I have to say I’ve not seen any problems with composts or ‘errant bean seeds’ through composting all the bean plants the past three years. Biggest issue around here for beans are droughts and warm nights. I’ve just been building an over-wintering pile with:
1. Cardboard (four separate layers up the heap).
2. Comfrey leaves, carrot foliage, Sarpo Mira potato foliage and runner bean plants (again four levels).
3. Rotted horse manure as well as fresher horse manure with plenty of straw in it.
It’s already rotted down significantly in terms of volume reduction and I’m getting ready to cover it for the winter with polythene now we’ve had another good batch of rain yesterday.
I can also say that the health of plants this year in the second season of no-dig has been broadly better than previously, especially this years spring cabbages planted out three weeks ago – they have taken beautifully, grown significantly and look much better than last years (which produced a healthy crop anyway).
I’m sure I’ve still got a lot to learn about producing optimal composts when you don’t have enough material often to build a cubic metre pile in a oner. But I’ve certainly not yet found any issues about using garden waste in the compost bins.