From Waste to Wealth: The RNG Rundown

In the ongoing push to test and diversify feasible sources of energy, renewable natural gas (RNG) rises as one of the top economical alternative fuel sources. Many landfills, dairy farms, and wastewater treatment plants are seeking to understand the RNG production and infrastructure development process. With a long history of natural gas infrastructure engineering and recent experience with RNG projects, HT Engineering is interested in contributing its expertise in RNG analysis, control, measurement, and transportation to the development of the RNG industry and specific projects.

In this article, we’ll review:

• RNG and its benefits
• Production methods & sources
• Uses of RNG
• Integrating with current infrastructure
• Future of RNG
• Risk and regulation

Introducing RNG

RNG is a reliable and ecologically friendly fuel source growing in popularity at a substantial rate within the energy industry. Last year, the RNG market was valued at $11.7 billion (USD) and is expected to grow to $105 (USD) billion by 2032.

RNG is a gaseous byproduct of fermented organic matter, most often currently utilized as a green alternative to conventional natural gas. RNG is considered to be a carbon-neutral fuel, i.e. one that has a net zero effect or better on carbon dioxide in the atmosphere. Depending on the production source or feedstock used to produce RNG, the associated carbon intensity of the production process can be significantly lower than fossil fuels. Controlled RNG production and use reduces greenhouse gas (GHG) emissions and the impact of energy use on the environment.

RNG offers economic and environmental benefits

RNG offers a unique opportunity to turn waste into wealth by converting organic matter such as manure and landfill solids into energy and is uniquely positioned to power local economies. The U.S. alone produces over 250 million tons of waste each year, 140 million of which goes to landfills. The natural decomposition process of this waste releases methane directly to the atmosphere. Methane accounts for about 20 percent of global GHG emissions and is more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere. RNG production can capture the emissions from the organic material in this discarded waste and bring it to market as energy – converting the methane from a liability into an asset.

RNG has economic promise as well. It offers a decarbonization and job market expansion within the energy sector, providing new opportunities in engineering, manufacturing, construction, maintenance, and operations. Governments and markets currently offer financial incentives that encourage investors and corporations to purchase RNG, providing them a viable path to meeting carbon emission reduction goals.

Producing RNG

RNG is produced from solid waste landfills, dairy farms, and wastewater treatment plants. Anaerobic digesters break down organic matter to create biogas. From there, the gas is processed and injected into natural gas transmission and distribution pipelines, or it can be used on-site by the producer.

Anaerobic Digesters 

Using bacteria, anaerobic digesters break down organic waste (e.g., solid waste, wastewater biosolids, animal manure) to create methane that is transformed into RNG. The decomposition process occurs in a sealed reactor, which varies in shape and size to fit the site and the characteristics of the organic matter. In addition to biogas, anaerobic digestion can produce another valuable product: digestate. Digestate is produced as both solid and liquid material, which can be used for fertilizer and other applications.

Anaerobic digesters are often coupled with processing equipment that eliminates water, oxygen, and other constituents from the biogas, allowing it to be injected into existing natural gas pipeline systems and used interchangeably with natural gas. It is at this stage of the process – getting the biogas to market – where HT Engineering, can help producers or buyers with the project.

Landfills

Landfills are managed disposal facilities for collected waste materials, coming from commercial, industrial, and residential areas. Landfills do not need an anaerobic digester to create gas. Landfill gas (LFG) is created unassisted underground, and, if not captured as fuel, escapes to the atmosphere as GHG emissions. According to the U.S. EPA, landfills are the third largest source of manmade methane emissions in the nation. Similar to the output from digesters, LFG can then be processed and used as RNG.

Dairy Farms

Manure is the 4^th-largest producer of methane emissions in the nation. On many dairy farms, anaerobic digestors can be used to help reduce GHG emissions while supplying RNG to market.

Wastewater Treatment Plants

Wastewater treatment plants are facilities that treat and remove harmful contaminants in wastewater. These plants can also produce biogas by digesting solids extracted during the wastewater treatment process.

In Action

On a recent project, a dairy farmer developing an RNG operation leaned on the expertise and experience of HT Engineering as a pipeline integrity and engineering firm to get the produced methane to market. The RNG producer installed an interconnect station to analyze the biogas quality from the anaerobic digester and processing facility before releasing it to the buyer. The RNG producer engaged HT Engineering’s team, who had expertise in designing similar systems for natural gas in the past, to design the analysis, measurement, control, and transportation station and pipelines, to support sourcing and purchasing of the required equipment, and to assist with managing the construction of the station.

Using RNG

Unlike other renewable alternatives such as wind and solar, RNG offers a consistent and reliable energy source, rain or shine, and it can be injected into existing natural gas systems. From there, RNG can be used as fuel for equipment such as generators, heaters, boilers, reciprocating engines, and gas turbines.

Integrating with Current Infrastructure

RNG takes advantage of existing pipelines and infrastructure, reducing the potential associated costs of development for new facilities. Unlike some other alternative fuels, RNG does not require system upgrades to be introduced or connected into larger utility systems. This allows for a seamless transition to RNG. This compatibility appeals to renewable energy investors and utilities alike.

Future of RNG

RNG is in high demand for its numerous benefits to the environment and economy. Areas with promising potential for RNG are those with the largest number of dairy farms or other production sites, including California, Wisconsin, Idaho, Michigan, and Texas, respectively. Of these, California has the greatest number of dairy farms while Texas has the most extensive natural gas pipeline network. With a rising opportunity for RNG within these areas, two of the largest natural gas utilities in Texas are currently seeking projects with landfills. Additionally, Wisconsin has emerged as a current leader with the highest number of anaerobic digesters.

Regulations & Risks

Rules and regulations for RNG vary at the local, state, and federal levels. Some notable standards and regulations in place include renewable fuel standards, gas quality standards, land use and zoning regulations, the Energy Policy Act, and environmental regulations.

Ultimately, RNG creates clean, reliable energy out of waste. RNG’s ability to enhance the job and decarbonization markets is likely to propel its prevalence in the future.

Contact us to learn about how HT Engineering can help you plan, design, and build the pipeline infrastructure you need to get your RNG to market.