Cows, with their four-chambered stomachs, have always been models of digestive proficiency, as anyone who’s dodged cow pies in a pasture can attest. These grazing bovines and other livestock produce thousands of pounds of manure daily.
Maura Keller is a freelance writer in Plymouth, Minnesota.

Energy conservation, coupled with the concern for the management of livestock waste, has revived an interest in generating biogas from livestock manure. As such, two key initiatives surrounding anaerobic digester clusters have garnered the attention of dairy farmers across the country.

Making inroads in biogas

In 2016, Calgren and its digester developer, Maas Energy Works, first approached dairies with the idea of using their manure to create biogas transportation fuel. Calgren has numerous dairy farmer neighbors, many of whom are also customers for the company’s wet distillers grain.

As Calgren president Lyle Schlyer explains, the main driver behind the program is California’s Low Carbon Fuels Standard, which incentivizes fuel suppliers to lower carbon intensity. Calgren already produced low-carbon ethanol using a highly efficient process. By using cow gas to offset some of its pipeline natural gas, Calgren’s goal was to produce ethanol with an even lower carbon score.

The company’s proposal was to build a covered lagoon digester on each dairy (or, occasionally, a pair of dairies) to collect biogas and transport it to Calgren’s renewable fuel complex via a private, low-pressure pipe.


“Initially, we signed up six producers and started construction in 2017. We created our first gas in 2018,” Schlyer says. “Our success on the first six dairies helped us sell the program to various neighbors and relatives. There was strong producer interest in expanding, which helped us build upon our good relationships in the community.”

At the same time, the market for low-carbon fuels was expanding. In addition to using the biogas as an input at Calgren’s ethanol refinery, the company built an injection facility to deliver natural gas into the Southern California Gas pipeline. SoCalGas owns and operates the utility pipeline, and Calgren delivers gas into their system that meets all utility requirements. Calgren also pays SoCalGas to transport the gas on their system. Plus, Calgren recently signed up to supply its biogas to their compressed natural gas (CNG) refueling stations.

As Schlyer explains, this program has given Calgren access to a second market, whereby the company can deliver conditioned biogas gas to third parties to be dispensed as CNG vehicle fuel.

“We have also added biodiesel production capability,” Schlyer says. “So we expanded both supply and demand in several rounds, extending our pipeline to encompass more neighbors.”

Today, Calgren has 10 dairy farms involved in the program, most of which are neighbors or relatives of Calgren’s first participants.

“We think if we deal fairly with one producer, we will be able to sign up more. So far, that has been the case,” Schlyer says. The farmer does not need to pay anything to participate in the program. Rather, Calgren funds any necessary improvements on the dairy (such as mechanical separators or sand lanes) and then builds the digester. The farmer receives an annual payment per cow for supplying the manure – forecasted to be over $100 per milk cow per year. And while Calgren has 10 digesters online at the moment, they have seven more under construction.

“The response from local dairies has been great,” Schlyer says.

Partners in progress

Similar to Calgren’s efforts, the Demeter RNG program was established by Brightmark in close coordination with Dane County, Wisconsin. The project will convert 90,000 gallons per day of dairy waste from three local farms into biogas and other useful products. After planned installation of gas upgrade equipment is completed, the project will produce enough renewable natural gas (RNG) to replace at least 50,000 MMBtu of conventional natural gas each year.

These digesters collect biogas from three dairy farms

“That is enough fuel to travel 1.27 million miles in a CNG bus, or from San Francisco to New York and back over 200 times,” says Bob Powell, founder and CEO at Brightmark, which purchased the digester from Clean Fuel Partners, who will continue its work on the project by providing operations and maintenance support.

RNG is natural gas produced from organic waste materials, including food waste and animal- and plant-based material. One of the largest sources of RNG this country has to offer is animal manure – making the idea to partner with farms a natural fit.

As Powell explains, Brightmark’s mission as a company has always been keenly focused on the idea of reimagining waste – not only pre- and post-use plastic waste but the vast amount of organic waste produced around the country at some of our nation’s many farms.

“The driving force behind the Demeter project wasn’t a Brightmark-focused one – rather, it was envisioned as a mutually beneficial initiative for both our company and the Dane County farms we’ve partnered with,” Powell says. “The program will yield benefits for the local environment, the regional economy and, most importantly, for the climate.”

After all phases of the improvement project are complete, the RNG collected from the anaerobic digester will be transported to the county’s recently completed landfill-gas-processing facility, where it will be injected directly into an interstate pipeline owned by ANR Pipeline Company. The Dane County facility is the first such facility in the U.S. designed to receive biogas from multiple off-site locations and connect that renewable gas with RNG stations locally and across the nation.

Back in 2016, Brightmark was formed by a group of engineers that decided to turn their focus away from other corporate ventures and dedicate their talent and expertise toward something far more important: the environment.

With the investments and partnership of the three farms in Dane County, Brightmark has brought anaerobic digestion technology to a new and crucial part of the nation. According to Powell, this agreement will help local farms continue to be environmentally friendly to this community and help to stay in compliance with environmental regulations.

By utilizing a process of anaerobic digestion in its program, Brightmark is able to capture raw biogas, clean it, upgrade it and compress it into RNG.

Anaerobic digestion has been shown to significantly reduce local pollution and greenhouse gas emissions. As Powell explains, the process recovers most of the nitrogen and phosphorus from manure so that it cannot escape into the air or local waterways via runoff, and uses these nutrients to create balanced biofertilizers that help grow local crops. Anaerobic digestion also prevents methane, a potent greenhouse gas, from being released into the atmosphere, thereby reducing the net greenhouse gas emissions from the dairy manure to be processed at this facility at a rate of 16,000 metric tons per year.

“Brightmark is honored to partner with farmers [who] take such pride in being excellent stewards of land conservation and ensuring their land is used not only in an environmentally conscious way but also in a way that is safe for them and their neighbors,” Powell says.

Chuck Ripp of Ripp’s Dairy Valley LLC says that as a participating farm, they are excited to have Brightmark as a partner since 2019 in anaerobic digestion of the manure from his cows. Ripp has 900 cows and farms 2,000 acres near Dane, Wisconsin. The family farm was founded in 1949.

“I try to do the right thing, and this is a win for us on the environmental side,” Ripp says. “We’re a large family farm, and we’re doing our part to cut back on greenhouse gases as well as removing phosphorus from our watershed.”

As Ripp explains, this agreement will help local farms continue to be environmentally friendly to the community and help them stay in compliance with environmental regulations. “The facility will offset 16,000 metric tons of greenhouse gas emissions each year. Renewable products generated by the project include biofertilizer, digested dairy fiber for use as cow bedding or as a peat moss substitute, and reclaimed irrigation water,” Ripp says. “The process of recovering and processing manure from the farms will prevent excess nitrogen and phosphorus from escaping into local air and water, reducing phosphorus runoff alone by 60 percent.”

Ripp says he feels very lucky to be a part of this project, as the Ripp family has always taken pride in being excellent stewards of land conservation and ensuring the land is a safe environment for their neighbors. “In the long run, this is going to help how people feel about farms,” Ripp says. “It seems to take the heat off when you tell people you use digesters and are removing phosphorus from the manure – people like to hear that story.”

What the future holds

There are significant environmental benefits of collecting methane gas and converting to RNG. Consider this: Installing a digester at a 2,000-cow dairy has the same greenhouse impact as removing 2,000 cars from the road. The digester also helps dairies comply with various air and water quality regulations, especially in states like California. Also, converting diesel vehicles to CNG reduces emissions of other combustion exhaust sources.

“The dairy industry is embracing these efforts, as the majority of medium and large California dairies have already signed up to host a digester,” Schlyer says. “And digesters are becoming much more common in other states as well, with financial and environmental support growing. Furthermore, the current generation of digesters and biogas handling technologies have performed much better than those in the past.”

This has also built up producer confidence in the technology. Of course, the boom in digester development leads to a lot of aggressive sales pitches. “Producers need to take care to work with a team with a successful record, good references, and avoid overly complex and expensive systems,” Schlyer says. “We value our relationship with Maas Energy Works immensely.”

Calgren intends to operate its digesters for decades, as the state’s demand for low-carbon transportation fuels appears very strong. “The market demand for alternative fuels such as hydrogen, power and natural gas is expanding,” Schlyer says. “They can all be met by cow gas. So we intend to keep working with dairy families to create more value for their operations. That’s the way we have designed our program. It only works if we have profitable dairy participants. So we are in this together.”  end mark

PHOTO 1: Calgren uses a low-pressure pipe to transport biogas collected on California dairies to its renewable fuel complex. Photo courtesy of Calgren.

PHOTO 2: These digesters collect biogas from three dairy farms in Dane County, Wisconsin. Gas upgrade equipment will be installed soon to produce renewable natural gas, which will be transported to the county’s recently completed landfill-gas-processing facility and injected directly into an interstate pipeline. Photo courtesy of Brightmark.

Maura Keller is a freelance writer in Plymouth, Minnesota.