Welcome to ERPNext. Here’s wishing you every success with ERPNext and hope you have an awesome experience with ERPNext and here on the community.
Are you talking about a BOM for building/manufacturing the BOM?
Or are you talking about using the bin in the BOM for the Mushrooms that you grow.
If it’s the latter, I don’t think it is a good idea to build into the BOM for growing the mushrooms. I think you need a way to track the number of bins you’ve deployed and for that you can create a warehouse called Bins to be Deployed. Matter of fact, you should consider having a separate Warehouse for each of the Grow Bins and you can drop the bin itself into that warehouse. Then you add seeds, fertilizer, water and all the significant material that you use to grow your 'shrooms into each bin that’s setup, as I said, as a separate virtual warehouse on ERPNext. Once the 'shrooms are ready to be harvested, you use the direct materials in that warehouse and pass a manufacturing entry using the items (other than the bin) that are in that warehouse and produce the 'shrooms.
But will your 'shrooms all have a single item code? Or will grade your 'shrooms have different item codes (Like High Quality 'shrooms, Medium Quality 'shrooms and Low Quality 'shrooms and similar) and a typical harvest have a mix of these items? If you do, ERPNext supports this type of a configuration. You just have to do a Stock Entry Purpose: Manufacture and put in the Input Items and associate a Source Warehouse to the Input Items (which is the warehouse you setup for the bin) and you add all the output items HQMushrooms, MQMushrooms & LQMushrooms for High, Medium and Low quality 'shrooms and associate a Target Warehouse for these items. (You obviously would pick a more marketable name like AwesomeMushrooms, Mushrooms and ValueMushrooms). You need to associate a valuation rate for these items and you could attribute 55%, 30%, 15% as the Valuation rates for the HQ, MQ & LQ. With a bit of scripting or customization, you should be able to accomplish this without having to key in the valuation rates manually. Once the Input Items are flushed out the the warehouse, you should have just the Bin remaining and you can do a Stock Transfer of the Bin to the “Bins that can be Deployed” warehouse and start the process all over again.
Apologies for the long answer, but I am intrigued by your use scenario and it would be great to hear from you about your successes and challenges in using ERPNext for growing mushrooms.
ERPNext has a agri module. Please feel free to check that out too.
Hope this helps.