How the super-chimney will trap CO2 and promote agriculture
As it has been explained, the super-chimney will make at least 300 square miles in a desert land arable. Normally, desert land is not a part of a CO2 exchange process because there are almost no plants in the desert. Thus, ordinarily CO2 cannot be trapped. By the same token, a desert does not contribute any CO2 to atmosphere because there are no decaying plants or soil to release CO2.
Adding water into a desert will change that desert into carbon sink. The CO2 uptake capacity of arable land will be determined by the type of vegetation grown on this land because some plants bind more CO2 than others. Trapped CO2 will be partially re-released back into atmosphere because people and animals will consume the plants, but some amount of it will be retained for good forming soil on the ground.
The impact of irrigation on agriculture will greatly depend on local conditions and on the kinds of plants grown. However, existing irrigated desert areas, such as those in Israel, demonstrate extremely high productivity. Moreover, tropical deserts can produce more than one crop per year. For example, in Egypt, the land produces up to 3 crops a year. Therefore, the super-chimney will ensure sustainable and very profitable agriculture in the surrounding areas.
The super-chimney will be the most productive in areas where climate is hot all year around because that will guarantee sustainable air draft. Economically, it makes sense to situate super-chimneys in tropical desert areas, because the land there in present state is not used for agriculture, and is otherwise worthless. Building a super-chimney or network of the super-chimneys in such areas will provide the necessary rainfall to ensure prospering agriculture and will transform the desert land into oasis. The super-chimneys can be built in places like the Sahara, the Arabian Peninsula and Australia. In USA, the super-chimneys can be built in many places in the South and in the West, such as Texas, Arizona, Nevada etc.