Can a Refrigerant Be "Natural"?

 

The other evening my wife and I went to a new ice-cream shop in town, and while I was having my usual cup of vanilla I happened to glance at a refrigerated glass-front cabinet where the employees kept decorated cakes for sale.  Way down on the lower left corner of the front was a green label that read "NATURAL [followed by a leaf symbol] Refrigerant." 

 

That got me curious.  I knew the "natural" label has great consumer appeal these days when applied to food and maybe clothing, but refrigerants?  So I did some digging and discovered that there is quite a history behind the various refrigerants that have been used since mechanical refrigeration was developed in the nineteenth century.

 

For readers who need a review of how mechanical refrigeration works, here's the brief version.  When you compress a gas, it gets hotter, and that heat comes from the work you expend in compressing it.  If you then remove the heat somehow (that's what the condenser unit does outside every air-conditioned building), and the gas is suitable for use as a refrigerant in the system designed for it, it will turn into a liquid when it's cooled down enough.  If you then send the liquid through a small opening into a place where the pressure is lower, it will evaporate back into a gas, and get a lot cooler than it was before.  That's what happens in the evaporator inside an air-conditioned building.  It's the same basic principle that makes you feel cooler when you're sweating on a hot day and a breeze comes up:  water evaporates from your skin and takes some heat with it.  Run this process around and around again with the same substance, and you have a mechanical refrigerator. 

 

All right.  When large-scale mechanical refrigeration systems operated by steam power became available in first Europe and then the U. S. in the 1880s, they used ammonia gas.  The bottled liquid we call ammonia is just a solution of pure ammonia gas (NH₃) in water.  The gas itself condenses to a liquid at atmospheric pressure at a temperature of -28 F (-33 C), but under moderate pressure it can be persuaded to condense at or above room temperature, and it carries a good amount of heat away when it re-evaporates at lower pressure. 

 

Nineteenth-century ammonia was about as natural and organic as you could get.  It was obtained mainly from the waste urine from packing houses, by distillation, and it was therefore fairly expensive.  It got a lot cheaper when the Haber-Bosch process for making it from hydrogen (obtained from natural gas) and nitrogen (obtained from air) was perfected in the early 20th century.  But leaks in refrigeration machinery were common and ammonia gas is nothing you want to get loose around customers.  So the industry sought a non-toxic, non-corrosive substitute, and along came a General Motors chemist named Thomas Midgely Jr.

 

Midgely was largely responsible for the development of leaded gasoline, which in the 1920s was viewed as vital to the efficient operation of gasoline-powered vehicles.  Fresh from this first long-term environmental disaster, Midgely devised a new chemical that used carbon, hydrogen, and fluorine to make what at the time appeared to be the ideal refrigerant, which was trade-named Freon.  It became wildly popular, but in the 1970s, just when we were phasing out Midgely's first brainchild, leaded gas, it was discovered that the original type of Freon destroyed ozone in the atmosphere, at a rate that promised to leave us unshielded from the harmful ultraviolet rays that are normally absorbed by the naturally-occurring ozone layer. 

 

Somehow, the world's engineers cooperated in 1987 to agree to the Montreal Protocol, which committed the signatories to replace ozone-destroying refrigerants with some that are less harmful to the atmosphere.  Since then, the overarching question asked about new refrigerants is whether they hurt the atmosphere, and if so, by how much?  So it turns out "natural" in the context we're talking about means "less harmful to the atmosphere," and not necessarily something that occurs only in nature.

 

For example, on a website that sells restaurant equipment, I found an article that rates many current types of refrigerant with red (Not Eco-Friendly), yellow (Somewhat Eco-Friendly) and green (Eco-Friendly) labels.  Something called R-450A has a green label, and may be what's keeping the ice-cream shop's cakes cool.  It's made of a chemical called hydrofluoroolefin (HFO), which is anything but natural in the sense that it's a highly engineered artificial compound.  But if it gets loose in the air, the nature of its chemical bonds makes it turn into a reactive acid that gloms onto something or other fairly quickly and leaves the air, never making it into the stratosphere where it could bother the ozone layer. 

 

If you want "natural" to mean "naturally occurring," there is the old standby ammonia, which is still used in large-scale industrial refrigeration where its toxicity and flammability can be kept safely under control.  Propane and isobutane, which are distilled from natural gas, can also be used as refrigerants, but they can burn and have to be used in carefully sealed systems for consumer applications.  And the bad boy of the climate-change movement itself, carbon dioxide, can also be used as a refrigerant, although it doesn't condense unless the pressure is raised to over sixty times atmospheric pressure, necessitating very sturdy compressors and containment pipes. 

 

As historian Jacques Barzun pointed out in his monumental From Dawn to Decadence, the notion that nature knows best about a wide variety of things has a life of its own, and was one reason the "natural" tribes discovered in North America were of such interest to the Europeans who eventually overwhelmed them.  In the context of refrigeration, it looks like a more accurate label than "natural" would be "eco-friendly," but the PR people know what words look good in public view, and they picked "natural." 

 

It's only pedants like me who would even think to quibble with what the word actually means.  Without rolling the cabinet out from the wall and looking at the nameplate, I couldn't tell exactly what refrigerant was being called natural.  And my curiosity has its limits—it was good ice cream, and I didn't want to cause a scene and get barred from the shop forever.  I'm just glad that once we found problems with the refrigerant that at first glance looked ideal, we changed course and developed a whole spectrum of other ones.  That's the way engineering should work, and in this case, it has.

 

Sources:  I referred to the website https://www.webstaurantstore.com/article/474/refrigerant-types.html?srsltid=AfmBOorPfBjgu4ChyoyuSMDiNc9uETNLojxoiL_gL91XRkUgPKAPtlym

for the list of eco-friendly-graded refrigerants, and to the Wikipedia articles on HFOs and Thomas Midgely Jr. 

Imagining Geoengineering

Okay, suppose some of the most extreme voices warning of global warming are right.  Suppose we really do face the inundation of much of the world's coastlines in a generation or two.  Even if, starting tomorrow, nobody ever burned a drop or a gram of fossil fuel ever again, the carbon dioxide now in the atmosphere might take hundreds of years to fall to pre-industrial levels.  So simply implementing restrictions on fossil fuels to reduce carbon-dioxide levels may not do the job fast enough.  What do we do in the meantime?  To use an automotive analogy, if you're going too fast and you see that the road ahead of you ends in a cliff, it might not be sufficient simply to take your foot off the gas.  You might actually have to apply the brakes.  David Keith says we ought to at least talk about applying the global-warming brakes.  But the question I have is, how could it ever get beyond talk?

Keith is a professor with appointments at both the Harvard Kennedy School, where he teaches public policy, and Harvard's School of Engineering and Applied Sciences.  An environmental engineer by training, Keith thinks that "geoengineering" ought to be considered along with reductions in fossil-fuel consumption as a way to reduce the effects of carbon dioxide in the atmosphere.  Geoengineering refers to intentional efforts to manipulate the climate.  So far, the only moderately successful geoengineering projects have been cloud-seeding efforts that arguably increased rainfall in some areas.  But Keith is talking about a worldwide effort to do something that will counteract global warming by artificially cooling the planet somehow.

Interviewed last March by the CBC (Keith is Canadian), he admitted that ideas such as spreading small sulfur particles in the stratosphere to reflect solar radiation as a way of countering global warming are a "brutally ugly technical fix."  But he thinks such geoengineering solutions should be on the table, rather than brushed aside scornfully, as they are by many environmental activists.

Let's try to imagine how such a geoengineering fix would work, not just technically, but politically.  Many of the geoengineering solutions that have been posed are not terribly expensive, globally speaking.  We are talking about industrial quantities of sulfur or other chemicals dispersed in the upper atmosphere, but the cost in terms of the global economy is miniscule.  There is no question that such a project could be mounted by even one well-prepared industrial nation.  The question I'd like to examine is:  could the nations of the world ever reach a consensus on what geoengineering solution to adopt?

If we examine the track record of united global action on the main cause of the carbon-dioxide increase, namely the use of fossil fuels, history is not encouraging.  The most significant effort in this direction is the Kyoto Protocol, adopted in 1997.  It is technically an extension of a 1995 UN agreement that parties signing it will reduce their emissions of greenhouse gases in accordance with certain goals spelled out in the document.  While 192 countries signed the accord, some of the most significant producers of greenhouse gases either did not participate at all (e. g. the U. S. A., China, India) or have not met their targets (e. g. New Zealand). 

The only global environmental agreement I can recall that actually worked was the way we kept chlorinated fluorocarbons (CFCs) from destroying the ozone layer.  CFCs were once used widely as refrigerant fluids (e. g. under the trademark "Freon"), but in the 1970s, scientists figured out that (a) these compounds lasted for a long time in the atmosphere and (b) they catalyzed the destruction of the important ozone layer in the stratosphere, which protects us from harmful UV radiation from the sun.  The Montreal Protocol, which went into effect in 1989, set its signatories on a path to eliminating the production of new CFCs and phasing out their use by finding alternatives.  By and large, the Montreal Protocol is a success story in international technical agreements, because most of the industrialized world signed on and actually did what they agreed to do.

Why can't we get such cooperation with the global-warming issue?  The simple answer is, it would cost more.  Telling the world economy to give up CFCs was like telling a dieter to give up the tutti-frutti milkshake he has every Shrove Tuesday.  CFCs were a minor part of the global economy compared to fossil fuels.  If we accept the most radical recommendations of those alarmed about global warming and implement restrictions as fast as they want us to, well, the point is, the world won't do it without something approaching a global police state.  Developing nations such as China and India will not willingly forego the advantages of wider use of fossil fuels to grow their economies.  It would take a world war and dictatorial economic domination by a single global-warming-prevention entity to make the world go on a fossil-fuel diet.  And that doesn't sound like a good tradeoff.

The thing that geoengineering proponents like David Keith have going for them is that many geoengineering proposals would cost a lot less than replacing fossil fuels with a sustainable alternative.  Whether geoengineering would work is another question, unfortunately even more complicated than the still-controversial question of exactly how bad climate change is going to get, and what adverse effects it will have in the future. 

Besides the technical issue of whether geoengineering would work, I think there is an esthetic or philosophical factor involved.  Many of those who advocate harsh restrictions on fossil-fuel use to avert further climate change seem to have bought into the "deep-green" assumption that humanity is really a net liability for Planet Earth.  Burning fossil fuels represents meddlesome tinkering with what Mother Nature was up to naturally, and geoengineering would be another step down that evil road of manipulating the environment.  Better we just fold our tents, globally and economically speaking, and go back to living off nuts and berries.  The trouble with that notion is that there would not be enough nuts and berries to go around unless we keep burning fossil fuels, or find an energy-equivalent alternative that won't bankrupt us.  Such an alternative is not yet at hand. 

I admire engineers like David Keith for thinking through important problems such as climate change to arrive at possible solutions that might actually work, at least technically.  Given the dismal track record of the Kyoto Protocol, the chances of arriving at a truly global accord to implement significant fossil-fuel reductions are vanishingly small.  If some of the more dire climate-change predictions come to pass, it might be easier to get international agreement on a geoengineering strategy than it would on fossil-fuel reductions, especially if the price is right.

Sources:  An article on David Keith's ideas about geoengineering appeared on March 29, 2014 on the Canadian Broadcasting Corporation's website http://www.cbc.ca/news/technology/give-geoengineering-a-chance-to-fix-climate-change-david-keith-1.2586882.  I also referred to Wikipedia articles on solar radiation management, the Kyoto Protocol, and chlorofluorocarbons.