Bedding Material

The store-bought bedding is too expensive. Can I use green pine needles?

I would recommend not using the needles since they aren't absorbent and the oils can really mess with a rabbit's airways (avoid cedar for the same reason). Shredded paper should work as a substitute, and a thin layer/heavy dusting of baking soda on the bottom of the pan or as a middle layer should keep odors down.

I started using wood shavings, followed by a kind of hay my rabbits refused to eat (they're picky and spoiled). Now we use the shredded paper from my husband's office.
A few times a year we have a shredding blitz, he has years and years worth of old receipts and bills stashed in our attic, at least this way they get used for something positive and I don't have yet another thing to buy (and store).
After we shred up a ridiculous amount I store the shreds in big trash bags out of the way and fill up a trash barrel with them for everyday use.

(after use, the soiled bedding shreds end up in the garden as mulch, generally on top of an area where I have buried bokashi waste or something else. They tend to mat down and not breathe too well, but they don't take as long to break down as I expected)

Straw is cheap, rakes up easily, composts well, and is pretty easy to get. They also enjoy playing with it, & burrowing in it. Pine and specifically cedar aren't recommended, for rabbits.