NW Iowa RNG Site Design

Gevo, Inc. | Doon, Iowa

The Northwest (NW) Iowa Renewable Natural Gas (RNG) Plant creates RNG at not one, but three, sites in Iowa using something the area already has in abundance: manure from dairy farms. The project was conceived by Gevo, a renewable chemicals and advanced biofuels company, as a source for low-carbon intensity (CI) thermal energy. To support Gevo’s sustainability goals, Merrick & Company (Merrick) provided Front End Loading-3 (FEL-3) engineering, detailed engineering, and total project integration for the three separate dairy farm sites and one common biogas upgrading site.

A traditional dairy RNG project with multiple sites performs the entire manure-to-RNG process at each site—from manure collection to anaerobic digestion to biogas upgrading. To save time, money, and land, our team streamlined this process for the NW Iowa RNG Plant. We successfully blended agricultural and industrial best practices to create a unique solution for the three dairy sites. Each site was designed with its own manure collection and processing, anaerobic digestion, and biogas conditioning systems. The resulting biogas from each site is then transported via a pipeline network to a single common gas upgrading site where upgrading to RNG for direct injection into a utility pipeline or loading for virtual transport occurs.

The NW Iowa RNG Plant produces more than 400,000 MMBtu of RNG per year. The plant was granted registration approval by the Environmental Protection Agency (EPA), allowing Gevo RNG to participate in the Renewable Fuel Standard (RFS) program and receive carbon credits through California’s Low Carbon Fuel Standard (LCFS) program. Gevo also has the right to use a portion of the NW Iowa RNG Plant’s RNG production as process energy at its Net-Zero 1 Project, other production facilities, and future net-zero projects.

Project achievements include:

  • Reducing the methane released into the air from manure traditionally placed in open-air lagoons
  • Blending agricultural and industrial standards to select equipment and processes that satisfy industrial standard requirements while maintaining the integrity of agricultural operations
  • Providing an economic boost to local dairy owners
  • Creating a customized design for each site to minimize disruption to existing operations and provide tailored solutions for individual site challenges
  • Minimizing land use through a single common gas upgrading site
  • Creating a cost-effective, scalable, and practical template for future multi-site agricultural RNG projects.



Front End Loading-3 (FEL-3) engineering; detailed engineering; project integration; process design; engineering


Excellence Award, American Council of Engineering Companies of Colorado

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