The use of waste as an agent for the removal of CO2 emissions by pyrolysis to 'biochar"has been supported by Gore, Hansen & Lovelock. They recommend that organic waste be used as "terra preta del Indio", an agricultural soil additive perhaps first used in native Amazonia, The idea of biochar soil addition as a carbon dioxide sequestrate, provides very important concept of an indisputably carbon negative component in the control of the carbon cycle & hence a potential antidote to global warming. However, on its own,char manufacture will not do much to remove CO2 while fossil fuels are still used.The incorporation of a biochar model allows one to propose three complimentary directions for a plan to combat CO2 emissions :
1) The addition of biochar to the soil. This will increase productivity and potentially avoids the use of underground injection of CO2 for carbon fixation. Essentially dry biomass is retorted, producing powdery charcoal & pyrolysis gas and oil that can be used for "in-situ" sustainable fuel and electricity generation. Though an excellent idea for using rural agricultural waste, in my opinion it is not appropriate for municipal and industrial waste. Urban waste is heterogeneous, full of toxic heavy metals and organic chemicals that on charring would probably form novel brews of carcinogens that should not be added to soil. It might be wiser to gasify or steam reform municipal & industrial waste, hazardous waste and sewage sludge to syngas. Syngas could form the basis of a municipal petrochemical complex, and along with the CH4 from an anaerobic waste water plant, provide clean water, petrochemicals metals and fuel for a cities needs. Perhaps, the combination between recycling ventures, waste gasification & water purification with methane capture could be termed a "sustainability complex". By contrast, in small towns and villages a simple retort & still could be used for the production of biochar etc.
2) Constructing a hydrogen/electricity based economy (as a subsitute for both fossil & agricultural waste derived biofuels). The hydrogen economy is already being established in N. Europe. The geysers of Iceland are used to turn steam turbines and generate H2 by electrolysis. Wind is used in Denmark and Scotland for similar purposes. Solar powered steam turbines are being installed in the U.S. Because of the difficulties of storing electricity derived from solar, wind, wave and tidal power etc. electricity could be supplied to the smart grid (when available). Where isolated, remote power generation is available, but not linked to the grid, then the power could be stored or trasported as electrolytic hydrogen derived from water. The hydrogen could be also used as a superior carbon substitute for most industrial applications - steel making, cement, glass, bricks etc.
3) The third recommendation would be the novel legal development of "green rights".Analogous to mineral rights, the purchase of "green rights" would give the owner to preserve and develop the vegetation of key areas of biodiversity for CO2 sequestration. These rights would be sold world - wide to governments, individuals and businesses that wished to purchase carbon credits or offsets. The money could be supervised by the United Nations or other international body. Competing demand for tropical lumber, soybeans, beef & palm oil by developed countries would have to be reduced using a carbon tariff. The desired end point would be carbon fixation by living organisms and conserving maximum indigenous biodiversity. Ways of marrying "green rights" with "slash & char" would need to ensure that areas set aside for biodiversity are relatively contiguous and that agricultural development of the new "international carbon reserves". A similar approach could be adopted for coral reefs.
I believe, in theory, that if these suggestions were to be implemented expeditiously, it may be possible to completely cease our reliance on fossil fuels by replacing them with hydrogen/electricity, and also permanently remove excess carbon dioxide from the atmosphere using biochar within a relatively short space of time - perhaps only as little as 7 years (time to replace most gasoline etc powered vehicles by electric ones, and to cover the world in biochar). The technology is already largely available & has been for some time.In my opinion, the principle problems to overcome are administrative, political & fiscal - not technical.