Mushroom varieties on spent coconut coir substrate from greenhouse tomatoes?

A client I'm working with generates a large amount of spent coconut coir from a medium scale greenhouse operation growing tomatoes, peppers, cucumbers, and other produce in a hydroponic system. Their organic vegetable substrate would contain only coconut coir and composted laying hen litter while the conventional vegetables are grown with additional chemicals or non-organically certified products.

What mushroom varieties, if any, would be a viable candidate for inoculation of this substrate?

Could the coir be blended with other substrates to promote colonization?

Will residual plant nutrients be a problem?

The client also uses a large amount of fuel wood each season and has the potential to generate mixed species wood chips. Potential to generate single species wood chips would take a little more planning and organization.

Also available would be a large amount of green plant residues, the majority being pruned suckers from tomato plants, second being waste produce bound for the compost pile.

Strong possibility of acquiring spent coffee grounds or brewery grain as farm is located in a more populated area, makes regular deliveries in a very large city and has solid relationships in the local food environment.

Project can be conducted in heated greenhouse environment suitable for solanaceous crops or outside, in the shade, with or without protection such as clear plastic or row cover.

Inside greenhouse mushroom substrate could be located beneath a rack used for growing out seedlings where substrate would be shaded well and receive regular watering.

Currently coconut is contained in 3 gallon black plastic grow bags. Would mushroom inoculation and grow out be more convenient and/or more productive growing in the bags or in some other configuration?

Thank you for any questions or comments. I'm sure I'll post more comments here as I answer these questions and develop a plan.

From what I understand, coconut coir is not used as substrate but often used as casing. That being said, it has excellent water retention capability and if included in a more nutritious substrate, it could benefit the substrate by retaining water for mycellium and fruiting bodies to use. The type of mushrooms this would work for probably depends more on what else you add to the substrate rather than the coir itself. Coco coir has almost zero nutrition and it is all tied up since coco coir breaks down so slowly (as I believe I understand it).

You are likely to run ino trouble using secondhand substrate. Because it is old and because it has been in contact with compost, there is likely to be a very high resident contaminant population. Rendering this substrate would likely require extra sterilization time.

I highly doubt that residual plant nutrition would be a significant problem,

Don't wait to use it as a secondary crop, at least not in the conventional beds. Shrooms are synergistic with tomatoes, king stropharia do well in garden beds and will improve tomato yields, disease resistance and taste.

What kind of hydroponic system? Is there a possibility of mixing the substrate and inoculation with mushrooms the same time the tomatoes are planted?

there's really only one way to find out if anything will work- try a small scale test. i would try some oyster mushrooms first. there are commercial spawn suppliers and hobby spawn suppliers.