Plastic mulches can be manufactured with a slick or embossed surface texture. The embossed plastic has visible patterns that make it more resistant to wind fatigue and cracking. The problem with all plastic mulch or construction film is that eventually, UV light and heat will cause it to become brittle, develop cracks, tears and holes. Surface pressure from tires and wind will further weaken it, increasing the rate of deterioration. Eventually, it will break down into flakes and disintegrate. How long it will last is dependent on these factors as well as the formulation.
Longevity studies on plastic mulch with spray-on titanium dioxide coatings have shown that it can last for at least 2 years before significant deterioration sets in (135). Some manufacturers claim their plastic film can last for up to 3 years in Middle Eastern desert climates (136). Other studies in progress are looking at the use of permanent (10 year lifetime) mulch consisting of black plastic painted white with latex paint (137). Painting of black plastic with white latex paint is used to allow the same mulch to be used in both cold and hot weather (138-142) and extend its lifetime in the growing of vegetable crops.
It is likely that the plastic cover to be used for large-scale surface albedo enhancement will have to be specially engineered for this application. A 2-year lifespan will be inadequate due to costs of replacement. Something on the order of 10 years is more attractive, since this would imply 15 replacements over the next 150 years and perhaps fewer if improvements in energy technology and land use can reduce GHG emissions much sooner.
The cost of plastic film is directly related to its thickness (related to the cost of resin, which fluctuates with market forces and the price of crude oil feedstocks, most notably ethylene) and the additives included. At present, 4-mil (0.004 inches thick) white construction film can be purchased commercially for 1.5 cents per square foot (SF) in lots as small as 2000 square feet. We purchased 2000 SF of this material for this research for around $30.
Assuming this material was used for surface albedo enhancement, its cost would be estimated at $418,000 per square mile. Covering 4 million square miles at 67,000 square miles per year would average around $28 billion annually just for the plastic. The actual cost of the plastic may be higher or lower depending on the production costs. A thicker plastic may be required.
For example, the 4-mil used in this study appears opaque to the eye, but on closer inspection, black lettering can be seen through the film. Thus, if some visible light is getting through, its reflectivity may not be high enough to meet the solar reflectance target of 0.8 (0.9 in the visible spectrum). However, we believe that the volume of plastic required may drive down the price significantly, perhaps to as little as 0.5 cents/SF, even if thicker and more custom engineered material is required.
