Human Colonys at Venus

One expert calculated that it would take 600 years to convert all the carbon dioxide to carbon and oxygen using all the solar energy that falls on Venus. So a million years may be how long it would take with present algae. Worse we would have to keep oxygen away from dead algae or they would burn like charcoal and return carbon dioxide to the atmosphere. I have an alternate plan, which is slightly faster, but not quite as Earth like.
The first steps in my plan is to develop a flying algae or equivalent by gene splicing. These would be released high in the Venus atmosphere where the temperature is as low as 55 degrees f. The cloud of algae would shade the atmosphere toward the poles of Venus so the cloud could extend somewhat lower in that direction except there would not be much sun light for photo synthesis. On the ground we would instal two "snow fences" each about 2400 miles long surrounding the North and South poles This would be like the Arctic circle and the Antarctic circle. The fence would catch dust, including dead algae and surplus fertilizer we would bring to the algae cloud. As the ring of hills grew taller we would have unbury the snow fence or replace it. In a few thousand years, the hills would be tall enough that surface wind in the direction of the poles, would rarely cross the hills. This might cause the poles of Venus to cool from 800 degrees f to 750 degrees f. Venus likely has a strong polar down draft, so the wind would continue to blow though the snow fence toward the equator of Venus, causing the Hills to continue to grow taller. Increasing the polar down draft may cool the poles from 750 to 700 degrees f. We would use some giant mirrors to reflect the wave length of light the algae can use for photo synthesis at the less lighted portions of the algae cloud. Other wave lengths would miss the planet, so as to avoid making Venus even hotter. Sun shades would cool the atmosphere in locations near the algae cloud so algae can expand into these volumes. In perhaps 1000 years the downdraft might be 1/10 % free oxygen, thanks to the efforts of the flying algae. It would then be necessary to sprinkle iron dust on any mounds of algae charcoal to keep the probability of charcoal fires low. This will remove some oxygen from the atmosphere, but we will have way too much oxygen if we ever get rid of most of the carbon dioxide. The algae cloud uses some of the solar energy to make more algae and the cloud shades the polar regions somewhat (combined with the cooling shades thousands of miles from Venus) perhaps cooling the polar regions from 700 to 650 degrees f.

Now we can start to deal with another problem; the layers of strong sulphuric acid in the upper atmosphere of Venus. Think of the polar regions as two giant swimming pools. We install two giant pool liners. We cool the polar down draft with sun shades, so it rains sulphuric acid for a week or two. Then we move the shades back where we were using them. The rain evaporates before it reaches the ground, The fertilizer dust and dead algae make mud in the giant pools. We put in a new liner on top of the very acid mud, cool the down draft etc until we have nearly all the atmospheric sulphuric acid in aquifers beneath the polar plataues which we have built from dead algae and surplus fertilizer. Now we may get some fresh water rain to make several more aquifers. By now the polar plateaus may be a mile higher than the average surface of Venus = cool from 650 degrees to 630 degrees f Can we allow the plateaus to grow taller? I think we risk stress on the crust of Venus if we add more weight resulting in Earthquakes = Venus quakes perhaps for the first time in a billion years. Perhaps by then we will have cost effective ways to cool the poles of Venus further.
A mile of material on top of the hot rock of the polar region will cool the regions to perhaps 600 degrees f. We can cool them another 500 degrees f with monster sun shades, but that has to be very costly even with very advanced technology. Neil