The cost of purifying biogas (removing sulfur and carbon)

The cost of purifying biogas (de-sulfurization and de-carbonization) is influenced by various factors, including the composition of biogas, processing scale, technical route, equipment investment, and operating costs. The following is an overview and estimated range of the main costs:

1. De-sulfurization cost
Sulfur compounds (H₂S) in biogas need to be removed first to prevent equipment corrosion and affect subsequent processes. Common methods and costs:
Dry desulfurization (iron oxide adsorption)
Investment cost: 50,000 – 200,000 yuan per set (small-scale device)
Operating cost: 0.05 – 0.15 yuan per Nm³ (biogas)
Applicable scenarios: Small-scale (< 100 Nm/h), low sulfur concentration (< 2000 ppm).
Wet desulfurization (biological desulfurization or chemical washing)
Investment cost: 500,000 – 2,000,000 yuan (medium-sized system)
Operating cost: 0.10 – 0.30 yuan per Nm³ (including chemical reagents, power consumption)
Applicable scenarios: Medium-scale, high sulfur concentration (> 2000 ppm).

2. De-carbonization cost
To increase methane purity (usually ≥ 90%), CO₂ needs to be removed. Main technology comparisons:
Pressure Swing Adsorption (PSA)
Investment cost: 3,000,000 – 8,000,000 yuan (processing capacity 500 Nm³/h)
Operating cost: 0.20 – 0.40 yuan per Nm³ (power consumption, adsorbent replacement)
Methane recovery rate: 85% – 92%.
Membrane separation
Investment cost: 2,000,000 – 6,000,000 yuan (500 Nm³/h)
Operating cost: 0.15 – 0.35 yuan per Nm³ (membrane replacement cycle 3 – 5 years)
Methane recovery rate: 80% – 90%.
Chemical absorption method (such as amine washing)
Investment cost: relatively high (requires a regeneration system)
Operating cost: 0.30 – 0.50 yuan per Nm³ (high energy consumption, requires thermal regeneration)
Applicable scenarios: High precision purification (such as injecting into gas pipelines).

3. Comprehensive purification cost estimation
Taking a biogas processing capacity of 500 Nm³/h as an example (initial methane content 60%, H₂S 1000 ppm):
Investment cost: 5,000,000 – 12,000,000 yuan (including pretreatment, de-sulfurization, de-carbonization, compression, etc.).
Operating cost: 0.50 – 1.00 yuan per Nm³ (including energy consumption, labor, maintenance, etc.).
Methane production: approximately 300 Nm³/h (purity over 90%), equivalent to unit methane cost 1.2 – 2.5 yuan per Nm³.

4. Key influencing factors
Scale effect: The larger the processing capacity, the lower the unit cost (such as a 10,000-ton project cost can be reduced by 20% – 30%).
Biogas source: The impurity content of landfill gas, livestock manure or industrial wastewater biogas varies.
Policy subsidies: Some regions offer subsidies for biogas (such as 0.5 – 1.0 yuan per Nm³).

5. Economic reference
Comparison of natural gas prices: If the local natural gas price is 3 yuan per Nm³, the purified biogas can be competitive (considering subsidies).
Investment payback period: Usually 5 – 8 years (without subsidies).
For specific project assessment, it is necessary to further calculate based on biogas composition analysis, processing scale and local energy policies.