Category: Non-disposable

Posts that may have some sort of permanent value, or that I consider to be the best of what I have posted here.

Post #1903: Hallelujah! Return to normalcy.

 

Background

Two nights ago my wife and I attended the 52nd annual Messiah sing-along at Clarendon United Methodist Church.  Because we do this every year, and I write it up, I can directly compare last year’s sing-along to this year’s.

For those of you unfamiliar with this tradition, Messiah is a baroque oratorio about the birth and death of Christ.  The words are straight out of the King James Bible (ca. 1611).  The music is straight out of the early 18th century (ca. 1741).  Despite these handicaps, the Christmas portion of it is still widely performed at this time of year (ca. 2023).  To reach for the LCD here, it’s where the Hallelujah Chorus comes from.

This is now one of my acid tests of how well we, as a society, have gotten past COVID.  That’s because a) sing-alongs are an extremely high-risk event for spread of airborne disease, and b) the typical in-person participant for this event, in the past, tended to be elderly. Continue reading Post #1903: Hallelujah! Return to normalcy.

Post #1803: Why are fine particulates (PM 2.5) so variable? It’s over my head.

 

One thing I’ve noticed about the AQI for particulates is how variable it is.  On any given day, my local hourly estimate from Accuweather will differ significantly from the EPA’s Airnow map.  Which, in turn, differs from readings just a few miles away.  For example, above, my AQI for particulates (as of 1 PM 7/6/2023 is either 63 (Airnow) or 33 (Accuweather).  Or somewhere between.

And readings within a few miles go as low as 13.  At the same time, the seemingly accurate meter I just bought shows “9”, sitting on my back screen porch.

At first, I chalked that up to instrumentation.  Maybe particulates are hard to measure, and what I’m looking at is more-or-less instrumentation error.

Because, serious, how could the air be so different, just a few miles away?  If I were to take some other measure of the atmosphere — temperature, humidity, pressure — it would vary smoothly over vast areas.   E.g., if it’s 90 degrees here in Vienna, VA, there isn’t going to be a pocket of 45 degree air five miles away in the City of Fairfax.  Yet you see that sort of apparent PM 2.5 disparity all the time.

So I thought, it must be poor instrumentation.  Then I bought a cheap air quality meter, noted above.  Not only are the readings stable from hour to hour, they are frequently in good agreement with the Accuweather numbers.  They clearly respond to ambient conditions in a hurry.  (The 4th of July fireworks briefly sent the meter into the “purple” AQI range, consistent with predictions from the Airnow map.)  The stated accuracy of the PM 2.5 measurement is +/- 10%.  All that, from a device that measures all five of the key air pollutants and costs under $75.

So, this isn’t due to instrumentation error.  Or shouldn’t be.  You can get reasonably reliable PM 2.5 measurements with a cheap off-the-shelf device.

Maybe my local variation is due to the presence of large local point-sources of PM 2.5.  But, to a large degree, we have no large point sources of particulate emissions in this area.  Largely because we are almost devoid of industry, in the DC area, and our power plants are (mostly) located outside of the metro area.

Which also matches my observation, because it’s not as if one area is consistently dirty.  It’s that the readings consistently vary a lot from place-to-place in this region.

So why do the PM2.5 readings in my area appear to be so highly localized?  Is there really that little mixing of the air between PM2.5 emitters, and local air?

Trying to understand how air mixes — a fool’s errand.

After about an hour of looking, I’m going to say that short of getting a graduate degree in atmospheric science, this ain’t gonna happen. 

It’s surprisingly complicated, but the joker in the deck is “turbulent mixing”?  Once I found out about that, I realized it was time to call it quits on trying to understand this.

First, physicists distinguish “bulk flow” (e.g., a breeze) from “diffusion processes” (molecules or particles moving through still air).  In this case, the latter would be the movement of water molecules or fine particulates through still air.

So, smoke spreads out because it 1) blows smoothly downwind, and because 2) the particles diffuse outward into surrounding clean air.

That said, it also spreads due to 3) turbulent mixing.  Any time the flow of air is not smooth (laminar, or layered), turbulent mixing is said to occur.  This sort of mixing can apparently distribute that smoke fully and more-or-less uniformly in the adjacent clean air.

Turbulent mixing occurs a lot in the atmosphere.  I’m pretty sure that it occurs at the level at which clouds form above the ground.  It occurs within clouds.  I occurs if sufficiently strong wind sweeps past fixed objects, e.g., tree branches.  And so on.  Anything sufficient energetic will kick the flow of the atmosphere from laminar flow to turbulent flow and turbulent mixing.

The bottom line is that there is no back-of-the-envelope way to determine how well PM 2.5 (including smoke) typically mixes into the surrounding atmosphere.  In the end, it’s all empirical, and depends on how hard the wind is blowing horizontally, how turbulent the atmosphere is in vertical profile, and so on.

Presumably, both water vapor and PM 2.5 move at the same speed, and mix at the same rate, when it comes to bulk transport and to turbulent mixing.  In both those cases, they are merely being carried along by the surrounding air.

But PM 2.5 diffuses a lot less rapidly than (say) water vapor.  A theoretical rule (via Einstein and Stokes) is that rate of diffusion is inversely proportional to the radius of the particle trying to diffuse.  Getting hold of some data (but not showing the calculation), that suggest that PM 2.5 diffuses about a thousand times more slowly than water vapor.

Diameter of a water molecule seems to be given as 2.75 Angstrom, where an Angstrom is 1/(10^10) meters.  Ah, round down to 2.5.  But PM 2.5 is in microns, or 1/(10^6) meters.  This means PM2.5 particle is about 10^4 = 1000 times larger than a water molecule.  Thus under this  simple theory, water (humidity) diffuses through still air roughly a thousand times faster than a PM 2.5 particle would.

At the end of the day, I have no clue whether that matters or not, with regard to widely varying PM 2.5 readings across my area. 

All I know is that even without big local point-sources of PM 2.5, it’s common to see big difference in (what appears to be) actual PM 2.5, across different locations in my area.  Whereas for other parameters of the atmosphere — temperature, pressure, humidity — true local variation in those quantities is tiny.

Seems kind of crazy to worry about it, but there has to be some good reason why this aspect of the atmosphere is so qualitatively different from others.

Maybe Hawaii wasn’t just a nice place to hang out.

Maybe my only clue comes from the Keeling curve (above) and how that is measured.  When Keeling started measuring atmospheric C02 in the late 1950s, he established his laboratory on the windward side of Mauna Loa.

And found average atmospheric C02 around 315 PPM.  Currently, it’s around 422 PPM.

But the point is why he chose that locale.  His goal was to get “well mixed” atmospheric gasses, and, apparently, having circa 6000 (?) miles of open ocean to windward was just the ticket for getting that.

By contrast, you can frequently find city air with C02 levels in the 1000-PPM range, near congested roads (reference).  That air hadn’t had a chance to get mixed with the rest of the atmosphere.

So, maybe Keeling located there for some reason other than it’s being a nice place.  Maybe you really need that much distance to ensure uniform mixing.  And maybe the mere 500 miles or so between me and the nearest Canadian mega-fire isn’t enough to ensure uniform mixing of the air.

So I’m guessing that the atmosphere doesn’t mix all that uniformly.  For whatever reason.  And that the small-area variation in PM 2.5 is true.  And that I should not expect it to get any smaller as the summer progresses.

Post #1794: Why filtering forest fire soot is not the same as filtering aerosol droplets.

 

I learned a lot about air filtration during the recent pandemic.  At some point, I wrote down and compared all the different standards used for air filtration.  For example, what does HEPA actually mean, and how does it compare to the various members of the MERV clan?  And how do all of those relate to N95? (Post 593, April 1, 2020).

The problem-du-jour isn’t about filtering tiny little viruses out of the air.  Instead, it’s about filtering tiny little soot particles out of the air.  In the U.S. Northeast, we’re now in an era of Canadian wildfires and the resulting air pollution alerts.

Nicely enough, I get to re-use what I think I already know about air filtration.  The knowledge that applied to filtering aerosol droplets (droplets less than 5 microns in size) applies equally to filtering fine particulates such as the soot from wildfires.  This soot typically falls into the PM 2.5 air pollution category, that is, any particulate matter in the air less than 2.5 microns in size.  (For comparison, a human hair is typically around 70 microns thick.)

Except that there is one key difference between filtering the air for pandemic purposes, and filtering the air for forest fire purposes:  Outdoor air is no longer our friend.  In fact, outdoor air is now the enemy.

When filtering viruses, outdoor air could be assumed to be clean.  The likely concentration of virus droplets in outdoor air was typically negligible.  Disease transmission in outdoor settings was virtually unheard-of.  You only had to worry about the “pollution” that you generated inside the indoor space.

But for forest fires, the entire problem IS the outdoor air.  In some sense, the entire battle to keep indoor air breathable is about dealing with the dirty air outside.

To crystalize this, recall that one standard suggestion for improving the COVID safety of (e.g.) schools and other spaces was to open the windows.  Perfectly rational if you’re dodging COVID.  Not so smart if you’re trying to avoid forest fire smoke.  So, from the get-go, you now see that dealing with forest fire smoke is a completely different engineering challenge from minimizing aerosolized COVID. 

Why does this matter?  Outside air is always leaking into indoor spaces.  For the virus filtering, that was a good thing.  Now it’s not, and you need to strategize your air filtration accordingly.  Why?  Because outdoor air doesn’t just leak into indoor spaces, it typically pours in.  The minimum standard for houses, from a health standpoint, is that outdoor air should replace indoor air at least once every three hours (reference).  But a typical well-constructed older home, in good shape (storm windows, caulked) would exchange all the indoor air with outdoor air once per hour (random reference).  Leakier construction (no storm windows, caulk missing) would experience air exchanges more rapid than that.

Whatever air filtration setup you use, you now need to account for that.

My particular problem.

My daughter lives in New York City.  Shown above, New York just had a bout of extremely bad air quality, due to Canadian forest fires.  At the peak, PM 2.5 (particular matter 2.5 microns or smaller) reached 460 micrograms per cubic meter.  This is way beyond what the EPA considers hazardous, and is maybe 10 to 20 times the typical value for that area.

Given that those fires continue to burn, I’m guessing this isn’t a one-and-done.

So I wanted to get her an effective air purifier for her apartment.  (And even if forest fire soot does not return, a New York City apartment would probably benefit from having an air purifier).

My options were to go with a redneck air purifier (20″ box fan, and a high-quality electrostatic air filter), or to buy a purpose-made room-sized HEPA air purifier.   The redneck air purifier is a variation on the “Corsi box”, a D-I-Y air purifier that was promoted as an easy fix for indoor air filtration during the pandemic.

You might normally say that HEPA must be better, because it’s a higher filtration standard.  In theory, HEPA filters must remove 99.97% of fine particulates in a single pass (based on the Wikipedia entry for HEPA).  In practice, I think 99.5% is more typically advertised.  Whereas a high-end air filter (in this case, Filtrete 1900) only removes about 65% of fine particulates in a single pass.  Seems like the case for HEPA is a no-brainer.

And if I were trying to filter the air in a hermetically-sealed box, HEPA probably is the better choice.  The only drawback to HEPA is the back-pressure of doing that high level of filtration limits air flow, for a given power input.  HEPA units advertised as “room-sized” air cleaners typically filter just a few hundred cubic feet of air per minute.  By contrast, the entire selling point of the 3M Filtrete electrostatic filters is that they achieve a reasonable degree of fine-particle filtering with minimal back pressure.  With a box fan on low, I can push 1000 cubic feet of air per minute, through a Filtrete filter.

My gut tells me that, for older construction, with a lot of air infiltration, the cheap setup (box fan and filter) is better than the equivalent purpose-built HEPA air filtration unit. A typical room-sized HEPA unit isn’t going to be able to “keep up with” the inflow of dirty outside air.  Or, at least, not as well as the high-air-flow fan-and-filter setup.  If a lot of air is flowing into the room, my gut tells me that that HEPA (high-filtration/low-volume) actually does a worse job than box-fan-and-filter (low-filtration/high-volume).

Many mathematical paths to the sea.

At some level, I realize that I’m trying to solve a classic calculus problem.  Typically, it’s a water tank with inputs and outputs.  Here, it’s a room with leaks and a filter.  There must be a classic closed-form solution that would tell me the final concentration of particulates in the air. Just plug in the parameters, and view the output.

Somewhere along the line, I have lost the ability to cast a problem such as this into that classic format.  No problem.   Much of what used to require actual intelligence and insight can now be done with brute-force computing power.

In this case, all I need to do is the simple numerical simulation, in a spreadsheet.  Start with a room full of dirty air, with a known rate of infiltration of outside air.  Turn on an air cleaner with known properties.  And just do the accounting, minute-by-minute.  Air in, air cleaned, air out.  And track the resulting concentration of pollutants in the air.

Does anybody ever care about the details of methodology?

Answer:  Only if they disagree with the results.  By contrast, if I end up saying something you agree with, you won’t care how I arrived at that.  That’s just human nature.  People just want to say Amen and move on.

My redneck air purifier consists of a box fan pushing 1000 CFM (on low), through a 3M Filtrete (r) filter.  The Filtrete is a 3M “1900”, rated at MERV 13.  It grabs 65% of the PM 2.5-sized particles with each pass, and about 95% of PM 10-sized particles.  For this simulation, I’m only tracking PM 2.5.

B

The only practical detail you should care about is that if you do this — a single filter stuck on the back of a fan — you must use a low-back-pressure electrostatic filter.  Otherwise, if you want to use el-cheapo MERV 13 filters, you need to go to the trouble of actually constructing a literal Corsi box, using four filters taped together.  That’s because with cheap filters, you need all that surface area to avoid the high back pressure that would starve the fan of air.  See this reference for Corsi box.  Even with that, my take on it is that it provides slower air movement than using a single Filtrete 1900 placed on the back of a fan.

Below is a literal Corsi box, via Wikipedia.  If you use cheap filters, go that route.

By contrast,  my theoretical HEPA filter pushes 100 CFM through a filter that grabs (say) 99.5% of PM 2.5 particles.  (Separately, I’ll show the results for a filter pushing higher rates of air flow).

The room is 20′ x 20′, with an 8′ ceiling, and has one full air exchange per hour, typical for sound older construction.  That is, enough outside air enter the room through various leaks and cracks that it would be enough to replace the air in the room once per hour.

The outside air is at 450 micrograms per cubic meter of PM 2.5, the peak of the air pollution in the New York City area.

Based on this, I’ve written the spreadsheet that does the accounting.  Air in, air purified, air out.

Results.

The results of my Excel-based numerical simulation validate what my gut was telling me.  Due to the high rate of air infiltration typical in older construction, filtering the air rapidly is far more important that filtering the air extremely well.

On the left, you see the results for my redneck, box-fan-plus-Filtrete air filtration unit.  It passes 1000 cubic feet per minute, but only filters out 65% of the finest (PM 2.5) particles.  On the right, you see the results for a slower HEPA unit.  It passes one-tenth of the air per minute, but it filters it more than 10x better.

The equilibrium level of particulates in the room is vastly lower with the high-volume, lower-efficiency filter (left graph above).  Why?  Because the slow pace of the HEPA filter (right graph) can’t keep up with the level of outside-air infiltration that is typical in older construction.

To get the HEPA filter to work almost as well as the simple Filtrete (r) 1900 plus box fan, in this typical leaky room, you’d have to crank it up to a much higher air-volume throughput.

A HEPA filter is a beautiful device.  It would work wonderfully in a hermetically-sealed room.  But in an actual room, with high-volume exchange of air between inside and exterior, it just can’t keep up.  You’re better off using a cheap box fan on low (1000  CFM) and a low-back-pressure air electostatic air filter, such as a 3M Filtrete (r) filter.

Is this a fair comparison?  Judging from what I see on Amazon, I’d say so.  When they even bother to show the approximate air flow rate, HEPA units offered as whole-room units typically run at:

Whereas the box-fan-and-filter turns over the air in my example room about 20 times per hour, at roughly 1000 cubic feet per minute.

Further, it makes almost no difference whether I use 99.5% efficiency or 99.9% efficiency for the HEPA unit.  At slow rates of air turnover, the HEPA filter gets overwhelmed by the infiltration of outside air.

Conclusion

I just sent my daughter two Filtrete 1900 filters.  Plus, oxymoronically, a stylish 20″ box fan.  Hoping that on low, the fan will be quiet enough not to be bothersome.

My final finding is that the folks who run Amazon don’t miss a trick.  If you search for a stylish box fan, Amazon suggests a few packs of MERV-13 filters, as an add-on purchase.

My conclusion from the above is that, between viruses and soot, a whole lot of people have figured out that the best and cheapest way to filter indoor air is with some form of “Corsi box”.  So these days, as soon as you pick your fan, Amazon is right there, suggesting the add-ons you need to do that.

G23-021: Dance of the mustard flowers.

 

Recall that I swore my mustard plants were moving.

Heliotropic?  That is, moving to face the flowers into the sun?

Maybe.

So I did a little time-lapse video.  This is one day of the mustard bed in my garden.  Roughly 8 AM to 8 PM, with a brief interruption in the middle to add a tin-foil shield.  All condensed into about 30 seconds via YouTube.

The dance of the mustard flowers appears far more complex than simple heliotropism.  And far weirder.

Enjoy.

 

Post #1790: Surface energy, or one of the many reasons why stone countertops are inferior.

 

The featured image above is from Formica.com

I dislike many aspects of the kitchen in my house.  The previous owners took a well-designed and well-built 1959 house, and basically screwed it up by, among other things, putting in a trendy “designer” kitchen.  Amongst the hate-able aspects of that kitchen are the obligatory granite countertops.

Today, as I was housecleaning, scraping little bits of crap off those perpetually-grungy kitchen countertops, I had a flash of insight.

Seems like stuff sticks to these granite countertops to an extent that never happened with our old Formica (r) countertops.  It’s almost as if granite countertops are mostly for show, and are a really poor choice if you are actually going to use your kitchen intensively.  Heck, I keep a plastic paint scraper at the sink, just for scraping up the most-stuck-on stuff from those countertops.  I’m pretty sure I never needed that with Formica (r).

Gunk just seems to glue itself to those granite countertops.

That’s when the light bulb lit.  It really isn’t my imagination that granite is tougher to keep clean than Formica (r).  My perpetually grungy granite is the flip side of the difficulty of gluing certain types of plastic.  If Teflon is at one end of the spectrum, then polished granite is somewhere near the other end.

It’s all about surface energy.

Continue reading Post #1790: Surface energy, or one of the many reasons why stone countertops are inferior.

Post #1789: The deadweight loss of credit card rewards

 

There are good reasons that economics is called “the dismal science.”

“The Deadweight Loss of Christmas” (Google reference for .pdf) is surely a case in point.  In that scholarly analysis, a Yale economics professor takes the time and effort to quantify the economic inefficiency of Christmas gift-giving.

The idea is simple.  If you buy something for yourself, you know exactly what you want.  By contrast, if somebody buys you a gift, they have to guess what you’d like.  And to the extent that they guess wrong — by a little or a lot —  the value of the gift, to you, may be well be below the purchase price.  And that gap between what the gift-giver paid, and what the gift-recipient would have been willing to pay — that’s the deadweight loss of Christmas.

Economists have a simple (if entirely soulless) solution:  just give money.  The gift recipient can then buy themselves exactly what they want, and the total satisfaction or “utility” of the transaction is maximized.   A gift of money eliminates the deadweight loss involved in trying to guess somebody else’s preferences.

A different deadweight loss

Which brings me to my newly-acquired, soon-to-be-cancelled Best Buy credit card.

I made a major electronics purchase a few weeks back.  The sales clerk at Best Buy talked me into getting a Best Buy credit card.  Normally, I say no to all such offers.  But the deal was that this would give me an instant 10% off the not-inconsiderable sales price.

Cash back, right?  Who would turn that down.

Only, this credit card doesn’t work like that.  What I actually got was, in effect, store credit.  I got “rewards” equal to 10% of the value of the purchase.  Rewards that could only be redeemed in Best Buy merchandise.  Worse, that’s how the card works for all purchases made on it.  There is no “cash back” feature.  All rebates are in the form of additional “rewards” that can be cashed in for Best Buy merchandise.

I guess this is a fairly good deal, if you have an ongoing need for the stuff Best Buy sells.  But I don’t.  Worse, I’m on a tear to get rid of stuff, the process of Döstädning, or Swedish death cleaning (Post #1667).  The last thing I need is yet another electronic doo-dad or small appliance.

And so, what ensued was not unlike the deadweight loss of Christmas.  I wasn’t given specific gifts, for sure.  But in order to get my money’s worth, in effect, I had to choose my gifts out of a catalog of stuff that I didn’t really need or want.

For something that was free*, it was a surprisingly grueling process.

*  As a responsible parent, and an economist, whenever my children used the f-word (free) around me, I would immediately snap “pre-paid”.  So I use the term loosely here.   The plain fact is that the cost of all such givebacks has to be worked into the original purchase prices, so that Best Buy can remain in business.  So these “rewards” aren’t free, they are merely pre-paid.

At my wife’s suggestion, I went for batteries, because those are consumables, and we’ll eventually use them up.  Once I got past about $50 worth of alkaline batteries, I was stumped.  But, gosh darn it, I was not going to leave money on the table.  So I spent hours swapping stuff into and out of my on-line shopping cart, in an attempt to get things I might use, whose prices summed to just over the total “rewards” I had been granted.

I recall buying a flashlight.  And a pocket knife (a.k.a, future contribution to the TSA).  Because you can always use another one of those.  The rest of it is a blur.

I hope I’ll be pleasantly surprised when the packages show up.  Or at least recall that I ordered it.

In any case, once I’d finally made my purchases, and burned up those rewards, I had the funny feeling that I had come across this process before.  But it took me another day to realize that what I was experiencing was the deadweight loss of Christmas.

In effect, I gave myself some gifts that I didn’t much want.

For sure, if there had been a straight-up cash-back option, I’d have taken it.  In fact, in hindsight, if they’d offered me half that dollar amount, as cash back, I’d have taken it.

Thus validating the fundamental insight of The Deadweight Loss of Christmas.

Post #1788: Recycling plastics, Part 2: My Town tells me to do the wrong thing. Does yours?

 

I am in the middle of looking at plastics recycling in my area.

Any internet search in this area feeds you a lot of pessimism about the entire concept of plastics recycling.  People say that it’s not worth doing, that it’s greenwashing, that it’s a scam, that it all ends up in the landfill, and so on.

But is that true?  It all seems to start from a figure that just 5 to  8 percent of U.S. waste plastic is recycled.

Less than an hour of internet search, and I now know that figure is totally irrelevant to the situation I’m investigating.  The often-cited 5% is for every conceivable form of plastic waste — stuff that was tossed in the trash, stuff that was tossed on the ground, plastic resins that are not recyclable, plastic items that are not inherently recyclable, plastic integrated into multi-material items, and so on.

That’s a problem, for sure.  But right now, I just want to know what happens if I properly handle a recyclable plastic object, where I live.  I want to know two simple things:

  • What plastic should go in the recycling bin, here in Vienna, VA, and
  • What fraction of (say) a clean #1 (PETE) bottle actually gets recycled?

Continue reading Post #1788: Recycling plastics, Part 2: My Town tells me to do the wrong thing. Does yours?

Post G23-013: Bee hotel success, Part 1

I try to maintain a reasonably bee-friendly property, out here in the wilds of Northern Virginia.

It’s not just that I need them to pollinate my vegetable garden. Or that bumblebees do, in fact, sleep in squash blossoms (aw!).  Or that the hum of bees at work in my garden marked the never-to-be-repeated peak of mid-pandemic suburban quiet (Post #G11).

It’s more bee-as-coal-mine-canary. If I’m doing something in the yard or garden that’s likely to be killing off my bees, odds are I shouldn’t be doing that.  It’s a quick way to rule out some environmentally stupid behavior.

In any case, I’ve had a couple of bee hotels (native bee nesting boxes) kicking around my yard for a few years now.  Shown above.  But those were never very successful.  It took years to get the first bees to use them.  And I might get a one or two tubes filled, per year.  There are clear exit holes on some tubes, so some new bees were produced.

But not a big hit, over all.

This year, on a whim, I bought a different model of bee hotel, at my local Home Depot.  The Home Depot mason bee box is already working vastly better than the previous model.  It’s been up a few days and I already have more tubes filled than I got in the first few years of the other model.  In short, my bees love this new bee hotel.

Now that I’m finally doing something right, I’d like to keep that going.  In a radical and very un-guy-like step, I actually read the directions.    And — surprise — I’ve been clueless as to how these things actually work. 

But now that I know, I realize this new bee motel is a fundamentally terrible design.  Not for what you can see — that part’s OK.  And, as noted, it’s definitely attracting bees.  The problem is that those bamboo tubes are permanently attached.  As discussed below, that’s a no-no.  You want nice clean new nesting tubes each year.  And that means that, unless I tear it apart next year, this lovely little bee hotel is a single-use disposable item.

So this post is going to summarize everything I think I learned about mason bee nest boxes (“bee hotels”).  And about the difficulty of making smooth-ended splinter-free replacement tubes for this, from bamboo I have on hand.

Three-minute tutorial:  Bee hotel or roach motel?

Key point: For best results, you need two bee hotels (or equivalent) for every site at which you wish to maintain a bee hotel.

You ideally want the female bees to use clean, new nesting materials each year.  The use of new (or carefully sanitized) nesting tubes each year minimizes the presence of diseases and parasites in the nest.  If you don’t keep the premises clean, your bee hotel can end up as the bee equivalent of a roach motel.  With poor enough conditions, the bees check in, but they never check out.  Your bee hotel becomes a catch-and-kill trap. 

The problem is that each spring, some bees are ready to check into your bee hotel before your existing guests have checked out.  Some are ready to lay their eggs before others have emerged from their cocoons.  The reason for this chaos is that these bees are quite short-lived.  The emerge, mate, forage for food, lay their eggs, and die, all in the course of a few weeks in the spring.

The solution is to put last year’s bee hotel (or, at least, the nesting tubes) aside in an “emergence box”, to give the bees time to emerge from their cocoons.  At the same time, you need fresh, new nesting tubes nearby, for the emerging bees to lay the next generation of eggs.  An emergence box is just an opaque weather-protected box with a small opening.  This allows the newly-emerged bees to exit, but prevents bees outside the box from seeing (and therefore attempting to re-use) the old nesting tubes.

No matter how you cut it, you would ideally have two sets of nesting tubes in rotation at each bee hotel site.  One set of clean, new tubes, for this year’s eggs.  And last year’s tubes, from which bees continue to emerge.  You want to keep the emergence box with last year’s nesting tubes near your new bee hotel, because, as noted above, the bees get right down to business as soon as they emerge.

Here are my five Ws for bee hotels.

Who?  These bee hotels provide nesting places for some species of solitary bees, that is, bees that don’t form big communal hives.  Mainly, that means these are NOT for honeybees.  The bees that use these devices are typically referred to as “native bees”, but that’s imprecise.  For one thing, bumblebees are typically native bees, but those are ground-nesting bees, and won’t use these tube-type bee hotels.  Your primary target bee is a “mason bee”, so called exactly because they build those little mud walls at the end of the nesting tube where they’ve laid their eggs.

What?   A bee hotel provides tubular structures into which a mason (or similar) bee lays eggs.  The bee lays a series of eggs in the tube, providing each with food, separating them with mud walls, and capping off the tube with more mud.  Over the course of a year (in some cases, two years), each egg hatches into a larvum (worm), eats the food that its mother left for it, pupates (cocoons itself), and eventually emerges from that cocoon, the subsequent year, as a bee.

When?  The eggs are laid in spring.  The eggs hatch/larvae emerge in summer.  They cocoon in the fall.  And they re-emerge as bees the next spring/summer.  (In some areas, there are species that spend two years in the cocoon, but I’m not sure how relevant that is to most places.)

Place your bee hotel outside in the spring.  It appears to be fairly important not to disturb this during summer, as the larvae are delicate.  That means you attach it to something solid in the spring, so it doesn’t shake around, and you leave it alone.  The larvae pupate in fall.  At that point — late fall, early winter — they are tough enough to be moved.  Place the bee hotel in a sheltered, unheated location (such as an unheated shed).  Then, next spring, place the bee hotel (or the tubes from it) in an “emergence box”, move them back outside, and let the bees emerge as the weather warms. Google “emergence box”, but it’s basically a sheltered box with a hole in it, to let the hatched bees escape.

Some experts “harvest” the cocoons as an extra sanitation measure.  They break open the nesting tubes, remove and possibly clean the cocoons exteriors, and place the cocoons in fresh material for eventual hatch-out in the spring.   The claimed advantage of this is that it separates the bees from various parasites that may linger in the nesting tubes and this allows them to emerge from overwintering parasite-free.  If you are going to do that, you need to use relatively fragile nesting tubes (paper liners, reeds) that allow the cocoons to be removed undamaged, and not sturdy ones such as bamboo tubes shown above.

As of this writing, it’s not clear to me how much of an advantage you gain by harvesting cocoons, or what evidence basis there is for it.  The only obvious advantage is that if certain fungal diseases are present in the nest, you’ll see them if you harvest the cocoon.  As I plan to use all-new materials each year, I’m not sure that’s much of a concern to me.

Where?  These bee nests ought to be protected from rain, protected from getting cooked in the afternoon sun, and so on.  he most common advice is to locate them to catch morning (but not afternoon) sunlight.  They need to be firmly attached to something substantial because the larvae are delicate and don’t want to be tossed about.  In plain sight, so the bees can find it.  And near a ready source of mud.  Because bees need mud to cap off their egg cells.

Upshot:  Facing east-ish, under eaves if possible, firmly attached to something, near water or mud, maybe 5′ off the ground, and plainly visible.

Why and how? Different bee species want different sized tubes.  So from the get-go, a rack of identical tubes limits the species that can use that particular hotel.   The tubes need to be closed off at the back, in some fashion.  The tubes need to be sturdy enough to keep out various bee predators.  Paper straws alone, for example, appear to be frowned upon, thought to be too fragile to keep out certain types of bee predators.  In rare cases, you need to put hardware cloth across the front to keep birds from pecking out the larvae.  That’s only necessary if you wake up one morning and all the previously-filled tubes appear empty.

The simple upshot of all this is:

  • Each Spring, put last year’s nest out in an emergence box.
  • Nearby, place a clean, new nest out to attract bees.
  • Each Fall, refurbish last year’s nest, to be placed out the next spring.

Post #1776: Gas versus electric mowing, Part 6: Why I’m not buying a battery-powered mower

Weird, eh?  I’m happy to rely on a (mostly) battery-powered car.  But I don’t want a battery-powered lawn mower. Even though I used a plug-in electric mower for years.

I swore off battery-driven power tools years ago.  So, for me, it’s not as if this is some new stance.

In this post, I explain why.  Why I’m not going for a battery-powered mower.  And why I no longer buy any power tools that run on batteries.

Let me emphasize that my decision isn’t due to ignorance.  If anything, it’s because I’ve had too much experience with big lithium-ion batteries.

A few things about lithium-ion batteries.

Practically speaking, your sole option for a walk-behind battery-powered mower is lithium-ion batteries.  There have been some riding lawn mowers powered by lead-acid batteries.  But I don’t think there’s anything on the market today not powered by lithium-ion batteries.

Point 1:  Maybe you can recycle them.

Almost no lithium-ion batteries are recycled in the U.S.

I’m acutely aware of this because a) I bought a 200-pound lithium-ion add-on battery pack for my wife’s Prius in 2008, and b) recycling of those big lithium-ion batteries has been just around the corner for the past 15 years.  I think my most recent post on that was Post #1715.

Still don’t believe that lithium-ion is rarely recycled? Here’s a handful of relatively recent references.

That last reference is particularly illuminating.  Read down to the part where the Federal government is still at the point of offering cash prizes for anybody who can figure out how to do it cost-effectively.  Its not merely that lithium-ion batteries aren’t recycled, it’s really that there’s not even one good, standardized, agreed-upon process for doing it, let alone doing it cost-effectively.

Post #1712 has the details, but the reason for the lack of recycling is obvious.  It costs money.  Reportedly, Tesla currently pays $4/pound to recycle is lithium-ion batteries.  Even with that, the cost of post-recycled lithium is higher than that of virgin lithium, making it an uneconomic source for production of new batteries.

Still, some stores — around here, notably Home Depot — have boxes where you can drop off old batteries weighing under 11 pounds.  That should cover most lawn tool batteries.

That’s free to you because Home Depot covers the cost of processing those via call2recycle.  This is an organization whose funding comes from battery- and battery-powered device manufacturers, or from organizations willing to pay to recycle those batteries.   For example, their board of directors has representatives from Panasonic, Sony, Energizer, and Duracell, among others, based on their 2021 annual report.

You can see examples of their retail pricing on this page.  It looks like they charge about $2.50 a pound to take boxes of mixed rechargeable batteries off your hands.  So Home Depot is paying on-order-of $12 to allow you to dispose of a 5-pound lithium-ion lawn mower battery.

What happens after that is a bit unclear to me.  For sure, the value of the materials recovered appears trivial.  Here’s their 2021 Annual Report, showing revenue sources.  Less than five percent of their revenues comes from the materials recovered from those batteries.

Source:  call2recycle 2021 annual report.

They do not break out their collection and recycling costs separately.  Combined, those account for the bulk of their costs.

At any rate, they are clearly at least paying to have those batteries disposed of properly.  What fraction of the materials actually ends up in new products — is actually recycled — is not possible to determine from their annual report.

Interestingly enough, when I look up their lithium-battery recycling partners, the only U.S. partner appears to be a 2021 startup.  Which again seems to emphasize just how iffy lithium battery recycling remains, at this time.

Fifteen years.  For fifteen years, I’ve been living with a 200 pound LiFePO battery pack.   And for fifteen years, large-scale lithium-ion battery recycling has been just around the corner.  Which is right where it is today.

Point 2:  Batteries trade lower fuel cost for higher capital consumption cost.

Which is a fancy way of saying, if you want to keep using the tool, you have to keep buying batteries.

We replaced the nickel-metal-hydride traction battery in my wife’s (now son’s) 2005 Prius somewhere around 178,000 miles.  Doing the math, the cost of that new battery ate up roughly half of the total lifetime savings in gasoline costs, from driving that efficient hybrid compared to a similarly-sized non-hybrid 2005 vehicle.

But it’s not just the dollar cost.  It takes quite a bit of energy to manufacture batteries, something that contributes to the multi-year “payback period” of a Prius relative to a non-hybrid automobile.  For the first couple of years that you drive a hybrid, from a carbon-footprint standpoint, all you are doing with your lower fuel use is paying back the higher energy cost of the vehicle’s manufacturing.

In particular, worst-case (made-in-China, meaning, made using coal-fired electricity), large-format lithium ion batteries result in the release of roughly 200 kilograms of C02 per KWH of battery (calculated from this MIT reference, 16 metric tons per 80 KWH battery pack).

And so, creating a typical lawn-mower battery — 0.3 KW (72 volt, 4 amp-hour)  would result in (200 KG/KW x 0.3 KW * 2.2 lbs/KG = ) 132 pounds of C02 released into the atmosphere.

I use 2 gallons of gas a year to mow my lawn.  That generates about 40 pounds C02 per year.  The upshot is that even if my electricity were carbon-free, I’d spend the first three years of battery-powered lawn mowing merely paying back that initial 132-pounds-of-C02 debt, for the manufacture of that disposable battery.

That’s not a huge surprise, to those of us who have been using big battery-powered objects.  It was an estimated two year payback period for a 2005-era Prius, where the battery and motors didn’t really power the entire car.  So, a three-year payback period for a small tool that’s entirely battery-powered?  To me, based on my experience with the Prius, that seems entirely plausible.

As for the energy cost of the rest of it, I’ll just point to the high energy cost of smelting copper.  Electric motors require quite a bit of that, which is another reason hybrids require more manufacturing energy than non-hybrid cars.  Plausibly, depending on expected lifespan, there may be no manufacturing energy savings in the non-disposable portions of the devices.

For an extremely-long-lived battery, such as one used in a car, that payback period usually isn’t much of a consideration.  You’re saving a ton of fuel, and the battery will typically last well over a decade.  Overall, it’s a winner, even if you fully acknowledge the energy cost of producing the battery.

Here’s the kicker:  How long do those lawn-mower batteries last?  Every website I visit seems to give the same answer of three-to-five years.  So they might last long enough to pay back that initial carbon-footprint debt.

The upshot is that a lithium-ion powered lawn mower is a fine way to reduce local air pollution.  It may not be such a winner from the standpoint of reducing your carbon footprint.  And since global warming/carbon footprint is my main concern, I’m not hugely attracted to those devices from an environmental standpoint.

In addition, knowing what I now know about lithium-ion batteries, I’d bet on the lower end of that three-to-five-year range.  My wife’s new Prius — a Prius Prime — arguably contains a $12,000 lithium battery pack.  With no warranty to speak of.  So I got kind of serious about not trashing that.  And that’s when I learned the rules for lithium-ion batteries.  See Post #1703.

The rules, in brief:  Lithium-ion batteries don’t like heat.  They don’t like to be fast-charged.  They don’t like rapid rates of discharge, either.  And they really don’t like being worked from fully charged to fully dead.  They much prefer shallow charge-discharge cycles.

And yet, every manufacturer seems intent on using them in all the wrong ways, in mowers.  These will see highest use in the heat of summer, and typically be stored in a non-climate-controlled space.  Everybody seems to charge their lawn-mower batteries at a “1 C” rate of charge or higher — from dead to fully charged in one hour.  (Presumably, that’s to all ow you to swap batteries continuously and mow very large lawns.)  I’m pretty sure manufacturers allow the full capacity of the battery to be used, unlike cars that reserve the top and bottom 10 to 15 percent as a buffer against over– and under-charging.  (That’s why a 72-volt battery pack can be advertised as 80 volts, because once you’ve absolutely fully charged it, that’s what it’ll read, despite the fact that charging it to that degree is bad for battery life.)

Point 3:  If you love buying name-brand inkjet cartridges, you’ll enjoy purchasing batteries for your lawn mower.

Here, I’ll just refer to the highest-rated 21″ walk-behind battery powered mower on Amazon.  This is the Greenworks Pro 80V 21″ model, with 4.0 Ah battery.

On Amazon, the complete mower, with battery and charger, is $425.  But the replacement 4.0 Ah battery, by itself, costs almost $300.

In short, your cost of the replacement battery is 70% of the total cost of the functioning lawn mower.  And, as with power tools of all sort, manufacturers go way out of their way to make sure that only their batteries will fit their tools.

This, more than anything else, is why I swore off battery-powered shop tools.  It’s the monopoly-exploitation aspect of the battery replacement.  Once you’ve bought into a particular manufacturer’s line, they’ve got you.  And as far as I was ever able to tell, generic batteries manufactured to fit those tools are all completely dreadful.  So if you want a battery that works, for that name-brand tool, you pay that name-brand price.

Once I bought my third $45 battery pack, for my $60 drill, I did eventually figure out that a battery-powered drill is an expensive way to make holes in stuff.   That drill eventually got to the point where battery packs were no longer available.  (Which, if you own one long enough, will happen.)   At that point, it too became just another particle in our great national solid waste stream.  And was replaced by a corded drill.

Point 4:  Caginess about power.

This is more of an irritation than a point of substance.  But take any battery-powered lawn mower on the market, and try to find out the peak power of the electric motor, expressed either as kilowatts or as horsepower.  Nobody will tell you that basic information.

At some level, the average power output is just basic physics.  The mower above has a 72-volt, 4 amp-hour battery, and claims to be able to run for an hour on that.  That should be sufficient to cut my half-acre lawn.

But do the math.  How much energy is at your disposal, for that hour of mowing?  Well, 72 volts x 4 amps = ~300 watts of average instantaneous output.  Or, over the course of an hour, you have 0.3 KWH of power available to you, to accomplish your hour of mowing.  For sure, your peak power output will be much higher than that.  But if that battery is going to last an hour, it can’t put out more than an average of 300 watts, over that hour.

One horsepower is about 750 watts.  So the average available power output is less than half a horsepower, if you’re going to get your hour of mowing out of that battery.  Again, peak output will clearly be many multiples of that.  But that’s what you have, to get through your lawn, on average, over the course of an hour.

In my case, there are parts of the lawn, at times of the year, that nearly stall the Honda 3.3 KW gas engine that runs my mower.   I would love to know that some prospective battery-powered mower has a peak power output that meets or exceeds that 3.3 KW instantaneous power output.

But here, I bring up the last thing I know about lithium-ion batteries.  If that battery could, in fact, produce 3.3 KW of instantaneous power, it would be discharging at more than a “10 C” rate.  (That is, at that rate, the battery would be dead in less than one-tenth of an hour.)  Discharges at rates like that are unambiguously bad for battery life, for traditional cylindrical-design lithium-ion cells.  So even if it could match the peak power of my current mower, I’m not sure I’d want it to.

In other words, just as was true for my old corded Black-and-Decker, I’m pretty sure that the mower will get through my lawn.  But I’m also pretty sure that I’m going to have to “baby” it when the going gets really tough. 

But short of buying one and using it, there’s no way for me to tell, because manufacturers do not disclose peak power output of these mowers.  And so, how well will some battery-powered mower cut through stands of uber-thick Zoysia grass?

Instead of providing me with the concrete information that would allow me to judge that, manufactures require that I take a guess.  And when I see something like that, I assume it’s because their product would appear in an unfavorable light, if that information were disclosed.

Let me put it this way:  If those battery-powered lawn mowers had peak power that exceeded that of a typical gas mower, you can bet that manufacturers would crow about it.  So I think the absolute silence regarding peak power output tells me more-or-less all I need to know.

Point 5:  Summary

For the time being, I’ve decided to continue using a gas-powered lawn mower.  It’s a modern overhead-valve design, and (best guess, see prior post) mowing produces as much smog-forming pollution per hour as driving a mid-2010s-era sedan for an hour.  That’s clearly a downside, compared to battery-powered mowing, but not an extreme one.  For good measure, I’ve tossing my antiquated gas can in an effort to keep my gas-powered mowing as clean as possible.

My main environmental concern is global warming, and it’s not clear that a battery-powered mower offers much advantage there, compared to gas.  That’s due to the carbon-intensive nature of lithium-ion battery production and the relatively short expected lifetime of those batteries in fairly harsh use conditions.

Otherwise, not switching to battery-powered mowing is mostly a question of avoiding annoyances.  No mower maker will bother to tell me peak power.  So I suspect that will be lacking.  Each mower maker uses proprietary batteries.  So I expect to pay an outrageous amount for them.

And the whole lithium-ion battery-recycling thing is one big question mark.  Yes, you can drop your dead lawn mower batteries off at Home Depot, and Home Depot will cover the cost of getting them recycled, to some degree.  The degree to which the material in these batteries is actually re-used is far from clear.

So that’s it.  I saw a compelling reason and significant gains from switching car transportation to electricity.  There, at issue was a considerable amount of gasoline burned per year, batteries with an extremely long projected life-span, and some guarantee of responsible end-of-life recycling via Toyota.  Maybe. And the driving experience is better under electricity than with gas.  For mowing the lawn, by contrast, at issue is just two gallons of gas a year, there’s no clear benefit in terms of carbon footprint, and I’m betting that it’s harder to mow with a battery-powered mower than with a modern gas mower.

So this is one area where I’m not going to electrify the task.