Carbon sequestration in your own forest

So it is now widely accepted that climate change is a serious problem in the world, but we are still figuring out the details about how to fix it. One major possibility that I discussed at length in the past here at Sunshine Saved is to reduce those activities that cause climate change, especially our consumption of goods and services that burn fossil fuels. The primer that I wrote on what a given family could do can be seen here. Then there are things that we can do to take greenhouse gases out of the atmosphere, broadly called ‘carbon sequestration’. There are currently many high tech proposals for factories that will do ‘carbon capture’, but I have yet to see one of these that has any chance of scaling up or being economically or energy efficient enough to accomplish much. I think that the current high-tech proposals will never go past ‘demonstrations’, and won’t actually help the problem. Perhaps next-generation high-tech carbon sequestration will be better. Finally there are ‘nature-based’ solutions, which is what I’ll be talking about for the rest of this post. All of these are basically about getting plants to do the work for us, to take carbon out of the atmosphere and store it somewhere that won’t quickly go back into the air. One of the many reasons that I started our farm, Ferme L’eau du ruisseau, was to do something tangible towards helping out the climate change and biodiversity crises that the world is now facing. While our efforts in farming continue, it turns out that managing forests holds much more promise for fighting climate change than farming could (at least in our region). This is because the primary chemical component of all parts of a tree is in fact carbon, and forests grow a lot of trees. And where does any plant get the carbon it needs to grow? It pulls it straight out of the air.

Agriclimat conference

In November of 2023 I had the pleasure of attending a conference put on by Agriclimat, a Quebec initiative to address climate change through farms and farmers. The full day conference was put on to educate a group of farmers about how farms connect to climate change and greenhouse gas emissions. It was wonderfully informative, and I took a lot of notes about the particulars, especially those that related to forests. On average, about 1/3 of each Quebec farm is forested, and in the Gatineau Hills where our properties are located, that number may more like 3/4 forested, which is about what our own properties are. So farmers in Quebec and elsewhere manage an enormous amount of forests, and everyone would like that to be good management. I’d like to share with you a bunch of the numbers about carbon and forests that I learned there. Unfortunately I don’t have the original sources of these data, but found a similar US source on forest carbon (pdf embedded below). The specific numbers between these two sources differ somewhat, but the basic story is exactly the same.

Sequestration rates.
Fact number one is that forests sequester a lot of carbon. Each hectare of forest sequesters about 1.75 tons of CO2 per year. This is for a middle aged forest with mostly 80 to 100 year old trees, which is typical of enormous swaths of southeastern Canada and the northeastern US. Very young forests (after a clearcut or other disturbance) may not take in as much CO2 in their earliest years as the individual trees are so small. And in old forests, say those around 200 years old and older, sequestration tapers off and reaches an equilibrium because the amount of carbon being sequestered matches the amount being emitted from dying trees, decomposing logs and other woody material on the forest floor. Those old forests do store an enormous amount of carbon, but the total amount doesn’t keep going up forever.

Something that was outside the scope of the conference was how different forest management practices may change those rates. If one uses really poor management, would the rate go down? With great management, would the rate go up? Looking at other types of forest outcomes, the difference between ‘managed’ and ‘unmanaged’ often seems to be about a factor of 2. Unmanaged forests produce about half as much timber as managed forests. While I don’t have definitive numbers, I imagine that it would be something roughly similar when one is managing for carbon storage – the right management may be able to roughly double the climate impact over no (or poor) management. I’ll be looking into these details further.

As a point of comparison, croplands in Quebec are on average releasing .5 tons of CO2 per hectare into the atmosphere each year. This is the opposite of sequestration, and is due to erosion, loss of soil carbon, and the fact that there is very little living plant matter making it through the winter season. Regenerative and organic farming techniques can do much better, keeping the soil living, healthy, and storing much more organic matter, but they can’t match forests. We need food and must continue to adopt great agricultural practices, but they aren’t going to solve the problem all alone.

How much total carbon and where is it?
So if a forest is sequestering close to two tons of CO2 per hectare each year, where does it all go in that forest? It turns out that there are three big pools. In that average 80 year old Quebec forest, there would be about 80 tons per hectare of living trees, the majority in the trunks, with the rest in the branches and roots. Then there would be about 25 tons per hectare of dead woody material, in logs and branches on the forest floor, as well as standing dead trees (snags). Finally, there would be about 150 tons of carbon per acre of carbon in the soil, known as ‘soil organic carbon’*** . This is in very small pieces, many of which are even microscopic. This soil carbon is integral to all of the microorganisms that live in the soil. All told, this is about 250 tons of carbon stored per hectare of forest. If that forest reaches old age (200 years or more), the total carbon storage may max out somewhere around 400 tons per hectare.

Disturbances and loss of forest carbon
So forests build up and hold a lot of carbon, but it’s not there forever. When there are major disturbances that kill a lot of trees, carbon can be released to the atmosphere. This is different from fossil fuel reserves buried deep underground, which would stay there for millions of years without our intervention. But forests are living systems that are always in flux, generally storing carbon for tens or hundreds of years, perhaps even thousands when circumstances are right. Natural disturbances that kill or damage trees and include fires, ice storms, wind events, floods, insect infestations, bacterial or fungal disease, and more. These kinds of events can kill some or even most of the trees in a given area, and when dead trees decompose, much of the carbon within them goes right back into the atmosphere. Then there are land use conversions, changing forest to other things like agricultural fields, roads, houses, etc. These generally wipe out the majority of the carbon store, and almost no other land use would be as effective at combatting climate change as maintaining forests.

A different kind of forest disturbance can actually help fight climate change. While counterintuitive, harvest/logging is a type of disturbance that can potentially fight climate change. This isn’t just any logging, but rather doing the right kinds of harvests in the right kinds of places. There are certain areas that should stay untouched, such as the few remaining old growth forests, and others that need the just right kind of management. While there are too many details to get into here, good management maintains a healthy forest and protects biodiversity, while also giving us wood products.

So how can logging help? Harvesting wood helps people to fight against climate change in two main ways. The more important of them is that using wood to meet human needs almost always uses less energy and creates less emissions than the alternative. We are going to want buildings, and packaging, and insulation, and so many more goods, and if we don’t use wood we will instead have to use more steel, concrete, plastics, or other products. If we assume that we are going to want those goods anyway, it is most often better to use wood products. There is a whole field of study called ‘lifecycle emissions’ that looks at these sorts of comparisons, and data is available out there to actually compare product by product. The second way that harvesting wood can help is with carbon storage directly in wood products. A board that goes into a house may stay there for 100 years or more, and all the carbon will stay sequestered inside that house as long as it stands. The Agriclimat conference gave a few key comparisons about these effects.

ProductSequestration time – averageTons of CO2 reduction by using one ton
wood instead of other materials
Firewood1 year.4 tons (from fossil fuel heating)
Paper products2 yearsnot available
Boards – construction lumber35 years.9 tons (from steel, concrete, etc.)
Paneling – plywood, particle board, etc.25 years.8 tons (composites, plastics, etc.)

So in reading this table, by using wood to do construction instead of steel and concrete, for every one ton of construction lumber you build with, you have almost a ton of reduced emissions as compared with making that same building with products like steel and concrete. There are of course some emissions associated with cutting trees, transporting them, cutting them into boards, etc., but this is far less than for other materials one could use. So generally, wood is good.

But one still has to take this with a grain of salt, as this is broad-scale averages and doesn’t apply in every single situation. For example, residential heating with wood. If one is taking low-quality locally harvested trees and burning them for heat in homes that would otherwise be heated using oil or propane, that is a great thing. But if instead of wood burning, you heat your home with a heat pump using clean electricity (there is a lot of hydropower in Quebec), wood burning doesn’t look so good. And when it comes to the wood pellet electricity generating plants, the massive harvesting of wood used to burn for electricity is far worse than renewables like solar and wind. There is always nuance, but using wood instead of alternative high emissions products and energy sources is a wise choice.

So how much can we actually accomplish at the Manitou?

Our own forests at the Manitou and Ferme L’eau du ruisseau add up to 144 hectares of forest of mostly middle-aged forest, so are sequestering about 250 tons of CO2 per year. How far does that forest go towards off-setting the carbon emissions of my family? Or those of my neighbours?

In 2019, the Canadian emissions per person was 15 tons CO2/year. Some of that is personal consumption, but a big portion is also each person’s share of government, industry, commercial, agriculture, shipping and the rest. As was mentioned above, each hectare of forest sequesters 1.75 tons CO2/year, which means each person needs 8 hectares of growing forests to soak up their share of emissions. Put another way, these 8 hectares would hold something like 1000 good-sized trees (25 cm diameter trunks or more) plus all the smaller trees and the understory. Each of those larger trees would then be pulling an average of 15kg of CO2 from the atmosphere each year. That really isn’t a lot for each tree, but since Canada has over 300 million hectares of forest, it really does add up.

My own family includes 2 adults and 3 small children. For the sake of argument, say that we are equal to 4 adults, or 60 tons CO2/year. So with our forests sequestering around 250 tons C02 per year, our forests will fully off-set the emissions of 4 families like my own. Making sure that this forest is cared for properly will have a bigger effect than almost anything else that our family could do in our personal lives – compared to taking less plane flights, living in a smaller more efficient house, giving up a car, etc. This is still just a drop in the bucket compared to the scale of the problem, but this is something that we can directly do, and it won’t cost us anything. Good management of our forests will even bring in a few dollars while we also accomplish a bit of greater good.

The last thing to mention is going to be about the details of doing forest management right. I’ll have much more to say about this in future posts. But the gist of it is that there is a really great balance that is achievable, where we will be able to protect our land and its biodiversity, while also sequestering carbon and producing economically valuable timber. This path isn’t necessarily an easy one since you must take all of these concerns into account at the same time, and find that sweet spot of actions to take. I’ll let you know how it goes.

Other reading

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*** Soil carbon limited by mineralization – This is completely an aside from the main story above, but it was a really interesting fact that I learned that same day of the conference and I just needed to share. This is about carbon mineralization, the process by which organic soil carbon is turned back into CO2 in the air. In the fight against climate change, we actually wish we could have much lower mineralization, to hold more carbon in the soil. It turns out that this mineralization is caused by soil micro-organisms that need both warmth and oxygen. Take away either of those, and more carbon stays in the ground. The most extreme cases are things like peat bogs – with no oxygen, there is almost no decomposition and they hold massive stores of organic materials (and therefore carbon). Cold boreal forests have higher rates of mineralization, but are still quite cool and have a ton of woody material on the surface and high percentage of carbon in the soil. As you go to temperate forests and then tropical forests, the mineralization gets faster and faster. Tropical soils therefore tend to have much lower soil organic carbon – microorganisms essentially eat it all and release it as CO2 very quickly. This also means that in the tropics, most of the carbon is actually stored in living trees and plants.

A warming climate will have an effect in Quebec on soil carbon. Warming will directly lead to more mineralization and more release of carbon from the soil to the atmosphere. As of 2020 data, the farms Agriclimat studied varied between 2.1% and 8.6% organic carbon in the top layers of soil. It is hard to quantify exactly, but those amounts will certainly go down as climate warms, giving one more headwind that we have to work against to reduce greenhouse gases in the atmosphere.