Hi Kelsey, thank you so much for this hint! Didn't think about that before, but you are probably right that most PP bags will have a PE coating. The reason is that PP is not UV-resistant, and as these bags are made for use in the garden, they would quickly wear in sunlight if they hadn't got a coating.
I'm not aware of any better alternatives without plastics, though. You might try a metal bucket, but it's difficult to heat up. So the coated bags, having just a thin PE layer to protect them from sunlight, might still be a viable solution. If you happen to find a better one, please let me know! Best, André

Thank you so much for the easy hay steamer tutorial! I did want to let you know that the BTSD gardening bags that you linked to (for US and Canada) is “durable polypropylene woven fabric with water-repellent PE coating”.. Some other brands don’t indicate that there is a PE coating, but I think it’s likely that most have one.

Regardless, your method is great and I plan on figuring out a way to make it work for me 🙂