Author: chogan@directresearch.com

Post #1582, COVID-19, post-Labor Day decline (?)

 

If you’ve been following along, you know the drill at that point.  Holidays disrupt the COVID-19 numbers.  Mostly, that’s just a disruption of data reporting.  But to some smaller degree, there will typically be a drop in formally-diagnosed new cases, once all the dust has settled.  Plausibly, people who are only mildly ill will be more likely to forego a formal test if their symptoms appear on a holiday.

As a result, you have to wait a couple of days past the holiday, in the hopes that the numbers will bounce back to their true trend.

FWIW, on paper, the U.S. stands at 23 new cases per 100K per day, down three from the Friday before Labor Day.  I expect that will bounce up a bit yet, based on what appears to be under-reporting in California.

That said, reported hospitalizations are down to 4400 per day, deaths are down to 350.  Both of those are improvements over the pre-Labor-Day period.  Continue reading Post #1582, COVID-19, post-Labor Day decline (?)

Post #1581: Excessively screwed.

A man with one garage knows where his tools are.  A man with two garages is never quite sure.

That’s the hardware version of Segal’s Law.

Take two garages, a basement, and a son who borrows tools at will.  Add in decades of hardware accumulation from D-I-Y home projects.  Season with a habit of leaving tools wherever I last used them.  Top off with limited storage space and an increasingly faulty memory.

The result is chaos.

These days, every significant D-I-Y project starts off with a 15 minute stream of questions.  Don’t I already own a blank?  Where the hell did I leave that blank?  Is that the blank that broke five years ago, or did I buy another blank to replace that?  Didn’t I lend that blank to somebody?  Which toolbox would I have put that blank in?

Honey, do you have any idea where I would have left my blank?

And, for those of us in the Washington DC area, the inevitable “I know I bought that blank at Hechinger’s.  It hasn’t been that long since they closed.  Has it?”  (Answer:  23 years.)

Increasingly, I’ve come up with one-size-fits-all answer to all of those pesky questions:

Just buy another one.

Even though I’m pretty sure I already own one, even though it’s inherently wasteful to run to the hardware store at the drop of a hat, arguably the biggest time-saver for the aging and disorganized D-I-Y enthusiast is just to shell out for another one of whatever you’re looking for.  Search for five minutes, and if it ain’t where you think it should be, just buy another one.  It’s quicker.

The time of reckoning, hardware version.

I turn 64 this month.  I’ve been on a rampage to reduce the amount of stuff that I own.  Call it my home-grown version of Swedish death cleaning.

It’s no great secret that once you qualify for Social Security, much of what you own can be expected to outlast you.

Some of that will be great, quality, usable, heirloom goods.  True assets.  Something that a relative or a stranger will enjoy after you’re gone.

But much of it is just crap.  If not crap to you, then crap to anyone but you.  E.g., a toilet plunger is a useful, perhaps even necessary, device.  A good one is practically indestructible.  But is somebody going to want mine after I’m gone?

Crap is not one large, amorphous category.  Household crap comes in hundreds of distinct varieties.  Absolutely the best categorization I ever saw was in the book “Clutter’s Last Stand“.  The author (Don Aslett) was the Marie Kondo of his day, and the book is well worth the read for the listing of different types of clutter alone.

Your own personal pile of crap is going to be most evident in whatever area of life you tend to go most overboard.  For some people, maybe it’s clothing.  Perhaps books, or art, or glassware.  Stamps, coins, guns, cars.  You name it.

My personal crap avatar (crapvatar?) is the coffee can of mixed fasteners.  Bolts, screws, nuts, and God only knows what else.  All the leftovers from all my D-I-Y projects, conglomerated into one great cloacal mass of hardware.  Too good to toss out.  Not worth enough to sort through.  Occasionally useful.

Unambiguously crap once I’m gone.

As part of this round of cleaning, I am consolidating all my hardware and tools, with the idea of getting rid of as much as possible.  Following the process outlined by KonMarie, I have started by gathering all I own, from all its various hiding places.  The first step to recovery is to face the full extent of your excesses, hiding nothing.

This is the point at which “just buy another one” comes back to bite me, as I discover duplicates, triplicates, and more, of pretty much any type of home hardware you can imagine.  Some of it seeing the light of day for the first time in decades.

It is appalling, but not unexpected.  Like cirrhosis for the alcoholic, or a heart attack for the obese, a lifetime of bad hardware habits is catching up with me.

But how?

I now need some strategy for disposing of this ridiculous lifelong accumulation of tools and hardware.  Everything from perfectly usable power tools down to the inevitable coffee can(s) of mixed fasteners.

Obviously, I could dumpster the lot and be done with it.  Keep back the minimal set of items I think I might need over the next few years.  Toss the rest in the garbage.  Dust my hands, and I’m done.

That’s wasteful.  Not merely from an environmental standpoint, but even more from a value standpoint.  At least some of my hardware hoard could be of utility to someone, if I could only get it into the right hands.

The goal, then is to generate as much value out of this hardware excess as I can.  Find the people who could use it, and get it into their hands.

And conversely, I need to acknowledge that large parts of it are virtually worthless, or not worth the cost of processing it.  In particular, if you look on Ebay, you do in fact see people selling what amounts to the contents of their coffee cans.  Everything from dealers in new fasteners combining odds lots from open boxes, to what appears to be literally a coffee can full of mixed steel fasteners.  And people will buy that, in large lots, for about $1 a pound.  So I guess there’s that, as a last resort.  I don’t think that’s worth the cost of shipping, really.

I’ve already had my son sell some high-quality but no-longer-needed tools on Ebay.  I don’t think I have much of anything left that is of enough value that it would pay the shipping costs to try to sell it.  Although, per the above, it’s surprising what some will pay good money for on Ebay.

As a result, I’m now in the business of trying to find ways to give this away locally, to produce the highest value for the ultimate end users.  Without paying shipping costs.  And that means I’ll be giving it away through my local Buy Nothing and Freecycle groups, and similar.

I haven’t evolved a complete strategy yet, but it’s clear that there is some low-hanging fruit.  For example, I have an open box of deck screws.  It doesn’t look like much, but at today’s prices this scruffy box with four pounds of screws is about $40 worth of fasteners.  Surely I can find a taker for that.  The same for (e.g.) functioning power tools that I no longer need.

The real trick is going to be getting any value at all out of the lower-end merchandise.  With the coffee can of mixed fasteners being the apex of that problem.  The question being whether there is some way I can easily repackage that so that someone in my immediate area would be pleased to take that off my hands.

One can find examples of D-I-Y devices to sort out the contents of the typical suburban coffee can of mixed fasteners.  Upon investigation, these seem to be either aids to manual sorting or Rube Goldberg contraptions that are unlikely to work well.  The upshot is that technology is unlikely to come to my rescue.  And in any case, do I really want to buy or make yet one more hardware-related device?

So, the question is, how can I pack up this excess in way that provides some value.  Otherwise, there’s always the option of turning it in as scrap metal.  But only as a last resort.

I’ll let you know how it goes.  But I’m keeping the stuff from Hechinger’s.

Post #1580, COVID-19, finishing the data week at 26/100K/day.

 

The COVID-19 new case count continues to drift downwards, now 26 new cases per 100K population per day, down one from yesterday.

Data source for this and other graphs of new case counts:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 9/3/2022, from https://github.com/nytimes/covid-19-data.”  The NY Times U.S. tracking page may be found at https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html

Schools and the return to normalcy.

As has been the case throughout the pandemic, back-to-school for elementary and high school students seems to be having no noticeable impact on the spread of COVID-19.  Early in the pandemic, most people (including me) expected to see some increased spread of disease as students returned to school.  But, as far as I can recall, that never materialized in any uniform fashion.  Michigan schools had some problems, particularly among “high contact” populations such as football teams (Post #1077).  But for U.S. students, in general, return to class (typically masked, sometimes distanced, frequently tested) didn’t increase the spread of disease significantly above the existing background rate in the community.

For example, last year I did a pretty good “natural experiment” analysis of Virginia schools, comparing the school districts based on the staggered school year start dates.  I found exactly nothing.

Note:  This is the 2021 school year opening.

This year, our local school district (Fairfax County Public Schools) continues to track the number of reported new COVID-19 cases among elementary and high school students.  That seems like a not-unreasonable precaution.

Source:  Fairfax County Public Schools.

By contrast, there were definitely well-documented COVID-19 outbreaks at many U.S. universities.  For example, at William and Mary, which my daughter attended at the time, widespread partying last St. Patrick’s day led to a significant upturn in new cases (Post #1099).

This year, William and Mary isn’t even bothering to keep track of new cases.  Checking a few other Virginia universities, this appears to be the norm.  That seems a bit odd, as there’s still plenty of COVID-19 in circulation, and students are still apt to party.  That makes further COVID-19 outbreaks on college campuses almost a certainty.  But this year, those outbreaks will be treated no differently from flu outbreaks, annoying but not life-threatening.

And so, things return to (the new) normal.  It resembles the old normal, except that we all have to contend with permanent widespread circulation of this disease.  But now, by and large, it’s like flu, just vastly more contagious.  It continues to add to our health care costs and to the U.S. mortality rate.  (As noted in a recent post, U.S. lifespan isn’t going to return to the pre-pandemic level any time soon.)  It’s now just the way the world is.  Today’s children will eventually view COVID as part of the landscape.

Post G22-059, first summary of this year’s gardening season.

 

I tried a number of new plants and techniques in this year’s vegetable garden.  As we move into September, it’s time to start sorting out what worked and what didn’t.

Drip irrigation (Post G22-026, Post G22-027, Post G22-037).  A huge success.  For a bit over $100 in parts, and maybe two hours of labor, I can now water my entire garden either by hooking up to my rain barrels, or by using water from the spigot.  I can reconfigure it and add to it at will.  Key takeaway:  Use 1/2″ drip line.

Portable electric fence as a deer deterrent (Post G22-018).  A winner.  This is another project that took almost no time and a bit over $100 to set up.  Push in some cheap plastic posts, run the “wire” (more like metallized twine) through them, pound in a grounding rod, and hook up a small fence charger.  With deer deterrents, it’s hard to tell whether they worked or you just got lucky.  But I’ve had essentially zero deer damage since this went up.  I suspect the deer really don’t much like it.  (And, having tested it on myself, I concur.)  Key takeaway:  The technology has changed to make these easy, cheap, and flexible.  If you only need a small fence, you only need a small, cheap fence charger.

Sprawl technique for tomatoes (Post G22-035).  Thumbs down.  This year, I tried letting one bed of tomatoes grow un-staked and un-caged.  Just let them sprawl.  It’s by far the easiest way to grow them, but I’m not going to do that again.  They grow just fine.  I didn’t see (e.g.) any higher levels of leaf diseases and such.  This bed is now a mat of interwoven vines.  It’s hard to see the ripe tomatoes, and I’m losing more tomatoes to garden pests than I would if I had staked them.  Key takeaway:  The problem isn’t growing them, it’s getting a good harvest after allowing the vines to sprawl in the garden bed.

Cold-tolerant (early season) tomatoes (Post G22-025, Ripe Tomatoes in June).  A big winner.  This worked out quite well.  Not only did I have tomatoes by the end of June, those plants are still producing a decent yield of salad-sized tomatoes.  They slowed down in the heat of the summer, but it looks like they’re picking up steam as the cooler weather sets in.  I also learned a lot about what “days to maturity” really means.  Key takeaway:  Pick the right varieties, and you can have tomatoes in June without having a hothouse.

Growing large seedlings in paper lunch bags (Post G22-012, Post G22-017).  Works well.  This year, my butternut squash and pumpkin seedlings outgrew the paper cups I started them in before I was ready to transplant them to the garden. I moved them to doubled-up paper lunch bags filled with potting mix.  The idea was to give them room to grow and to avoid transplant shock by planting them bag and all.  Coincidence or not, I’m having my best butternut squash year ever.  Key takeway:  Double up the bags, and handle them gently when it’s time to plant.

More to come.

Post #1579: No change in new COVID-19 cases, but an interesting finding on vaccination-after-infection.

 

U.S. new case counts continue a slow decline.  We’re now at 27 new cases per 100K per day.  You can either view that as down one from a few days ago, or essentially unchanged since mid-May.

Data source for this and other graphs of new case counts:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 9/2/2022, from https://github.com/nytimes/covid-19-data.”  The NY Times U.S. tracking page may be found at https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html

Still just over 5000 hospitalizations a day.  Still around 400 deaths a day.

Both deaths and hospitalizations remain concentrated among the oldest old.

And within the elderly, lack of vaccination remains a significant risk factor.  These are observational data, so you should take them with a grain of salt.  But the gist is pretty clear:

Source:  CDC COVID data tracker.

An interesting piece of research on COVID vaccines was in the news today.  It’s this piece, in Nature:

SARS-CoV-2 vaccination induces mucosal antibody responses in previously infected individuals

It’s a bit of a slog cutting through all the science-speak, but the gist of it seems to be that if you’ve already recovered from COVID-19, if you then get vaccinated afterwards, you appear to develop really good resistance to further infection.

Being scientists, they can’t actually come out and say that, because that’s not exactly what they tested.  But it’s pretty clear that’s what they think, due to this little bit of rumor-mongering tucked neatly into the conclusions section of the paper, emphasis mine:

Of note, among participants in the longitudinal observational Protection Associated with Rapid Immunity to SARS-CoV-2 (PARIS) study, breakthrough infection cases after vaccination have - in the pre-Omicron era - only been identified in individuals without SARS-CoV-2 infection prior to vaccination, and not in individuals with SARS-CoV-2 infection prior to vaccination (personal communication, data not yet published).

As I read it, if you’ve had COVID, and you’re wondering whether its worth getting a vaccine or booster after you’ve already had it, this study seems to be pushing pretty strongly in the direction of “yes”. 

Separately, this piece, also in the news today, looks at the same issue, but the other way around.  There, in a population that was almost fully vaccinated to some degree, the folks with a prior COVID-19 infection had stronger immunity against the new BA.5 variant.

Again, the conclusion is that the combination of prior infection and vaccine provides greater immunity than vaccination alone.  Which seems pretty reasonable to me.  And points to the same answer to the question of whether or not it’s worth getting vaccinated or boostered if you’ve already had COVID.  As I read the current research, the answer is yes.

Post #1578: And it ain’t gonna get much better this year, by the looks of it.

 

Source:  NY Times, today.

You read it here first, in Post #1575, a few days ago.

I have nothing new to add to my prior analysis.  Based on the 2022 data to date, things aren’t going to improve much this year either.  That’s all in my prior post.

I guess the only thing I have to add is this:  If you’ve never used U.S. mortality data, you probably don’t grasp how incredibly unusual this is.  I had to study those numbers, from time to time, over the course of a 30-year career as a health economist.  If, at any time, you’d put this graph in front of me, I would have sworn that somebody screwed up the numbers.  I wouldn’t have believed it was possible.  But it’s real, and it’s not over yet.

Source:  Federal Reserve Bank of St. Louis (FRED) system.

G22-058: Of wood heat and black carbon.

 

Edit:  This post is obsolete.  See Post #1893.  The most recent estimate for the impact of black carbon is much lower than it was when I wrote this post.  (But still within the error bars of that prior analysis).  From a global warming perspective, if you have a modern air-tight wood stove, the drawbacks of wood burning are much less than I estimated for this post.

Original post follows:

I bought my wood-burning fireplace insert circa 2007.  The idea — consistent with scientific thinking at the time — was that I could reduce my global warming impact by burning wood (“biomass”) instead of fossil fuels. 

And, as far as C02 emissions goes, that’s right.  Over a ten-year time frame, the wood I burn is essentially a carbon-neutral fuel source.  I’ll show the math below.

But that was before the global warming impact of black carbon (airborne soot) had become well-known.  Over the time since I bought that wood stove, the estimated global warming impact of soot had grown significantly.

This year, as I get ready to have the chimney cleaned and purchase my usual two cords of wood, I’ve decided to take a good, hard look at that issue.  And, roughly speaking, the tiny amount of soot that my wood stove puts out completely offset the benefits of using a carbon-neutral fuel.

Bottom line:  With the grid getting cleaner every year, it now looks like my most carbon-sparing heating option, by far, is just to run my ground-source heat pump. 

I guess I should have seen that coming.  This is really part-and-parcel with the decision to go to electrically-powered miles via a Prius Prime.  The de-carbonization of the electric grid makes electricity the preferred fuel from a global warming standpoint.  Not just for the car, but now also for the home. 

Sometimes the tree of knowledge is not the tree of happiness.  Not even if it’s cut down, split up, kiln dried, and turned into a nice, cozy fire.

Why burn wood?

Firewood is very nearly carbon-neutral within a roughly one-decade timeframe.  For me, at least.  Sure, burning wood generates C02, just like burning any other carbon-based fuel.  The difference is that my firewood was atmospheric C02 just ten years ago, on average.  Ten years ago, C02 was deposited out of the atmosphere in the form of wood.  Now it goes back into the atmosphere as C02.  The net impact on atmospheric C02, for that ten-year period, is zero.

It may surprise some to hear that my firewood is just ten years old, on average.  That’s because the age of the wood is not the same as the age of the tree.  The typical piece of wood I’m burning has about 30 annual rings on it.  It is, if you will, a “30 year old tree”.  Or tree limb.  But:

  • Only the very center of the wood is 30 years old.
  • The outside edge of the wood is a year old.
  • Trees get bigger as they grow.

You can work out the math any number of ways — from calculus to setting up a spreadsheet — but the average age of the wood will always work out to be somewhere around one-third of the age of the tree.  So, by weight, the wood in my “30 year old trees” is, on average, just ten years old.

The upshot is that if you think in terms of the impact over ten years, burning wood added nothing to atmospheric C02.  It just re-injected C02 into the air that had been extracted (by a tree) a decade earlier.

I bet some of you thought I burned firewood because I’m cheap.  I am cheap.  But in this locality, firewood at (say) at $350 a cord (stacked!) is a more expensive heat source than natural gas at around $1.50 a therm.  Just wanted to make that clear.

A few ifs, ands, and buts

There are some nuances to the simple carbon-neutral argument.

First, some fossil fuel is consumed in harvesting and transporting the wood in the first place.  But by any account, that amount is negligible compared to the energy value of the wood.  The heat value of cord wood varies by species and condition, but a good round-numbers value for a typical hardwood is that a cord contains about 20 million BTUs of energy, and weighs about a ton and a half.  Even if that has to be trucked a total of 50 miles from source to delivery (including deadheading), in a typical small dump truck (roughly 7 MPG), the roughly 7 gallons of diesel consumed contain less than a million BTUs of energy.  In the absolute worst case, the fuel required to truck the wood around eats up 5 percent of the energy value of the wood.

Second, no trees were harmed in making this firewood.  By that I mean that in this urbanized area, firewood is mostly a waste byproduct of tree trimming services.  Trees weren’t cut down to make firewood. Instead, my firewood comes primarily from trees that were going to come down in any case.  Frequently, it’s from trees that had already died.

One way or the other, once a tree is dead, it begins the process of returning to C02.  It’s just a question of speed.  Smaller pieces can end up chipped into wood mulch, which then becomes C02 in a few years as that mulch rots.  The larger pieces of wood can’t be disposed of that easily.  If left above-ground, and not turned into lumber, they’ll rot in a few years to a few decades.  And they can always end up in the landfill.  There, they might last longer, but their anaerobic decomposition produces methane (which, if not captured and burned, results in global warming).  If nothing else, processing the downed trees into firewood keeps them from ending up in the landfill.

Because urban firewood is largely a byproduct of tree-trimming, the fossil-fuel inputs are lower than for trees purpose-cut for firewood.  These trees were going to get trucked away from where they fell, no matter what. The only incremental transportation fuel used in the firewood process is for the delivery trip.)

The upshot is that production of urban firewood is the exact opposite of clear-cutting a forest.  If you take standing biomass of a forest and purposefully cut that down and burn it, that definitely increases atmospheric C02.  (E.g., the ongoing destruction of tropical rainforests is accounted for in estimates of man-made C02 production.)  Urban firewood is more like waste disposal than like forestry clear-cutting.  In the main, you’re only using trees that were coming down anyway.

Third, in my house, I obtain a secondary environmental benefit from burning wood.  Burning wood makes my ground-source heat pump more efficient.

The main heating/cooling system for my house is a ground-source heat pump.  Using about 6000 feet of plastic pipe buried in my back yard, this system extracts heat from the ground in winter, and disposes of heat into the ground in summer.

Heat travels slowly through the ground.  (That’s why this system needs so much pipe — it needs all that surface area.)  Ideally, the injections and withdrawals of heat should be matched.  If not, excess heat withdrawals during the winter will cool the ground field and so reduce the wintertime efficiency of the heat pump.

This is not a small matter.  In my area, heating demand is about five times cooling demand, when measured in heating and cooling degree-days.  Thus, I need a significant additional heat source if I’m going to keep that ground-source heat pump operating at peak efficiency.  Which is supplied nicely by burning a couple of cords of wood each year.

Fourth, wood burning raises real health concerns.  No matter how hard you try, a wood burning stove will pollute your indoor air to some degree.  Every time you open it up to add wood, you’re letting something out into your house that you’d really be better off not breathing. And, to some degree — typically less than the indoor air, due to dilution — you do the same to nearby outdoor air.

Those problems tend to be more significant:

  • In areas where many people use wood as the sole or principal source of heat.
  • In areas where older, higher-polluting stoves are in use.
  • In tighter home construction, with fewer air changes per hour.

I use a new, relatively clean stove (rated at under two grams of soot per hour), in an old leaky home that probably gets a complete air change every half-hour.  I’m also the only person within at least a half-mile radius who routinely heats with wood.

In short, I just ignored the health-related issues.  I don’t think they are a huge concern in my situation.

Fifth, on the positive side, heating your home with wood teaches you a lesson in just how damned much fuel a modest suburban home consumes.  Every year, I buy and burn roughly three tons of wood.  Every piece of it gets picked up and moved three times.  By the end of the heating season every year, I’m right tired of firewood.

The mass of that firewood is obvious.  But it’s only modestly greater than the mass of the fuel I would burn if I heated entirely with natural gas.  Two cords of wood weighs about three tons and generates about 40 million BTUs.  That’s the heat value of 400 therms of natural gas, which would weigh (in round numbers) about one ton.  With firewood, you are constantly reminded of the enormous mass of the fuel being used.  With natural gas, it’s still an enormous mass of fuel, but you are completely blind to the order of magnitude.

So chalk that one up in favor of firewood.  It never lets you forget that you’re burning tons of fuel to heat your home each year.

In summary, as of 2007, on balance, wood heating:

  • reduced my carbon footprint,
  • increased the efficiency of my ground-source heat pump,
  • made me aware of the large amounts of fuel I was using, and
  • posed seemingly small heath risks.

The evolution of thinking on black carbon a.k.a. soot.

When I bought my wood stove, the importance of black carbon (soot) emissions for global warming was only starting to be realized.  I believe that the 2007 report of the Intergovernmental Panel on Climate Change was the first time that black carbon made it into the summary for policy makers.  If I look back at an earlier (2001) report, it wasn’t even clear at that time that all soot much mattered.  They just didn’t know one way or the other.  Just read that 2001 chart.  The level of understanding about black carbon was very low, and the estimated impact was quite low as well.

Source:  IPCC, 2001: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change [Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnson (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 881pp.

By the time of the IPCC fifth assessment report (2014), they had enough understanding of the issue to start suggesting that reducing soot emissions was a good way to slow global warming.  This AR5 report showed this history of the estimate of radiative forcing (the impact on global warming) of black carbon.  It’s only a modest exaggeration to say that every time they reconsidered it, the estimated impact on warming doubled.

Source:  Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza,
T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA.

Currently, the U.S. EPA uses a value of just over 0.6 (watts per square meter) as its estimate of the impact of black carbon.  So it’s a pretty good guess that the IPCC’s estimate is going to go up in its next (Winter 2022) summary report.

Source:  US EPA

In short, between the time I bought my stove and today, the estimated importance of soot as a source of global warming has increased dramatically.    At present, black carbon (soot) is now reckoned to be the third most important contributor to global warming.  Only C02 and methane are judge to be more important.

A little soot goes a long way.

But can this possibly be that big a problem?  For me, I mean?

Rather than fuzzy-think my way to avoiding the issue, I decided to do a quick calculation.  If I shut down my wood stove and fired up the equivalent amount of natural gas heat, would that increase or decrease my contribution to global warming?

I figured this had to be a no brainer. Just look at the facts.

Properly run, my wood stove produces under 2.0 grams of soot an hour.  Some of that gets trapped in the flue.  The rest of it stays in the atmosphere for (on average) just a couple of weeks. And my black carbon gets carried out over the Atlantic, and so doesn’t cause the darkening of snow surfaces that’s an important part of the overall impact of black carbon.

Seriously, how bad can that be?

Turns out, a crude calculation shows that it’s uncomfortably close to a wash.  Based on the published estimates of the 100-year “global warming potential” of black carbon, the grams of soot emitted by my wood stove, hanging in the atmosphere for a couple of weeks, matter just about as much as the kilograms of C02 put out by my natural gas furnace, hanging out in the atmosphere for the next century.  All that, for producing the same amount of heating.

What I thought was a no-brainer is nothing of the sort.

Here’s the crude calculation, comparing the soot from my stove, to the C02 from my gas heater, for an equivalent amount of heat energy.

First, I need to be able to compare the impact of soot to the impact of C02.  That comparison is defined as the global warming potential (GWP) of soot.  The GWP shows how much global warming you would expect from emitting a gram of any given substance, compare to the warming you’d get from emitting a gram of C02.  The GWP is generally cited over a given period of time, say 20 years or 100 years.

I simply have to accept somebody’s reasonable estimate of that.  Estimates vary, but a reasonable mid-range value for the 100-year GWP of black carbon is 900.  That is, each gram of black carbon emitted causes as much warming, over the next century, as 900 grams of carbon dioxide emitted.

(I will note in passing that this is truly a mind-blowing number, given that the black carbon only stays in the atmosphere an average of about two weeks.  While the C02 is, for all intents and purposes, practically forever.  Apparently, a black carbon particle is just about a perfect absorber of sunlight, and so provides an enormous amount of heating to the atmosphere during its brief lifetime).

Next, let me produce 100,000 BTUs of heat with either my wood stove, or a natural gas furnace.  And compare the global warming impact of the soot from the wood stove and the C02 from the gas furnace.

I use a Lopi Revere fireplace insert.  At a typical burn rate, that produces about 30,000 BTUH, and is certified to emit less than 2 grams of soot per hour.  Let me assume all that soot goes into the atmosphere (as opposed to being deposited in the flue).  In round numbers, to produce 100,000 BTUs of heat, my stove emits 6 grams of black carbon.

When I take my six grams, multiply by the GWP factor of 900, and convert to pounds, I find that six grams of soot, from my wood stove, produces warming that is equivalent to 12 pounds of C02.

But here’s the punchline.  To produce 100,000 BTUs of heat with natural gas, you (by definition) burn a therm of gas.  Burning a therm of natural gas, to create the same amount of heat, releases just under 12 pounds of C02.

In other words, as a rough cut, and with a lot of uncertainty, heating with wood has no benefit from a global warming standpoint.  Those six stinking grams of soot, from burning my carbon-neutral firewood, have as much global warming potential as the C02 from the natural gas that the wood replaces.

When the facts change, I change my mind.  What do you do?

The above is a quote from John Maynard Keynes, arguably the most influential economist of the 20th century.  I believe it has general application outside the field of economics.

There’s surely a lot of uncertainty in this calculation.  Mostly, it’s uncertainty about that figure of 900 for the global warming potential of soot.  At the minimum, I should try to remove the portion of that attributable to the darkening of snowpack from soot.  Where I’m located, that just doesn’t apply to any material degree.

Beyond that:

On the one hand, a lot of the soot from the stove ends up stuck to the flue pipe.  Exactly what fraction is hard (maybe impossible) to determine.  For sure, that’s not a question that gets asked every day.  Best I can figure, based on one reported experiment, I should expect half the soot to end up in the flue and not in the air.  But clearly that has to depend on the (e.g.) the length of the flue.

On the other hand, I believe that two-grams-per-hour figure is for a perfectly maintained burn.  It doesn’t include the warm-up time.  It doesn’t include any time the fire is smouldering (no visible flames).  It doesn’t account for imperfectly cured (high-moisture-content) firewood.

All of those factors — cold operating temperature, smouldering, wet wood — result in higher soot emissions.  The two grams figure just generally doesn’t account for all the forms of operator error that can result in a smoky (high-soot) fire.

If nothing else, this has convinced me to switch entirely to kiln-dried wood.  In general, the drier the wood, the less soot it produces.  I have bought air-dried wood from a trusted supplier for years.   But two years ago I was forced to buy some kiln-dried, due to a badly cured batch of wood.  Not only does kiln-dried burn much more readily and with less soot, my best guess is that the increased heat output from the kiln-dried wood more than pays for the fossil fuels used in the kiln drying process.

I’m also going to re-evaluate my heating mix in light of the ever-cleaner U.S. grid.  Years ago, I compared emissions from my gas furnace to estimated emissions from my ground source heat pump.  I decided that they produced more-or-less equivalent C02 emissions for a given amount of heat.  But as the grid has gotten cleaner, it’s probably smarter to use the heat pump more, and other sources less, even if that reduces the efficiency of the heat pump somewhat.

(Best guess, my heat pump nets out to a coefficient-of-performance of about 3.0.  That is, I get about three KWH of usable heat energy for every KWH used to run the equipment.  You’d think it would be higher, but you spend a lot of energy pumping water through pipes, and a lot of energy moving air through crappy old ductwork.)

And when I do that calculation, the now-cleaner Virginia grid makes this almost a no-brainer.  With cleaner electricity, the heat pump beats the gas furnace hands-down.

The heat that would have generated 12 pounds of C02 when generated by my (efficient!) natural gas furnace would only generate a little over six pounds of C02 if generated by my heat pump.

It’s starting to look like the right answer for me is just to run the heat pump all the time.   That’s about as un-romantic a solution as you can get.  But the numbers are what they are.