[hguant]

I think you're misunderstanding entropy; it only really applies in a closed system. By using energy from the sun to "decrease" entropy on earth, what you've don't is just expand the system to include energy from the sun. You've converted solar energy into kinetic and potential energy (moving things around, ordering them, building walls etc). That transformation isn't perfectly efficient - friction, electrical resistance, etc. create waste heat, which disappeared and can no longer be used. You've cleaned up one area of the system (decreasing entropy) but the means you used to do so used more than you gained. Entropy ALWAYS increases.

[krastanov]

Entropy always increases in a closed system. Entropy of a part of a system (i.e. an open subsystem, e.g. the Earth) is a well defined quantity (it is even a thermodynamical potential, hence completely independent of the history of the system, only dependent on the current state) and can be decreasing (and even the most basic thermodynamics textbook has plenty of examples).

And yes, the entropy of Earth is decreased by cleanup efforts. Only when including the Sun you get a system in which the total entropy increases. But this would be quite useless thing to do, given that the Sun is an infinite source of energy for practical purposes.