I've been growing microgreens for a few months. I am aware of two soil-less media products for growing in 10x20 trays. SuretoGrow pads are a light fiber mesh and MicroMats are a compostable
wood pulp sheet that expands into a mushy goop when watered. Both cost $1.40 per tray. I use the MicroMats for small seed like brocolli, arugula, and amaranth.
For larger seed like peas, sunflower, and beets I use a loose organic potting soil media. I imagine that the water retention and structure of the media are more important than the nutrients when growing microgreens (10 days to harvest). Since the seed cost is much higher than the grow media cost, I have not yet experimented with soil alternatives. Perhaps a mix of shredded newspaper and used
coffee grounds (free from Starbucks) would be a good option. For comparison, organic potting soil costs about $1.00 per tray.
Pea shoots taste like peas, except without the sweetness. The bottoms of the shoots can get a little tough and stringy when eaten raw. Sunflowers are my most popular crop so far. They are very tender and delicious.