State health officials have begun monitoring a facility that converts cow manure into natural gas after elevated levels of an unhealthy and flammable – but also naturally occurring – gas were recently detected.

The Colorado Department of Public Health and Environment reported excessive amounts of hydrogen sulfide were discovered through instruments readings at Platte River Biogas near Lasalle.

Hydrogen sulfide, informally referred to as “swamp gas” or “sewer gas,” is known for its odor that is similar to rotten eggs. The gas occurs naturally in crude petroleum, natural gas, volcanic gases, and hot springs, according to the National Institute of Health. It is also produced by human and animal wastes and results from the bacterial breakdown of organic matter.

Hydrogen sulfide is also used or produced in a number of industries, such as oil and gas refining, mining, tanning, pulp and paper processing, and rayon manufacturing. It can be deadly at higher concentrations.

CDPHE started measuring air levels around Platte River Biogas after receiving reports of odors. The agency did not state when those reports were received nor when it tested the air. 

CDPHE did state in a press release that it is “using various monitoring technologies to take readings both at the facility and among the dwelling units that are approximately 2,000 feet away.” 

While health officials have not found any indication of an acute public health risk to nearby residents or workers at the facility, it is working with Weld County Public Health and other agencies to further assess the situation. 

Platte Valley Biogas was, when it was built in 2010 and first commenced operations in 2016 as Heartland Biogas, considered the largest co-digestion anaerobic digester project in the world, per its manufacturer. That process converts manure and food waste into methane and/or natural gas. The facility pipes renewable natural gas (RNG) directly into a pipeline connected to Xcel Energy’s system.  

Neighbors complained almost immediately about odors from the plant, according to media reports.

The plant also produced a liquid fertilizer, but that part of the project brought about big problems. A year after production was launched, state and county officials notified the operator that the plant did not have proper licensing to produce and store the liquid fertilizer. The plant shut down a month later. A contractor which supplied the plant with waste for processing eventually sued the plant operators for breach of contract. The supplier was awarded $9 million after a jury trial. The plant operators failed in an attempt to appeal. 

In 2020, a new ownership group approached Weld County about restarting the plant. 

Platte River Biogas is now owned by a consortium of dairy farms, according to its website. Ownership claims it is now the fourth largest operation of its kind in North America. It is also said to produce an acre-foot of clean water for agricultural use every day.  

Which dairy farms constitute the primary ownership the plant dairies is not stated on the website nor directly shown in public records. But Platte River Biogas LLC is registered with the Colorado Secretary of State and its headquarters are located on the property of a dairy farm in Eaton, the Hunter Ridge Dairy. 

Platte River Biogas also lies adjacent to the Shelton Dairy. 

The Shelton Dairy was investigated by the U.S. Occupational Safety and Health Administration in 2021 when a truck hauling manure drove into a holding pond. The driver later died at a hospital.