Managing emissions at our LNG facilities
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 the following:
High-efficiency gas turbines: Our aeroderivative gas turbines limit nitrogen oxide (NOx) emissions. The efficiency results in less natural gas being used in the liquefaction process per unit of LNG produced.
Electric drive turbines: We are using electric drive turbines at our Corpus Christi facility expansion, which improve efficiency and reduce emissions compared to gas-powered turbines.
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.
Floating roof tanks: We use floating roof tanks on condensate tanks to keep surface hydrocarbons from being released. Boil-off and ship vapor recovery: We capture and reuse boil-off gas (LNG that is vaporized during normal operations 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.
Managing methane emissions
Methane constitutes only a small fraction of the total GHG emissions from our operations. 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 activities described in the pipeline emissions reductions section below, our programs to reduce methane emissions include:
Closed-loop cooling process: We capture volatilized methane during the cooling process, and recirculate it back into the liquefaction process, rather than venting it into the atmosphere.
Leak monitoring and repair:
We perform 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 Environmental Protection Agency (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 overpressure 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.
Managing emission from flaring
At our liquefaction facilities, we use active flare management in which an operator manages air tuning during flaring events to maximize flare efficiency. 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 to 6 years, which results in a 50% reduction of the flaring required during flare tip replacements.
We have implemented additional flare reduction efforts at each facility specific to its 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 both the need to defrost our operations — and the associated flaring — by 50%.
We have also implemented processes that allow us to increase the temperature specifications for LNG ship loading operations, which reduces the need to flare off LNG vessels.
Managing emissions from our pipelines
We operate three pipelines, all of which were constructed using several best practices for managing emissions. For instance, it is our standard practice at compressor stations to use zero-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 “blowdown” 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 the pipeline compressors to move as much gas as is 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 blowdowns — 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. In 2022, we enhanced this technology, allowing a compressor to remain pressurized after shutdown for several days.
We utilize state-of-the-art engines to drive our pipeline compressors that limit NOx emissions, often well below permit requirements.
Managing emissions at our offices
Our headquarters in Houston and our office in Washington, D.C., are each located in certified Leadership in Energy and Environmental Design (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 heating, ventilation and air conditioning (HVAC) use when our offices are closed. We also encourage employees to reduce their own footprint by reimbursing those who opt to commute to our U.S. corporate offices via public transportation.
Managing supply chain emissions
We are working to further enhance industry transparency and improve performance by encouraging collaboration across our supply chain. Since 2018, Cheniere has focused on reducing methane emissions across our supply chain, including by co-founding the Collaboratory to Advance Methane Science (CAMS). Today, we are using our LCA and QMRV work to support our own and our partners’ understanding of methane emissions sources. For example, our LCA illustrates that methane is a primary contributor to LNG’s GHG footprint in the upstream and midstream sectors. Reducing methane emissions, for example through leak detection and maintenance, offers a strategic and cost-effective opportunity for reducing overall supply chain emissions.
Cheniere has publicly voiced our support for new federal regulations on methane emissions for a number of years, including the EPA’s recent proposal to regulate methane emissions.
In addition, we host an annual supplier sustainability workshop to promote best practices of methane management, and we work with suppliers to assess the emissions profile of our supply chain.
Reducing emissions from LNG shipping
The shipping segment is an important contributor to the LNG supply chain’s GHG life cycle emissions, with shipping emissions dependent primarily on the length of the voyage.1 Where feasible, Cheniere Marketing (CMI) charters vessels with the most efficient propulsion and containment systems to help reduce these emissions.
By the end of 2023, we expect the vast majority of of CMI’s long term chartered fleet to feature the XDF/MEGI/MEGA propulsion technologies, the most efficient vessels available on the market.2 CMI continues to work with Ship Owners and Shipyards to further improve shipping efficiency and ultimately reduce emissions. LNG Carriers (LNGC’s) are unique in that they traditionally use the cargo “LNG that has boiled off” as the primary source of propulsion fuel. The LNG used has a significantly lower CO2 emissions profile than typical marine fuels.
As part of our LCA and QMRV efforts, we are installing Continuous Emissions Monitoring Systems (CEMS) on the majority of CMI’s long-term charters. Utilization of CEMS was a recommendation from the previous study completed with Queen Mary University London on board the Cheniere chartered LNGC Gaslog Galveston. Read more here.
Cheniere will use the CEMS to continue to identify strategic mitigation activities, both technical and operational, to work with our Chartered fleet to further reduce shipping emissions which ultimately to supports the new Shipping Emissions Regulations.