The pictures on these pages will hopefully give herb farmers an idea of the simple equipment I use to dehydrate different parts of herb plants. The first photo shown, I spent $600 on materials and second hand blowers and heaters. The roller drum dryer I built not only dries herb but extracts dust and dirt in the process, and cost $1500. They are both waterproof and can be heat assisted by rolling them outside in the hot sun saving gas.
Last month I started a new project, building another dryer for myself. Because of the interest in growing herbs, the drying side of herb farming is a very busy time over the summer for us here at Pleasance Herb Seeds. We dry herb seed, our crops of echinacea and peppermint, as well as tomatoes and the occasional stick of timber for my half built house. They are very versatile machines.
The loading and unloading of drying machine, is a heavy task for even the strongest of backs and if the system of holding fresh plant material is not thought out properly, it then creates extra backbreaking work that no farmer wants.
Over the years I have tried several racking systems for all the different types of herbs and will display them here over the next few issues of this page.
I first started with a converted room in a shed, with a double hot drum system fired by wood. Cheap to run, if you have a paddock of wood to burn, but very time consuming handling herb and stoking fires all night. The rack system is ok for small amounts of herb but for larger crops you have to shift to a larger system of dehydration.
I tried an insulated shipping container next for larger crops and ended out so successful I had growers from all over the state wanting to dry big crops of 1/4 acre and up. This machine can hold three quarters of a tonne of fresh material (for example Echinacea) and when dry it can yield 230 kilos of dried hammermilled herb. Inside this container I built three bins from scrap metal, and designed it so the Echinacea would stand up, and hooked it up to a 12 inch blower from and old hotel air con system. I built a small but effective heating device running on gas made from a barbecue heating burner, and covered it over with a hood so no plant material would fall on it and burn the place down. All up It cost me $2000 for the container, $500 for the blower and motor, $32 for the gas burner and $100 for the steel needed to build the handling system.
It works great for larger crops, but sometimes I receive a load of herb like Feverfew or Comfrey and its all leaf. Well try and dry Comfrey successfully in a bin. I can be done but you need spacers in between the thick mass of fresh leaves. The trick is to not turn it into compost. If you make up some wire pipe looking things out of hinge joint fencing wire and throw them in with the herb, spacing the leaves out, you will dry leafy crops successfully. The temperature must be above forty degrees C with leafy crops, otherwise there is trouble.
Mould forms between the leaves and rots, forming a cloud of poisonous dust when unloading. It's a must to wear breathing apparatus when unloading and hammermilling a load of dried herb. If your working Feverfew, Phytolacca roots, Nettle or Rue you will understand why.
So I went to a rotating dryer system for the roots I was pulling up. I built an 8 foot long drum and put it in a cradle. Powered it with a small washing machine motor through a 250:1 gear reduction to turn it round and round. The hot air was pumped in through the main pivot arm which was on a set of six bearings. I had a machine that could hold a ute load of fresh material and a mixing machine all in one. I still use it today for drying seed and knocking rosemary leaf off the stems.
The new machine I built this month is a 1200 x 1200 mm drying box 2 meters high and having two levels of fixed racks, with another four levels of removable racks for heating up hammermilled herb that was not completely dry from a container load.
I built a frame from 25mm box steel and cladded it with sheet metal. I could Insulate it but I don't think it necessary yet as the air flow is hot, but not a great deal of moving air. Its a bit like the clothes dryers we used to have where a coat hanger method was used. Fruit dryers have a similar system.
The ultimate system is the same dryer running on the heat generated from the shed roof. More about this in the next issue in May 99.