Anaerobic Digestion in Ontario: Techs and Specs Workshop
Integrating New Heat and Energy Sources into Your Existing Operation

Ron MacDonald
Agviro Inc.
Guelph, ON
519-836-9727
rmacdonald@agviro.com
www.agviro.com

Introduction

• Heating fuels and electricity are typically a small part of the cost of production
  
• Energy plays a significant role in feed conversion and crop condition management
  
• Reduce energy costs, improve performance
  
• Main three energy users: heating, ventilation, and lighting
  
• Refrigeration, for those requiring it, can be substantial as well

Conservation and Renewables

• Conservation: the cornerstone of an energy efficient farm

Benchmarking

• Compare energy use (input) to output
  • kWh/kg; MJ/ft2; etc.
• Compare to monthly, annual results
• Compare to similar operations

Benchmarking

• Effects that can skew results
  • On-site processing
    
  • Local weather
    
  • On-site feed preparation
    
  • On-site residence
  • Etc.

Lighting Systems

• Light critical for growth and reproduction
• Proper Design; integrate with ventilation, uniformity of light pattern
  
• Comparison of typical light sources and their efficiency

Ventilation

• Fans properly sized and energy efficient
  
• Independent fan tests - AMCA, BESS
  
• Consider Dual Ventilation
  
• Water based cooling

No Insulation/Insulation
Example: 1000 Cows

• 250 kW generator @ 25% efficiency
  
• 75% is waste heat = 2.0 MBH
  
• Assume 50% recovery via exhaust (temperatures over 400 C) and coolant system (temperatures about 85 C) heat exchangers;
  
• Some used to heat digester
  
• Considered low grade, but useable heat
  
• 1,000,000 BTU/h waste heat
  

Hot Water Heating

• Hot water thermal capacity over
  4 times that of air,
  density 750 times greater
• Typically low temperature, <120 o F when in-floor heating
  

How to use the heat

• Preheat manure
• Dry the digested output:
  create bedding
  low or pathogen free digested manure sales
  
• Typical Mesophilic digesters (35 C)
  
• Could go thermophilic (60 C) which requires much more heat but has faster digestion rates, greater pathogen destruction
  

Capturing the Waste Heat

• Requires heat exchangers;
  
  • exhaust gas to fluid
    
  • coolant to fluid
    
• Losses/efficiencies
  
• Maintenance
  
• Costs

How to use the heat

• Winter:
  
  • Home: space and domestic hot water heating
    
  • Barns: space heat, wash water
    
  • Sheds
    
  • Maintenance/repair buildings
    
  • Neighbours?
    

How to use the heat

• Summer
  • Pool
    
  • Some heat required year round: farrowing piglets, milk system and facilities (pressure) washing
    
  • Combined cycle cooling:
    
    • Uses heat to drive a refrigeration system (similar to propane powered refrigerators)
      
    • Relatively low grade heat so not very effective

Hot Water Heating

• Usually single largest annual energy consumer
  
  • Broilers: up to 75 % of annual energy is heat
    
  • Swine nursery: up to 60% of energy is heat
    
  • Farrow creep heat: largest single energy consumer is creep heat; year round
    
• In-floor
  
• Hot water pipe
  
• Forced air
  

House and pool

• Retrofit can be a radiator installed in the furnace
  
• Perimeter hot water radiators with individual zone controls
  
• Heat exchanger on the pool pump system, or any other
  

Hot Water Heating

• Fin/heating pipe is convective heating
  
• More uniform heat
  
• Large thermal capacitance (lead/lag)
  

Hot Water Forced Air Heat

• Forced air systems heat entire air space
  
• Air Re-circulation recommended
  
• Unit heaters typically have low capital cost
  
• Reduced insurance premiums over "box" heaters
  

Hot water Issues

• Design of the hot water system and controls is critical
  
• Management is different, especially with passive systems
  
• Capital costs are higher
  
• Maintenance is required: system water quality, calibration, monitoring

Other Uses

• Greenhouse
  
• Aquaculture
  
• Pasteurization
  
  • Regardless, there will be more complexity
    
  • Partnerships/alliances?
    

Conclusions

• Hot water is a good option with an AD
  
• Systems design, control, installation, maintenance and operation are essential to a functioning system