Principle of Separation

The solubility of CO2 and CH4 in water differs sufficiently to make posible the separation of these molecules by absorption under certain conditions of pressure, temperature and flow. Only water is used. This is regenerated and used in a closed cycle to reduce water consumption. The separation means is water, which is free and independent of any provider of separation media such as membranes, adsorbents or amines.

Design Constraints

Biomethane plants dealing with biogas from organic waste must work over a range, not at a point, because the biogas produced fluctuates in flow and composition.

All separation processes entail losses of the target gas, but these are controlled by flash distillation, which recovers the CH4 absorbed in the water.

Operation and Maintenance

The absorption and desorption processes are strongly non-linear, so that the operation of AGF is fundamental to ensuring the production of gas that is valid within the design range.

In turn, for the plant to work for as long as possible, a preventive maintenance plan and the supply of critical spare parts are necessary. The main consumable of the plant is water, in amounts of less than 1 m3 per day. The principal operational cost is electricity consumption.

Control |

The stability and automation of the plant require a complex control engineering design to permit autonomous operation. The integration of the elements is applied to match biogas and biomethane plants optimally. The biomethane plant is adapted to process the output of the biogas plant. The latter, in turn, produces biogas as determined by the situation. The result is that the biogas plant can work at constant dome level.

plant models


BM model. Biomethane.

Low Pressure gas pipeline.


High pressuer gas pipeline.

Virtual gas pipeline. For virtual gas pipelines, AGF offers the complete solution of filling system and injection module to control gas discharges.

main references

our biomethane plant projects


PR 138 | PE 2 BM 500
Biomethane production plant. Separation by absorption in water without chemical reaction.

Minimum biomethane flow 150 Nm3/h.

Maximum biomethane flow 300 Nm3/h

Commissioning. September 2021.

First injection. 25/9/2021.

Average injected flow: 210 Nm3/h.

Biomethane quality: 97.5-99.5.

Consumption: < 0.25kWhe/Nm3

Certified losses <1.6%.

Injection pressure: 6 bar.

Plant promoted by SUMA CAPITAL and ENAGAS.

First biomethane injection by private company into Spain’s low pressure gas grid.

Installed at Biogasnalia biogas plant site, it uses the gas generated in the biogas plant to produce biomethane.

Primera inyección de biometano en España por iniciativa privada



PR 131 | PE 1 BMC 850

Compressed biomethane production plant. Separation by absorption in water without chemical reaction, with final compression.

Minimum flow 350 Nm3/h.

Maximum flow 600 Nm3/h.

Nominal flow 500 Nm3/h.

Commissioning. February 2022.

First start-up. February 2022.

Average injected flow: 500 Nm3/h.

Biomethane quality: 97.5-99.5.

Consumption: < 0.25kWhe/Nm3

Certified losses <1.6%.

Output pressure: 70-250 bar.

Compressed biomethane plant, able of producing biomethane at different discharge pressures. Designed for direct injection into high pressure gas grid or for virtual gas pipelines.

First injection by private company into Spain’s high pressure gas grid.




AGF está construyendo la primera planta de biometano comprimido de España