We have implemented a wide range of technologies and processes to increase the efficiency of our operations and reduce our own Scope 1 and 2 GHG emissions. Our LNG facilities are our largest source of energy consumption and Scope 1 GHG emissions, primarily due to the power used for refrigerant turbines and thermal oxidizers. They are a primary focus of our GHG emission reduction efforts, but we are also working to reduce emissions from our pipelines and offices.
Reducing GHG emissions from our own operations
Our Sabine Pass and Corpus Christi LNG facilities use the highly efficient Optimized Cascade® process. In addition, we have implemented a number of processes and technologies aimed at achieving the maximum possible thermal efficiency, minimizing losses and emissions including:
- High Efficiency Gas Turbines: Our state-of-the-art aeroderivative gas turbines limit NOx emissions below our strict operating permit requirements, and their high efficiency results in less natural gas being used in the liquefaction process per unit of LNG produced.
- Waste heat recovery: Our LNG trains capture waste heat from the exhaust of refrigeration gas turbines and thermal oxidizers, and this recovered heat is reused in other processes throughout the facility.
- Boil-off and ship vapor recovery: We capture and reuse boil-off gas (LNG that is vaporized during normal operation as well as during ship-loading), returning it for re-liquefaction instead of flaring it.
- Seal gas recovery: We have installed refrigerant compressor seal gas recovery systems to reduce the volume of refrigerant lost to flare.
- Half rate trip controls: We have automated our controls to improve plant stability, maximize production, and minimize thermal stress and losses in different operating scenarios.
- Maintenance plan improvements: Through a combination of internal expertise and partnership with key equipment providers we are extending the intervals between our turnarounds and minimizing losses associated with planned activities.
- Production optimization: Through a range of production optimization activities, we have opened up flexibility on the LNG trains to share load across the different refrigeration compressors further improving LNG train efficiency and achieving a reduction in the specific power required to produce a unit of LNG.
Reducing methane emissions
Methane constitutes a small fraction of the total GHG emissions from our operations (just 0.73% in 2021). However, because methane has a much higher global-warming impact than CO2, we are very focused on reducing these emissions. Methane emissions primarily result from leaks and flaring. In addition to the pipeline emissions reductions described below, our programs to reduce methane emissions include:
- Leak detection and repair: As a prudent operator, we perform leak detection and repair at our terminals and compressor stations to monitor fugitive emissions, including methane. We monitor for leaks across our operations utilizing Optical Gas Imaging (OGI) cameras or EPA Method 21 techniques on a quarterly to annual basis. We also conduct routine Audio Visual and Olfactory (AVO) inspections at our LNG facilities and incorporate leak detection and repair results into estimates of fugitive emissions.
- Pressure safety valve integrity monitoring: We carefully monitor pressure safety valves to maximize operational reliability and minimize the occurrence of over pressure events, both of which reduce methane emissions.
- Compressed air valve control: We use compressed air instead of natural gas to control valves and other equipment, which reduces fugitive emissions.
- Low- or no-bleed devices: We use these lower-emission technologies at meter stations and control valves.
- Pipe flange management: We use specialized pipe flanges and undertake ongoing inspections and maintenance to reduce potential fugitive emissions.
At our liquefaction facilities, we use flares with 99% methane destruction efficiency to combust waste gas and control emissions from process upsets. We have implemented a range of flaring reduction initiatives to further reduce our methane emissions. For example, we redesigned the flare tips at our Sabine Pass and Corpus Christi liquefaction facilities to extend their useful life from 3 years to 6 years, which results in a 50% reduction of flaring required during flare tip replacements.
We have implemented additional flare reduction efforts at each facility specific to their designs and processes. At Sabine Pass, for example, we have installed seal gas recovery on all compressors and we route emissions from our acid gas removal unit to a thermal oxidizer to reduce the volume of gas sent to flare. We also implemented a new exchange cleaning process that reduces the need to defrost our operations, and associated flaring, by 50%.
At Corpus Christi, we use nitrogen rather than natural gas as much as possible to maintain positive pressure throughout our system which reduce emissions and the minimizes flare size, an important benefit to local communities.
We have also implemented processes that allow us to increase the temperature specifications for LNG ship loading operations, which reduce the need to flare off LNG vessels.
We operate three pipelines, all of which were constructed using several best practices for managing emissions. For instance, it is our standard practice to use no emission compressed air pneumatic controllers on valves and other equipment rather than high-bleed natural gas pneumatic devices, to eliminate methane emissions.
- Reducing maintenance and “blow-down” emissions: We have partnered with major equipment providers to extend the life of critical equipment, thereby reducing the need for equipment maintenance and associated maintenance shutdown emissions. When we are required to take a section of pipeline out of service for required maintenance, we use pump-down compressors to move as much gas as reasonably possible into adjacent sections of the pipeline before blowing the section down, lowering the volume released. We have also minimized the number of pipeline “blow downs” — necessary releases of gas from a pipeline to reduce pressure for maintenance, testing or other activities — by keeping compressors pressurized for up to 12 hours after required shutdowns We have started a program to enhance this technology and further reduce blow downs by installing equipment that will allow a compressor to remain pressurized after shutdown for several days.
- Low NOX Compressor Engines: We utilize state of the art engines to drive our pipeline compressors that limit NOX emissions often well below permit requirements.
Our headquarters in Houston and our office in Washington, D.C. are each located in certified LEED Gold buildings. We use a range of energy-saving strategies in all our office buildings, including energy-efficient lighting and building management systems that minimize HVAC use when our offices are closed. We also encourage employees to reduce their own footprint by reimbursing employees who opt to commute via public transportation to our US corporate offices.