I appreciate all the thought you put into this, and if nothing else I'm happy to have shown someone something new! Some thoughts are below. In general I think the biggest practical problem for me would be space to store the buckets plus finding a weeeee bit of motivation when it's the end of a gardening day and I don't want to deal with one more thing.
I was not familiar with this process until you mentioned it. An anaerobic process you are playing with in winter boredom that is supposed to increase microbes in the soil. I would expect the fermentation to kill any rhizomes or such (things like the nuts from nutsedge) and seeds too. There are a lot of seeds I don't want in my compost pile either. I'd think they are all targets for this processing. For your goal of neutralizing and recycling certain noxious weeds I'd think the process has possibilities. The devil is often in the details. You don't owe me any answers to these questions, just brainstorming things for you to think about.
Yeah, the seeds dying would definitely also be a nice benefit! Maybe adding one more stressor to any leftover plant diseases that end up in the compost too. Most of my weeds aren't the kinds that make seeds when they're small but some of my flowers could be dealt with this way before they spread. Calendula, and poppies, for example, will take over if I let them. They're nice weeds but there are limits.
You are playing with the process now. If you try this it won't be during the winter boredom months. How labor intensive is this? Will you have time during summer? I read about tapping run-off, just how and how often would you do that? Things like that.
The first bucket I did was two weeks worth of food scraps that I collected and froze while the bran was fermenting. As you might imagine, that gave off a ton of water, even the next day. The bucket I"m working on now has a couple of inches of old coir and potting mix in the bottom to absorb liquids, and so far nothing has come out. I can also get all the sawdust I'd need in the summer, so if I kept some buckets prepped with sawdust in them ahead of time I think I could skip the taps entirely. Even if it's not perfect, it's more likely that I'd be storing these in a barn or shed rather than my basement, and I still think it'd accomplish the goal of killing the weeds/seeds.
How much volume are you talking about. You can get the buckets and lids but do you have a suitable place to put them? How temperature sensitive is the process? I'd assume you continue collecting those weeds in the tub until you get enough for a batch, maybe collect other stuff to go with the weeds. Are those weeds of a size they'll fit in the buckets? I understand you don't want air trapped in there.
I mulch most of my gardens pretty heavily so the weed volume is fairly low. I could definitely fill some buckets, especially early and late in the season, but don't need to worry about filling barrels (although .. that's something to think about). I already use buckets to collect the weeds and already tend to pack them as I go, mostly to minimize trips to the pile. I
would need to add some bran as I went to do this properly, though I suspect a winter in a bucket with a top on it would accomplish the same thing with the lactobugs on the weeds themselves. The weeds are all small enough to go in buckets without problems.
How would you use the final products? My understanding is the prime benefit is to get the microbes, the stuff may not be broken down enough for the plants to immediately use the nutrients. I'm not real clear on that part of the process.
The food scraps I have right now are going to go in a tumbler with other compost, sawdust, and whatever other carbon and bacteria sources feel right to add at the time. An added benefits to saving food scraps this way, at least in theory, is that I can batch compost rather than continuously adding to a tumbler that's never finished. The scraps still look roughly the same after fermenting but they apparently break down pretty fast once they're in an environment that allows it. The main benefit to doing this inside in the winter with food scraps is that you can store buckets of food scraps without your house smelling like you're storing buckets of food scraps.
As far as the final products of the weeds .. I'm not sure. Some might get added to the tumbler, but I suspect I could just bury most under my mulch. People online bury fermented food scraps a bucket at a time in open spots in garden beds. Unless they have peat/coir based raised beds, I suspect that most of their nutrients are just leaching away since the c:n ratio is waaaay too low for the soil to be binding much. If nothing else I could always add the fermented weeds to my static pile once I was confident that the weeds were dead.
In theory it sounds great. How practical is it for you to actually execute it in the volume you are thinking about?
On paper I think it's all sorts of practical if I can find an out of the way place to put the buckets and forget them for a while. I suspect it'll mostly come down to motivation.
Thanks for 'talking' this out with me!