Every stage of the LNG chain is described elsewhere in this course on its own terms — how much energy liquefaction consumes, how boil-off is handled, what regasification costs. Lifecycle accounting adds them all up and asks what it means for the climate.
The stages, and what is well known about each
Production and processing. Extracting and treating gas has its own energy cost and its own leakage — venting, flaring, and fugitive losses from wellheads, compressors and processing equipment. This is also the stage with the largest measurement uncertainty, discussed below.
Liquefaction. Consumes roughly 8 to 12 per cent of the feed gas as fuel for the refrigeration cycle. This figure is well characterised, because it is a large, deliberate, metered energy flow at a single facility rather than a diffuse leak.
Shipping. Fuel burned by the vessel plus any methane slip from the engine, both reasonably measurable for a specific ship on a specific route.
Regasification. A small addition, one to two per cent of throughput, well characterised for the same reason as liquefaction.
Combustion. The final burn at the point of use, which is identical to burning any other natural gas and is the most precisely known number in the entire chain.
Where the disagreement actually lives
Every industry estimate agrees closely on liquefaction, shipping and combustion, because those are metered, single-point, verifiable flows. Studies of the same route rarely differ by much on these stages.
They diverge sharply on upstream production and processing, for a specific reason: leaks are diffuse, intermittent and hard to measure directly. Official inventories have historically relied on engineering estimates — assumed leak rates for equipment types, multiplied by count — rather than direct measurement. Independent verification, particularly by satellite and aircraft surveys over the last decade, has repeatedly found real leakage higher than those inventories assumed, sometimes considerably so, and concentrated in a small number of large, intermittent “super-emitter” events rather than spread evenly.
This is why two lifecycle studies using the same combustion data and the same liquefaction data can reach very different headline conclusions: they used different upstream leakage assumptions, and that single input dominates the result.
Against coal
For power generation, LNG’s combustion emissions alone are roughly half those of coal per unit of electricity generated, and this advantage is large enough that LNG typically comes out ahead on a full lifecycle basis even under fairly pessimistic upstream leakage assumptions.
This comparison is the one usually invoked to describe gas as a “bridge fuel,” and it holds up reasonably well across most published methodologies, because the combustion gap is wide enough to absorb a good deal of upstream uncertainty.
Against piped gas
Here the comparison is less favourable to LNG almost by construction. Piped gas delivered from the same field to the same customer skips liquefaction and shipping entirely, so it starts from a lower baseline before any leakage assumption is applied.
LNG can still win in specific cases — a very long, leaky pipeline against a well-run liquefaction chain, for instance — but as a general rule, the same gas costs less in emissions terms delivered by pipe than by ship, which is one more reason pipelines are preferred wherever they are actually available.
What a careful reader should ask
Before accepting any lifecycle figure: what upstream leakage rate did it assume, and was that rate measured or estimated? What engine and slip rate did it use for shipping? What time horizon did it use for methane’s warming potential — twenty years or a hundred? And what is it being compared against — coal, piped gas, or nothing at all?
A number that answers all four questions explicitly is doing honest work. A number that states a single lifecycle emissions factor with no stated assumptions has usually picked one set of defaults among several reasonable choices and presented it as settled.
What this site does and does not do
This site presents the physical and commercial structure of the LNG chain — the assets, the technology, the vocabulary — from Global Energy Monitor’s tracker and from public technical sources. It does not compute or endorse a specific lifecycle emissions figure for any project, route or company, because doing so credibly requires primary measurement data this site does not have and a set of methodological choices that are genuinely contested. Where emissions are discussed, as here and in methane slip, the aim is to explain what the disagreement is actually about rather than to resolve it.