Plastic Extrusion and Molding (PEM) - It does not appear eco-friendly to discuss manufacture of plastics here, but if we are talking about working with bioplastics, such as cellophane from trees, for purposes such as year-round greenhouses for local food systems - then plastics have a highly relevant place in an ecological, localized economy. Extruded plastic forms include sheets, tubes, and others. Relevant for greenhouse glazing with polycarbonate extrusion (Lexan Thermoclear), or even UV-stabilized polyethylene (Solexx). Tubing for water pipes or irrigation, plastic shapes and sheets are all doable with slight modifications of a basic extruder. The key may be a ram extruder (simple design) with inductive heating, to which various dies are adapted for profiles (extrusion), or molds for shapes (injection molding), or blowers and molds (blow molding). This is one example of a product where cheap feedstocks (ex, <15 cents/lb for virgin polyethylene resin (50 lb/cu ft)) - where each square foot of Solexx weighs on the order of a quarter pound) produce very expensive products (about $1/sq foot for Solexx) - where the feedstock price in that dollar of product is under 5 cents. If an extruder is available - combined with the knowhow - then localized production of such glazing could probably yield cost predictions of something marginally higher than material costs, under the DIY-flexible enterprise scenario. The challenge is producuring the knowhow for extruder fabrication and material extrusion - where the material costs for the device are expected t be around $5k for the machine - structure, hydraulic ram, inductive heating, and die. This is a prime example of market inefficiency - where middlemen, R&D costs, company overhead, competitive waste, and proprietary technique - make the price so much higher than the open source flex fab scenario. The flex fab innovation required here is the fabrication of a generalized device for die extrusion, injection molding, and blow molding in one, where dedicated machines serve each purpose today.