This is a simple four-in one idea (for a shortcut, see drawing).
1. Recent research suggests that merely painting roofs and sidewalks in the world's largest cities white can help cool the planet considerably. Changing the albedo of the planet is not such a ridiculous idea after all.
2. My albedo
technology takes us to the Sahel, where desertification, erosion, deforestation and water scarcity are huge, interrelated problems.
3. The material used consists of highly reflective, cheap metal plates which are bent at the bottom so as to form a half-pipe.
4. The plates are positioned in a 45° inclination facing the Sun (or whichever inclination is best to bounce back sunlight at the project place). When you look at them horizontally, they are also placed in a very slight inclination. This is needed to channel water through gravity. The screens are attached to simple poles, while the halfpipe rests on the ground.
5. Now consider the advantages:
-sunlight is bounced back in a major way: this brings in 'albedo credits' (similar to 'carbon credits'). This cash should be sufficient to finance a big part of the project (see below).
-the reflectors also provide shade and cool the soil behind them.
-furthermore, the screens act as a wind-breaker, which is very important so as to limit erosion and nutrient-loss of the soil.
-last but not least, it does rain occasionally in the Sahel, some 200 to 500mm per year, depending on the location. Not enough for a thriving agricultural industry, but enough to grow something.
The large surface area of the screens, with their halfpipe, are perfect to catch rainwater and channel it to a large centralised cistern where it is stored.
-a simple set of photovoltaic panels and a drip irrigation system (a tube), are installed behind the screens.
-when all these things are in place, it becomes possible to start using the soil and grow hardy fruit trees, wood trees and shrubs.
-you keep the screens in place as long as you need to water the trees. Say, after 5 years, you can remove them, because the trees will have established themselves well.
-obviously, this biomass that is now capable of growing will sequester copious amounts of CO2, thus fighting climate change once more.
-after the trees have matured and grown deep roots, you can take away the screens and move them to a next place.
-the strong trees now take over the role of the reflectors: they provide shade, act as a wind-breaker, thus reducing erosion, they trap moisture in the soil, their falling leaves and branches add biomass and nutrients to the soil, bringing it alive, and they have a reflective quality of themselves (high albedo). This micro-climate now makes it possible to grow food crops between the rows of trees.
Let's look at the economics of this highly integrated little idea.
According to the research mentioned earlier, a 1,000-square-foot (92m²) white roof could offset 10 metric tons of carbon dioxide. Note, a metal reflector can bounce back even more sunlight (don't know how much, tough, so we'll stick with the white roof quote).
For the ease of calculation, we say that one reflective panel is 92m² in surface area. (Say 30m long and 3 meters wide).
The current carbon price in Europe is 23.2 euros per ton.
So you get for 1 panel, a one time sum of 232 euros.
I calculate that the steel costs and installation costs amount to 5 euros per square meter. This requires a total investment of 460 euros. Minus 232 = 228 euros needed to break even.
Per 30 meters of shadow, you can plant, say 3 big trees and 3 small shrubs. Combined, this biomass will sequester something like 200 kg of carbon dioxide per year, over a lifetime of, say 30 years. This sequestration effort is worth: 200kg * 30 = 6 tonnes. At an average carbon price of 40 euros per ton (CO2 is expected to become costlier in the future), this represents 240 euros.
Okay, so we have already broken even (the 12 spare euros go to solar panels, the drip irrigation tube and the seedlings).
Now the added advantages are: the halt of desertification and deforestation in the Sahel; the opportunity to grow food, which is very important in this region, because people there have some of the world's highest fertility rates (abundant food and food security is needed for them to develop and transit to lower fertility rates); and of course climate mitigation at a cost of *zero* euros/dollars.
The potential profit from food production will go to offsetting the emissions caused by making the steel and shipping it to the Sahel.
Should be okay!! Perhaps!
(Reminder: the metal would bounce back more sunlight than a white roof, so it should fetch higher albedo credits, making the economics look better still !!!)
I made a drawing of the idea.