Green buildings are designed for minimized impact to the natural environment through all the stages of material appropriation, construction, and throughout their life cycle. Green building research and construction techniques cover a broad range of approached and technology. For example, on one hand they involve the use of alternative materials such as straw-bales on one hand and technologically advanced high efficiency systems for maintaining the interior engineered climate on the other.
A sustainable building, in the true sense, is a building that requires no non-renewable resources or energy to construct an operate, produces no pollutants that cannot be harmless absorbed by natural systems, and destroys no habitat. There are almost no sustainable buildings anywhere at present, and this is a very challenging goal, albeit inevitable in the long run. However, an increasing number of buildings are being built that are "green" or that are more sustainable.

An Introduction to the Challenges and Goals of Green Building

Thesis (pdf) - Alex Lukachko's Master's Thesis on Environmental Ethics in Architecture.