cyccommute 

As magnificent...and frankly ugly...that tree is, it illustrates part of the problem of using "cottonwoods" as energy crops. As with most "crops" we tend to want things that are uniform in shape and size because they are easier to handle in an industrial setting. The multitude of arms in that picture would make harvesting and processing of a tree like that too difficult. Additionally, the extra branches increase the lignin content of the tree which is mostly useless utilizing current methods of biomass conversion. Processors want to make either fiber (paper) or ethanol out of trees. A high lignin content caused by the various branches and reaction wood decreases both.

For energy crops, and/or for paper, straight tall trees are desired. Take a look at your tree plantations again. I've been by some in Oregon along the Columbia River. Yes, they are "poplars" and they are related to cottonwoods because cottonwood is a member of the Poplus family. But the trees in the plantations have tall straight stems with very little branching until the tops of the trees. This occurs mostly through self-pruning where the bark squeezed out the excess branches.

"Cottonwoods", whether the eastern or western variety branch everywhere and have multiple branches and often split stems like the one in your picture.

I have not said that "you don't see cottonwoods" in your area. I said that the trees you see in plantations aren't "cottonwoods". Your seed picture illustrates another aspect of plantation trees that is undesirable...that is seeds. Hybrid poplars are bred to not to produce seeds because you'd have to deal with seedlings in the plantation which means extra labor and effort to keep the trees at the optimal distance for maximum biomass production and making seeds robs the tree of energy that could be used to put on growth. Sterile organisms tend to grow more and faster because little energy is put into making offspring.