BP substrate

[Bogertophis]

No, I'd never do that- you could introduce all sorts of pathogens & even parasites to your pet. From wild animals as well as roaming cats & dogs, etc. Also, the park might have been sprayed with chemicals- or someone might have dumped stuff there, you have no way of knowing- it's way too risky.

The cheapest substrates aren't the best for BPs only because they don't hold humidity, which BPs need. BUT, if you provide a good (effective!) humid hide, you can get away with these other substrate options. I don't currently keep BPs, but I have in the past (about 10 BPs); I'm more of a colubrid keeper, & most of my snakes don't require so much humidity- those that do, have humid hides. One thing I use is clean shredded "office" paper (I shred all my bills & such). If you happen to use UTH heat, you'll also find that heat rises more readily thru these paper shreds. I first put down one layer of paper towels though, as it makes clean up much easier. (I also blend in about 1/3 Carefresh with the paper shreds, but don't use that for BPs- it's hygroscopic.)

Another thing that makes an excellent substrate is backless nylon (or polyester) indoor-outdoor carpeting, cut to fit. This is even better for a heavy-bodied snake like a BP because it stays in place. It's washable & can be disinfected & almost "never" wears out- seriously. So you'll save lots of money on substrate, but you will have to hand wash it, so there's that. But it offers good traction that snakes love (need), can be spot cleaned, & it allows heat to easily rise up through it. The best place to buy it is from the big 12' rolls in Home Depot- Lowe's type stores- it's sold by the foot, & can easily be cut to fit with scissors. No, it won't hold humidity, but you can do a humid hide, & if you can't afford sphagnum moss, use new, clean sponges instead (in a humid hide) to provide humidity. This carpeting isn't expensive, & will save lots of money in the long run, & it also makes a lot less waste.

This is an example of the carpet option: (it comes in lots of good colors too- it looks nice!)
https://www.lowes.com/pd/Select-Elem...pet/1000411979

BTW, if you go this route (indoor-outdoor carpet), get enough to cut several carpets to fit, so that a clean one is always ready when the snake soils their home. That way you can clean & replace very quickly. You can either scrape off the fecal material into your toilet, or scrape it off into your garden outside (that's what I do) before washing it. I use dish soap on the soiled spots, & handwashing the whole thing in my laundry sink, & then give it a thorough rinse. For a snake that wants/needs humidity, you don't even have to wait for it to dry (which it does pretty easily- hang it up vertically, the water comes out quickly). But you can also just shake it out & install it if you want- especially if you're using UTH, it will dry anyway, & add some humidity.