Hawaii Biogas: Custom Designed RNG Skid System

Project Profile

Stark RNG designed a programmed control system for Hawai’i Gas in their biogas upgrading efforts for the feed compressor to be integrated with their existing control system. Being operational since 2018, the project was awarded the “Biogas Project of the Year” in 2019 by the American Biogas Council.


In need of a custom design and fabrication of an RNG skid system. The skid system needed to tolerate the harsh oceanic environment. A feed compressor skid must also be designed to fit inside a separation membrane container. These unique space requirements presented significant design challenges for piping and equipment placement. This had to be accomplished with short lead times, as the customer had a quick and inflexible project timeline.

Stark Tech Solution

Stark Tech’s engineering team took the process diagram and created a piping and instrumentation diagram (P&ID) to detail the necessary components of the skid. We then developed a 3D model to address the feed compressor’s space limitations and examined the design’s feasibility. Finally, we designed and programmed a control system for the feed compressor that could be integrated with their existing control system.

  • Feed compressor skid to increase gas pressure upstream of the membranes.
  • Feed blower and dehydrator skid, outfitted with an enclosure for sound-dampening and additional environmental protection.
  • Standalone vacuum blower assembly with silencers and supports for the permeate side of the membrane.
  • Complex heat exchanger network to minimize the chiller size and energy consumption, which included an ambient air heat exchanger and several brazed plate exchangers.
  • The use of hot compressor discharge gas to reheat the chilled, dehydrated gas, which eliminated the need for additional heat sources
  • 316 stainless steel piping to resist the corrosive effects of the harsh marine environment.

Project Result

Hawai’i Gas was able to meet its deadline for injecting gas into the utility pipeline. Hawai’i Gas held a blessing ceremony to mark the completion of the project. Hawai’i Gas is the main provider of gas energy. The biogas upgrading allowed for Hawai’i Gas’ 1,100-mile underground utility pipeline to supply clean and safe energy to nearly every major market such as, agriculture, education, food service, government, health care, hospitality, military, and residents.