The 3E’s of Sustainability

I’m new to this blog, and blogging in general, and I thank Henry for inviting me to contribute to Earthniversity.

I recently obtained (2012) my MEd in Educating for Sustainability, from Antioch University New England. Through the two years of study, I have developed a lens for sustainability, which means I see the 3E’s wherever I go.

Does anyone know what the 3E’s are?