Possibly of interest: What are some sustainable alternatives to peat for potting compost?, several answers there.
TL;DR: my favorite substitute for peat is fully-composted horse manure (with a wood-based bedding product), holds water a lot like peat.
Quoting my answer from that question:
My (peat-free) recipe for potting soil is:
5 gal sifted garden soil
5 gal sifted mature horse manure compost (we use a wood-based bedding product, and the compost has some of the desirable properties of peat)
5 gal coarse sand
"sprinkling" of equal parts lime, greensand, and rock phosphate -- strength depending on what I'm potting
Depending on what I'm planting and how much I have, sometimes I substitute sifted garden compost for all or part of the horse manure.
I arrived at this recipe because the major components are free, it uses what I have on hand (it's basically impossible to run out of anything but fertilizer), and it has been very successful for getting seedlings off to a strong start.
Based on what you have available locally (this is the essence of sustainability), experiment starting with my recipe or something similar and develop your own potting recipe. Nothing that comes from a Big Box is really all that sustainable.