Thanks for your question.

It is, however, difficult to answer since there are many different definitions of “organic mulch”. Red mulch has chemical dyes added to it so it is hard to conceive of it being “organic” or “natural”. IMO, there are two broad ways to look at things and you certainly touched upon them. First, are the materials comprising the mulch “environmentally friendly”? Your reference to cedar mulch is spot on in this regard. The same might also be said about cypress mulch. Secondly, what is done to the mulch prior to its sale? A number of environmental negatives can occur. In short, there really is not a single, simple, and good answer to your question let alone a list like you might want. In shorter words yet, there may not be any environmentally friendly mulch. I think that the real question is what mulch incurs the least negative effect upon our environment? As a long-time environmental activist, let me just describe what I do and you can take it or leave it. During the summer I bag about half my grass clippings. The other half remains on my yard. I do not use any chemical fertilizers or herbicides on my yard so I feel that these clippings are pretty much “natural”. The pollinators love my Creeping Charlie, dandelions, and white clover! Neighbors may not. I continue to do this during the summer season and then leave them there over the winter. I also cut back most of my perennials in the fall but leave them where they fall in order to protect the residencies of pollinators who may be over-wintering there. Then in the spring (mid-April or so), I remove all this debris and compost it. It is labour intensive and certainly is not amendable to a “neat” garden. But it is consistent with my views that gardening should not be an intrusion upon the natural world but coexist with it.

Here are some other viewpoints:

https://www.gardeningknowhow.com/garden-how-to/mulch/best-mulch-for-garden.htm

https://lawnlove.com/blog/best-organic-mulch/

https://simplysmartgardening.com/best-organic-mulch/

Good luck and please feel free to get back to us with any additional questions.

Just rereading my response to you. I use my bagged grass clippings as mulch on my gardens during the growing season. Apologies for the discontinuity in my answer. 

Again thanks for using our forum. 

Sounds like a great idea.  Good luck with things.  Please feel free to get back to us with any further questions.