I have vegetables growing in raised beds. In response to another question I posted, someone recommended adding mulch. Can I use home made compost as mulch or would I need something purchased from a store?
Yes, absolutely. You do not need anything from the store, and you can use your home made compost as a mulch without adding anything on top. If your compost has been produced using a hot aerobic system rather than cold and anaerobic, there's no more risk of weed growth from that than there is from ordinary soil. Even if the method you used was cold and anaerobic, provided you didn't add seedheads from weeds and other plants to it, nor added anything that might grow from stem or root pieces, the risk of weed growth is still no greater than that with open ground.
There's nothing wrong with buying in composted materials (composted animal manures, leaf mould, spent mushroom compost, anything like that) but if you have lots of home made compost, that saves having to buy stuff in. For weed suppression, it needs to be a minimum of 2 inches thick, preferably 3, but because it's humus rich, it will disappear quite quickly, being taken down into the ground by various soil organisms.
What you're doing is in the time honoured fashion of no dig gardening, where you just lay humus rich, or organic, materials on the soil periodically without actually cultivating it. It has the convenient effect of suppressing weed growth for a while, and helping to retain moisture, together with improving bio diversity in the soil itself, important for healthy plants. Cultivating the soil as little as possible is better for soil structure, though of course, for most of us, specially for growing vegetables, a degree of soil cultivation is necessary in order to plant.
A mulch is anything that can be used to slow down evaporation of water from the soil, and inhibits the growth of weeds. You can use plastic, stones, and tree bark and other organic material. If you use things like wood chips, or tree mulch, it needs to be aged prior to adding as a mulch, and it will eventually add nutrients to the soil.
If you want to add nutrients to the soil now, then put your compost layer down first and then a mulch on top of that.
The best mulch one could ever use is DECOMPOSED COMPOST. Stuff you buy from the store is usually only partially decomposed. The best is if you are making the compost yourself. You have NO idea what is in any compost unless it is the human poo/sawdust compost I dearly love but not for vegey gardens! I've used other composts, topsoils commercially that I couldn't grow a pansy in!! It is tough to produce enough on one's own unless you've been at it for awhile. Use your own. You know what is IN your compost. Non decomposed mulch is crap for covering topsoil. The decomposers have to decompose the stuff so that the micro and macro soil organisms can eat it. Then they eat it and go back into the soil profile to poop it out mixing organic matter into your soil with no work by you! And done far better. The ONLY way to improve any soil is the addition of decomposed organic matter, NOT UNDECOMPOSED wood chips...straw.
Keeping decomposed organic mulch or compost on top of your soil suppresses weed growth, FEEDS your soil. It is the best thing one can do! Do not expect mulch to replace fertilizer. To have a huge biological community in one's soil is the best thing for proper soil texture as well as aiding plants with uptake of chemicals the plants need to make their own food.