CO₂ split for permit dossiers and early sizing discussions.
- Plant operator / aggregator: quantify the impact of changing a marginal substrate (e.g., adding biowaste) on annual CH₄ and digestate logistics.
Model
78 variables — inputs, calculations and outputs, with their dependencies.
Model
78 variables — inputs, calculations and outputs, with their dependencies.
| Variable | Value | Unit | Depends on |
|---|---|---|---|
| 90 | % | — | |
| 55 | % | — | |
| 5000 | t/year | — | |
| 25 | % | — | |
| 80 | % | — | |
| 220 | Nm3CH4/tVS | — | |
| 15000 | t/year | — | |
| 8 | % | — | |
| 75 | % | — | |
| 250 | Nm3CH4/tVS | — | |
| 4000 | t/year | — | |
| 30 | % | — | |
| 90 | % | — | |
| 320 | Nm3CH4/tVS | — | |
| 3000 | t/year | — | |
| 28 | % | — | |
| 90 | % | — | |
| 450 | Nm3CH4/tVS | — | |
| 2000 | t/year | — | |
| 5 | % | — | |
| 85 | % | — | |
| 300 | Nm3CH4/tVS | — |
| Variable | Formula | Unit | Depends on |
|---|---|---|---|
if((<)+(>100)+(<=)+(>100)+(<)+(<)+(>100)+(<)+(>100)+(<)+(<)+(<)+(>100)+(<)+(>100)+(<)+(<)+(<)+(>100)+(<)+(>100)+(<)+(<)+(<)+(>100)+(<)+(>100)+(<)+(<)+(<)+(>100)+(<)+(>100)+(<)>,1,0) | bool | ||
* | ratio | ||
clamp(+*(-*),,) | — | ||
* | kWh/Nm3 | ||
* | t/year | ||
** | tTS/year | ||
** | tVS/year | ||
* | Nm3CH4/year | ||
* | t/year | ||
** | tTS/year | ||
** | tVS/year | ||
* | Nm3CH4/year | ||
* | t/year | ||
** | tTS/year | ||
** | tVS/year | ||
* | Nm3CH4/year | ||
* | t/year | ||
** | tTS/year | ||
** | tVS/year | ||
* | Nm3CH4/year | ||
* | t/year | ||
** | tTS/year | ||
** | tVS/year | ||
* | Nm3CH4/year | ||
* | ratio | ||
max(--,) | ratio | ||
* | kWh/year | ||
* | kg/year | ||
* | kg/year | ||
(+)/max(,) | t/year | ||
* | kWh/year | ||
/max(,) | MWh/year |
| Variable | Formula | Unit | Depends on |
|---|---|---|---|
**0.01 | h/year | ||
++++ | t/year | ||
++++ | tTS/year | ||
++++ | tVS/year | ||
++++ | Nm3CH4/year | ||
/max(,) | Nm3/year | ||
* | Nm3CO2/year | ||
/max(,) | MWh/year | ||
max(-,) | t/year |
Assumptions
15 assumptions used in the calculations
Assumptions
15 assumptions used in the calculations
Prevents division by zero and unstable calculations when CH4 fraction is very small.
Market range Not applicable
0.000001Numerical stability constantUsed to translate capacity factor to equivalent operating hours.
Market range 8760 for non-leap year convention
8760h/yearCalendar constantConverts percent inputs (0–100) to fractions (0–1).
Market range Exact
0.01ratio/%Unit conversion constantAvoids inline numeric literals in expressions.
Market range Exact
1Algebraic constantAvoids inline numeric literals in expressions and supports clamping to non-negative values.
Market range Exact
0Algebraic constantThe energy_mass_balance category requires a load penalty node; for this feedstock BMP calculator the penalty is set to zero so it does not affect results.
Market range 0 (disabled) to ~0.3 (in some part-load penalty models)
0CATEGORY_RULES scaffold coefficient (disabled)Ensures load penalty is not less than 1 in the mandatory clamp() expression.
Market range Typically 1
1CATEGORY_RULES scaffold boundSet equal to 1 so the load penalty remains 1 (no penalty) for this calculator scope.
Market range 1 to ~2 in some part-load penalty models
1CATEGORY_RULES scaffold bound (disabled)Auxiliary energy consumption is not required for the requested outputs; kept at 0 to satisfy mandatory node structure without adding unrelated assumptions.
Market range 0 to ~0.1 kWh/Nm3 (site-dependent, if used)
0kWh/Nm3CATEGORY_RULES scaffold term (disabled)Requested outputs focus on CH4 and CO2; trace gases (H2S, N2, O2, H2O vapor) are neglected for a first-pass split.
Market range 0 to 0.05 (often small but variable)
0ratioSimplifying biogas composition assumptionUsed to convert methane volume (Nm3) to mass for the simplified digestate wet mass balance.
Market range Approximately 0.65–0.75 kg/Nm3 depending on reference conditions
0.716kg/Nm3Gas property at normal conditionsUsed to convert CO2 volume (Nm3) to mass for the simplified digestate wet mass balance.
Market range Approximately 1.8–2.1 kg/Nm3 depending on reference conditions
1.977kg/Nm3Gas property at normal conditionsConverts methane volume to chemical energy (LHV) for screening energy potential.
Market range About 9.5–10.2 kWh/Nm3 depending on reference conditions
9.97kWh/Nm3CH4Methane LHV at normal conditions (typical engineering value)Converts kilograms to metric tonnes for mass balance outputs.
Market range Exact
1000kg/tUnit conversion constantConverts kWh to MWh for energy outputs.
Market range Exact
1000kWh/MWhUnit conversion constant