Since this comes up a lot: Carbon neutral is the carbon coming from sources already in the biosphere. Energy density problems for portable energy storage being

Since this comes up a lot: Carbon neutral is the carbon coming from sources already in the biosphere. Energy density problems for portable energy storage being what they are, even if we completely stop fossil fuel extraction (far and away the primary source of increasing atmospheric and biosphere carbon) there will still likely be significant combustion engine and thermal combustion usage. The hopeful goal being that their fuel will be created from non-carbon power (solar, nuclear, etc) processes that take existing biosphere sources and produce ethanol, methane, bio-diesel or in this case a heavier kerosene relative. Such processes run off excess nuclear or off-peak wind/solar generation could even potentially be used to re-inject biosphere carbon back into the ground in relatively stable forms.