RAW MATERIAL MIXING USING COMPOST MIXERS

Revision Date: 05/00
Process Code: Navy/Marines: N/A; Air Force: N/A; Army: N/A
Usage: Navy: Medium; Marines: Medium;Army: Low; Air Force: Low
Compliance Impact: Low
Alternative for: N/A
Applicable EPCRA Targeted Constituents: N/A
Overview: Compost mixers are used to mix raw materials such as food, yard waste, paper, and sewage sludge uniformly before composting. Mixing is an important step to distribute the carbon and nitrogen materials evenly and to assure fast, clean smelling decomposition. For materials such as food waste and sewage sludge, mixers can be used to incorporate bulking agents such as wood chips that add carbon to the mix and break up wet clumps.

Mixers are large containers with mobile paddles that are used to mix compostable materials. They are used for larger composting operations where (1) mixing with a loader is impractical, or (2) compost recipes require precise mixtures of carbon and nitrogen. The paddle mixer, pugmill mixer, and rotary drum mixer are the most common compost mixers. The units may be stationary or mobile, and may be powered electrically or by diesel engine. Some pieces of equipment designed for mixing other products such as animal feed can be used to mix compost.

Compost reduces the amount of waste to be disposed. Complete recovery of yard waste will reduce the amount of waste disposed in landfills by an average of 15.9% (EPA, 1994).
Compliance Benefit: Composting will help facilities meet the requirements under Executive Order 13101 requiring executive agencies (e.g., DOD) to incorporate waste prevention and recycling in their daily operations.

States and/or localities may have additional regulations on composting which should be followed. The compost mixers may increase fuels on site which may increase a facility’s need to comply with SARA (40 CFR 355 and EO 12856) reporting requirements and SPCC (40 CFR 112) issues. In addition, the mixers may also contribute to a facility’s need for an air permit (40 CFR 70 or 71). If electric mixers are used additional electricity will be used at the facility. Under EO 12902, federal facilities are required to be as energy efficient as possible.

The compliance benefits listed here are only meant to be used as a general guideline and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g. the amount of workload involved.
Materials Compatibility:
N/A


Safety and Health: Safety issues for using compost mixers deal with the operation of power equipment. Operators should be specifically trained in the proper operation of the mixer. Machinery should not be used if workers are on medication. Proper personal protective equipment (PPE) including gloves, eye protection, and hearing protection should be used if needed.

Consult the base safety office on proper protective gear and training prior to using mechanized equipment.
Benefits:
  • Thorough mixing speeds up the composting process by making nutrients available to microorganisms.
  • Fast, efficient mixing of compost materials compared to mixing with a loader.
  • Can handle a large volume of materials.
  • Breaks up clumps of material that can become anaerobic and odorous in the compost pile.


Disadvantages: None


Economic Analysis: Compost mixers cost from $30,000 to $60,000 for units that process from 20 to 40 tons/hr. Maintenance costs are approximately $500/yr excluding labor. Compost mixers are available as either stationary units with an electric motor or mobile units with a diesel engine. The ecomomic analysis presented is based on an aerated static pile compost operation. The capital costs include compost pads with air lines, blowers, a tub grinder, compost mixer, trommel screen, front end loaders, and offices.

Assumptions:

  • Process 25,000 tons/yr of wood and yard waste.
  • Produce 15,000 tons/yr of finished compost.Capital Costs: $3,000,000
  • Solid waste disposal costs: $13/ton
  • Operating costs (labor & maintenance): $25/ton
  • Avoided topsoil purchases: $50/ton
  • Hauling to landfill: $5/ton
  • Hauling to composting facility: $2/ton

Annual Operating Cost Comparison for Diversion and Disposal Using a Composting Facility

 
Diversion
Disposal
Operational Costs:    
Labor & maintenance: $625,000 $0
Landfill costs: $0 $325,000
Hauling costs: $50,000 $125,000
Total Operational Costs: $675,000 $450,000
Total Recovered Income: $750,000 $0
Net Annual Cost/Benefit: $75,000 -$450,000

Economic Analysis Summary

    Annual Savings for Composting Facility: $525,000
    Capital Cost for Diversion Equipment/Process: $3,000,000
    Payback Period for Investment in Equipment/Process: < 6 years

Click Here to view an Active Spreadsheet for this Economic Analysis and Enter Your Own Values.
Approving Authority: Approval is controlled locally and should be implemented only after engineering approval has been granted. Major claimant approval is not required.


NSN/MSDS:
Product NSN Unit Size Cost MSDS*
None Identified $  

*There are multiple MSDSs for most NSNs.
The MSDS (if shown above) is only meant to serve as an example.

Points of Contact: Navy:
Mr. John Comstock
Naval Facilities Engineering Service Center
1100 23rd Avenue
Port Hueneme, CA 93043-4370
Phone: (805) 982-5315

Mr. Wallace Eakes
Naval Facilities Engineering Service Center
1100 23rd Ave.
ESC 426
Port Hueneme, CA 93043-4370
Phone: (805) 982-4882
DSN: 551-4882
FAX: (805) 982-4832

Vendors: The McLanahan Corporation
P.O. Box 229
200 Wall Street
Hollidaysburg,  PA   16648
Phone: (814) 695-9807 
FAX: (814) 695-6684
  Detcon
P.O. Box 2249
Farmingdale,  NJ   07727
Phone: (732) 938-2211 
  Knight Industrial Division
PO Box 167
Brodhead,  WI   53520
Phone: (608) 897-2131 
FAX: (608) 897-2561

Sources: Mr. John Comstock, Naval Facilities Engineering Service Center, May 1999.
The F. B. Leopold Company, Inc., March 1995.
The McLanahan Corporation, March 1995.
Detcon, March 1995.
Knight Industrial Division, March 1995.


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