An all-American visionary in the tradition of Thoreau and Buckminster Fuller, the architect Mike Reynolds has spent the last few decades designing and constructing environmentally sustainable houses in the New Mexico desert. Like the more modest tinkerers profiled in Agnes Varda's The Gleaners and I (2000), he specialises in reclaiming "trash" for his own purposes: his favoured materials include old tyres, glass bottles and aluminium cans. While he refers to his dwellings as "earthships", they look as though they could have landed from another planet, given their unseemly bulges and their walls studded with luminous circles like the patterns on the base of a Dalek.

With unkempt silver hair and an inspirational gleam in his eye, the loquacious Reynolds is a born preacher, if not a prophet of doom. Like most people bent on saving the world, he could be taken as a bit of a crank, and Oliver Hodge's documentary makes clear that the "earthships" aren't always flawlessly designed. Leaks develop, heat lingers, unconventional plumbing systems go awry. But what else would be expected from a maverick with a passion for trying out new ideas? Cunningly, Hodge ensures our sympathy with Reynolds by focusing on his legal battle for the right to experiment with building techniques. In its final act, Garbage Warrior becomes a classic tale of an underdog who challenges the system, with a climax recalling the great films of Frank Capra.