Maple Syrup Production

In 2016 Wisconsin produced approximately 235,000 gallons of maple syrup, according to the Wisconsin Agricultural Statistics, from 765,000 taps. Production has doubled since 2006 when about 100,000 gallons was produced. In 2012 there were 1155 producers up from 638 producers in 1997.  According to the Ministry of Agriculture and Food, Ontario, Canada, it takes between 2.7 to 3.4 gallons of fuel oil to produce 1 gallon of maple syrup or between 4 to 500,000 BTUs per gallon. Based on Wisconsin’s average production of 235,000 gallons, it would require 106 billion BTUs of energy to produce or the equivalent of 766,000 gallons of heating oil. Several different fuel sources are use for processing including wood, heating oil, propane and natural gas. According to the summary of a 2003 survey of Wisconsin Producers, the breakdown of primary fuel types was 45% wood, 49% fuel oil, 4% natural gas and 2% Propane. Wisconsin is ranked a distant 4th in maple syrup production in 2015 behind Vermont, New York and Maine, producing 6% of the U.S. production. Energy is a major component in the cost of production, accounting for 26 to 34% of the production costs without reverse osmosis and 8 to 11% with reverse osmosis based on using wood or fuel oil , respectively (2012).

There are several technologies and devices that can reduce the energy costs in producing maple syrup.

  • Evaporator and burner maintenance – Typical maintenance issues include cleaning nozzles, insulating fireboxes, correct size nozzles, cleaning build up off of pans, proper air mixture.
  • Pre-heater – A Sap pre-heater increases the efficiency of an open pan evaporator by using the steam coming off the evaporator pan to preheat the sap before it enters the pan. The heat exchanger is typically copper tubing that is suspended under a hood over the evaporator pan. The steam condenses on the cooler pipe surface, transferring heat to the sap. A drip pan catches the condensate and drains it away from the evaporator pan. A properly sized pre-heater will commonly increase the efficiency of an evaporator by 15%.
  • Piggy-back or economizer units – These units are a combination pre-heater and evaporator. The unit sets over the evaporator pan and uses steam from the evaporator pan to pre-heat the sap to as high as 200°F. From manufacturer’s literature, it appears to increase production by 60% to 65% with no increase in energy usage.
  • Reverse osmosis – Reverse Osmosis systems have been used commercially in maple syrup production since the mid 1970’s. The technology works the same as desalination of salt water except water is the by-product and the sugar concentrated sap is the product. Reverse osmosis can remove 75% of the water from the sap, reducing energy usage by 70% over open pan evaporation. The equipment is pricey and is therefore only economical on larger operations but it can reduce energy use to about a gallon of heating oil per gallon of syrup produced.
  • Evaporator designs – New designs of evaporators incorporate pre-heaters and economizer units as well as preheating of fuel oil and air for more efficient combustion, air tight and insulated combustion chamber and combustion chambers design to maximize the heat transfer rate.

Energy Efficiency Studies

In a 1988 study, 15 sugaring operations were provided energy audits with 11 of the operations determine to have energy conservation opportunities that would reduce energy costs an average of 31%. There were eight recommendations to increase burner efficiency, four to install or upgrade a sap pre-heater, 3 to install economizer units and one recommendation to install a reverse osmosis unit. The paybacks ranged from 0.3 to 7.4 years. Increasing burner efficiency and installing a preheater had the lowest cost and fastest payback. A 2003 survey reported wood fuel efficiency of producing a gallon of maple syrup ranged from 170,000 BTU for a producer that used a preheater, economizer and a reverse osmosis unit to 5,343,000 BTU per gallon for a hobbyist. Non-wood fuels ranged from 133,250 BTU per gallon for a producer using a reverse osmosis unit to 454,000 BTU. Large producers were more efficient as well as those using non-wood fuels. Large producers were more apt to use some type of energy efficiency equipment.

Maple Syrup Production Energy Use Survey Summary“, Scott Sanford, University of Wisconsin, 2003.

Links

If you have questions about the information on this site, please contact
Scott Sanford, Distinguished Outreach Specialist, University of Wisconsin, sasanford@wisc.edu.