biogas blending in gas grid

[daly-h]

Currently, biogas is going to individual sectors rather than being blended in the grid, which is not plausible (unless for specific industries off the gas grid, like rural dairy processors, or captured freight fleets).

In particular, the residential sector is meeting its target by replacing NG with biogas from 2023-26. This may be resolved when we add plausible growth constraints for biogas. But it would be good to either blend biogas to the fuel techs entering sectors or else add share constraints so the proportion of biogas:NG for sectors is the same.

[olejandro]

Related #5
@daly-h, it is difficult to represent blending explicitly, because it will not be possible to dynamically estimate emissions factors from such a blend, unless the blending shares are fixed beforehand.

[daly-h]

@olejandro then can the blending happen in some fuel tech? it would require post-processing in the results to be able to display the bend in each sector. Right now it's not credible that biogas would go to an individual sector (unless off-gas-grid industry, for example)

[olejandro]

The main issue with blending is that we cannot assign dynamically the correct emission coefficient to the blend. So emissions would have to be accounted for at the blending point. This means that either:

• we won't be able to account for those emissions in sectoral budgets, only in the system-wide one, if blending is done before sectors
• the blend will be different for every sector if blending is done within sectors (this is what we have now implicitly)