Any feasibility study on a new plant should consider this option and variations on it. Landfill gas will need multiple stages of compression, this, interestingly enough, can be used in the gas clean up and purification process. It is easier to purify high nitrogen natural gases in the liquefaction stage, however. Pretreatment is where any oxygen present must be detected and removed. Liquefying natural gas is easy . . .
Liquefaction requires energy.
The source of that energy, along with installed capital costs, set the liquefaction cost. Low cost gas means low cost fuel which may mean low cost liquefaction. Most favorable are those that liquefy large quantities of methane as part of normal operation. A small side stream of LNG can often be taken from these plants without upsetting the thermodynamic balance, particularly in the evening hours. These also require fairly small capital investments.