CBG/ Bio-CNG conversion efficiency & Mass Balance
A complete mass balance for a 10 TPD CBG plant showing how much water is added, how much biogas is produced, and how much digestate exits the digester for five feedstock types — from agri waste to animal waste.
| Feedstock (10 TPD) | INPUT A (Feedstock) | INPUT B (Added Water) | TOTAL INPUT (A+B) | OUTPUT 1 (Biogas) | OUTPUT 2 (Digestate) | TOTAL OUTPUT (1+2) |
| Agri Waste | 10 Tons | 80 Tons | 90 Tons | 1.2 Tons | 88.8 Tons | 90 Tons |
| Pressmud | 10 Tons | 15 Tons | 25 Tons | 1.4 Tons | 23.6 Tons | 25 Tons |
| Energy Crops | 10 Tons | 20 Tons | 30 Tons | 1.1 Tons | 28.9 Tons | 30 Tons |
| Municipal Waste | 10 Tons | 10 Tons | 20 Tons | 0.9 Tons | 19.1 Tons | 20 Tons |
| Animal Waste | 10 Tons | 8 Tons | 18 Tons | 0.2 Tons | 17.8 Tons | 18 Tons |
Beyond definitions
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How to read this table
- INPUT A is the dry feedstock; INPUT B is the water added during pre-processing. TOTAL INPUT is their sum.
- OUTPUT 1 is the biogas captured; OUTPUT 2 is the digestate (liquid plus solid). TOTAL OUTPUT equals TOTAL INPUT — mass is conserved.
- All figures are in tonnes per day for a 10 TPD feedstock input scenario.
- Biogas output here is raw gas weight — actual CBG produced after upgrading will be lower, as upgrading removes CO2 and H2S.
About this table
This mass balance table is the numerical foundation for planning a Compressed Biogas (CBG) or Bio-CNG plant. It answers the most basic engineering question: for every 10 tonnes of feedstock that enters the plant, what goes in and what comes out? The answer varies significantly by feedstock type, and understanding those differences is essential before selecting a site, sizing equipment, or signing a feedstock supply agreement.
Water addition is the biggest surprise for first-time developers. Agri waste requires 80 tonnes of water per 10 tonnes of feedstock — an 8:1 ratio — to dilute the fibrous, high-solids material to the pumpable slurry consistency (below 15% Total Solids) needed for a wet Continuously Stirred Tank Reactor (CSTR). Pressmud needs only 15 tonnes of water (1.5:1 ratio), and animal waste just 8 tonnes (0.8:1), because both already have higher moisture content. This water demand directly determines pumping capacity, pre-processing tank size, and the total digestate volume that must be managed.
On the gas side, pressmud produces the most biogas per tonne of feedstock at 1.4 tonnes of gas daily from 10 tonnes of input, slightly ahead of agri waste at 1.2 tonnes. Municipal Solid Waste (MSW) yields only 0.9 tonnes and animal waste a modest 0.2 tonnes — reflecting lower volatile solids content per unit weight. The mass balance closes exactly in every row (Total Input equals Total Output), confirming conservation of mass through the digestion process.
Developers should use this table to estimate three things before finalising a feedstock choice: the daily water supply requirement, the gas yield per tonne of available feedstock, and the total digestate volume they will need to store, process, and market as Fermented Organic Manure (FOM).
Key insights
- Agri waste requires 8 tonnes of added water per tonne of feedstock, the highest of any feedstock type — a critical factor for water availability assessment at the site.
- Pressmud produces the most biogas per tonne of input (1.4 tonnes per day from 10 tonnes feedstock), making it the highest gas-yield feedstock by weight.
- Animal waste yields only 0.2 tonnes of biogas per day from 10 tonnes of input — acceptable for mixed-feedstock plants but not viable as the sole input for a gas-maximising strategy.
- The mass balance closes exactly in all five rows — Total Input equals Total Output — confirming digestate accounts for everything not captured as gas, with no material loss.
Methodology & sources
Values represent typical industry mass balance outcomes for a wet anaerobic digestion process at mesophilic temperature (35–40°C). Biogas weights are raw gas output before upgrading. Water addition ratios vary with feedstock moisture and the target slurry total solids percentage. Actual plant performance will differ based on feedstock quality, digester design, and seasonal variation. Use as a planning baseline; commission a site-specific mass balance from your technology provider before finalising the detailed project report.
Related data tables
Bio-CNG Production Yield & Output - Expected Bio-CNG yield
Expected Bio-CNG output in kg/day from a 10 TPD plant for five feedstock types — pressmud gives the highest yield at 1,000 kg/day, while cattle dung gives the lowest at 175 kg/day — with vehicle fuelling equivalents for each.
Bio-CNG Production Yield & Output - Quantity Breakdown (Based on 10 TPD Input)
Daily digestate output split into solid Fermented Organic Manure (FOM) and liquid FOM for four feedstock types in a 10 TPD Bio-CNG plant — the numbers a developer needs to plan digestate storage and off-take.
Feedstock Categories for Bio-CNG Production
Five feedstock types for Bio-CNG production mapped against sources, Indian regional availability, seasonal patterns, and gas yield — a practical reference for site-specific feedstock planning.
Process Differences by Feedstock type
A comparison of five feedstock types for CBG plants showing the primary digestion challenge for each and the unique pre-treatment step that addresses it — from lignin-heavy agro-waste to pH-sensitive industrial effluents.