All Things Organic - The pros and cons of on-farm cleaning plants

By Ian Cushon
January 29, 2004

Until recently, organic farmers have been able to use seed from non-organic sources. However, changes to the seed rules now require organic farmers to use only organic seed for certified organic production. Some exemptions still exist related to lack of supply.

To qualify as certified organic, seed must be cleaned in certified organic cleaning plants. There are only a few of them on the Prairies and many of the biggest are busy cleaning for commercial organic markets. Regional shortages exist in many areas and transportation costs to distant plants add costs and inconvenience.

The use of organic seed is now the single biggest expense on most organic farms. This has many farmers thinking about using their own seed and cleaning it on the farm with their own equipment. There are several questions about whether an on-farm cleaning facility is the right choice. Accessibility to nearby certified cleaning facilities plays an important role in the decision. The cost of building and maintaining a cleaning plant can be high compared to the cost of using a custom seed cleaning service. If you only need to clean your own seed and most of your crop is sold without being cleaned and bagged, then on-farm cleaning may be an expensive alternative. If you can easily access a nearby certified facility, that may be your best choice. However, it's not always easy. Many pedigreed and commercial seed facilities have little interest in cleaning small lots of organic grain. The time and cost of switching to meet organic requirements and the paperwork and cost of organic certification limit the number of commercial cleaning plants that want to do this work.

Many organic farms also need cleaning facilities for marketing. Like the special crops industry, many organic products are sold cleaned and bagged. Considering the capital investment and operating and labour costs, the economics of setting up a cleaning plant may still not justify the risks for individual farms. As a result, several groups of organic farmers have built or are planning co-operative cleaning and processing facilities. If you have your heart set on running a full-blown certified organic commercial plant for custom cleaning, processing and bagging, then that is in another class. While these facilities exist on organic farms, in many cases they are the dominant business. Developing such a business requires careful study, a good business plan, lots of money and a lot of luck. Recent droughts and overcapacity have hit the pulse processing industry hard, with several high profile closures.

The basic principles of cleaning grain are not that complex, but setting up and operating an effective plant requires a lot of experience. If you are still interested in on-farm seed cleaning, here are the basic machines you should know about:

• Air screens are the workhorses of most cleaning plants. As the name implies, they use fans and various screen sizes to scalp (separate large unwanted heads and weed seeds) and sift (let the small unwanted seeds fall through and save the good seed). They also use air flow to remove chaff and lighter seeds.
• Indent machines use seed length and centrifugal action to separate material and seeds of different sizes. They are rotating drum machines with pockets that pick up and drop certain seed sizes or reject unwanted sizes. They were installed in many wooden elevators across the Prairies. Combined with an aspirator and scalping screen, the elevator machines were the number 32 and 33s that cleaned a lot of prairie seed over the years.
• Disc separators work in a similar way to indent drum machines, but the pockets are on rotating discs instead of inside the drums. They are often referred to as carter discs and come in various sizes. They are generally considered more accurate than indent machines but have less capacity.
• Graders use width separation as the primary sorting method. They are usually rotary screens that can also efficiently finish the sifting process while improving overall quality by dropping smaller or damaged kernels.
• Gravity tables are perhaps the most complex grain cleaning machines. They use air flow and relative density to separate seeds on an oscillating screen deck. Gravity tables can be used to clean out similar-sized kernels of differing densities or materials that other machines can't easily remove. Gravity tables are adjustable and allow almost infinite settings for seed separation and quality grading.

Two manufacturers have built machines that efficiently combine several machines in one. While no single machine will do everything, some will effectively clean on-farm seed that is easily cleaned in one or two passes. Additional machines will be required for more complex cleaning.

Ian Cushon
Moose Creek Organic Farm Inc.
P.O. Box 85
Oxbow, Saskatchewan
Canada, S0C 2B0

Tel. 306-483-5034
FAX 306-483-2799
Cell 306-483-8257
E-mail: coldridge@sasktel.net