Build A Greenhouse From Plastic Bottles: http://www.livinggreenandfrugally.com/build-a-green-house-from-plastic-bottles/
Reduce, reuse, recycle, upcycle, repurpose in the garden
Adapted from Growing Food in the Southwest Mountains: A guide to high-altitude, semi-arid home permaculture gardens:
I encourage gardening methods that require naturally-existing and fully compostable materials, and discourage techniques that rely on industrial, petroleum-based products like plastic (plastic mulch, Walls O’ Water®, plastic cold frame covers or greenhouse panels, etc.) or electricity, such as using Christmas lights to provide nighttime heat.
I do, however, appreciate the value of repurposing scavenged, garage sale or thrift-store items like plastic bottles, old windows and car windshields, old bed sheets, objects that could be used for container gardening, and “urbanite”—broken chunks of concrete from redeveloped properties (urbanite chunks are easy to stack or make pathways with because they have flat upper and lower surfaces. From the side, the uneven pebbly texture looks quite attractive). Repurposing materials will be a major preoccupation of the 21st century as peak oil and climate change make the creation of new petroleum-based products unattractive.
Dumpster diving is a great way to find material for building garden beds, cold frames, pathways, trellises, mulch and other garden needs. (Note: dumpster diving is often prohibited by local regulation.)