My backyard carbon sink

Can planting trees offset your carbon footprint?

Posted by Eric de Place (Guest Contributor) at 3:00 PM on 18 Sep 2007

Read more about: climate | carbon offsets | ecological footprint

When my wife and I bought our house, the yard was typical for our neighborhood: a mostly barren plain of lawn so sunbaked that you could bounce a tennis ball off it. So being eco-groovy types, we've tried to improve the place: we put in a rain barrel, built a natural drainage system, and added topsoil planting berms. But I'm most proud of the trees we've planted: a pair of akebono cherries in the parking strip and a white-star magnolia in the front yard; and in the backyard, a shore pine, a Chinese dogwood, a couple of vine maples, a Japanese maple, and a limelight cypress.

I recently began wondering how much carbon our new trees are soaking up. Since tree planting is the sine qua non of carbon offset programs, how much of my emissions are offset by my yard? Enough, perhaps, to justify moving from a dense, highly walkable neighborhood to a still-urban but less foot-friendly place? (My Walkscore dropped from 92 to 80.)

The answer, I'm afraid, is "no."

I estimate that in an average year my nine trees will soak up right around 100 pounds of carbon-dioxide combined. (Brief methodology note at the end of this post.) That's the emissions equivalent of burning five gallons of gasoline -- or actually just four gallons, if you consider the "lifecycle" emissions of gas. In other words, my tree planting allows me to burn about one-third of a tank of gas guilt-free each year.

That's certainly better than nothing. But then again, the average American is responsible for about 45,000 pounds of yearly CO2 emissions from energy use alone. Nine trees like mine offset about 0.2 percent of those emissions -- and much less when nonenergy sources are considered.

Even giving myself a big benefit of the doubt -- my electricity is carbon-free hydropower and I take other steps to reduce my climate footprint -- it's highly unlikely that my trees are offsetting more than half a percent of my annual emissions. Plus, half of those tree offsets belong to my wife. So that means at the very, very most I'm offsetting about one-quarter of one percent of my own emissions.

I could do more for the climate by simply avoiding a couple of trips in my car.

Admittedly, we could fit a few more trees into the yard, though things would start to get crowded. And, in fact, we do have a few trees besides those I mentioned -- an apple, a yew, and two thickets of arbor vitaes -- which are also adding their own biomass and carbon each year. I didn't count their carbon sequestration because I can't take credit for them. They'd be around whether or not I owned the property.

In any case, it's hard to see how small-scale tree planting can be a viable solution for carbon offsets. After all, not everyone has an empty yard, just waiting to be stocked with trees. The better choice for the climate might be to do without a private backyard in the first place.

What's worse is that the carbon stored in my trees is only temporary. Someday, they'll die and they'll be chipped, or maybe they'll decay, and most of the CO2 will be released back into the atmosphere. It's possible that a portion will remain trapped in the soil (my backyard soil is vastly richer than it was before), but most will be lost. So when I take the long view, I haven't even effectively offset my emissions, I've just delayed them. In the accounting of global warming, the delay won't help at all.

Now, in defense of trees, it's worth mentioning that they do have some other climate benefits. Properly placed trees can shade buildings in the summer, lessening the energy needed for cooling. In the winter, they can act as wind breaks and slow the heat escaping from buildings.

And I should say this too: I love trees. I love all kinds, and I love them for all different reasons. In our yard alone, some have springtime flowers that dispel the winter's angst, while others have autumn foliage so brilliant it's heartbreaking. Still others provide food and shelter for the juncos, chickadees, flickers, and finches that are now common visitors to our property. They help screen our yard from the neighbors and the street, and they give our outdoor space more depth and appeal. In time, they'll help buffer city noises, shade our exposed lot, and soak up water in places that are inclined to be soggy. But the one thing they don't do, I'm sorry to report, is offset my carbon emissions.

A note about methodology. Calculating carbon storage in trees is notoriously tricky for many reasons. For this post, I tried to make a decent estimate -- about 100 pounds of CO2 per year -- but I'm not claiming great precision. I made some educated guesses about about my trees' growth rates, mature sizes, and lifespans, but I could be off by dozens of pounds of CO2 per year, and perhaps more. If others are interested in ballparking trees' carbon benefits, here's a metric tree carbon calculator based in Australia. I wasn't able to find any calculators from Canada or the U.S., but I may simply have overlooked them. Please share, if you know of others.

For story: My backyard carbon sink
20 Comments | Post a Comment

Give up on carbon neutral myth yet?

Thank you for that final few paragraphs where you get into what is really important about tress. I think that your excercise paints the perfect picture of how far most people (even extremely conscious people like yourself) have to go to reach carbon neutrality in their lifetimes. It basically is impossible.
It pushes people to actually except the stark truth. To be carbon neutral basically personal cars are not viable and never will be. Homes must be net zero, or negative CO2 if you own a bunch of products that involved energy intensive manufacturing, which is everything in our modern life.
We need people to give up their notion of what modern life looks like. I'm not advocating the stone age lifestyle. I'm talking about a renaisance where modern life is simpler by a thousand and smarter by a million.

The Black Car Project Killing cars before they kill us!

by wildleaf at 3:31 PM on 18 Sep 2007

Motives

Eric,

Thank you for the post.

I was under the illusion that my own project, a 2-acre prairie remnant, was paying for itself just sequestering carbon. I was dismayed to learn that it was removing, at most, 4 tons of carbon from the atmosphere each year... net, even after burning the top off every few years.

My reaction, posted elsewhere on this website...

"Yahoo... all the effort, all the fuel burned, all the days in the hot sun rather than reading a book... hell, the water I pumped out of the ground to keep myself hydrated... is currently worth -- as judged by the free market -- about $16.40 per year."

But I added...

"Good thing that is not my primary motivation or I would not bother. I know preservation of biodiversity, setting an example for others, and the pure aesthetic value is worth more than that."

It is very important to point out -- AS OFTEN AS POSSIBLE -- that planting trees and other vegetation appropriate for a region is worth far more than what the market will ever assign to it. And there is more to preserving our natural environment than removing CO2 from the atmosphere.

I applaud your work and thank you for setting an example for others to follow. Even if your yard only stimulates a single child's interest in caring for the rest of the Earth, the effort you put into selecting and caring for the plants was worthwhile. And you never know... that apple tree might save a native pollinator's life and prevent an species from disappearing.

by wiscidea at 3:48 PM on 18 Sep 2007

Yeah Eric Mon

The reason to plant trees was traditionally for a wind screen to prevent wind erosion, and then for shade. We like them because they attract birds as well. I've been a native tree "nut" for a long time and would never even consider trading carbon credits for a tree. Oops, I think that is your point!

There seems to be some wild concept that if you plant a tree, it could absorb via photosynthesis all those guilty man-made CO2 emissions. Folks, it doesn't work that way. We could stop every car, industrial stack, and every combustion source in the world and you know what, those trees would do perfectly well - if not better.

Forgot to mention that stack and exhaust pipe emissions also contain ozone, sulfur acids, and other bad actors that TRY TO KILL TREES.

Face it, the whole thing is a sham. Enjoy your trees and take care of them as you can. Some bug, storm, fungus, or chainsaw is just dying to cut her down, so stand up for your rights, mon.

Onward through the fog

by Sam Wells at 4:06 PM on 18 Sep 2007

a straw man

I'd bet most carbon offset projects that plant trees are far bigger than your backyard project, but forget about that.

No one, except maybe a handful of people, argues that offsets are a silver bullet for global warming.

At this point, I don't understand attacking the merits of offsets. The voluntary carbon markets have hit the ground and taken off running, you're not going to stop it but you can provide information to make them better.

The only message I would take away from this piece is that buyers of carbon offsets should research what they are actually buying and decide if they think that's adequate to meet their desires for emissions reduction.

by naturescene at 4:30 PM on 18 Sep 2007

i also say

that if trees aren't any good for offsetting carbon, we should still consider using market concept to encourage the planting of vegetation.

That is, stop calling them carbon offsets. Make them biodiversity credits, habitat credits, environmental credits, etc. Eco-conscious people should still want to pay for them (after all, the purchasers of offsets are already environmentally-minded).

by naturescene at 4:35 PM on 18 Sep 2007

I like that

You seem to talk some truth, Nature Scene. However, your comment that offsets are going to happen and the implication "better get out of the way" is rather sad. If I plowed and burned down 10,000 acres of native plants, grasses, and habitat to put in date palms every 20 feet, I should feel better? No. I'd be one pissed off monkey!

Tell me one, just one excellent bio- or geo-engineering project that makes sense to offset man-made CO2 with something else. Gosh, on an annual basis (not forecasting for 30 year growth) I can't think of a single one. But you're smart, maybe you have some ideas.

DO YOU KNOW HOW STUPID IT IS DO OFFSET PRESENT DAY CO2 EMISSIONS WITH FUTURE REDUCTIONS THAT MAY OR MAY NOT EXIST, SUCH AS A TREE FARM?

I'm sure you do ... just checking.
sammie

Onward through the fog

by Sam Wells at 6:47 PM on 18 Sep 2007

Carbon Offsets

At this point, I don't understand attacking the merits of offsets. The voluntary carbon markets have hit the ground and taken off running, you're not going to stop it but you can provide information to make them better.

Actually from what I have read on this site, most people aren't against the idea of carbon offsets. They are against their current implementation and the existing problem with no regulation.

For carbon offsets to work, we need more immediate solutions. Everyone pushes trees because they are cheap. They are pushing the message that everything can be offset with planting trees. Instead of planting trees, why not introduce neighborhood power generation? Wouldn't that have a more immediate effect and truly offset carbon usage? Look at Pacific Gas & Electric's program. They are selling trees that already exist and have offset their carbon to make people feel good about their electrical usage. However if they promoted tidal power generators along the breakwaters in numerous bays along California's coast or use the cash flow to provide needy families with solar panels on their homes, they would actually do more. Maybe they could figure out a way to generate wind power on the thousands of power transmission towers criss-crossing the state. New clean power generation without requiring more land would be nice.

Offsets or the ideas of offsets are nice. But promoting trees when their contribution is really not that great isn't. Planting a few million acres of rainforest in Brazil would definately help but its a lot more than trees that go into that equation.

by wayneluke at 7:01 PM on 18 Sep 2007

OK, clue me in ...

Hey if one wants to put offsets such as practical tide turbines, wind turbines, waves machines, and solar generators I'm all for it - but usually that juice is sold as peak and base-load electrical power, not as an offset. Bummer.

Onward through the fog

by Sam Wells at 8:00 PM on 18 Sep 2007

Yeah, good one naturescene

I suspect that trees are going to play a huge role in carbon sequestration. It just has to be done right. Trees in cities are nice but probably should not be a part of any sequestering plan.

In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world

by biodiversivist at 9:38 PM on 18 Sep 2007

Sam...

California just updated its Renewable Energy Standards. Seems they are going to hit the 20% goal early. In 2010 instead of 2017. The new goal is 33% by 2025. That is pretty significant. Southern California Edison already sits at around 18% and they are continuing to add to it. PG&E already sits at 10%. Also the state has banned these utilities from purchasing power from plants that produce more pollution than Natural Gas plants. This effectively bans coal. It would seem that at least some offsets are having an affect.

http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/12/14/B ...

I would say the problem is that only 25 states have RES programs and some range as low as 5.5% (Texas). This would be from a lack of federal standards. However as more states mandate renewable purchases, the amount of coal will decrease. It isn't an overnight solution. Nothing would be.

by wayneluke at 10:37 PM on 18 Sep 2007

"appropriate for a region"

This, by WiscIdea, is excellent:

<<
It is very important to point out -- AS OFTEN AS POSSIBLE -- that planting trees and other vegetation appropriate for a region is worth far more than what the market will ever assign to it. And there is more to preserving our natural environment than removing CO2 from the atmosphere.
>>

And I love NatureScene's suggestion about "biodiversity credits" and "habitat credits."

But I am puzzled, therefore, that we should judge Eric's tree-planting efforts to be well done on those terms. Are the trees that he chose to plant native to the Seattle region? He tells us that they have attracted birds, which is a very good thing. But will they attract native pollinators in the Spring?

I am only asking for information, and do not mean to imply any criticism. Quite the contrary: Eric did a praiseworthy thing by bringing down the curtain on the tennis-court lawn, and by planting trees.

Chickens deserve our true friendship! So do fish! So do other sentient beings! Let us learn to be kind.

by caniscandida at 10:49 PM on 18 Sep 2007

Good point, Canis

It might also be smart to think of timber trees rather than ornamentals. Instead of eventually rotting or burning out the carbon gets to stay sequestered in furniture or framing.

The true meaning of life is to plant trees, under whose shade you do not expect to sit.

by spaceshaper at 4:40 AM on 19 Sep 2007

Hydro NOT Carbon Free

Sorry to disappoint you, Eric, but hydroelectricity is not carbon free. Even worse, it may be a big contributor to global warming.

In the first instance, dams kill rivers. A riperian landscape is rich in wildlife diversity, fertile soils and oxygenated water. When you take a river away from a landscape - leaving a tiny apparition of its former self - the land dries, and carbon dioxide is released from the soil. Carbon dioxide is also no longer absorbed by the rich flora that can no longer survive in a dry land. Furthermore, the fertile soils now have to be fertilised if they are to be farmed (note what happened to the Nile valley after the High Aswan Dam was installed). Artificial fertilisers take energy to make, or you can fertilise using belching methane machines (cattle) - your choice.

Secondly, the stagnant environment of the reservoir is a major source of methane (see this article for context). Where biological matter builds up methanogenic bacteria get to work and produce methane, so this alone could offset any energy saving benefits of hydroelectricity.

Hydro may appear to be a source of green energy, but it is just a way of producing large amounts of controllable power on the cheap.

Keith Farnish www.theearthblog.org

by farnishk at 6:58 AM on 19 Sep 2007

good point

There was an interesting program on PBS long long long ago, so someone might want to verify this...

Damn degrades river and blocks salmon migration -- two strikes against the salmon.

Bears, raptors, and other predators can no longer hunt salmon, which they apparently drag or drop some distance from the river and consume only part of it.

Bear scat and scavenger scat no longer replenish nitrogen in soil.

Lack of nitrogen ptrevents healthy tree growth and forest regeneration.

Forest cover no longer protects stream from silt or maintains low water temperature for salmon.

The entire ecosystem collapses -- my extension of the horrible chain of events -- and no longer efficiently sequesters carbon.

by wiscidea at 8:02 AM on 19 Sep 2007
[ Parent ]

Couple of replies

Keith,

My understanding is that the "ghgs from hydro" argument has been somewhat overblown. I'm not closely familiar with the literature, but I've been told by knowledgeable folks that the problem is much pronounced in tropical settings where there is much fluctuation in the water level (more biomass grows quickly and is subsequently innudated). I think it's a less serious problem in temperate zones. (Please correct me if I'm mistaken!)

In any event, my power, which is supplied by Seattle City Light, has been subjected to fairly rigorous audits and it is considered the only large U.S. utility with zero net emissions. Still debatable, I suppose, but I'll leave it for another time...

On a related point, damns definitely degrade river systems -- no doubt about it. While City Light's power doesn't come from dams that block migrating fish, much hydro power does. And I'm not saying that hydro is environmentally benign, just that it's climate-friendly.

Finally, to caniscandida's point, about half of my trees and other plantings are native to western Washington. I live in an urban area where the terrestial ecosystem conversion is somewhere near 100%. So my backyard efforts aren't aimed to restore the native coastal forests and bog-meadows -- what I'm doing is just not comparable to wiscidea's laudable prairie restoration -- but simply to support some of the native critters, even while I make it a great place to hang out. It's been pretty successful for birds. Some of favorite, though rare, visitors include downy woodpeckers, golden-crowned sparrows, and even a sharp-shinned hawk. But I don't know enough about pollinators to have even the foggiest idea about whether my yard can be successful on those terms.

by Eric de Place at 9:22 AM on 19 Sep 2007

Trees do not "Soak Up" carbon

While all of the nuveau "Science" guys have everyone believing in their program to soak someones money away from them by thinking that they will benefit this earth by purchasing some carbon,I just roar with laughter that all of you would go for it.Ya know,this old earth scientist says again for those who refused to process the news I have shared on this forum previously. Photosynthesis does not make oxygen,the oxygens frequency does from the cymatic grid that runs this planet(And all others too)When you have some sweet sap ,maple to be exact on your Johnny cakes from time to time,please ponder that that is a "CARBO" hydrate,made in the roots to feed the tree its nutrition for growth and its fruits.That tree (and other plants) must have a process for exhausting its waster from its nutrition,just as you do.That tree and other plants have pores(Stomata) that opens with a tone.Do you want to know which one opens it?Ask me ,as it is another conversation,so back to my mission.The oxygen hangs around trees in the first place because it seeks the ground,through our gravity process,which is another one of those little further conversations.The oxygen goes into the stomata and helps purge the used up carbo-hydrate component of the tree (or plant) and combines with a carbon molecule and VIOLA!!! You receieve a Carbon dioxide.All of the plants and trees could be removed from this earth and we would breathe just fine,we just would have nothing to eat.It really is simple,if you look at it in the correct"Scientific" way.Now if anyone "REALLY" wants to understand the "Glbal Warming"cycle we are enjoying at this time.I have shared that before,but,ya know,all of you were spoonfed science that garbage at your higher learning institutions and most of you refuse to believe they took your money and your time and blew one hell of alot of smoke up your ass and you cannot process as a result. This was on purpose,but thats not my fault,IS IT ? My mission has been to bring earth science knowledge to your attention,so you dont make this earth worse off than it actually is.Yet we do have a very serious problem on the earth that will,if gone un-checked remove all possibility of life in about 100 years,and no one but I,(That I know of) speaks to it.Why is that? But anyway,I digress,as I know you folks would rather just stay in the dark as it is much more comfortable there.

Earth Shaman

by Earth Shaman at 12:53 PM on 19 Sep 2007

Ignorance abounds

That's certainly better than nothing. But then again, the average American is responsible for about 45,000 pounds of yearly CO2 emissions from energy use alone. Nine trees like mine offset about 0.2 percent of those emissions -- and much less when nonenergy sources are considered.

Let's just take this at face value and not try to find a source. Assuming that your house has 2 occupants the CO2 needing to be sequestered for those two amounts to 90 thousand pounds yearly. Of that 1/3 (.2727 actually) of the weight is carbon.

Doing some math 90,000x.2727 = 24,545 lbs of carbon that would have to be returned to the ground in mineral form each year in order for your household to claim carbon neutrality. Adding a bit (6%) for ash that would amount to some 13 tons of charcoal that you would have to bury on your lot each and every year.

Think of it as 3,000 ten lb bags of charcoal to bury just to break even on your households current emissions. That's only 70 lbs a day, about a 30 gallon trashcan full, 365 days a year. Making your own charcoal you only need to cook, in a retort, 280 lbs of dry wood (varies greatly) daily to get that weight of charcoal.

Using oak cordwood at about 3500 lbs to the cord....365/(3500/280)= 29.2 cords of wood converted to charcoal yearly to offset the emissions of two US residents. That's just about 2 1/2 cords of wood per month. (local value $500)

That is why carbon offsets are a stupid idea. They can do nothing in the face of continued emissions. We could quibble about my math but even the thought of burning 140 lbs. of dry plant matter daily just to bury and level your carbon emissions is insane.

We have to stop burning fossil fuels. There is NO ALTERNATIVE.

http://bioenergy.ornl.gov/papers/misc/energy_conv.html

Put the Carbon Back

by Pangolin at 1:40 AM on 20 Sep 2007

What?!

Earth Shamen, I can only just make out what you are saying, but if I understand rightly, you are saying that the act of photosynthesis does not emit oxygen into the air. If there were no trees (I assume you also mean shrubs, perennials and so on) then the atmosphere would have a lower level of oxygen in it, and most creatures on Earth would die.

On the other hand, you are saying that the carbon dioxide in trees is not really in the trees, it is in your maple syrup, or something. Well, I don't know where you learnt your biology, but I don't remember the bit where all the carbon is immediately released back into the air.

Or maybe you are just a mad troll who has wasted my time. No matter, you still need to be told off.

Keith Farnish www.theearthblog.org

by farnishk at 6:14 AM on 20 Sep 2007
[ Parent ]

Couple of comments

Hi all,

Interesting discussion. A few comments:

Since tree planting is the sine qua non of carbon offset programs...

This isn't true in theory or in practice. Tree-planting projects are a very small percentage of offsetting projects worldwide. They're just what most people seem to have heard of.

That is why carbon offsets are a stupid idea. They can do nothing in the face of continued emissions. We could quibble about my math but even the thought of burning 140 lbs. of dry plant matter daily just to bury and level your carbon emissions is insane. We have to stop burning fossil fuels. There is NO ALTERNATIVE.

This is confused, to say the least. Carbon offsets are a funding mechanism for whatever means of carbon reductions you prefer, including alternatives to fossil fuel use. Far from being a "stupid idea", they are an enabling mechanism for the types of changes you would like to see take place -- changes that won't otherwise occur.

www.terrapass.com/blog

by Adam Stein at 9:16 AM on 20 Sep 2007

Three Replies

Adam Stein,
You write, "Tree-planting projects are a very small percentage of offsetting projects worldwide." Fair enough. I overstated the centrality of tree planting to offset projects.

Pangolin,
I have no idea what your point is. If you read my post, you would know that I think tree planting, especially on a small scale, is useless for offsetting emissions. And that finding ways to avoid emissions in the first place (i.e. less driving) is key.

Earth Shaman,
Dude, you are blowing my mind.

by Eric de Place at 9:52 AM on 20 Sep 2007

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