Sustainable furniture is made of material that has certain characteristics:
Recycled or Recyclable: The furniture should be made of recycled or re-purposed materials, or be recyclable itself. It could easily be both. Barnwood furniture is an example of furniture that re-uses materials from old barns. Metal can also be re-purposed along with wood.
Renewable: It should make use of materials that are organic and can be easily re-grown or replaced. For instance, bamboo is increasingly gaining in popularity because it grows back ver quickly.
Safer Materials: The piece of furniture has been made using materials that are safer for the environment by being less toxic and that have no, or lower off-gassing.
Stewardship Sourcing: The furniture is made of raw materials that come from fairly-traded sources or certified low impact sources such as FSC-approved forests.