Bakers use refrigeration systems to control ingredient temperature, dough temperature, for comfort cooling in offices and production areas, and to freeze product. The two most common refrigeration and freezing systems use ammonia or organic compounds.
When considering a refrigeration system think about:
• Location — Alaska vs. Arizona;
• All of the uses of refrigerants in the facility, from office air conditioning, to chillers, to giant freezers;
• Required temperature levels — trough room or freezer;
• Design to worst case, heat of summer all year, or not;
• List the requirements for the system, including maintenance and record keeping.
Ammonia is a common, naturally occurring compound of nitrogen and hydrogen. Commercial ammonia refrigeration systems have been used by the food industry since the 19th century. Now, closed-loop ammonia systems are used to cool glycol or other liquid, which then circulates to mixers, other equipment and to cool spaces.
Ammonia refrigeration systems may cost 10% to 20% less to install than other systems. Thermodynamically, ammonia is 3% to 19% more efficient than other refrigerants and therefore uses less electricity. Ammonia costs less than other refrigerants. The price point where the benefits of using ammonia balance the costs of safety plans has changed considerably in recent time. Ammonia systems now come in many sizes and deserve a look.
Ammonia may be hazardous. Risk management plans are required by the Occupational Safety and Health Administration and the Environmental Protection Agency (E.P.A.). The E.P.A. also requires special reporting of any releases. Local fire departments monitor the specifications and installation of systems.
Ammonia does not deplete the ozone layer and does not contribute to global warming. Ammonia has an odor that minimizes leaks.
The American Society of Heating, Refrigeration and Air Conditioning Engineers, Inc. (ASHRAE) has produced many publications about the construction and use of ammonia and organic refrigeration systems. Also, see the International Standards Organization (ISO) 5149, Refrigeration Safety and 1662, Refrigerating Plants-Safety Requirements standards.
Ted Gartland is a refrigeration consultant who has worked with the baking industry for many years. The following narrative summarizes Mr. Gartland’s comments about the use of organic compounds.
In 1924, Thomas Midgley Jr. synthesized the first modern fluorocarbon refrigerant. To demonstrate its safety he inhaled the refrigerant and blew out a candle. The low toxicity and non-flammability of the new refrigerant spawned a revolution of safe efficient refrigeration and air conditioning. Combinations of carbon, fluorine, chlorine and hydrogen make up the chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs) used globally today.
Over time it was determined that the stability of the chlorine containing molecules (CFCs and HCFCs) allowed them to work their way to the stratosphere where the sun would break them down and the resulting chlorine component would react with ozone and create a hole in the ozone layer. The ozone layer protects the earth from ultraviolet radiation.
One staple refrigerant of the baking industry has been R-22, a HCFC. A ban on the production and import of R-22 will be implemented by 2020. The E.P.A. has a goal to reduce use 85% from the 2008 baseline to 2014. The 2015-20 allocations are undetermined but are under significant pressure for an even faster phase-out. Recovered and recycled material will increase in value as reductions are implemented.
In the 1990s manufacturers introduced chlorine-free HFCs. Examples are R-134a, R-507 and R-404A. Even though these refrigerants are ozone friendly their stability enhances their global warming potential. One pound of R-507 has the same global warming potential as 3,985 lbs of carbon dioxide. Carbon dioxide is one product of burning fossil fuels. Global warming is a contributor to climate change.
Organic refrigerants are low pressure and efficient. Although the refrigerant cost is higher than for ammonia, the construction of systems may be lower. Motor, compressor and coil technology is lowering the average system charge and increasing efficiency at a high rate. The superior system-safety may lessen maintenance and contractor costs.
The E.P.A. requires leak management and accurate record keeping for organic refrigerants. Failure to bring a system under the proscribed leak thresholds may result in substantial fines. HFCs have a no-venting requirement. HFC refrigerants are covered by international agreements with the E.P.A. showing a clear intention to regulate them in the near future.
Maintaining a leak free system is the most economical and environmentally friendly thing a baker can do. Bakers should implement a leak reduction plan with modern leak detection equipment and consider replacing aging equipment with technology to reduce the refrigerant charge.
Ammonia systems have improved in scale and function. Ammonia is hazardous. The E.P.A. has a stated environmental preference for ammonia systems. Organic refrigerants are non-toxic and increasingly efficient. The cost of replacing organic refrigerants, as the atmospheric science changes, may be costly and time consuming. Bakers need to consider the age of their equipment, their refrigeration needs and their long- and short-term costs.