Straw mattress filling for mulch?

I just took apart an old 'straw mattress' that was left in the property I just moved into in rural France. I'll have use of the timber from the frame but wondered if I can use the filling as mulch or a compost additive. It looks more like hemp than straw. My only concern is that I have heard of old generations dousing things harsh chemicals to keep insects and rodents away. Any advice would be much appreciated!

It's honestly hard to say. Even something relatively harmless, like borax, may not treat your plants or compost pile kindly.

I'm a hardcore "recycle everything" guy, but personally I would hesitate to put this on my garden.

Thanks thats good to know. I'll have to find a non food based use for it!