It is my opinion that all the components of a "hydraulic planting" slurry can easily be "organic", with the exception of chemical fertilizers.
Mulch--whether paper, virgin wood, or the newer grass straw/paper mixes, or even cotton waste are all organic. Some jobs are now calling for 50% compost (min. #6 on the Solvita scale) and 50% wood or paper.
Seed--certainly organic
Fertilizers- these can be organic. And fertilizer does not need to added through the hydroseeder (Finn trademark) or hydromulcher (Bowie trademark) or hydraulic planter (generic term). They can be incorporated into the soil or applied as top dressing. Grass seed does not need fertilizer at the time of germination. It is we who have become lazy and want to apply it as part of the slurry.
Tackifiers- Many types of tackifiers are being used and even pre-mixed with mulch (bonded fiber matrix, organic, and polyacrlamides (pam), chemical. I prefer to mix tackifiers on site, otherwise you are dictated to by what is in the bag !! And what's in the bag may not be what is ideal for that job.
And I always recommend a "2-Step" application method, especially for turf. The first step is a small amount of mulch to cushion the seed as it goes through the pump (in recirc type machines the seed damage can be great because the seed goes through the pump multiple times). Also in thsi first step is the fertilizer, if used, and the tackifier. This assures that ALL of the seed is in direct contact with the soil and not up in the mulch.
The 2nd step would be just the required mulch, as a top dressing, with some tackifier to "glue" the mulch in place. If using pam, it should all go on in the first step, as pam is a flocculant and you want it all on the soil to work.
These are my ideas and observations. But after 39 years in this industry, I still don't know everything!!
Your thoughts on this issue?