If Frodo went green and decided to live a private space that fulfills that philosophy, he'd probably go for one of these miniature pods from Eco Hab.
Eco Hab is a company that specializes in designing small houses that are environmentally friendly. These abodes are more like pods, but the size is adequate enough to fit a couple chairs, tables, a work space and even a bed. Products such as the O-Pod help to reduce energy consumption and retain energy and consumption. It's a pretty cool way to go green in a space that you can call your own.
If you're looking for a private workspace that doesn't eat up the electricity bills and is eco-friendly, check out Eco Hab and its subsidiary brand, the O-Pod.