1/ For AD biogas, grid injection looks best today. For AD or LF biogas far from gas pipes, gas boilers for heat and power iff that replaces fossil fuel.
2/ Seriously "distant" biogas could be upgraded and liquefied to bioLNG and trucked wherever.
3/ Whether use as truck fuel makes sense or not depends on whether we have time for a whole generation of fossil gas powered vehicles before the inevitable electrification(+H2 likely). Climate modelling suggests not.
4/ All AD biogas->biomethane upgrading plant will need CO2 liquefaction + trucking in tankers to CCS disposal hubs to improve carbon accounting by 2030. (And near-zero methane slip too.)
5/ For old LF biogas too dilute to be worth energy: careful flaring to CO2 or maybe methanol production. By 2030 the carbon value means that liquefaction+CCS makes sense for much of that too.
6/ Biogas in CHP makes less and less sense as it is mostly baseload and so power competes increasingly with lower carbon wind, PV and nuclear. Better use for pure heat by mid- or late-2020s, not CHP. Storing biogas for peaks makes sense.
7/ All the above are provisional, based on current poor data for biogas carbon accounting. All need whole-system modelling to discover whole-system greatest value for biogas as function of time and elec. grid decarbonisation.
