As humanity ramps ups its plans for a green future, alternatives to traditional fossil fuels are being explored much more aggressively than ever before. The topic of renewable natural gas is one area that is of particular interest to conservation groups and corporations alike. It has also piqued ours, and, today, we explore whether the “renewable” assertion is true or just a click-bait oxymoron.
Renewable natural gas is made by extracting and cleaning biogas from natural waste products like dead plant matter and animal waste. This process is carried out anaerobically in a controlled environment like a digester tank. One common approach is to use bacteria from cattle manure to produce methane and other biogases for processing.
Without further ado, let’s take a closer look at one of the green movement’s cornerstones. The transition to renewable energy is crucial and, at this point, inevitable. As such, we examine the past, present, and future of renewable natural gas.
How renewable is natural gas?
When we think of the term “renewable energy” we immediately think of the classic definition which refers to the energy that “comes from natural sources or processes that are constantly replenished”.
While that is a fine definition, Omar Ellaba, Frede Blaabjerg, and Haitham Abu-Rub (writing for the Renewable and Sustainable Energy Reviews journal) came up with an even fuller one.
The trio defined renewable energy as “useful energy that is collected from renewable resources, which are naturally replenished on a human timescale, including carbon-neutral sources like sunlight, wind, rain, tides, waves, and geothermal heat”.
With regards to natural gas, we must make a clear distinction between “natural gas” (in the classical sense) and “renewable natural gas”. It is important to note that the former is actually NOT renewable.
This is especially true if we go by the Renewable and Sustainable Energy Reviews definition of “human timescale”. Natural gases are derived from fossil fuels such as coal.
These are not in a typical human timescale because the process of decomposing, pressurizing, and molding dead biomass into coal takes millions of years. That makes traditional natural gas a non-renewable source of energy.
RENEWABLE natural gases are made from a combination of methane and carbon dioxide that is known as “biogas” (usually harvested from animal manure), which can quickly be cleaned and refined into gas that is just as efficient as regular natural gas.
The production of renewable natural gas is a much more environmentally-friendly endeavor than that of the fossil-fuel-based kind, which often involves burning coal to extract the biogas.
The good thing, for us, is that cows poop every day. This allows the renewable form of natural gas to fit snugly in the human timescale requirement. As a result, we have both renewable and non-renewable forms of natural gas. At present, fossil-fuel based natural gas is the more prevalent of the two in the United States.
Canada aims to use renewable energy as the main actor in the 30 by 30 initiative, an aim to conserve 30 percent of the country’s land and water by the year 2030.
How is renewable natural gas produced?
Renewable natural gas is only produced from biogas. However, biogas can be obtained from a wide variety of sources.
- Livestock
Livestock operations and ranches are a veritable gold mine when it comes to methane. Cattle manure is the most frequently used form of animal waste in the production of natural gas. It takes a lot of the stuff to produce a sustainable supply of gas, so large-scale cattle operations are the best source.
Once the manure is gathered and collected, it is moved to an oxygen-free environment. The common practice these days is to use anaerobic digester tanks to house the process. Bacteria in the manure respire and produce methane, carbon dioxide, and other waste gases that combine to form biogas. At this point, the gas refinery cleans and purifies the gas to make it ready for market.
Today, there are nearly 300 anaerobic digester systems across U.S. farms, most of which are used for electricity. Some farms have also begun developing natural gas for vehicles.
Fair Oaks, a commercial dairy farm in northern Indiana, has taken major strides towards a fully gas-powered fleet of vehicles. At present, only the farm’s milk delivery trucks are fully-gas powered but expect that to change soon. A publicly accessible compressed natural gas station has also been built on-site to cater to these (and more) gas-powered vehicles. A massive underground digester tank will house the fermentation process, as waste from the farm’s 11,000 animals is converted into biogas.
This massive endeavor is projected to help the farm reduce diesel consumption by up to 1.8 million gallons per annum. In carbon footprint terms, that’s a massive 25 percent reduction!
- Landfills
Landfills are another trusty source of precious biogas that is useful for the production of renewable gas. According to the U.S. Department of Energy, landfills are “designated locations for disposal of waste collected from residential, industrial, and commercial entities”.
The U.S. Environmental Protection Agency (EPA) has determined that landfills form the third-largest source of methane emissions in the U.S. With 16.4 percent of total methane emissions (as of 2016), landfills are only behind enteric fermentation, especially in agriculture and ranching (25.9 percent), and natural gas systems (24.8 percent).
Biogas sourced from landfills is also known as “landfill gas” because the process of breaking down matter takes place underground. This is unlike the aforementioned anaerobic tanks used to create biogas from animal waste. The end product is the same though, a renewable form of natural gas that is ready to be used in any domestic or commercial setting.
Landfills have long been regarded as a blight on society, especially aesthetically, so repurposing them as sources of renewable energy is a wise move. At the time of writing, there are nearly 570 landfill gas projects that are up and running in the United States.
Most of these are oriented towards producing gas for electricity, although a handful, such as the St. Landry Parish Landfill in Louisiana, are involved in developing natural gases for the automotive and transport sectors.
- Wastewater treatment
We can also source biogas by breaking down any solid waste products that are filtered out of the wastewater treatment process. A Water Environment Research Foundation (WERF) study asserted that, in the U.S., wastewater treatment could facilitate the production of enough electricity to meet the needs of 12% of the country.
The EPA has held that 100 gallons of wastewater could potentially yield enough waste products to generate a cubic foot of biogas. Of the 16,000 wastewater treatment plants that are currently active in the U.S., nearly 1,300 make use of anaerobic digester tanks to produce biogas. Again, most of this gas is for electricity and heating, although some of these plants are venturing into producing gas to power vehicles.
What is renewable natural gas used for?
Renewable natural gas can be used for a wide range of things, and the list is expanding rapidly. Traditionally, natural gases were used for lighting in the streets and buildings.
In the modern era, the uses of gas have expanded to a point where its uses are unlimited. From 1950 to 2020, U.S. natural gas consumption has gone up from 5 trillion cubic feet per year to nearly 30 trillion cubic feet per year.
Electricity generation
Since the turn of the century, electricity generation has been the primary use of natural gas. The U.S. Energy Information Administration (EIA) found that natural gas contributed nearly 38 percent of the total electricity generated in the country in 2019. In an age of aggressive innovation, we cannot predict how much of an influence natural gas will have on electricity production. However, with the world moving towards sustainable forms of energy, renewable natural gas could rise to be a major player for the foreseeable future.
Heating
Heating is another major use of natural gas. Half of all American households use natural gas for heating. Gas heating is much more effective and efficient than electric heaters and heating pumps.
Forced-air systems are the main delivery method for natural gas heating. These often deliver air at temperatures of 122-140oF, a significantly higher range than the 86-95oF range that is typical of electric heating pumps.
Transportation and Industrial
Traditionally, natural gas was primarily used in the industrial sector. Activities such as the production of hydrogen, fertilizers, and other chemicals have relied on, and still rely on, the use of gas.
In the modern era, the use of gas has expanded to the transport sector as well. While it is unlikely that natural gas will ever replace petroleum as the world’s main automotive fuel, it still powers 3 percent of all vehicles in the U.S. With all of the hype, marketing, and gimmicks surrounding electric vehicles, electricity only powers one percent of all vehicles in the U.S.
Domestic
Natural gas is also used for many uses in the home.
In most households, gas is primarily used for cooking. Gas stoves tend to be faster and more efficient than their electric counterparts. Temperature control is also easier on gas stoves.
Gas-powered air conditioning is another great way to lower your heat bill. While conventional air conditioners also make use of gas at some stage, very few domestic ones are powered by it. If you can get your hands on one, you are in luck.
Other applications of natural gas in the home include gas-lit fireplaces and gas-powered water heaters.