Can you say more about what you are hoping to obtain, or avoid, by having your worm bedding be "organic"?

The USDA does not certify worm bedding, so USDA certification is not relevant. You could look for OMRI (Organic Materials Review Institute) certified products, which are products to be used in organic operations including farming, gardening and livestock raising. Looking at the list here

http://www.omri.org/omri-lists/download

under "crop products,' I see coconut coir, compost, and peat moss products listed. These are all suitable to use for worm bedding. I don't know about expense. You may have to mail order if you can't find these products near you.

Other environmental factors to consider are the energy and resource cost of using materials that must be processed, packaged and shipped, when you may instead be able to substitute the use of materials that are close at hand, free or very low cost, and which can be diverted from the waste stream or recycling stream.

Peat moss is additionally concerning because it is mined and is not renewable within any reasonable time frame. Coconut coir is a waste product, but it also must be transported long distances from the tropical regions where it is produced. (An alternative might be crop wastes from products that are organically grown in your locality.)

I primarily use shredded cardboard and paper as worm bedding. I don't think ordinary cardboard and paper products are "contaminated" with anything specific that I need to be concerned about.

You could also use leaves from your own trees, or yard waste from your own property.

Organic is a very, very, cough, VERY loosely defined term. Get yourself some coconut coir or some peat moss and don't worry about the fine details. Both are good materials and your use in a worm bed probably amounts to some 0.001% style figure of overall usage of either of those products,

From the USDA
"Organic agriculture produces products using methods that preserve the environment and avoid most synthetic materials, such as pesticides and antibiotics. USDA organic standards describe how farmers grow crops and raise livestock and which materials they may use.

Organic farmers, ranchers, and food processors follow a defined set of standards to produce organic food and fiber. Congress described general organic principles in the Organic Foods Production Act, and the USDA defines specific organic standards. These standards cover the product from farm to table, including soil and water quality, pest control, livestock practices, and rules for food additives.

Organic farms and processors:

Preserve natural resources and biodiversity

Support animal health and welfare

Provide access to the outdoors so that animals can exercise their natural behaviors

Only use approved materials

Do not use genetically modified ingredients

Receive annual onsite inspections

Separate organic food from non-organic food"

Pretty vague guidelines. Pretty much says use/do whatever you like as long as it is not a genetically modified product.

Parsely,

Thanks so much for the suggestions and the tip on OMRI. Perhaps I can find a local feed store that sells OMRI approved straw? Coir will do in a pinch, but I would prefer to stay more local (Nor Cal) and less expensive. I'm very much interested in reducing my footprint. BTW, my non-organic plant based waste is all either recycled or composted through my municipal waste system, so none of it is ending up in land fill.

I wonder if I can get ahold of organic corn stalks, or sugar cane pressing (bagasse?) or rice hulls, or something? I'm not even sure where to look for those kinds of things.

Potato,

Yes, "organic" is a rather loosely defined term, but quite a bit falls under "Only use approved materials"... and that regulation is exactly what I'm after.

For example, I do not want to introduce formaldehyde into my garden. Many paperboard products (including many cardboards and some newspaper inks) use formaldehyde in their glue and binder chemistries. Does the formaldehyde breakdown somewhere between the worm bin and the salad on my plate? It depends a great deal on conditions, but generally not completely. Even so, many of the break down products are also known carcinogens and several of these are clearly taken up by various leafy greens (kale, fennel, artichoke, are some of my favorites). Formaldehyde is only one example of a very large set of chemicals that I want to completely avoid introducing... none of which are approved form use in "organic" produce or products.

Right now, my worm bin is fed 100% with the "organic" plant waste generated by my garden and my "organic" vegetable kitchen scraps. But it is too wet and to rich, and so I am looking for a high carbon, organic, supplement.

Assuming you've already tried contacting various organic farms, shops and restaurants... more woody waste may be the easiest for you to source. Specific to california (as I heard due to biomass energy plants shutting, there's now an excess), organic nut growers - you'd mostly be getting hulls and shells, which would be very high 'carbons' and dry, kind of like smallish woodchips, but should be fine with your wet kitchen waste. With nut shells, like from almonds or pecan shells, you wouldn't need very much and they'd break down slowly - probably fine at stage of harvesting your vermicompost, as long as you're not trying to sell/give to those who want 'pure' vermicompost. In the end, organic/natural sawdust or woodchips from clean forests would probably work too. Let us know how it works - only general issue with sawdust is that it's maybe a bit too fine and can get compacted and possibly anaerobic, so turn from time to time.

Yard waste is debatable as many people will use chemicals of some kinds and this being the case is not a good addition. For myself I blend coir, peat, shredded paper, a little shredded cardboard, handful of compost and coffee grounds. Some people say just use shredded paper and cardboard, those items very moist still dont work for me by themselves.

Try adding some leaf mould as bedding. I did a clean-out on one side of my bin and re-stocked it with shredded newspaper and leaf mould, then added some of my usual kitchen scraps. Within a few days the new side is thick with worms loving the the new stuff! Very few worms left on the older side so I'll probably harvest that side next and replace with the leaf mould/newspaper mix.

I wouldnt worry so much about all the details about whats organic and what is not. Try to maintain a nice balance of greens and browns and things will be fine , it will not be too wet or too dry if the balance is correct. Do you have drainage/leachate? I do not nor have I ever. If you use a drainage tray is it just dry , moist , or wet . That should give you a good reading on your bedding, whether you need to adjust something or not. In my opinion wet is the worst of the three options. Just like in your own life good balance is what we strive for and the worm bin should be no different.