Natural gas is a far more environmentally friendly source of power than coal, oil, or diesel. Yet work is being done to further improve its emissions credentials in a variety of different ways.
Blending hydrogen with natural gas is one approach A 20% hydrogen blend might lower carbon emissions by up to 10%. However, the downside of hydrogen is the lack of availability. There isn’t an abundance of cheap hydrogen to hand in most regions, and green hydrogen remains costly and energy intesive to produce.
Alternatively, renewable natural gas (RNG) is gaining ground. Also known as biomethane, RNG is a biogas derived from anaerobic digestion of organic waste matter, such as livestock waste, landfills, wastewater sludge, food waste and other organic waste operations. It is processed to remove water and impurities until it has a methane concentration of 90% or greater. That enables it to become a direct substitute for natural gas.
RNG offers many advantages. As it utilizes existing infrastructure, once it is produced, there is little cost involved in bringing it to the consumer. In areas remote from a large gas field and at the periphery of the pipeline network, RNG is often much needed due to the limited supply of natural gas. Its production also helps to reduce odor and runoff from landfills – and it enhances fuel diversity. Environmentally, RNG lowers greenhouse gas emissions and reduces agricultural methane release into the atmosphere. Additionally, it lowers emissions of nitrogen oxides and particulate matter and contains almost no ethane, propane, butane, pentane, or other hydrocarbons. Regarding carbon emissions, RNG is over 90% cleaner than U.S. Environmental Protection Agency standards and 125% cleaner than the cleanest diesel technology available.
For an RNG project to work, there needs to be reliable feedstock. Feedstock suppliers, producers, consumers, and the natural gas pipeline system are all beneficiaries as they contribute to a sustainable solution that turns waste products into gas.
Take the case of the Full Circle Dairy Renewable Natural Gas Facility in Lee, Florida. RNG is produced at the facility from manure. The plant captures and redirects more than 1,100 metric tons of methane per year into a renewable energy source. This is the emission reduction equivalent of powering 3,500 homes for a year. The RNG is transported by Chesapeake Utilities’ subsidiary Marlin Gas Services distributed to customers in the area.
“People overwhelmingly support RNG because it offers a sustainable way to turn waste products into low-emission energy to power people’s daily lives,” said Justin Stankiewicz, Director of Business Development – Pipelines, Virtual Pipelines and Renewables at Chesapeake Utilities Corporation. “Converting manure into renewable energy benefits the farmer, the local community, the environment, and the homes and businesses who consume the energy.”
Another common RNG application is to use spent corn and grain from distilleries. 3 Rivers Energy Partners, for example, has teamed up with whiskey producer Jack Daniels to use its spent grain to provide more than 900,000 million British thermal units of RNG annually to 3 Rivers Energy Partners’ anerobic digesters. Spent grain is well suited to RNG as it doesn’t contain chemicals, metals and other impurities. However, there is still water, carbon dioxide and a small amount of hydrogen sulfide to remove. The leftovers from the RNG process are used to fertilize agricultural land where it makes more corn that is used to make more whiskey and produce even more RNG.
3 Rivers’ treatment equipment removes unwanted elements to deliver pipeline-quality methane. This is accomplished using various technologies and approaches, including cooling and compression to remove water, separation, pressure swing adsorption and amine scrubbing.
“We inject pipeline-quality methane into the natural gas pipeline system owned and operated by Atmos Energy,” said David Johnson, owner and executive advisor at 3 Rivers Energy Partners. “Atmos Energy verifies that the RNG meets their quality specifications and passes it on to the consumer, as there is no detectable difference between it and traditional natural gas.”
