I recently spoke with someone who claimed to be an experienced gardener (in Spokane, Washington) who now lives here. She apparently was new to composting. This summer, she tried an open compost pile and became upset when weeds starting growing in her compost. What was her solution? She sprayed her compost with Roundup. Her weed problem was now solved. She then used that compost to "fertilize" her garden. Guess what...she killed her entire garden. Fortunately she has a container garden to fall back on. She is not a dumb person; she is a retired high school English teacher. She decided to talk with more experienced gardeners in this area. Hopefully no one here is so "thoughtless". I personally never use herbicides. but if you do, please know what you are doing and think about the consequences.
If you hot compost, you can "cook" the seeds too. It requires repeated turning and an eye for C:N balance.
I compost a lot of stuff, but I don't think I'll use Roundup. I have a large compost pile, and I don't have a problem with weeds. Something might sprout up from time to time but after it gets buried in the next layer of compostables, it just adds to the compost. Any weeds that I pull up from my gardens go into the compost, and I don't worry about the seeds.
I set up a compost system when I first moved in here, but after I did I realized I could never gather enough greens to keep the thing going properly...as Don said, the C:N balance. Regarding using RoundUp:
I turn my big pile with the tractor and weeds just get buried repeatedly. We only have chickens now and getting the manure out of the pen in tough. When we had goats, sheep, etc., the additions were easy. We scrounged fresh goat manure this spring from a friend's farm and the fresh manure had the pile steaming in two days when it was turned in. Horse manure has pretty good nutrients but is full of weeds, as the horse digestive system is inferior to other herbivores. Poultry manure must be composted prior to use as it is too high in nitrogen to apply directly. Rabbit manure can be applied directly, as sheep and goat if it is dried and in pellets. Cow manure generally is also composted as well. Don't put anything in the compost you don't want on your garden. As @Ken Anderson has shown, cardboard and paper are generally fine unless they have been treated with something, as is sawdust and such if you have a lot of nitrogen to go with it. Leaves can be made into leaf mold that is high in trace minerals and adds tilth to the soil, but it isn't really compost. Leaf mold can be made in small quantities by raking leaves into a plastic trash bag, spraying a small amount of water in, and closing it up for the winter. In most cases, it will be ready for use the following spring if you don't have really cold winters that will keep it frozen the entire time. Of course, you could bring the bags into a cool barn or such.
I don't have that luxury, so I let it take longer to compost fully. I'll occasionally turn it over with a pitchfork, but that just reaches the top of the pile. I also start harvesting from the bottom while I'm still adding compost to the top, which moves it around some and adds oxygen to the pile. I'm also more liberal in what I compost since I do not use my compost in food gardens. Rather, it goes into the flower garden in the back and onto my lawn, little by little, to build some more soil over the coal ash base. Hence, I use compostable cat litter and compost the cat waste and litter, which I wouldn't do if I were using it in a food garden. You can (in my opinion) use cat waste in food garden compost if you are willing to wait an extra year or so, but I'd rather not. We can get free compost from the town site, so I just use that instead. I could use the town compost for my flower gardens and lawn too, but that would require hauling the compost from the townsite, and if I wasn't composting my compostables, I'd have to haul that to the town's transfer station, and those extra trips don't make sense to me.
We have trees in wood all around the lawn so in the fall we put huge piles of leaves and grass on the pile. Last year, I tried the compost from under the pile after about eight years of sitting. It did not make good planter soil. Not sure why.