Seed Cleaning Facility Guide

A guide for those considering building a seed cleaning facility

To view or download the entire PDF, click below.

SEED CLEANING RESOURCE FACILITY MANUAL

TABLE OF CONTENTS

1. Introduction

2. Seed Cleaning Tools Guide

3. Module Zero

4. Module One

5. Module Two

6. Module Three

7. Equipment Specification Table

8. Equipment Manufacturer Resources

9. Cleaning Operation Resources

INTRODUCTION

The art and science of seed cleaning is broad and complicated. Many seed cleaning facilities are primarily for agricultural production and are often designed to clean only a few crops. A farm combine, for instance, is itself a one-person harvester and seed cleaning machine and operates all in one, collecting stalks in one end and delivering cleaned kernels from the other. Given that native seeds come in all sizes, shapes, weights, etc., cleaning them is nonstandard and is more similar to a Rube Goldberg laboratory- with any number of different types of machinery, including combines, sometimes used in tandem, all to maximize cleaning efficiency.

A word about weed seed. Any weed seed that ends up in the harvested bulk material needs to be separated from the desired crop seed. Sometimes agronomic practices can be employed that ensure the weed seed will not get harvested with the crop seed, but that is not covered in this document. If the weed seed differs sufficiently from the crop seed in shape, size, or weight, then there are steps in the cleaning process that will ensure it can be separated out, provided the right equipment is available. A final note. The presence of any state or federally listed and prohibited noxious weed that remains in the finished clean crop seed, will make its sale to end users illegal. Careful planning to exclude weed seed is a critical step in the seed cleaning process.

Given the mostly underdeveloped state of regionally and locally based native plant material (NPM) supply chains, the ability to commercialize the production of regionally native, genetically appropriate seed is lacking in many places. However, many more growers could be encouraged to produce regionally native perennial grasses and herbs in helpful quantities if the infrastructure was in place to grow, clean, store and market them efficiently.

There is a growing interest in growing NPMs, but many potential producers are new to production, don’t know where to start, are short on the technical knowhow, and lack the capital to invest in the machinery and infrastructure to begin a business or expand into new markets. However, not all of the infrastructure and equipment needed for a large, regional operation is needed by a small startup.

Beyond the more modest level of investment needed for individual growers to clean their own seed, it is possible and desirable that larger facilities could be run as cooperatives or fee based operations in service to growers of varying production levels.

Our objective is to incrementally break down into steps the necessary components of a new seed cleaning operation, from a basic level to an advanced, larger capacity level. We break the process down into four modules showing the costs associated with each module. We begin by considering the facility requirements, the initial tools, and the staffing needs that we recommend to get started. Progressing to the next module, we consider the set of tools and equipment that would expand one’s ability to clean seed more efficiently and effectively. We will introduce many tools and pieces of machinery used in the NPM seed cleaning industry, describe what they do, how they work and consider the varying sizes and potential place for them within a seed cleaning operation. We will list the names of manufacturers, models, costs and contact information for each piece of equipment (current as of 2020).

From there, we will provide information on secondary issues such as expected equipment usable life (depreciation), footprint, operating space requirements, and filtration requirements. We will also discuss comprehensive facility-wide filtration systems, including their own purchase prices and costs of maintenance.

Our basic assumption is that the reader is considering cleaning and processing seed collections of many varying sizes and shapes, not just one or two species. We also assume that the producers are drying the seed elsewhere, prior to the cleaning of the seed. Most often seed will not be cleaned immediately after harvest, and the collected bulk material must be stabilized by removing excess moisture from the material. Oftentimes, this is done right at the production site or in a separate building from the seed cleaning facility. Additional staff time and space requirements beyond our estimates would be required if seed drying and holding of stabilized bulk material was incorporated into the cleaning facility itself.

From the earliest stages of designing a facility, consideration of the size of the building and the intended functions of the building must be considered. The size of the building will inevitably limit the amount and kinds of machinery that it will house and potentially limit further expansion should it prove desirable. Oftentimes, a particular arrangement of machinery is desirable to facilitate the flow of work from one machine to the next, thereby increasing time efficiencies. Similarly, it may be desirable to isolate certain functions, if space and costs of construction allow for it. For instance, a producer may want to have an open-air building for dusty threshing or a separate building for seed storage.

There are many other brands, models, types, and sizes of virtually every machine listed here. The world of seed cleaning machines is vast with many useful tools yet to be developed or adapted to seed cleaning. Also, new machinery can be cost prohibitive. Fortunately, much of this equipment is durable and there is a large market for used equipment. Many used models are very effective, albeit generally, not as effective as their more modern counterparts. We have included contact information for those used seed cleaning equipment brokers we are aware of (there likely are many others), as well as some additional vendors for some of the equipment we’ve described. Inclusion or exclusion of a make and model of any particular equipment is neither an endorsement nor a rejection of any particular piece of equipment. Decisions about specific makes and models are solely that of the reader. Similarly, exclusion of a type of equipment is neither an endorsement nor a rejection. We ourselves may be ignorant of or may have no personal experience with a particular type of equipment. Seed cleaning and native seed plant material development (NPMD) are constantly changing.

Similarly, we are not responsible for the estimates we have attached to materials, equipment, real estate costs, buildings, utilities, taxes, staffing, etc. We are merely hoping to provide the reader with a ballpark estimate of overall costs to operate at the various levels of production described. We make no claim to knowing or having any expertise in federal, state, municipal and or local laws that may require additional expenses or may impose restrictions. The goal of this document is to aid those starting out to determine for themselves the best pace and direction of their operations by providing basic information to help them make sound decisions and to educate themselves further going forward.

SEED CLEANING TOOLS GUIDE

Machine Tools

Threshing and Winnowing

Threshing is the process of exposing seed by breaking up seed head and stem material, often used in the early stages of processing seed. A threshing machine is set up with beaters within a chamber that rasps the plant body. All threshers have an inlet for feeding. Some threshers have a walker or conveyor that directs seed and chaff into separate piles. Threshing is generally a very dusty process.

Winnowing is a process by which chaff is separated from grain, usually by weight, size and density. Winnowing usually follows threshing and will be discussed in its own section.

Threshing Tools

Standard Thresher

The standard thresher comes in many forms, from bundle and plot threshers which combine the threshing and winnowing processes, to simpler designs that thresh but do not winnow, and from mobile to stationary units.

Brush Machine

A machine that uses brushes connected to a beater bar set inside a cylinder that may or may not feature gauged holes. The brushes sweep the interior of the cylinder to aid in the removal of pappus, fluff or seed hulls. Brush machines can be retrofitted with a vacuum seal modification that can be added for dust reduction.

There are several sizes and brands of brush machines. The Lab size is useful for small batch seed cleaning but is suboptimal for anything larger. The mid-size machine is recommended for the typical collection because of its versatility. The large model is used more with extra-large quantities of bulk material.

Hammer Mill

The hammer mill is a threshing device that spins metal arms to break down hard substances. In native plant seed cleaning, this is only used with variable speed motor for breaking seeds out of hard seed shells. It is very important to use this only on hard seeds and at a slow rotation. Hammer mills are used for many purposes in addition to seed cleaning and can be very destructive to seed if used improperly. Many different screen sizes are available.

De-awner/De-bearder

This is a specialty machine used to remove hairs or awns or to break up head material and to separate heads, designed with an enclosed case and a shaft with staggered metal beater. The de-bearder runs at a lower speed than a hammer mill and separates materials by using friction and beaters.

Combine

A stationary combine on a smooth floor to break down bulk materials. This is a quick and effective method of pulverizing stems and seed heads.

Winnowing

Winnowing is the separation of seed from other inert material and/or undesirable species and was traditionally performed by shaking or tossing threshed grain and allowing the wind to carry away the lighter dust and plant material. The following machines can achieve that separation using size, weight and density using air and screens.

Winnowing Tools

Fanning Mill

The fanning mill is a seed cleaning tool that holds single or multiple shaking screens that shake over a variable speed fan, used to separate material both by size and weight. This is not a perfect air separation, so success is generally achieved by having appropriately sized screens, proper distributions of fed materials, adjusting airflow and by running the seed through multiple times.

The fanning mill is a vital machine in the seed cleaning process. Multiple sizes of screens are available between several manufacturers, but all have the same basic design. Cleaning efficiency increases when this machine is manually fed. Very small models called office testers are available; they are useful for small lots or testing screens sizes for larger lots.

Gravity Table

The gravity table is used to clean seed by weight and density through vibration, tilt and upward air flow. This is a more challenging machine to master but has proven useful in many seed cleaning facilities to separate out similar sized seeds or to aid in scalping early on in a seed cleaning process. The size of the gravity table is important due to the amount of material that needs to flow across the machine to be effective, and several different sizes are available. Ability to have continuous flow of material is necessary.

Aspirator/Continuous Airflow Seed Separator

This is a continuous air flow machine is a finishing tool designed to aid in removing dust and light chaff. A viewport is typically installed for the operator to monitor material flow and make fan speed adjustments as necessary.

Indent Cylinder

The indent cylinder is a finish cleaning machine used to separated small sticks and undesired seed. It consists of a shell with a spinning cylinder around an interior trough. The spinning cylinder has indents or dimples that separate seed by size using centrifugal force. The indents accept the material small enough to fit within and drops it into the trough. The rest of the material moves through to the end of the cylinder, while the trough contains an auger that moves the lifted material to a different exit. The cylinders are interchangeable and are available in 45 different sizes.

Three sizes of indent cylinder are available: Lab, Medium and Standard. The Medium version is cost prohibitive, and the Standard indent can be spatially prohibitive. The cylinders of the Standard machine are fairly difficult to change so many operations have multiples of them for their most commonly used indent sizes. This machine is best used when material is fairly clean and is the most efficient when fed with an automatic feeder. This is a final cleaning machine within a cleaning system. The Lab model is best suited for small to medium-sized seed cleaning facilities because it can be set up easily, run continuously and occupies limited space.

Rotary Drum Seed Cleaner

The rotary drum seed cleaner is designed to first separate by air then using a drum cylinder screen and tilt to separate material by size. Similar in design to an indent cylinder but uses openings instead of dimples to help scalp larger material from small. This is similar to a fanning mill in ways but may be better suited for flowable materials. This machine could also be used as an early step in the process to remove general dust and assorted chaff before using a finish cleaning machine.

Conveyors and Feeders

Vibratory Conveyor

A conveyor that uses vibration and gravity to move material. Vibratory conveyors are easy to clean without seed loss. Most often suited for finished or near cleans seed but may have broader applications.

Belt Conveyor

A motor driven conveyor useful for moving material in elevation and or across a span. There are many different sizes, lengths and angles with some seed loss. Getting the correct belt conveyors for your operation is very useful.

Bucket Conveyor

A conveyor that uses buckets to move material up from a lower level to a higher level. Bucket conveyors can be very useful for systematic cleaning and moving fairly clean seed from one machine into another for a continuous flow. Can be difficult to clean and may need modification for least amount of seed loss but has a small footprint when space is limited.

Common Fabricated Feed Bin

A bin that holds and conveys material in systematized mid to large-sized seed cleaning facilities. Generally, material of one seed lot is dumped into the feed bin. When activated and set to the correct speed, it offloads slowly to a secondary conveyor directed to another cleaning machine. This can take the place of a person hand feeding a large amount of material and allows them operate two or more processes simultaneously.

Drying and Storage Equipment

Following field collection, drying of bulk plant material must begin immediately, both to prevent rotting and mold, and to prevent early germination from excess humidity. Bulk material drying can be accomplished by several methods, but all require adequate air circulation over the entirety of the plant material. This can be as simple as the frequent turning of vegetation spread on a floor, or other methods more economical to labor and floor space as described below.

Drying Racks

For small collections and production, a drying rack system can be easily fabricated with a modest materials budget. The design is modular, consisting of a deep base box housing a powerful fan. Racks with wire mesh bottoms can be stacked on top, each containing a collection or a portion of a collection of bulk seed each contained in mesh bags. Racks can be stacked vertically until adequate airflow through the system becomes restricted and remain stacked until the material is dry. While dimensions can be altered to suit space requirements, the following system can be manipulated by one person yet is large enough to accommodate several medium-sized collections at once.

Base box: 18-24” x 4’ x 8’
Racks: 1” x 4’ x 8’ with a pair of 4’ long 2x2s in the center, shoulder-width apart; bottom made of galvanized welded wire mesh.
Fan: Industrial fan mounted into a hole in the base box.
Mesh bags or sheets: For use in storing the bulk material inside the drying racks. The mesh gauge must be smaller than the seed diameter.

For midsize to large seed production, seed drying can be difficult and expensive. Creating a forced air-drying area indoors often requires fabrication and space. Most agricultural systems for drying are set up for flowable seed (such as corn or soy), that is already clean. This does not mean that some hidden drying systems of the past aren’t out in the world, they are but they are few and far between. Some native seed operations have fabricated a bin system that is similar to the smaller drying racks, just larger, with larger fans. This is a good system, but still fairly limiting if you consider certain species needed in extremely large quantities such as for post wildfire reseeding over large acreage. For very large collections a more elaborate drying system is necessary.

Filtration

Seed cleaning facilities can generate a tremendous amount of dust, which presents both a breathing hazard to staff working in the facility and an explosion hazard when fine particles concentrate too heavily in a confined space. Some machines are equipped or can be retrofitted with dust collectors, and combined with air circulation in the shop space, this may be an adequate safety system for a small facility. Larger facilities with multiple machines running simultaneously typically require a custom filtration system or ventilation system to meet dust collection needs.

Storage

Short term bulk material storage will be needed while awaiting seed cleaning. This can often be a challenge when considering your space. Once a species is dried, having shelving, bins and/or hanging system will be essential. Ideally, seed would be cleaned immediately after storage but in the real world it may sit for a duration of time. Remember, the longer this seed sits in high humidity areas the more it will lose viability. Having a low humidity, cool storage unit for this generally is not feasible but may be worth it considering the cost of some of this seed.

Conversely, long terms clean seed storage is a matter of great importance. Ideally all orthodox seed is being used on a restoration site or for production within 5 years. Some seeds may store longer and some shorter but as a general rule of thumb you should be storing seed in a relative humidity of 20% and as cool as possible. Viability will go down regardless of where you store it but the cooler and less humid the area the more likely your seed will stay viable longer.

There are OSHA and local fire department rules and regulations that are beyond the scope and expertise of this document. Health and safety issues should always be addressed by appropriate professionals and with a full knowledge and compliance with local, state and federal laws and regulations.

Module 0

Module 0 is a hypothetical model designed for a very beginning stage operations that could be set up in most spaces. This module considers the use of used machines available on the market, an air-conditioned area for storing seed, basic drying racks and hand cleaning tools. The goal of this module is to recommend a modest investment in tools and startup costs for new organizations getting started in small production and wild collections. Module 0 is not sufficient for processing increased seed and other large quantities.

Module 1

This module is an attempt to breakdown of the costs associated with building a brand-new facility, the tools to get started and potential operating costs. This is hypothetical, with the goal of understanding what the costs incurred would be in designing and implementing a ready to use seed cleaning facility with short term and mid-term seed storage already in place. The tools chosen for this module are mainly for cleaning and thrashing small to medium amounts of bulk seed and wild collected seed. This Module and the tools selected would be limiting for large seed production and would likely only be able to clean hundreds of pounds per day.

Module 2

This Module adds additional machines, staff, and filtration to Module 1 with the goal to increase production. In this module we add important varieties of threshers and extra fanning mills. Also, it would be able to clean more efficiently by utilizing feed bins and conveyors in order to directly feed the cleaning machines. This module, plus module 1 would potentially be able to clean around a thousand pounds per day, more or less depending on what you are cleaning and how large your lots are. Beyond that, within this module we would recommend putting in an air filtration system for the health and safety of employees.

Module 3

This module is an addition, to Module 1 and 2, of very large tools and more staff for the potential to greatly increase your seed production. The goal in investing in this additional equipment would be an order of magnitude increase in seed cleaning capacity, including large lots of bulked seed with systematized movement of the material, especially for species such as graminoids used heavily in restoration work. Many additions could be made in this module and will depend on your operations and desires. Over time you will see your bottleneck issues and consider more cleaning machines, more conveyors, more space or more hand cleaning tools.