Notwithstanding the debate on anthropogenic climate
change...
Atmospheric CO2 levels show a very distinct seasonal
cycle, ostensibly as a result of northern hemisphere
deciduous forests. [i’ll link, but it’s the Mauna Loa NOAA
CO2 data I think]
Assuming that it would be a good thing to
sequester
atmospheric CO2 in the most cost-effective, least-
energy-
intensive way...
Every autumn, billions [pending data] of tonnes of CO2
and
methane are emitted by decomposing seasonal leaf
litter.
The biomass of autumn leaves could be collected, and
processed by pyrolysis, to produce Biochar (which can be
used as a soil improver for agricultural soils, and
permanently [link pending] sequesters atmospheric
carbon), and pyrolysis gasses and oils which can be used
as
feedstocks for fuel oils or synthetic chemicals, or to
generate electricity or heat, or an adjustable
combination
of those.
Which overcomes some of the arguments against large-
scale biomass-pyrolysis-Biochar sequestration.
The downside might be that the “active carbon” in the
forest soils would be reduced, and this might have a
detrimental effect on overall soil health.