Reverse Osmosis for Maple Production: Making the Sweet Stuff More Sustainable

As Old Man Winter continues to march toward spring, the natural resources department is getting started with maple syrup production. This much anticipated time of year falls sometime during the late winter to early spring realm. Days above freezing with nights below freezing provide the best conditions for sap collection. About mid-February the electric drills come out and tapping begins. Sugaring technology has certainly come a long way since the days of wooden buckets and cast iron cauldrons. The electric drills are just one example. As technology continues to increase the efficiency of the process, Frost Valley strives to stay up to date on the best ways to save energy and resources. This year will mark the 3rd season that our reverse osmosis machine has been in use for maple syrup production.  The integration of this tool into our maple sugaring process has proven to be a valuable asset, saving both time and resources during production.

A little maple sugaring background info:

Maple sap is mostly water, it typically only consists of about 1%-2% sugar. Maple syrup is made by boiling maple sap to evaporate most of the water until we are left with 66% sugar. Our evaporator is heated by a wood fire and it usually takes around 50 gallons of sap to cook down into one gallon of syrup. That’s a lot of boiling, and a lot of firewood!  Since we started using the reverse osmosis machine (RO) we have seen a drastic reduction in the amount of wood we use to make syrup. Before the RO, with a cord of wood we could cook about 12 gallons of syrup. Now a cord of firewood is enough to cook 24 gallons! This is not surprising because passing sap through the RO removes half of the water before the boiling process even begins.

Here’s how it works:

The RO consists of a large membrane through which raw sap is pumped in order to remove water and increase the concentration of sugars prior to the evaporation stage. To imagine the RO, picture a humongous roll of paper towels resting inside a metal tube. This is basically what the RO looks like. For this mental image, the paper towel roll represents the membrane and the metal tube is the membrane housing. The membrane cannot be seen as it is fully contained inside the housing. The metal housing sits upright with one hose feeding into the bottom, one hose coming out the side near the top and one hose coming straight out the top. Sap is pumped into the housing through the bottom hose under high pressure. This sap enters the housing on the outside of the membrane. As the sap is forced upward, the pressure causes water to permeate through the walls of the membrane. The tiny holes in the membrane allow water molecules to pass though but are too small for sugars to fit through. The water that passes though ends up in the center of the membrane and is now referred to as “permeate” because it has permeated the membrane. By the time all the liquid reaches the top of the membrane, the permeate exits the housing though the topmost hose as pure water. Meanwhile, the sap on the outside of the membrane has significantly increased in sugar content. This extra sugary solution is referred to as “concentrate” and exits the housing through the side hose.

This technology isn’t just used for maple sugaring, it has various applications. In fact, reverse osmosis is what is used to turn ocean water into drinking water on large ships. The difference here is simply that in ocean water desalination, the pure “permeate” water is the desired product rather than the extra salty “concentrate” water.

It is easy to see how this technology has greatly benefited our maple sugaring operation. Moving forward, we will continue our endeavors to be increasingly more efficient and sustainable. Our plans for the future include a fully redesigned maple tubing system. This network of tubing will increase our vacuum suction throughout the sugarbush. The increased vacuum should allow us to harvest a higher yield of sap per tap, further increasing our efficiency and reducing our use of fuel and materials.


Dan DeChellis

Growing up in his home state of Pennsylvania, Dan acquired a love of the outdoors at an early age. He is the Natural Resources and Environmental Science Coordinator at Frost Valley. Throughout his time at Frost Valley, Dan has worn many hats and developed a deep connection with the land. He is thrilled to be part of the management and stewardship of the place he has grown to love.

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