No, seeds starting mix is finer so that roots do not get torn up when you pull seedling apart when separating community flats/pots. It is mostly vermiculite peat moss and a bit of lime/dolomite to adjust pH. Potting mix is coarser and usually contains composted materials such as pine bark and other (originally) woody materials, often with a fluffer such as perlite or styrofoam, and lime/dolomite for pH adjustment. It can be used for starting seeds if you are not planning on pulling the plants out of the mix (I use it for starting everything). Potting soil is often much denser/heavier because it contains actual soil, I have seen it advertized for things that are to be permanently grown outside in containers like shrubs in planters, but someone else might have more info on this than me. Potting mix is usually better for most things than potting soil. For all of them you would have to check the bag to see if they contain starter fertilizer.

The smell is caused by bacteria growing in it, just like if you had a bucket of kitchen waste full of water. If it's worth it to try to keep it, spread it out fairly thinly on something that drains well. Vinyl window screening cut to fit the bottom of some flats comes to mind. And sit them out in the full sun until they're dry. If it's going to rain again, put them under shelter. You CAN put them in the oven, but the smell is worse than you can believe -- really bad! If it isn't crucial that you use this particular bag, just toss it into the garden like Calistoga suggested. If you have seeds that are very important to you, don't use this soil to start them. And keep your potting soil out of the rain. Sue

Haven't we learned the difference between "bedding" and "food" yet? Bedding is high in carbon. Food is high in nitrogen. What MichyTan is describing is probably balanced. It can be considered both bedding and food. Or neither, depending on how thoroughly it has been composted. Having said that, I, like Wormsome, wouldn't use it exclusively as bedding or food. Toss some in the bin and see how the worms respond to it. You describe 95% of what is in it. I would want to know what the other 5% is. It may be something the worms don't care for.

I would say it depends on what the "mulch" looks like. You need nuggets, not shavings, as the nuggets offer the shape and texture and durability the potting mix requires. Shavings will break down too rapidly. If not able to locate the reptile bedding available at just about any pet store, fine orchid bark works equally as well. Both are perfectly viable substitutes for the pine bark and I would favor either of them over a cedar shaving mulch.