Introduction of Commercial Shell Crushing Technology to the BC Oyster Aquaculture Industry

Final Report

Taylor Shellfish Canada ULC

AIMAP 2011-P17

Executive Summary

The disposal of waste shells from shellfish aquaculture is a worldwide issue. In 2006, the Canadian farmed oyster production was 12,488 tonnes valued at an impressive $18.5 million dollar industry. Sixty percent of this volume was produced in British Columbia.

As the production of oysters increase, so does the volume of waste shell. In British Columbia, waste shells have been recycled within the oyster farming industry as a substrate, known as ‘clutch' for settling oyster larvae. Although some oyster shell waste is recycled within the aquaculture industry, significant quantities of unused waste shell still remain.

Taylor Shellfish Canada ULC doing business in Canada as Fanny Bay Oysters (Fanny Bay) is one of the major growers, processors, marketers and distributors of farmed shellfish in British Columbia. Oyster shucking production at Fanny Bay Oysters' Union Bay site produces approximately 160,000 shells, weighing about 3000kg per day.

The following report is a full feasibility report of a shell crushing operation as we investigated the best technology for crushing large volumes of waste shell in the most efficient and cost-effective manner.

In our first study (Proposal A) we evaluate the various technologies that are used to reduce oyster shell volume for the purpose or lowering material handling costs and preparing the shell for secondary markets. Our study tested three different technologies that could grind the oyster shell into smaller particles. The three technologies were the dual rotor shredder, the hammer mill and the cage mill. To ensure versatility, each machine was tested utilizing the pacific oyster shell in the following conditions: dry seasoned, wet seasoned and green.

This report will demonstrate that while the hammer mill and dual rotor shredder yielded both advantages and disadvantages, the hammer mill is clearly the more robust and versatile machine for long term use.

Proposal B, is a full benchmark report that analyzes the different markets that currently exist for crushed oyster shells in Canada. The potential markets include the following: poultry and chicken feed, industrial gardening and soil amendments, eutrophication, restoration and regeneration, lime substitute for concrete, decorative use, medicinal use and industrial media blasting.

Our research demonstrated that there are several viable markets for crushed oyster shell by-products in Canada. In fact, there is an immediate demand for crushed oyster shells by the poultry industry which currently imports shells from the United States. It is also a cost effective solution for the rapidly growing issue of eutrophication.

There is currently no commercial scale shell crushing technology that is being used in British Columbia and this report clearly indicates that we have completed the marketing research to support the feasibility of a shell crushing operation in Canada. Along with the cost of the two systems required for this process (both mobile and stationary), we also were able to identify the best equipment for processing the oyster shells efficiently and in a cost effective manner. In addition, our benchmark report clearly demonstrates that there are many existing opportunities for crushed oyster shells in a variety of industries.

The introduction of a shell crushing technology in British Columbia is an opportunity to increase environmental performance and fill the needs of other industries. We believe that this technology will benefit the entire shellfish industry and Fanny Bay is in an excellent position to help introduce this solution and lead the way for sustainable production.

PROPOSAL A - Shell Crusher Test Results

1.0 Introduction

The purpose of the study was to locate a suitable technology to reduce oyster shell volume for the purpose of lowering material handling costs, and prepare for post processing for secondary markets. Secondary markets include animal feed supplements and water filtration.

Three technologies were tested - dual rotor shredder, hammer mill, and cage mill. Each machine had pacific oyster shell run through them in three different conditions - dry seasoned, wet seasoned, and green.

Both the dual rotor shredder and the hammer mill performed very well, while the cage mill is not a viable option due to material feed issues. All of the machines produced much finer particle sizes than expected. 

The hammer mill has the advantage of producing a larger range of particle sizes, and the ability to easily pass the occasional rock however at the expense of higher horse power consumption. The dual rotor shredder is also a good option. It produces a limited range of particle sizes, but consumes less horse power than the hammer mill. However it has more difficulty passing rocks through its system and maintenance is more labour intensive than the hammer mill.
While the dual rotor shredder and the hammer mill both have advantages and disadvantages in the short term; in the long term the hammer mill has the advantage of being a more robust machine for this application which leads to lower maintenance and down time.

2.0 Project Requirements

• Reduce whole and clusters of oyster shells down to a particle size of 20mm and below
• Machine should demonstrate the ability to feed raw material into machine with little bridging and jamming
• Machine should demonstrate it has the ability to process green shell, dry seasoned shell, wet seasoned shell
• Ability to process up to 10 tons/hour
• Economical to purchase and maintain

3.0 Study Variables

• Volume Reduction
  • Starting volume and weight
  • Post process volume
  • Density before and after processing
• Particle Size
  • Screen at several different sizes and determines particle size distribution
    • Oversized
      • 25mm opening screen for particles 25mm and larger
    • Coarse
      • 13mm opening screen for particles between 25mm and 13mm
    • Medium
      • 6mm opening screen for particles between 13mm and 6mm
    • Fine
      • Particles that pass through 6mm and finer opening screen
• Particles properties
  • Shape
  • Thickness

4.0 Shell Conditions

• Green Shell
  • Processed within 2 weeks of shucking
• Dry Seasoned Shell
  • Stored on land for a minimum of 2 years
  • Minimal moisture content of shell
  • Simulate seasoned shell in the summer months
• Wet Seasoned Shell
  • Stored on land for a minimum of 2 years
  • Soaked in tank for a minimum of 24 hours then drained
  • Simulate seasoned shell in the winter months

5.0 Machine Technologies Tested

• Dual Rotor Shredder
  
  The dual rotor shredder uses low speed and high torque counter rotating saw shaped teeth to reduce material to smaller particles by three actions: shearing, tearing, and fracturing. Shearing action involves the actual cutting of material like scissors. Tearing involves pulling the material with such force that it comes apart. Fracturing applies to materials that are brittle, such as glass, hard plastics, and certain metals, and tend to be broken or shattered.

• Hammer Mill
  
  The hammer mill is an impact type crusher that utilizes high speed rotating hammers to shatter and disintegrate the material being reduced. Size reduction hammer mills provide a finished product size that is dependent upon the size of openings in perforated screens; the number, size and type of hammers; the setting of adjustable grinding plates and the speed of the rotor.

• Cage Mill
  
  The cage mill is also an impact style crusher that uses high speed counter rotating bar cages to crush, grind, pulverize, blend and mix abrasive or non- abrasive, wet, and sticky materials. Material can be ground to different consistencies based on the number of cages installed and the speed at which the machine is run.

5.1 Machine Care and Feeding

• Batch Feeding
  
  Batch feeding involves dropping large masses of material into the hopper, either by some sort of grapple or loader. Batch feeding is common with appliance destruction, demolition work, or bale processing.
  
  While batch feeding is simple and straightforward, it can also be inefficient. If not properly sized for the job, batch fed shredders are more likely to clog or take on more than they can shred at one time.

• Meter Feeding
  
  Meter feeding involves introducing material to the hopper in a steady, controlled stream, usually by conveyor. If a material can be meter fed, the shredder can monitor its own intake and operate more efficiently. Meter feeding can result in fewer clogs and shut downs. This is the preferred method of feeding any of the machines tested in this report.

6.0 Double Shear Shredder Test Results

6.1 Dry Seasoned Shell Test #1

• Particle Distribution
  • 1” Mesh - 100% Pass through
  • 1/2” Mesh – 100% Pass through
  • 3/8” Mesh – 100% Pass through
  • 1/4” Mesh – 93% Pass through
  • 1/8” Mesh – 56% Pass through
• % Moisture - 12.0%
• Reduction of volume 49.6%
• ½ “ screen
• RPM 293
• Feed rate 7500 lb/hr

Notes:

• Machine clogged at 10,000 lbs/hr reduced feed rate to 7500 lbs/hr.
• Particle size vey small so increased screen size to ¾” to increase feed rate.

6.2 Dry Seasoned Shell Test #2

• Particle Distribution
  • 1” Mesh - 100% Pass through
  • 1/2” Mesh – 99.4% Pass through
  • 3/8” Mesh – 91.0% Pass through
  • 1/4” Mesh – 66.1% Pass through
  • 1/8” Mesh – 34.2% Pass through
• % Moisture - 12.5%
• Reduction of volume 48.0%
• 3/4 “ screen
• RPM 293
• Feed rate 10,000 lb/hr

Notes:

• Increased feed rate to 10,000 lbs/hr
• Increased screen size to ¾”

6.3 Wet Seasoned Shell Test #3

• Particle Distribution
  • 1” Mesh - 100% Pass through
  • 1/2” Mesh – 100% Pass through
  • 3/8” Mesh – 91.8% Pass through
  • 1/4” Mesh – 68.5% Pass through
  • 1/8” Mesh – 36.3% Pass through
• % Moisture - 13.4
• Reduction of volume 50.2%
• 3/4 “ screen
• RPM 293
• Feed rate 10,000 lb/hr

Notes:

• Wet shell had a slightly finer particle size than the dry shell

6.4 Green Shell #4

• Particle Distribution
  • 1” Mesh - 100% Pass through
  • 1/2” Mesh – 100% Pass through
  • 3/8” Mesh – 96.0% Pass through
  • 1/4” Mesh – 83.1% Pass through
  • 1/8” Mesh – 54.2% Pass through
• % Moisture - 23%
• Reduction of volume 54.2%
• 3/4 “ screen
• RPM 293
• Feed rate 10,000 lb/hr

Notes:

• Green shell contained a large volume of sand
• High moisture content helps to reduce shell to finer particles than dry shell

6.5 Double Shear Conclusions

• The double shear roller worked very well reducing all types of shell down to a coarse grind and at fairly low hp requirements.
• While it is a simple machine with few parts to replace the typical wear parts requires 6-8 hours to complete.
• There is some adjustability of the grind size but it is limited to larger particles.
• Abrasion tests indicate that the wear expectations for the clean shell is about $0.60/ton wear cost and for green shell which has a higher sand content will have about a $1.00/ton wear cost.
• The machine was able to pass the occasional rock but the wear on the machine was immediate. As a result wear cost may be higher depending on the rock content of shell material.
• Machine cost sized for our application $39,980.
• Annual Electricity ($0.11/kWh) cost of machine based on operating 2000 hours/year - $3278/year.

7.0 Hammer Mill Test Results

7.1 Dry Seasoned Shell Test #5

• Particle Distribution
  • 1” Mesh - 100% Pass through
  • 1/2” Mesh – 100% Pass through
  • 3/8” Mesh – 100% Pass through
  • ¼” mesh – 99.8% Pass through
  • 6 Mesh – 96.8% Pass through
  • 20 Mesh – 52.9% Pass through
  • 40 Mesh – 33.8% Pass through
  • 60 Mesh – 22.3% Pass through
• % Moisture - 7.6%
• Reduction of volume 52.5%
• 3/8” bar grate
• RPM 1800
• Feed rate 10,000 lb/hr

Notes:

• Due to the finer grind size additional screen sizes were added

7.2 Dry Seasoned Shell Test #6

• Particle Distribution
  • 1” Mesh - 100% Pass through
  • 1/2” Mesh – 100% Pass through
  • 3/8” Mesh – 100% Pass through
  • ¼” mesh – 100% Pass through
  • 6 Mesh – 99.3% Pass through
  • 20 Mesh – 79.1% Pass through
  • 40 Mesh – 58.6% Pass through
  • 60 Mesh – 41.7% Pass through
• % Moisture - 7.9%
• Reduction of volume 48.0%
• 3/8” bar grate
• RPM 3600
• Feed rate 10,000 lb/hr

Notes:

• Increased RPM to 3600 which produced finer particle size

7.3 Wet Seasoned Shell Test #7

• Particle Distribution
  • 1” Mesh - 100% Pass Through
  • 1/2” Mesh – 100% Pass through
  • 3/8” Mesh – 100% Pass through
  • ¼” mesh – 99.5% Pass through
  • 6 Mesh – 99.9% Pass through
  • 20 Mesh – 76.0% Pass through
  • 40 Mesh – 54.5% Pass through
  • 60 Mesh – 35.6% Pass through
• % Moisture - 13.0%
• Reduction of volume 46.0%
• 3/8” bar grate
• RPM 3600
• Feed rate 10,000 lb/hr

Notes:

• Unlike the shredder, the hammer mill produces a larger size particle with higher moisture content shell.

7.4 Green Shell Test #8  

• Particle Distribution
  • 1” Mesh - 0% Pass through
  • 1/2” Mesh – 0% Pass through
  • 3/8” Mesh – 0% Pass through
  • ¼” mesh – 0% Pass through
  • 6 Mesh – 0% Pass through
  • 20 Mesh – 0% Pass through
  • 40 Mesh – 0% Pass through
  • 60 Mesh – 0% Pass through
• % Moisture - 21.0%
• Reduction of volume 0%
• 3/8” grate
• RPM 3600
• Feed rate 10,000 lb/hr

Notes:

• Mesh too fine for green shell. It coated the inside of the machine and no material exited. Changed machine from 3/8 bar grate to ¾” hole mesh.

7.5 Green Shell Test #9  

• Particle Distribution
  • 1” Mesh - 100% Pass through
  • 1/2” Mesh – 100% Pass through
  • 3/8” Mesh – 100% Pass through
  • ¼” mesh – 98.1% Pass through
  • 6 Mesh – 85.3% Pass through
  • 20 Mesh – 32.0% Pass through
  • 40 Mesh – 16.0% Pass through
  • 60 Mesh – 11.1% Pass through
• % Moisture - 21.0%
• Reduction of volume 54.2%
• ¾” round hole mesh
• RPM 3600
• Feed rate 10,000 lb/hr

Notes:

• After switching to ¾” round hole grate, green shell passed through the machine without clogging.

7.6 Hammer Mill Conclusion

• The hammer mill as a machine has the most versatility for the application. By adjusting the speed of the machine and the size of the grates the machine has the ability to reduce the oyster shell from coarse grind to flour consistency. The only draw back to this machine is the higher HP requirement than the double roll shear crusher. More HP is required to reduce the shell to a finer size.
• The hammer mill is a very simple machine with all of the wear parts easily changed with in an hour. Also to change grind size is a simple change of sorting plates which is about a 20 minute procedure.
• Abrasion tests indicate that the wear expectations for the clean shell is about $0.60/ton wear cost and for the green shell (which has a higher sand content) about a $1.00/ton wear cost.
• Machine cost sized for our application $46,478.
• Housings can be made of 304 or 316 Stainless for corrosion resistance at additional expense.
• Annual Electricity ($0.11/kWh) cost of machine based on operating 2000 hours/year - $12,298/year.

8.0 Cage Mill Test Results

8.1 Dry Seasoned Test # 10  

• Test never completed due to feed throat restriction. We were never able to successfully feed any material through.

8.2 Cage Mill Conclusions

• This machine is not a viable option for this application.

PROPOSAL B - Market Opportunities:

In British Columbia, waste shells have been recycled within the oyster farming industry as a substrate, known as ‘clutch' for settling oyster larvae. Shellfish hatcheries also recycle shell by crushing and grading it to produce small chips, which are then placed into tanks with settling oyster larvae to yield individual oyster seed.

Finding resourceful ways to utilize oysters shell waste has been studied and pursued around the world for many centuries. Known for the calcium and phosphorus nutrients benefits, historically, crushed oyster shells have been utilized in a variety of by-products such as agriculture fertilizers, poultry feed, sand and liming agents to create construction material and clay to make pottery.

Most recently, waste oyster shells have been used to control eutrophication since pyrolyzed shells can efficiently and economically remove phosphates from wastewater.

We analyzed the different markets that currently exist for crushed oyster shells to ensure that there are feasible opportunities for oyster shell by-products within Canada. This helped to determine which markets to actively pursue as well as the consistency and quality of crushed oyster shells that will be required by certain markets.

Our research concludes that there are several viable markets for crushed oyster shell by-product. In fact, crushed oyster shells are currently in demand by the poultry industry. It is also a cost effective solution for the rapidly growing issue of eutrophication.

At a time in which waste shells from shellfish aquaculture is a world wide issue, Fanny Bay has the ability to help provide a solution that could benefit the entire shellfish industry by promoting better waste management and transforming the waste into usable by-products that will assist other industries.

Currently there is no commercial scale shell crushing technology that is being used in British Columbia. Large quantities of shell waste are becoming landfill when industries such as the Canadian farming industry have been importing crushed oyster shells from the United States for chicken feed. This seems to be unnecessary when we have the ability to provide quality product in Canada.

The introduction of shell crushing technology is an opportunity to increase environmental performance, create sustainable production and fill the needs of other industries. And with a creative marketing strategy, launching crushed oyster shell products to the Canadian market could be relatively easy and cost effective.

Project Report Conclusion

We are extremely satisfied with our report as the results have confirmed that the introduction of a shell crushing technology in British Columbia would benefit the entire shellfish industry by reducing the volume of waste shells. We have measurable data that indicates that a shell crushing technology will create a significant economic benefit from the reduction of landfill costs, in addition to promoting sustainable production.

Our tests have determined the most efficient and cost effective shell crushing technology is the utilization of the hammer mill; the most robust and versatile machine for long term use. We have also established the cost required to implement and maintain a hammer mill machine for the purpose of large volume shell crushing.

Our bench mark study has revealed that there are many existing markets for crushed oyster shells by-products in Canada. We confirmed that crushing waste shells will not only reduce the volume of waste to landfills, but also provide viable products for a variety of industries. Understanding which markets are currently in demand for crushed oyster shells such as the farming industry, has helped establish which markets require large quantities of crushed oyster shells and which industries to actively persue.

During our research, it has also been revealed that sustainable standard required by the industry is that oyster shells be 100% recyclable in order to be classified as a sustainable green project. Major buyers such as Whole Foods are now demanding that shell disposal be responsible and completely recyclable. In fact, they encourage restoration and regeneration and request that shells not be disposed of as garbage and sent to landfills.

In conclusion, the introduction of a shell crushing technology in British Columbia will increase environmental performance and fill the needs of other industries. Equipped with the knowledge and data provided within this report, Fanny Bay is in an excellent position to help introduce this solution and is poised to lead the way for sustainable production.