Midnight mushrooms and their exhalations: why wood-fired power generation is not carbon-neutral

“Ye elves of hills, brooks, standing lakes and groves… that / By moonshine do the green sour ringlets make… you whose pastime / Is to make midnight mushrooms… .”

Hemlock Varnish Shelf (Ganoderma tsugae), a deadwood-eating mushroom whose preferred woody meal, as its name implies, is hemlock. The carbon dioxide this fungus breathes out is part of the global natural carbon cycle. If we humans burn the hemlock for heat or electric power, the CO2 produced by the combustion must be categorized as anthropogenic. Photo by Margaret Yee, Johnson Trail, Muskoka County, Ontario, November 2012.

Hemlock Varnish Shelf (Ganoderma tsugae), a deadwood-eating mushroom whose preferred woody meal, as its name implies, is hemlock. The carbon dioxide this fungus breathes out is part of the global natural carbon cycle. If we humans burn the hemlock for heat or electric power, the CO2 produced by the combustion must be categorized as anthropogenic. Photo by Margaret Yee. Location: Johnson Trail, Bracebridge, Ontario, November 2012. Click to enlarge.

I first read that passage from The Tempest (Act V, Sc. I) decades ago. I still get goosebumps when I read it today. It is not just that it occurs in the midst of the most profoundly optimistic and counter-instinctual juncture in Shakespeare, but it also brings to life the sheer, sometimes unsettling, magic of the woods by moonlight. Olden-day folklore had it that mushrooms, many of which materialize overnight, are made by elves. Incorrect perhaps, unless you consider the fungal mycelia, which send up the fruiting bodies we call mushrooms, to be elves. Still, it is a beautiful and fitting explanation. Mushrooms are so mysterious and seemingly unlike us humans that any explanation of their behaviour almost begs for something exotic and otherworldly. But humans and fungi are, on the Tree of Life, close neighbours on the same major branch, taxonomically speaking: we are not only fellow Eukaryotes but fellow Opisthokonts as well. More to the point of what I cover in this blog, we both produce as part of our natural functioning carbon dioxide (CO2), an important greenhouse gas in the planet’s atmosphere. This is because we both oxidize carbon as our basic metabolic activity. But humans also produce CO2 by burning carbonaceous fuel, for heat and electric power. Some of that fuel is wood—which, for many mushrooms, is food.

I had an interesting discussion with someone at an energy conservation event a few days ago. We discussed whether the CO2 from wood-fired power and heat generation should be categorized as carbon-neutral. My interlocutor argued that it is carbon-neutral; if it isn’t, then all the research and work into developing algae-based biofuels is wasted.

My position is that wood-fired power and heat generation is not carbon-neutral. It is an anthropogenic activity, and therefore the CO2 it produces is anthropogenic. Yes, dead wood will eventually turn into CO2 anyway—fungi worldwide, like the Hemlock Varnish Shelf in the photo above, put eighty billion tons of it into the atmosphere every year as the result of direct wood consumption or symbiosis with living trees and plants. But that is part of the natural carbon cycle. Us burning it is not. Whatever goes into the atmosphere right now, natural or anthropogenic, is increasing the CO2 concentration in air; see Item A1 at the top left. If we burn it, then fungi can’t eat it, it’s that simple. Therefore, the CO2 from wood combustion is anthropogenic.

Why is Ontario deliberately making electricity so expensive that its rural residents are forced to switch to wood, the dirtiest and most carbon-intensive—and labour-intensive—fuel? This is directly contrary to the philosophy that underpinned the First and Second Electrifications of our great province.

The discussion came up after I described two people I know, one of whom lives in rural Ontario, the other in rural Quebec. Both have wood-fired central heating distribution systems that heat their houses and other buildings on their properties. One, the guy who lives in Ontario, only recently installed his system. He did so because electricity prices where he lives are so high that electric space heating is no longer affordable. The guy in Quebec (who recently passed away, R.I.P.) had recently decommissioned his wood-fired system in favour of electric heat—the province of Quebec has long had a policy of providing cheap electricity to its citizens.

I argued that the Quebec case is how Ontario should be. Our power should be as it was designed by the father of our electric grid, Sir Adam Beck, to be: cheap, abundant, and everywhere. I would only add “clean” to Beck’s criteria.

Electricity in both Ontario and Quebec is, currently, extremely clean. Quebec’s grid CIPK is somewhere around 2 grams (see Environment Canada’s “National Inventory Report 1990-2009, Part 3,” Table A13-6); Ontario’s, according to my automated real-time calculation in Table A1 on the left was 42 grams at seven a.m. this morning (November 25). Yes, Ontario’s grid CIPK is several times higher than Quebec’s, but if we were our own country we would get an easy buy into Group 100 of the World Cup of Carbon (see the table at the very bottom of that article).

Why is Ontario deliberately making electricity so expensive that its rural residents are forced to switch to wood, the dirtiest and most carbon-intensive fuel? This is directly contrary to the philosophy that underpinned the First and Second Electrifications of our great province. In those drives, electricity was seen as a public good. The grid was brought to rural Ontario by electricity revenues from urban rate-payers; that was the only way the economics could work. Today, it’s just the reverse. Electricity is priced so that urbanites get the cheapest rates; rural residents can freeze in the dark or switch to less expensive fuels like wood.

Which puts humans in direct competition with mushrooms for all that wood.

This shouldn’t be happening. And people who fancy themselves conservationists should not be supporting it. The natural division of labour has fungi, not humans, disposing of wood. Nature has reserved for us humans a fuel of infinite superiority: uranium. Uranium releases many millions of times the energy of fossil fuels that are themselves far more powerful than wood. For example, methane, the main ingredient in natural gas, releases on combustion 810,000 Joules of energy per mole; that works out to about 8.39 electronvolts per reaction at the molecular scale (an electronvolt is 1.602176565 x 10-19 Joules). Uranium-235 on the other hand releases around 200 million electronvolts per fission (exactly how many electronvolts per fission depends on which elements each U-235 atom splits into). Those 200 MeV come with absolutely no CO2.

The sheer superiority of uranium relative to even the most powerful fossil fuels is an extremely recent discovery. This discovery, in 1939, was part of the breathtaking scientific revolution that occurred in lock-step with the Second Industrial Revolution. In fact, it was in part because of the wide availability of reliable electric lighting, which was perhaps the hallmark of the Second Industrial Revolution, that scientific discovery exploded so dramatically after the late 1800s.

Nature revealed to us, in 1939, her secret store of clean energy. Our use of uranium and other fissile elements as the replacement of carbon-heavy fuels will be our measure as a species.

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Luke Collie
5 years ago

While leaving the wood in the woods, and in general leaving natural systems alone when possible is certainly a good idea, I don’t think it is helpful to change the definition of anthropogenic CO2 as you have done here. It is essentially a question of timescale. The carbon cycle is slow, and the climate system has huge thermal inertia. It doesn’t matter whether CO2 is released now or next year, and matters very little whether it is now or in 2050. The CO2 that made a tree has been taken out of the atmosphere over the last century or so, and will go back over the next one, one way or another. Integrated over the relevant timescale, nothing changes, *provided that* you plant a new tree, or at least allow one to grow. Fuel wood is carbon neutral if it is treated like a crop. Cutting down the forest so it can’t renew itself is not.

John ONeill
5 years ago
Reply to  Luke Collie

‘It doesn’t matter whether CO2 is released now or next year, and matters very little whether it is now or in 2050.’
In fact it matters a lot. The biosphere can deal with all the carbon we’ve put into it, but it does so in its own good time. If we’re burning in one year the fossils that took a million years to lay down, we’ll get ahead of the carbon sinks, and atmospheric CO2 and ocean acidity will go up. The same if we burn a tree that took fifty years to grow: the fact that we planted another tree might mean we break even in fifty years, but the seedling could just as well succumb to pest, forest fire, or somebody else with a chain saw before then. It’s just been shown that mature trees keep taking up carbon faster than young ones, and chain saws and log trucks burn fuel too. Even a decaying, naturally dead tree will release its carbon much more slowly than your log burner would.

Stephen Hood
5 years ago

All good points Steve but I have another to add. Burning biomass produces anthropogenic CO2 but we can also anthropogenically absorb it. Example being a miscanthus or switchgrass crop which absorbs in a year what can be produced in a year. Problem is on how large a scale can this be done? What percentage of our energy need can be served this way? I have my doubts.

But by the Anthropogenic definition this and only this method can be carbon neutral. All other biomass combustion is as you say fancy accounting (deceptive and not at all clever). Taking a few hours to burn a tree which took 50 years to grow – a moments thought on the matter and most people would see the fallacy.

Cheers

5 years ago

We need to collectively form a pro nuclear activist group to help get the message that we need to be smarter about energy creation. Otherwise the economy suffers. Ontario is a great place but the energy policy is stupid. We are foolish to accept this trend towards austerity and scarcity. Abundant energy is not a sin. Screwing with nature while pretending to care as the green movement does is a sin. Stupidity should be illegal.

Robert Budd
5 years ago

“Fuel wood is carbon neutral if it is treated like a crop”. It’s certainly not bio-diversity or sustainability neutral.
The dead wood we use as fuel for heating is also the fuel that drives biodiversity in a forest. Yes it breaksdown and releases C02, but it also feeds a vast array of life forms along the way as well as effecting moisture retention, soil structure etc.. You can’t take that “fuel” out without greatly symplifying these systems.

It has boggled my mind for years how well people can convince themselves that biomass removal from these forest ecologies is doing them a favour.

Oscar Archer
5 years ago
Reply to  Robert Budd

That is also my conclusion, Mr Budd. No matter how technically carbon-neutral your biomass is, combusting it volatilises much of the essential elements that would otherwise feed organisms and enrich soils. I’d rather we hoe it back in, if we must chop it down at all.

5 years ago
Reply to  Oscar Archer

I bet that incorporating carbonized biomass into the soil will create a much more durable store of carbon than measures that only increase organic carbon.  Not that organic carbon is a bad thing, but 1% organic carbon vs. 5% biochar is a huge difference.

Andrew
5 years ago

Burning biomass, like wood, is unambiguously not CO2 neutral. A really simple example illustrates why at a conceptual level.

Suppose we have a hectare of deciduous forest that deposits a metric ton of carbon onto the forest floor each autumn in the form of fallen leaves, and that over the course of the following year, 10% of the carbon in the previous year’s leaf litter will be liberated as co2 via decay. After about 100 years, the forest’s carbon budget will have reached a steady state. At this point, ten metric tons of carbon will have accumulated on the forest floor, and the additional ton of carbon added to it each autumn will be equal to the metric ton of carbon subtracted from it via decay.

Now suppose we institute a biomass burning program in which we remove 100 kgs of leaf litter from the forest each autumn and burn it for energy. We reason that the leaf litter would have decayed and released its carbon back into the atmosphere anyway, so we regard burning it as co2 neutral. What happens under this program in this little model?

Via combustion, we instantly release 100kgs of carbon per hectare into the atmosphere. Our net emissions are actually higher than this though, because carbon continues flowing out of our ten ton forest floor carbon reservoir at a rate of 10% per year, and the one ton of carbon that initially flows out of it exceeds the 900kgs of carbon now flowing into it. Our net emissions in the first year of our program actually equals 200kgs of carbon. Over decades, our net emissions will steadily approach our emissions from biomass combustion as the forest’s carbon reservoir drains and its level approaches the new steady state value of 9 tons per hectare. In this simple model, when we reach this point, our program will have caused an additional ton of carbon to have been emitted into the atmosphere.

If burning biomass is co2 neutral even though it does contribute to atmospheric carbon dioxide, as I’ve illustrated above, then fossil fuels are also carbon neutral. After all, the same biogeochemical processes that created the coal in the first place are still at work today, and whatever coal we burn now will eventually be sequestered as coal again at some point in the future.