Baking it won't help and will only stink up the oven and the house. Add it to the garden or mix it in some big containers to use later but I wouldn't use it for starting seeds. That is when plants are most vulnerable so for best results, get some fresh mix or moldy seedlings will likely follow.

Mix should be stored from season to season, well sealed in a totally dry, cool environment.

Dave

OK ... bummer. That stuff is expensive!

You can still use it for containers...I just wouldn't trust it with seeds/seedlings.

Yeah you don't have to throw it away! Just don't use it for germinating seedlings.

Dave

If you are going to keep seeding mix in a shed or even in a basement you have to keep it dry. Get yourself a garbage can with a tight fitting lid and use it exclusively for potting mix. Mine has soil in big red letters so it won't get used for anything else by mistake. I buy a 3.8 cu foot bag of it every spring when I open my greenhouse and it does me all summer and I still have some left in the spring. It never gets musty as long as I keep it well sealed.

I keep that one in our garden shed. I have a 5 gallon pail with a tight lid that I fill from the big one for the greenhouse and I bring it into the basement when I close the greenhouse. I use this for fall planting and fill again for the spring. It never gets musty either. Pro mix will last a long time as long as you keep the moisture away.