March in the Midwest brings maple syrup season—a time when maple trees across northeastern North America are tapped for their sugary sap. Having spent two season happily tapping trees in Wisconsin, I still instinctively take note of temperatures and tree types as I walk through town this time of year. Not having maple trees of my own right now, I am left to rely on my local syrup makers for my yearly supply of this essential food group. So, imagine my dismay at the increasingly dismal outlook for Sugar Maples in North America. In the face of climate change, these trees are experiencing declines due to range limits, soil acidification, pests, and even lack of decomposition on forest floors. The body of research and reporting on climate change impacts is growing, but my hours spent sitting next to an oil-burning evaporator during my syrup-making days brought to mind another angle to consider in the story of syrup:
To what extent does the maple syrup industry actually contribute to the climate change threatening its future?
Google was surprisingly unhelpful in answering that question. So if at first Google does not succeed, try again… with an easier question. First, we need to look at syrup production. Because production is completely weather dependent, with trees needed temperatures below freezing at night and above freezing during the day, the total amount of syrup produced varies annually. In 2009, trees and their tappers around the world (which really just means Canada and the U.S.) produced 13,320,000 gallons of maple syrup to sell commercially. That syrup starts as sap which is collected, boiled, bottled, and shipped to people across the world.
It typically takes about 43 gallons of sap to make 1 gallon of syrup. To boil off the 42 gallons of water in that sap, it can take up to 4.1 gallons of fuel oil, though efficiency measures can reduce that to 3 gallons. If wood is the fuel of choice, a cord of wood can get you 15 gallons of syrup.
A 2003 survey of Wisconsin syrup makers showed 46% of syrup was made using wood and 48% using fuel oil. If we were doing a more accurate accounting of fuel usage in maple syrup production, we wouldn’t base all of our calculations off this one study (might people in Quebec use more wood than oil?), but since it was the only one I could find, we’ll use these numbers and keep in mind that this assumption could lead to inaccuracies in our final estimate.
- 48% of 13,320,000 = 6,393,600 gallons of syrup made with fuel oil in 2009
- 46% of 13,320,000 = 6,127,200 gallons of syrup made with wood in 2009
Note: Using production numbers from 2009 and fuel use numbers from 2003 isn’t completely fair either. We’ll also just ignore the leftover 6% of syrup produced using neither fuel oil nor wood for now.
- 6,393,600 gallons of syrup x 3 gallons of fuel oil/gallon of syrup = 19,180,800 gallons of fuel oil used in 2009
- 6,127,200 gallons of syrup ÷ 15 gallons/cord = 408,480 cords of wood used in 2009
Another note: We’ll assume most producers are using efficient evaporating techniques that use only 3 gallons of fuel per gallon of syrup.
While carbon dioxide (CO2) is not the only greenhouse gas of concern when it comes to climate change, we’ll use this as an indicator of climate change impact because the data is readily available. Using the EPA’s estimate of CO2 emissions from fuel oil, we get:
- 19,180,800 gallons of fuel oil x 1/42 gallons/barrel x 429.61 kg CO2/barrel = 196,196,749.71 kg of CO2 emitted from boiling sap with fuel oil in 2009
And since this Swedish study estimates that wood burning produces about 60% of the total CO2 emissions of oil, let’s try this calculation:
- 196,196,749.71 kgCO2 ÷ 15 (because it takes 15x less wood than oil to make 1 gallon of syrup) x 60% = 7,847,869.99 kgCO2 from boiling sap with wood in 2009
Yet another note: I completely disregarded the 2% difference in production of syrup using wood vs. fuel here. My math skills are failing me. Also, the 60% emissions estimates takes logging and transportation into account, but a lot of maple syrup producers use their own wood for fuel. I have no idea if the estimate of fuel oil emissions accounts for production or just burning.
In 2009, all of us humans collectively produced 31.3 billion metric tons of CO2. So, our last calculation of the day gives us:
- (196,196,749.71 kgCO2 + 7,847,869.99 kgCO2) ÷ 31.3 billion metric tons = 0.000000656 x 100% = 0.0000656% of total CO2 emissions in 2009
Well, that’s kind of anti-climactic after all that math.
But do you buy my math? How many of my assumptions were valid? And what else is missing from this calculation?
To chase down a better answer to my original question, we could calculate the increase in acid rain from these CO2 emissions or maybe predict how much it contributes to temperature rising (Edit: As Robb points out below, the impact on acid rain would need to be calculated from the accompanying sulfur dioxide and nitrogen oxide emissions and not just CO2). But I’ll save that for the climate scientists among us.
This emissions-calculating thing is tough. My estimates here would not stand up to the peer-review process, since I’m missing a lot of information and making a lot of assumptions. My appreciation for folks that actually estimate emissions has just grown exponentially!
I guess if you can put any trust at all in these very rough estimates, you might feel a bit of sympathy for maple syrup producers. Their livelihoods seem to be affected disproportionately by climate change. Yes, their production and transport of maple syrup contributes to climate change more so than the maple syrup producers of old, but they are making strides to become more efficient in energy use.
So, enjoy your next pancake brunch with real maple syrup…while it lasts!