greenhouse heat with Rocket heater or ?

I have the following items to work with 8 in pvc pipe ( the kind thats for main water lines). I cant afford metal pipe, I need to heat a 24 foot x 16 foot greenhouse, and have a lot of stuff to work with but no metal pipe. My question is can I use this or should I try something else. We have a wood heater but it would not hold heat for the night. Anyone have any ideas that are extremely cheap. thanks

Where are you located? I would love to get some of the plastic pipe from you if you are close, as in sell the pipe to buy steel duct.
kent

can you get wood chips from a local tree service or utility company? piling them up against the shady side of your structure could provide some heat as they decompose. using the pipe you've got to duct air from the greenhouse, through the pile, and back into the greenhouse might work even better. after the chips have cooled off, use them as mulch and get new chips to heat for the next cool season.

thanks for the ideas. I'm in North Carolina. But that might be an idea to trade some.

build a pocket rocket (you dont need much pipe) and use soil around it to give thermal mass. build your compost pile in the green house. dig your beds deep and layer compost under the beds about 8 inches deep then cover with ten or so inches of soil. there lots of ways to keep a green house warm.