If you are considering building a low wall for a conservatory or greenhouse, this might be a viable option for you. We built the front wall of our conservatory with tyres, stones and some chicken wire for very little cost, both to us and the environment. To make the wall stable it is important to ram the tyres with earth and spend a good bit of time pounding the earth with a sledgehammer. You can read more about building with tyres in this post here.
thegreenerdream 