Win-win renewable power opportunities

Given that wind power disturbs wildlife, wave power kills dolphins, and transmission to any sort of renewable energy creates all sorts of problems, one could be pardoned for thinking there aren't any win-win renewable solutions out there. I'm not saying these latest two are, but it's certainly encouraging to hear ideas that actually alleviate existing environmental problems (or, for the latter, seem to have a minimal footprint).

First, in the WSJ, entrepreneurs are looking to harvest the algae that flourish in the dead zones created by excess nitrogen fertilizer run-off in the Gulf of Mexico. The dead zones move around, so the operators would be a sort of modern maritime shepherds:

"This is the sea equivalent of traveling goats: you have algae, we'll bring the fish," [LiveFuels] says, referring to companies that rent out goats to eat up grasses on California hillsides to reduce the danger from wildfires. They would truck in the fish and release them into a cordoned-off area. Cages would be used to keep carnivorous fish out.

The idea is that the fish oil would be harvested and converted to biodiesel. I'd want to see a rough EROEI calculation of a fuel production technique that involved driving a boat trailing catfish cages before committing any capital, but the idea of capitalizing on the dead zones and reducing the algal blooms has a nice ecological elegance.

The second idea, in Green Inc., is to retrofit existing dams for power generation. What?!? That was my first reaction too. Turns out:

Only 3 percent of the 80,000 dams in the United States are used to generate power, according to Norm Bishop, a vice president at MWH, a water engineering firm. They were built for other purposes, such as flood control, recreation, irrigation or water storage.

Umm... if true, yeah!!! The 3% number seems absurdly small to me, though (maybe it's number of dams, rather than a better metric like cubic meters of water flow? i.e. Hoover Dam counts the same as a small dinky dam). And if my calculations are right, $1.9bn for 350 MW comes to about $5,400/MW, which is not nuclear but not exactly cheap. A utility in Ohio appears to be going ahead, though, so maybe the economics can be made to work...