Not corn syrup. That takes way too much CO2 and water to produce. Not even corn itself I suspect.
It's partly the problem alleged marshland and forest sequestration schemes face, alongside the assumption they're going to grow well in the changed climate.
(Limited experimental data suggests this works up to some 500 ppm as long as there's excess water and minerals. If the conditions are bad you lose capture potential. And what do you do with the methane releases from these systems? It's much more diffuse than from landfills.)
