Composting Weed Seeds
The general advice is that weed seeds should not be composted as while weed seeds will be killed hot composting providing an adequate temperature is maintained they will usually survive cold composting techniques and the advice is Do Not compost them. The problem is that if they survive the composting process, they will be in the compost you spread as a mulch soil improver and you will end up with a crop of weeds. Hence the advice not to add the seeds to the bin by pulling up the weeds before they seed but when community composting you may not have the choice others will fill your reception bin with weeds that are in seed.
When hot composting at 55oC for a week will most weed seeds and a month at 63 ° C) will kill the most resistant one as well as their roots. Amongst these resistant seeds are those of Common groundsel (Senecio vulgaris) which are shown in the photo.
However, many garden or allotment compost bins will not be large enough to reach and hold the right temperature and/or turned often enough to expose the seeds to the hot core of the compost. Exposing all the compostable material to sufficient temperature even when community composting with a large bin turned requires good management of the system and dedicated volunteers.
There are many composters who are accept that we weed seeds will survive as they “have a hoe” and are happy to deal with the seedlings as they germinate,
There is however another approach. Larry Hodgson the Laidback Gardener
(https://laidbackgardener.blog/2018/08/26/how-to-kill-weed-seeds-in-compost/) suggests the use of solarization to kill seeds at the end of a composting cycle by spreading a layer of compost on a hot sunny surface and covering it with a sheet of transparent plastic, held in place with bricks or wood. The compost will heat up in this mini greenhouse killing the seeds or any seedlings that germinate. This technique is dependent on hot weather and will require a suitable space.