How Sustainable is Maple Syrup?

    Written for my La Terre Noire blog in 2015

    Last summer I attended a talk by Eric Toensmeier, in which he apologetically (since he was speaking to a Northeast North American audience) declared that maple syrup probably wasn’t a very sustainable source of sugar because its yield per acre is far below cane sugar. Was he right? Should we all be eating sugar from sugarcane instead of from maple trees?

    The first objection that came to my mind was yield per acre is a poor measurement when one is comparing cultivated fields with forestland. Naturally a cultivated field, planted to a monocrop, will yield far better of that one crop than a wild growing forest. But a forest is a rich, diverse ecosystem, supporting a multitude of life, while a monocrop is pretty much a sterile desert but for the one crop. The forest also provides a suite of services to the larger ecosystem, including buffering of flood waters, creation of rain through transpiration from leaves, erosion control, soil formation, air cleansing, cooling of surface temperatures, and on and on. A well managed sugarbush can also yield additional crops, such as ginseng, ramps, goldenseal, elderberries, mushrooms, wild game, timber, firewood, and recreation. Forests are also the best way to sequester excess carbon from the atmosphere. And they do all this while occupying some the poorest land around – hilly, rocky, thin soils – land that could never be used to grow field crops.

    Boil, Baby, Boil

    Eric Toensmeier would probably be the first to agree with all of the above. But a further criticism of maple syrup is that it is highly energy intensive to produce. Forty litres of maple sap need to be boiled down to make one litre of syrup. Maple syrup producers use pretty much every kind of heat source to do so, but the two most common are oil and wood. At Ferme et Forêt, we’ve chosen to go with wood, because it gives us control over our fuel supply (firewood from our own bush), and it’s carbon neutral.

    I’ve been told to have 40 face cords (about 13 full cords) of wood on hand to produce the maple syrup we’ll get from our 3000 taps (with no vacuum pump). We’ll see this spring what our actual usage is.

    We’ve designed our shack without permanent walls; the walls are our firewood stacks, and we literally will burn our walls in wood every year. There are about 29 face cords stacked here. Back up a bit, and you’ll see another 9 cords stacked in the field.

    When I first saw all this wood stacked, I have to admit, I was a little shocked. Maybe maple syrup is too energy intensive. But back up a little more, and look at the bigger picture.

    In comparison to the amount of wood available in our sugar bush, the wood stacks in and around the sugar shack suddenly look pretty insignificant. A well managed, productive bush can sustainably produce a full cord of firewood per acre per year. Even from a slow growing bush, one should conservatively be able to harvest one face cord (1/3 of a full cord) per acre per year. That will likely be less for us, since we’ll be tapping a good number of our trees for maple syrup, but even then, 40 face cords a year from our 100 acres of bush should easily be sustainable.

    Not only does responsible harvesting of wood (with light equipment like ATVs or horses, in frozen or dry conditions) not harm the forest, it actually improves the growth and health of the remaining trees, as they will have greater access to light, water, and nutrients. A lot of people feel they are being responsible forest managers by “cleaning up” deadfall. In fact, dead trees are the life of the forest, attracting insects and wildlife, and contributing nutrients and organic matter to the soil. It is far better to cut a live tree that is too close to another tree; the remaining tree will increase its growth and make up for the wood taken out of the system through harvesting.

    It should be noted that the discussion of firewood, properly managed, as a sustainable fuel source is in the context of an abundance of wood available in the sugar maple region of the world – northeastern North America. When Europeans first arrived, they cut down most of the forests that the Native Americans had been managing for centuries to make room for agriculture. However, much of this cleared land turned out to not be very suitable for agriculture, and as more crops were produced from less land, and people began making their livings from things other than farming, much of this land reverted to forests. However, the forests that re-emerged were not the same open, spacious ones the natives had carefully managed; they were thick and crowded. These forests could benefit from active human management once again. They can be thinned, the surplus wood going to firewood, and the remaining forest will be healthier than before.

    But humans have certainly overused this resource in the past, denuding the landscape in a search for fuelwood. It wet climates like Britain this doesn’t have catastrophic results – the ground is covered in pasture and grazing animals have a heyday. But in most regions of the world, which receive less rain, deforestation quickly leads to soil erosion and desertification.

    The Northeast is not a “brittle” landscape like this. It can and has survived deforestation, and ignored by humans for awhile, forests grow back pretty rapidly. However, the land and the people who depend on it are impoverished by the loss of forests, and any effort to harvest firewood needs to be done in a way that preserves large stands of forest. It is possible that, when the oil finally runs out in a few more decades, our forests will once again come under intense pressure to produce the energy our civilization has grown accustomed to. There is already talk of harvesting wood in British Columbia for biogas. Hopefully it won’t come to that, and we’ll turn to more benign technologies like wind and solar (not to mention reduce our energy consumption through efficiencies).

    But in this time and place firewood makes sense, not for everyone (because then it would quickly be gone), but for some.

    Cool the Fire

    If we ever think that we are burning too much wood, there are various ways we could cut down on our wood use drastically. One way we do plan on doing this, as soon as we can afford the $4,500 price tag, is to install a hood with a preheater. This uses the steam coming off the evaporator to preheat the cool sap before it goes into the evaporator, thus increasing the efficiency of the boil. We could also follow the lead of most sugarmakers and get a reverse osmosis unit to filter out much of the water from the sugar before boiling it. Using a bit of electricity to run the osmosis, the sugar content of the sap can be increased from the 2% it typically comes out of the tree at, to 10% to 20%, thus saving lots of boiling time and energy. A third possibility would be to upgrade to one of the new super-efficient evaporators now on the market. These “gasifier” units blow air into the combustion chambers, so that flue gasses coming off the fire are forced back down into the fire, producing a complete combustion of the gasses and a very fuel efficient burn. All these technologies come with their own costs – drawbacks that for now have led us to chart a more low-tech approach (see my earlier blog post about this).

    However, low-tech does generally mean less efficient. But we don’t see our higher energy use as too much of a problem, because we see our energy source – firewood from our own bush – as totally sustainable. The bigger problem for us is the amount of time needed to cut the wood. If we’d rather put this time towards something else, or if we find our bush is becoming depleted, we’ll switch to more efficient technologies.

    One low-tech way to not burn less wood, but to cut less live wood, would be to make use of the vast stream of waste wood moving through our economy. From lumber slab to dumpsters full of 2×4’s, the wood is definitely out there. You don’t need to burn the top-quality hardwood that most people would heat their house with to boil maple syrup; in fact, softwoods are often better, because they burn fast and hot.The issue is finding it, transporting it, and dealing with junk like nails that may come along with it. If syrup makers could get the waste collection companies to dump suitable construction waste at their local sugar shack, instead of at the dump, we’d be on to something.

    Another possible alternative to cutting firewood from forests would be to plant a fuelwood coppice, from a fast-growing and high BTU species like black locust. We would cut wood from this planting on a rotation (say, every 10 years), cutting everything down to stumps, which would then regrow and be cut again in another 10 years. Such as system can last hundreds of years, and you get more firewood per acre than from a natural forest.

    One last way that we could improve the energy efficiency of our syrup-making – an approach that I personally find fascinating – is to select and plant trees that give sweeter sap. The average sugar maple produces sap that is about 2% sugar. However, there are trees that have been identified and propagated that consistently produce sap with 5% sugar. This is huge: at 2% sugar, you need to boil about 44 litres of sap to get one litre of syrup; at 5% sugar, you only need to boil about 17 litres of sap! It’s almost like having a reverse osmosis machine built into the genetics of your trees. Cornell University has bred a “Super Sweet” sugar maple variety, which you can buy. Alternatively, when you’re thinning your sugarbush, make sure to test the sap sweetness with a refractometer before deciding which trees to thin. Over time, you can increase the sugar content of the sugarbush overall. Since it takes about 40 years for a sapling to grow to tappable size, with either approach this is definitely an intergenerational project. But still worth undertaking, in my opinion.

    Outdoor Plumbing

    Another possible critique of modern maple syrup production is the amount of plastic used in the tubing that transports the sap to the evaporator. For instance, for our 3000 taps, we’ll be installing about 20 km of tubing! This tubing will most likely last for between 10 and 20 years, before the UV degrades it and it needs to be replaced. I am aware of some work being done to develop products that make use of recycled tubing (such as plastic plywood for boats), but I imagine a lot of it still ends up in landfill.

    Buckets are not really a viable option for commercial sugarmakers anymore. They cost as much or more than tubing to buy, their yield is lower (compared to tubing under vacuum), and their labour costs, for collection, are far higher. If you already have buckets, or can find a lot of used ones at a good price; if your land is relatively flat and you can drive a tractor through it pretty easily; and if you have a large, cheap labour force (like a big family) willing to collect sap from buckets, bucket collection might be marginally viable.

    But for most sugarmakers (ourselves included), tubing is the only real option. The best course for the maple industry as a whole is to find good markets for the tubing to be recycled into. The Recycling Agricultural Plastics Program at Cornell University is one good effort in this direction.

    The Blood Suckers

    One last potential criticism I’ll mention is the idea that tapping maple trees – especially with high vacuum – harms them. Intuitively this sounds plausible – you are “stealing” a bit of the life blood of the tree, and under vacuum even more so. Yet centuries of experience with tapping, and decades of research with vacuum has not found a negative impact on the trees. You are taking only about 5% of the total sap of the tree – well within its abilities to handle.

    The tapping guidelines that place limits on the number of taps to put on each tree, depending on its diameter, have much more to do with being able to find places to tap in subsequent years than preserving the health of the tree. It is very hard to kill a tree by tapping it. However, every time you drill a hole in a tree, it creates a wound and sap is directed away from that area in the future. The wound extends maybe a foot above and below the hole, and a few inches on either side. If you try putting another tap into that area next year, you won’t get any sap. So you need to find fresh, unwounded wood to tap into. As the tree slowly grows outward, it eventually grows new sapwood over the old wound, and you can tap into that same spot on the tree again. How long this takes depends on how fast the tree is growing. If you put too many taps into too small a tree each year, it can’t grow fast enough to heal over all those wounds, and eventually you’ll have a hard time finding any sapwood to tap into. At Ferme et Forêt, we follow the conservative tapping guidelines of one tap if the tree is over 10″ diameter at breast height, and two taps if it is over 18″. Never more than two. This should ensure sustainable tapping for generations to come.

    So there are the main criticisms of maple syrup that I can think of: low yield per acre, high energy use, high use of plastic, and being hard on the trees. However, none of these criticisms, in my opinion, carry much weight. Low yield per acre? Forests are actually very high yielding – of a multitude of products and services. High energy use? Firewood is renewable and carbon neutral, and modern technology can reduce energy use substantially. High use of plastic? It can be recycled. Harmful to the trees? Not so.

    How Does Cane Sugar Stack Up?

    Now, let’s look at the main alternative sweetener: cane sugar. Although sugar is also made from beets and corn, beet derived sugar is mostly in Europe, and corn sugar (the infamous high-fructose corn syrup) is generally only used in the industrial food system, not home kitchens. I want to compare what most people would reach for at home to add some sweetness to their cooking – the little white or brown crystals of cane sugar, or maple syrup. (Honey would be another alternative. It’s a wonderfully sustainable choice, but a little less versatile than maple or cane sugar.)

    Cane sugar production has a bad reputation. It has the highest water requirements of all major crops; 1 kg of sugar takes between 1500 and 3000 litres of water to produce. Tillage and bare ground creates erosion, which runs off – along with pesticides and fertilizer – into waterways, often damaging coral reefs. Large amounts of decomposing plant matter washed out of sugar mills can consume all the oxygen in the water and cause massive fish die offs. The WWF says that sugar may cause more biodiversity loss than any other crop.

    Working conditions are often poor as well. About 50% of sugarcane is harvested by hand; workers are often paid less than $2/hour for grueling labour in the hot sun. Child labour is reported in some countries, and harvesting sugarcane has been called the most dangerous of all agricultural work, because it is done with machetes, and injuries are frequent.

    Of course this is looking at the worst case examples of sugar production. Above, I painted more of a best case scenario for maple syrup production, so it’s only fair that I do the same for sugar. There are ongoing efforts to improve the way sugar is produced, such as the Bonsucro certification, which in a few years has signed up enough producers to account for 3.7% of land worldwide under sugarcane production. The Brazilian Sugarcane Industry Association and the Brazilian Trade and Investment Promotion Agency have a website, in which they describe the best practices and ongoing efforts to improve the environmental impact and labour conditions of sugarcane. Perhaps it’s all greenwashing from the world’s largest producer of sugarcane, but reading about their best cultivation practices, it sounds as if sugar can be produced in a much less damaging way. For instance, it can be grown semi-perennially, only replanted every 6 or 7 years. Some sugarcane varieties can even fix nitrogen. Then of course there is sugar grown on certified Fair Trade and organic farms.

    I am struck by how many steps must be taken to turn raw sugarcane into the pure white crystals we all know. Here are the steps briefly summarized:

    1. the canes are harvested
    2. then trucked to the mill
    3. then crushed
    4. then pressed to extract their juice
    5. then mixed with sulphur dioxide vapours to bleach them
    6. then mixed with powdered lime to clarify them
    7. then left in a settling tank for the sludge to settle to the bottom
    8. then boiled in an evaporator to increase the sugar concentration of the juice from 15% to 60%
    9. then left in another tank so the residue can be skimmed off the surface
    10. then microscopic sucrose crystals are added to aid in the crystallization of the syrup
    11. then boiled again in a vacuum evaporator
    12. then put into a centrifugal machine to separate the crystals from the molasses
    13. then bleached again for white sugar
    14. then finally dried with heat to a moisture of 0.02%

    According to a journal article entitled The Energy Cost of Sugar Production in the Philippine Context, it takes 61.68 litres of diesel to grow and mill 1 ton of sugarcane, and it takes about 8 tons of cane to make 1 ton of sugar. Since it takes 3.5 to 4 litres of oil (or firewood equivalent) to produce 1 litre of maple syrup (which weighs 1.33kg), you can then do the calculations to conclude that, despite all the steps outlined above, sugar production uses 1/6th the energy of maple syrup production.

    Much, if not all, of the energy used to produce cane sugar can come from burning the bagasse – the sugarcane pulp leftover after pressing. This is one area where there is a similarity between cane and maple sugar production: both burn by-products to power their processing – in the case of maple syrup, surplus wood from the sugarbush can be burned.

    Another interesting parallel is with ribbon cane syrup, which used to be popular in the southern US. Basically, sugarcane was crushed to extract the juice, which was then boiled in evaporator pans, not unlike maple syrup evaporator pans, to produce a syrup.

    However, that’s about where the similarities end. The following table sheds some light on the differences:

    I mentioned at the beginning of this article that yield per area was much greater for sugarcane than maple. Sugarcane yields on average 60-70 tons per hectare (although much more is possible) – which can be made into about 8 tons of sugar – while sugar maples only yield about 270kg of syrup per hectare (at 1 L per tap, times 200 taps). In other words, sugarcane yields 30 times more per hectare than maple.

    Partly this is because sugarcane is what’s known as a C4 plant, able to photosynthesize much more efficiently than most plants. Partly it’s also because sugarcane grows in the tropics, where it receives much more photosynthetic energy than sugar maples growing in temperate regions.

    What To Make of It All

    I started off my research for this post thinking I could easily discredit cane sugar when compared to its maple equivalent. However, I’ve developed a grudging respect for the Saccharum genus and it’s amazing level of productivity. I now see Eric Toensmeier’s point. Although sugarcane is often currently grown in ways that cause a lot of harm to the environment and the people who harvest it, it is possible to produce it in much more benign ways. For instance, if situated in the right region, with ample rainfall, it can be grown without any irrigation. It can also be grown without chemicals, and as a semi-perennial, cropped for up to 10 years before replanting. Under the Fair Trade system, it can provide good livelihoods for farmers living in some of the lowest income countries in the world.

    The sugar maple industry also has a good and an evil side. Burning 4 litres of oil to produce 1 litre of maple syrup clearly isn’t sustainable. But energy use, through technologies like reverse osmosis, can be brought down significantly, and firewood is not a net producer of greenhouse gasses like oil is.

    It seems that the main reason cane sugar takes 1/6th as much energy to produce as maple syrup is that cane juice, once pressed, is 15% sugar, while maple sap is only 2%. So it takes far more energy to bring the maple to syrup stage than the cane. However, with a reverse osmosis machine and a bit of electricity to run the pumps, maple sap can be brought to 15% sugar too. Osmosis reduces the amount of oil needed to produce 1 litre of syrup from 4 litres to 1. That narrows the gap between maple and cane to 1.33kg of maple syrup and 2.02kg of cane sugar produced from a litre of oil, respectively.

    That gap can be eliminated, and maple can in fact come out ahead, if one of the new, high-efficiency wood-burning maple syrup evaporators are used. They can reduce wood use by 40%, meaning one could produce 2.2kg of maple syrup from a litre of oil (or wood equivalent), compared to 2.02kg for cane sugar. Granted, it takes more energy to produce crystalized sugar than syrup, but we can see that the two forms of sugar are pretty close in terms of energy use. Cane sugar, of course, has the added energy cost of long-distance transport, if you live in the North.

    The fact is, it’s not that maple sugar production is sustainable and cane sugar is not, or vice-versa; it’s that both forms of sugar can be more or less sustainable, depending on how they are produced. The devil, as usual, is in the details.

    As a consumer, if you want to buy cane sugar, you should choose organic, Fair Trade, or possibly Bonsurcro, sugar. Less refined, or brown, sugar takes a bit less energy to produce, and retains more of the sugarcane plant’s natural minerals, so it would be a better choice.

    If you want to buy maple syrup – or sugar – we have in the Northeast the great advantage of being close to the suppliers, so, unlike with cane sugar, we can get to know them. Personally, I’d rule out any syrup made by burning fossil fuels. Organic certification, in my opinion, is not nearly as meaningful when it comes to maple syrup as it is for most agricultural products. Maple syrup is essentially a wild food, and few producers – organically certified or not – use any kinds of pesticides, herbicides, or chemical fertilizers in their bushes. Many maple operations are open to the public during sugaring season, which is great opportunity to check them out and see if you like the feel of them.

    Despite the impressive qualities of the sugarcane plant, for me, what makes maple syrup win out – at least for those of us living in its home region – is that it is produced locally, and that it comes from healthy, intact forests. (It also tastes better and is more nutritive – but that’s another post.) A field of sugarcane may produce impressive yields for up to 10 years, but it’s still just a field, producing little but sugarcane, and will eventually need to be tilled and replanted. The total yield of a forest, when one takes everything into account, is surely far greater, and it will never need to be tilled, fertilized, or replanted. It will produce sweet maple sap, which can be harvested by humans with next to no impact on the species that call the forest home. Forever.