Removing Water from Sap:
Increasing Energy Efficiency with
New Technologies

Fresh sap flowing out of the maple tree contains anywhere from 1 6% sugar. Finished maple syrup is 66-67% sugar. To increase the sugar concentration of sap, many gallons of water need to be removed. For example, to produce one gallon of syrup, 43 gallons of sap with 2% sugar content are needed. This means that 42 gallons of water must be removed from the initial 43 gallons of sap.

In most maple operations, the water is removed by boiling the sap. The cost of fuel needed for boiling is a large part of the total cost of producing maple syrup. Therefore, any increase in fuel efficiency during this process will benefit the maple producer.

Can you think of any ways to increase the efficiency of removing all that water from sap to produce syrup?

In Table 1 we have included eight different means of processing sap to syrup. The wood-fired and oil-fired evaporators are basic means of boiling sap. The sap pre-heater increases the efficiency of boiling sap, by recycling steam from the evaporator to warm the fresh sap. The piggyback (steam-enhanced) unit uses both recycled steam and forced air to warm and concentrate the sap before it enters the evaporator. The reverse osmosis, freeze concentration, vacuum evaporator, and vapor compression evaporator use different means to concentrate the sap before it enters the evaporator.

All of these systems have been created by maple producers who enjoyed designing and experimenting with new ways of processing sap. Even today, some of these systems, such as freeze concentration, are still experimental and not commercially available. If you get an opportunity to visit maple producers, you may find some who have designed other systems to recycle steam and increase efficiency. And you may be able to come up with new ways of increasing the efficiency of producing syrup from sap.

We have included "functional" designs of the different systems to help you understand the overall process of syrup production. We also hope these designs will get you thinking about other energy-efficient systems to produce syrup from sap.

For detailed designs of the different evaporators, contact the manufacturers or access the U.S. Patent Office web page.

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