power consumption requirements (electricity requirement)

Power consumption requirements describe the total electrical energy demand of a CBG plant to operate its mixing, pumping, gas treatment, compression, and ancillary systems. It is typically expressed as kWh per tonne of feedstock processed, or as a percentage of the gross biogas energy produced — the parasitic load. Indian commercial CBG plants typically consume 30-60 kWh per tonne of feedstock, equivalent to 7-12% of the gross calorific value of the biogas produced.

Major load contributors and their typical shares are:

• Biogas upgrading and compression: 35-50% of total — the largest single consumer, dominated by the compressor train moving raw biogas through water scrubbing or PSA and then to 250 bar storage.
• Digester mixing: 10-20% — mechanical, hydraulic, or gas mixing systems.
• Slurry pumping: 8-15% — feed pumps, recirculation, digestate transfer.
• Heating circulation pumps: 3-6%.
• Solid-liquid separation: 5-10% — decanter centrifuges or screw presses.
• Lighting, controls, and utilities: 5-8%.

Sizing the connected load determines the plant's grid connection class, transformer capacity, and backup power requirement. A 10 TPD plant typically needs a 250-400 kVA connected load; a 100 TPD plant requires 1,500-2,500 kVA. Most Indian CBG plants secure HT (high-tension) industrial connections at 11 kV, paying tariffs of 7-10 INR per kWh depending on state.

Operators reduce parasitic load through several levers, each with trade-offs. Variable frequency drives (VFDs) on pumps and agitators trim consumption 15-25% but add 8-15% to motor capex. Heat recovery from compressor cooling cuts steam demand for digester heating, saving 3-8 kWh per tonne. Sizing compressors for actual flow rather than design peak avoids running oversized machines at part-load efficiency penalty. Some plants install rooftop solar or biogas-fired CHP engines to offset 30-50% of grid demand, reducing both opex and grid dependency. Power consumption is the second-largest operating expense after feedstock, so 1 kWh per tonne saved scales meaningfully — at 8 INR per kWh and 100,000 tonnes per year, a 5 kWh per tonne reduction saves 40 lakh INR annually.