Harvesting Comfrey

We are going to start our comfrey fields (about 5 acres) this week, and would like to know how to harvest it. What kind of drying will keep the leaves green? How many dry pounds can I expect per acre of comfrey field? Thank you for your time.

Comfrey requires some serious considerations in handling it from the field. It cannot be sun-cured, as it will tend to rot (mucilage). Moving toward (but not answering) your drying question, let the cut leaf come to a 50% sun-cure wilt, and then pick it up with a flail-chop to be taken to a drying facility (i.e. hop kiln, corn dryer, grain bin, etc.). Tobacco dryers and plywood kilns are other alternatives for dryers.
Comfrey is easy to grow, but the key to success with this crop lies in proper dehydration and handling. This aspect is proprietary, and can only be shared under non-disclosure/non-competitive contracts. I spent almost $10,000 and more than 2 years learning how to handle this crop. I used large vacuum pick-up systems and hop kilns.
Grain bins can be used, but must be modified. I am available as an outside consultant whenever this becomes more than questions. There are several papers at my website which also might be helpful.
www.nwbotanicals.org/oak/altagri/comfrey.htm
and
www.nwbotanicals.org/oak/altagri/farmproject.htm