compost question

hi everyone-

i'm new to this site, and new to growning my wheatgrass. so far, my trays are awesome, and i am so happy i've figured it out! i want to start composting the used mats, and will get my bins this weekend.

here's my question:
i saved a couple of mats to get my compost started with, and i've noticed some mold developing on one of them. can i still use this for my compost? will all compost materials get moldy as they compost?? anybody know?

thanks so much!