Hi, an answer depends on the inventory model you use, attributional or consequential. Since attributional LCAs are strictly speaking linear systems, you can simply multiply by whatever extrapolation factor you imagine - evidently, a largely increased system might not be realistic any more, which asks you to apply rather a consequential modeling, where you try to catch, simply speaking, the consequences of consuming the modeled quantity, over the life cycle. There is quite some literature about this, in LCA books e.g.. I do not want to start a large discussion here but it is probably fair to say that in consequential LCA, a challenge is to identify the changes caused, and to reflect these then in your model. Answering questions like: If your system consumes 1 million ton of NG, do other consumers have sufficient gas, or do they switch to other fuels, and if yes, to which ones.
