Renewable Natural Gas (RNG), also known as biogas, biomethane and bio-CNG, with various identifying brand names such as Redeem used by Clean Energy Fuels Corporation, is undoubtedly a fuel with high quality environmental characteristics. But just how clean is methane as a fuel for transportation? Where does RNG come from? And should policymakers focus on it or leave it out of the evolving energy matrix? California-based clean transportation and energy consulting firm Gladstein, Neandross & Associates (GNA) argues for inclusion, and with good reason.
GNA published the following article last December in ‘ACT News’ as part of the build-up to a “Rethink Methane Symposium” planned for February 6-7, 2018 in Sacramento, California.
WHAT IS RENEWABLE METHANE?
Natural gas, and its primary constituent, methane, has long been valued for its clean and efficient combustion properties. In comparison to coal or petroleum, when burned methane emits significantly lower amounts of smog-forming pollutants, toxic air contaminants, and gases that contribute to global climate change.
Because it is the cleanest hydrocarbon, methane is the dominant fuel in the U.S. for cooking, heating water, warming our homes, power generation, and other applications. For a number of years, environmental activists and air quality regulators advocated for the increased use of natural gas as an alternative to coal and nuclear in power generation, and to petroleum-derived fuels in transportation.
In fact, most of the recent reductions in greenhouse gas emissions throughout the U.S. are attributable to switching from coal to natural gas in power production.
Fracking and Emerging Opposition
Attitudes toward the utility of natural gas as the environmentally preferred fuel began to change when technologies to effectively extract natural gas from local shale formations—a process called hydraulic fracturing, or “fracking”—became widely used.
Although the U.S. was able to dramatically increase its domestic supply of natural gas and reduce its dependence on foreign sources of oil, these fracking techniques became the target of opposition, as questions were raised regarding water quality, increased seismic activity, and land conservation impacts.
Most recently, concerns have been raised about the near-term greenhouse consequences of methane leaks, a powerful climate altering compound, from the use of natural gas.
Given this recent history, emerging opposition to the production and increased use of methane may be understood, but it is shortsighted.
Transportation-Related Emissions Effect on Public Health
Whereas exposure to smog has lessened since the passage of the Clean Air Act Amendments of 1970, most urban areas have yet to meet ozone standards set in 1979, let alone the new National Ambient Air Quality Standard established by U.S. EPA in October 2015.
For most urban areas, the leading source of airborne carcinogens and mutagens is diesel exhaust. While exposure to toxic diesel exhaust has diminished in recent years, it still remains a major public health threat, particularly to disadvantaged communities. Between them, smog and toxic air contaminants are estimated to kill over 200,000 Americans every year.
The U.S. faces the daunting challenge of continuing economic growth while simultaneously mitigating the triple threat of smog, toxic air contaminants, and climate change. While progress has been made these three pollutants, each of these dangers continue to loom large in public consciousness and on lawmakers’ policy making agenda.
To achieve immediate headway in the effort to eliminate exposure to dangerous diesel exhaust, increased use of methane as an alternative fuel must be an option.
Methane as a Critical Part of our Energy Future
It is crucial that policymakers not pursue a path that eliminates methane as a key element of the strategy to reach environmental goals; such an outcome would likely make achievement of these objectives more expensive and time-intensive.
Nor should hysteria fed by unusual and unprecedented incidents lead to misdirected conclusions about the valuable contribution that methane can and should play in our energy future.
Much of the opposition stems from the fact that most of the methane currently consumed is “prehistoric.” That is to say, much of the methane in use today is the result of the decomposition of plants and animals that lived millions of years ago that, through natural forces, have been converted into common hydrocarbons—coal, oil, and natural gases. There, in the crust of the earth, this accumulated carbon has been trapped for countless millennia.
From a climate perspective, the problem is that we are quickly releasing vast quantities of this sequestered carbon into the earth’s atmosphere in a blink of geologic time.
Burning coal and petroleum are far more harmful to the atmosphere than combusting methane, but releasing and burning prehistoric methane is not without consequences, particularly to the climate.
So how can we continue using methane while reducing negative impacts? By aggressively displacing prehistoric methane with renewable methane.
Recover, Reuse and Recycle Existing Carbon
Renewable methane is derived by harnessing the methane that naturally cycles through the biosphere. It is created daily through the natural decomposition of organic matter. The majority of methane in our atmosphere, particularly in California, comes from these “contemporary” sources – the treatment of wastewater, municipal solid waste, and agricultural processes.
Increasing the use of renewable methane allows us to recover, reuse and recycle this carbon already circulating in the biosphere. Harnessing renewable methane not only creates the opportunity to sustainably manage waste products, but it also poses the possibility of developing whole new industries to grow, harvest, and harness new biological feedstocks for anaerobic digestion, such as switch grasses and algae, not dependent on using arable land or potable water.
Renewable methane can also be derived from the gasification of organic waste, which creates new opportunities to manage dead trees in our forests caused by years of drought and insect infestation, and help prevent forest fires, the largest source of the worst climate pollutant, black carbon.
Biological sources of methane (biogas) are crucial to the nation’s efforts to reduce the carbon content of transportation fuels.
For instance, some sources of biogas produce transportation fuels with the lowest carbon content under the California’s Low Carbon Fuel Standard (LCFS). In some instances, biogas achieves a negative carbon intensity, meaning that using the organically-derived fuel actually removes carbon from the atmosphere. In fact, two thirds of the compressed natural gas used in California for transportation comes from renewable sources.
Renewable Methane from Wind and Solar
Increased use of biogas as a transportation fuel is an important tool in the effort to protect the climate. Equally as exciting, renewable methane can be also derived from renewable power, such as wind and solar.
The development of renewable methane helps provide the feedstock for renewable hydrogen. At present, almost all hydrogen comes from the steam reformation of terrestrial natural gas. But renewable hydrogen can be produced from another source, as can more renewable methane.
One of the biggest obstacles to increasing the use of renewable power is the lack of technology to store this electricity when there is no immediate consumer. Many consider batteries as a solution to the renewable energy storage conundrum, but massive dependence on batteries has its own energy, environmental, and social justice consequences.
Yet across Europe, technologies are currently in place to utilize surplus electricity to produce hydrogen gas through the electrolysis of water. By running an electric current through water, the water molecule decomposes into hydrogen and oxygen. The hydrogen is then captured and is either used directly or mixed with carbon dioxide to create methane.
The methane can be injected into existing natural gas infrastructure where it can be stored indefinitely, or used for any imaginable purpose, including power production, vehicle fuel, residential heating and cooking, manufacturing or as an industrial feedstock. This technology, called Power-to-Gas, provides a solution to renewable energy storage, helps communities decarbonize their gas supply and can supply potentially endless volumes of clean hydrogen and renewable methane to power transportation.
If we are to take full advantage of the air quality and climate benefits of fuel cell technology—the commercialization of which is essential to the deployment of zero-emission alternatives to diesel in heavy-duty and high horsepower equipment—we will need to dramatically increase supplies of renewable hydrogen and methane. Power-to-Gas, as well as investment in the capture and beneficial reuse of biogas, can help make this dream a reality.
The Future for Renewable Methane
From the perspective of those who must live and work near the nation’s highways, distribution centers, ports and other concentrations of heavy-duty diesel trucks and equipment, natural gas engines present the quickest and least expensive path to relief from the harmful impacts of diesel engines. To ensure that we can both enjoy the air quality and climate protection benefits of these currently available near zero emission natural gas engines, they should be fueled by renewable methane.
But there are still many challenges to the development of renewable gas. Cost, misguided opposition, and poorly conceived or executed public policy are among the leading impediments. Policymakers need to take a fresh look at the important role that renewable gas can play in our energy future, particularly methane from renewable sources.
Methane is a natural energy carrier, one which we produce every day through the course of normal life. We must do all that we can to harness this organic resource to help achieve our sustainable energy, environmental protection and economic development goals.