Patent on manure in your fields?

Interestingly enough it turns out that a Michael Markels of Springfield, Virginia, has US patents on artificially fertilising the ocean to increase sea food production in the ocean as well as sequestering carbon dioxide this way. The patents were filed from between 1994 and 2000. For carbon sequestering he invisages that a ship moves in a spiral pattern over deep water, dispersing fertiliser to create a bloom of phytoplankton. The plankton sink to the bottom of the ocean when they die, taking with them the carbon they absorbed at the surface. He has performed experiments by adding iron salts to an area of the tropical Pacific. The phytoplankton volume increased by a factor of 27 over nine days, yielding 272 kilograms of plankton per kilogram of fertiliser. He estimates the cost at $5 per tonne of carbon stashed away.
His patents can be found at the US Patent & Trademark Office:
5,535,701 – Method of increasing seafood production in the ocean
5,967,087 – Method of increasing seafood production in the barren ocean
6,056,919 – Method of sequestering carbon dioxide
6,200,530 – Method of sequestering carbon dioxide with spiral fertilization
I find it hard to belive that there isn’t enough prior art to invalidate a carbon sequestration patent filed in 2000. There is some interesting reading there though with regards to potential impact of adding of fertiliser to the oceans, which the cold “waste” water from an OTEC can be used for.