By Jonathan Cristiani, Black & Veatch
Many climate activists and clean energy enthusiasts warn against the continued use of, and investment in, natural gas infrastructure, insisting it isn’t a substitute for clean energy. They are correct.
The U.S. should not expect to keep its current fossil-based natural gases systems indefinitely.
However, it is likely to be foolish to develop and build new natural-gas infrastructure at this stage of the sustainable energy revolution. At the same time, the world isn’t ready, able or – quite frankly –willing to make an immediate switch to 100% clean energy. Given the current technological limitations and investments, the transition towards all renewable energy must be gradual and multi-phased.
The U.S. isn’t ready to abandon fossil-based natural gas completely, even though it tends to be not low enough in carbon intensity. And we aren’t the only ones – many other countries will require natural gas to serve as a so-called “bridge” fuel while they continue to transition to zero- and low-carbon energy sources.
(Plan to attend “Decarbonization Goals: How Do We Get There?” live in Dallas on January 26 as part of PowerGen International.)
With this in mind, the energy industry should take a hard look at natural gas to consider how it might use existing infrastructure to benefit ratepayers across the globe and ensure the fuel doesn’t inhibit decarbonization initiatives.
Renewable natural gas (RNG) derived from biogas, landfill gas, woody biomass and waste sources of carbon dioxide could provide a near-term solution while the world seeks to minimize or eliminate more carbon-intense energy sources such as coal and oil.
In diverting greenhouse gases (GHGs) from the atmosphere, RNG shows promise in lowering the carbon intensity of the overall natural gas supply blend by avoiding many of the environmental impacts associated with fossil-based natural gas production. RNG can play an important role in the net zero carbon economy if it is produced, distributed and used responsibly.
What is Renewable Natural gas?
RNG, also known as biomethane, is pipeline-quality natural gas that comes from renewable sources rather than from fossil-based sources. RNG is often produced from biogas, meaning it is derived from the anaerobic digestion of wastes from industrial processes such as livestock farming and wastewater treatment. RNG can also be produced via methanation, in which either synthesis gas from biomass gasification or carbon dioxide emissions from a variety of sources are converted into methane in combination with green hydrogen.
RNG is a promising alternative to fossil-based natural gas. It diverts and repurposes GHGs that would otherwise have been emitted by normal practices, instead of relying on carbon intensive extraction methods like hydraulic fracturing (also known as fracking). Methane from untreated livestock manure lagoons can be anaerobically decomposed to produce biogas for RNG production, rather than being directly released to the atmosphere.
RNG is also attractive for its ease of use as a fuel for power generation, or applications that cannot easily be electrified. RNG can be interchangeably with fossil-based natural gases, which has extensive infrastructure.
Bridge Fuels are Essential
It is not unreasonable to expect all countries in the world to make a transition to a clean energy economy overnight, even though it is obvious that this is a necessity. Many countries need natural gas to serve as a bridge fuel over the next couple of decades as they retire more carbon-intensive assets but have yet to fully build out renewables, hydrogen and other clean energy sources. Transitioning to clean energy too quickly without proper consideration of all variables could ultimately risk a global energy crisis.
Currently, investment in clean energy resources is estimated to be at about half the level needed to meet a variety of net-zero carbon targets with a 2050 deadline. As these investments accelerate, and clean energy resources increase, fossil fuels may still be required to supplement the supply chain to avoid disruptions.
Insufficient reliance on intermittent renewable energy resources, such as solar and wind, without taking into account the complementary nature of natural gases energy resources (and vice versa), could lead in supply and demand mismatches.
RNG is one alternative that can help alleviate these disparities by providing a middle-ground option that lowers the carbon intensity of current power generation systems while other low-carbon resources are developed and implemented. Since the infrastructure for natural gas already exists, the potential for RNG as a cleaner alternative to fossil-based natural gas is immediate, offering benefits without a significant transition period or development of new infrastructure.
Numerous industries are unable to fully rely upon renewable energy or electrification in order to achieve their decarbonization targets. These include food and beverages production, heavy-duty transport, mining and steel as well as cement and chemical production. These industries offer great opportunities to use RNG.
RNG is not a panacea. It can be used in combination with other technologies to achieve zero carbon emissions. This allows for decarbonization of hard-to-abate industries while still allowing them the ability to operate with current practices. Some RNGs, such as those made from livestock manure can even be net-negative in carbon emissions.
Responsible use of RNG
RNG must be responsibly sourced in order to be meaningful in a net-zero economy. This can be done by combining RNG use with carbon capture technologies. RNG can still be used as a fuel source, but it can be combined with carbon capture, utilization, and storage technology to ensure that the carbon is sequestered and reused. Captured carbon can be used in many ways, including as a fuel source through methanation or as a building material.
Biogas produced from waste, landfills, and livestock manure is a great source of RNG. As a GHG, methane is 25 times more potent than carbon dioxide; thus, producing RNG from these resources can result in net-negative GHG emissions overall in some cases, as the GHGs that would have been released into the environment through the original process are higher than those released when the resulting RNG is burned.
Although fossil fuel use will eventually need to be phased out, the shift away from fossil fuels will take time as new infrastructure and technologies are developed that scale and support or store energy from low-carbon resources such as biomass, renewables, and hydrogen. It is crucial that RNG be considered in this period of green energy development.
RNG can be used to decarbonize difficult-to-abate areas, giving economies time and flexibility to adapt to changing energy production landscapes. It also diverts emissions from industries like agriculture and wastewater treatment, and avoids environmental impacts from fossil fuel extraction. All this while using existing infrastructure for transport and usage.
RNG offers significant promise as a bridge for the world’s efforts towards a net-zero-carbon future.
Jonathan Cristiani is a Black & Veatch project manager and advanced power fuels engineer who is primarily focused on bioenergy and hydrogen consulting services, including technology evaluations, resource assessments, feasibility studies, proforma economic analyses, conceptual engineering and engineering/project management assistance. Cristiani has significant experience with the conversion of biogenic feedstocks to electric power, process heat, and solid, liquid or gaseous biofuels. His portfolio also includes the production of hydrogen for industrial, energy storage and transportation fuel applications. Over his career, Cristiani has worked in research and development with a variety of power and energy technologies.