Decarbonization in Natural Gas Applications

"Renewable" describes an energy source that can be replenished at the rate it is used by natural ecological cycles. Sources such as wind, sunlight and water occur naturally, are present in unlimited amounts and can be reused. Natural gas is a fossil fuel that is formed under the earth's surface from decomposed organic matter over millions of years and is considered non-renewable.

Referred to by various names such as compost gas, swamp gas and marsh gas, biogas is naturally produced from the decomposition of organic waste. It is a mixture of gases, mainly methane, carbon dioxide, hydrogen sulfide and siloxanes. When organic matter such as animal manure, food scraps, wastewater and sewage are subjected to anaerobic ( 'without air') digestion, it is broken down by microorganisms through fermentation to release biogas. Due to the high methane content, biogas is flammable and can be purified further to produce biomethane or Renewable Natural Gas.

Organic waste in landfills ( food, paper, yard waste etc.) produce a mixture of gases as they decompose. Methane, carbon dioxide  and volatile organic compounds in the mixture migrate upward through the pore spaces and have significant negative impacts on the environment. Methane has 28 to 36 times the environmental warming effect as compared to CO2, producing a more significant impact. Hence, capturing fugitive landfill gas to process, purify and upgrade it to pipeline quality reduces emissions and can replace high-carbon fossil fuels with low-carbon renewable fuels.

Renewable Natural Gas (RNG) is a term used to describe biogas that has been upgraded for use in place of conventional natural gas. It is produced from multiple sources, including landfills, farms, wastewater and municipal organic waste.  The raw biogas is captured and purified for a variety of end uses: as transportation fuel, in heating applications,  electricity generation and as bio-product feedstock. The ability to blend RNG in the existing gas infrastructure is accelerating the transition to a carbon neutral energy supply.

Hydrogen is one of the smallest molecules and thus tends to leak more than natural gas.  In fact, hydrogen can leak up to three times as much as natural gas on a volumetric basis due to its low density.  Hydrogen molecules can also permeate directly through metals and elastomers. Emerson’s evolving portfolio includes hydrogen blending skids and pressure control products designed to meet industry standards and tested to ensure that the risk of leakage and permeation is mitigated.

Hydrogen embrittlement, also known as hydrogen-induced cracking or hydrogen-assisted cracking, is the reduction of a metallic material’s ductility caused by the absorption of hydrogen.  Many metallic materials are susceptible to hydrogen embrittlement, especially at very high pressures.  However, just because a metal is susceptible to hydrogen embrittlement does not mean it cannot be used since most natural gas distribution pressures are low enough that hydrogen absorption does not cause a significant reduction in ductility. Emerson’s portfolio includes hydrogen blending skids and pressure control products that are suitable for hydrogen service in various applications.