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Diary digester cluster for RNG distribution and RCNG transportation

Introduction – Challenge

With over 1,600 dairies, California has the largest dairy industry in the United States. To take advantage of economies of scale, the idea of a centralized dairy digester projects has been developed.

The customer’s goal was to create a fully integrated solution for RNG pipeline injection, high-pressure trailer filling and pressure reduction systems for RNG utilization. They needed a partner who could help them implement a “hub and spoke” model that would efficiently gather and distribute biogas from local dairies.

The Diary digester concept, often described as a «hub and spoke» model, is fairly straight forward.
The «hub» would involve a centrally located operation where diary raw biogas could be gathered from a cluster of existing dairy operations.

At the hub, the customer installed a state-of-the-art biogas upgrading system that cleaned and conditioned the raw biogas to pipeline quality biomethane. This renewable natural gas could then be used for electrical distributed generation and RNG distribution and transportation. The customer also installed a low-pressure PVC pipeline system that connected the participating local dairies, allowing for efficient gas gathering.

The «spokes» would involve a gas gathering system of low-pressure PVC pipelines that interconnect the cluster of participating local diaries.

In addition, IMW provided a high-pressure trailer filling solution that could fill trailers to over 300 barg, making it easy to transport the RNG to other locations. They also installed a decanting and pressure reduction system for RNG utilization, ensuring that the gas was used efficiently and safely.

Custumer requirement – Project SoW

Pipeline injection site


Inlet pressure

bar 6 – 8

Inlet pressure

barg 310

Discharge Pressure

bar 97

Discharge Pressure

bar 17


Sm3/hr 1670


Sm3/hr 1696

RNG Distribution

Biogas needs to be processed and compressed in a central facility to be injected into the utility pipeline

RCNG off-site distribution

Biogas in a dairy facility to be compressed as RCNG and loaded into GTMs (Gas Transportation Module) and transported to the pipeline injection site for scrubbing and further processing the injected iti the pipeline.

Remote compression site

Loading station

Inlet pressure

bar 7.5 – 9
Loading station

Discharge pressure

bar 310
Loading station


Sm3/hr 480

SAFE solution - contribution


IMW has developed a RNG pipeline injection solution consisting of a variable capacity RNG booster compressor based on a proven non-lubricated CleanCNG 2.0 modular design, ensuring high quality and the cleanest natural gas injection into pipeline. CEC modular CleanCNG 2.0 compressors can be configured as trailer loading compressor or booster compressor all within the same package.

The solution included an electrical PRS to offload the gas from the remote RNG sites after being compressed to the GTMs.

High performances and efficiency

• The variable capacity boosters provided the ability to cover the full range of operation for the digester system.

•The capability of compressing the RNG to 310 barg allowed high delivery volume from the remote sites to the pipe injection site.

•The pressure reduction system allowing biogas to be delivered at the desire flow with minimal pressure drop and well controlled discharge temperature to the downstream consumer.


The Electric PRS keeps energy forward towards fully decarbonization, being fully compliant to US environmental regulation: its design and technology guarantee ZERO emissions and, therefore, no gas vent or leakage in the atmosphere.

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