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58 have suggested that enhanced plant growth would raise the emissions of N2O, which is a far stronger greenhouse gas than CO2 and would thus cancel out the total CO2 reductions. Another obvious concern is the production of methane that could be released to the atmosphere. As biomass decays, a fraction will be released as methane rather than CO2. Methane is a much more powerful greenhouse gas than CO2 and even if only a few percent of this additional biomass find their way into the atmosphere as methane, the net advantage of storing organic carbon may be cancelled out.

86 Electrochemical separations are usually more efficient. One requires at least one electrochemical step in the cycle, where one produces H2 from H2O, or CO from CO2, or possibly a combination of the two from a mixture of CO2 and H2O. In effect, one uses an electrochemical means of freeing the oxygen that is tied up with carbon and hydrogen. It is only necessary to perform electrolysis on one of the two compounds because it is quite easy to shift the remaining oxygen from carbon to hydrogen or vice versa.

However, second-order effects are likely to be quite different. For example, the greenhouse effect will lead to the largest amount of warming in Polar Regions, while a simple change in albedo will lower temperatures most dramatically where the sun shines. Geo-engineering methods that create a change and do not need to be maintained are more easily managed than geo-engineering methods that require continuous maintenance. In the case of managing the climate, not only does one require continuous maintenance, but also a constantly increasing level of albedo modification.