Research Triangle Energy Consortium

The last time the NC State men’s basketball team slipped into the NCAA tournament, they made the selectors look like clairvoyants. The selection was roundly criticized. Until the Pack cut down the nets on April 4, 1983. Are we set for a Wolfpack déjà vu?

This time there was no argument about being included. Winning the ACC tournament gave them the slot by rule.  A strong belief was that but for this, the team would not have been selected. This belief was bolstered by the paltry 11^th seeding given to the team. Even that other time, they received a 6^th seeding. Lowly, but not bottom of the drawer.

The ACC certainly was under underappreciated this time around. A perennial powerhouse, they only got 4 selections and the mandatory one for NC State. Yet, 4 reached the Sweet 16. So, the ACC Tournament victor could have been presumed to have some chops. Indeed, that has been proven to be the case, reaching the Final 4 even from a lowly 11 seed position. They beat Duke to get there. A different pairing, and who knows, the ACC might have had two in the Final Four, as was the case two years ago.

In that 1983 tournament, Houston and Louisville were considered to the class of the affair. The luck of the draw had them meet in the semifinal, which was widely considered to be the “true final”. The matchup exceeded all expectation on entertainment. Both teams had high-flying forwards and much of the match seemingly was played above the rim. Houston won that game, led by Clyde Drexler and Akeem (later named Hakeem) Olajuwon. Clyde had been a lightly recruited local Houstonian and Akeem was relatively new to the sport from Nigeria. The title was seen as a mere formality against the surprising NC State Wolfpack.

Jim Valvano, the coach of the Wolfpack, had one key thing going for him. He could slow down the high flying by holding onto the ball. These were the days before the shot clock. Almost as boring as baseball. Or cricket before they wised up and invented the limited overs format, resulting in the sport catapulting into the number two spot in revenue behind the NFL. Baseball is still fiddling with little tweaks.

Back to the championship game. These are my personal memories from watching the game and may be wanting in some respect. Houston had scored 94 points in the semifinal game. The moribund pace of this one had thrown them off their game. The score was tied at 52 with a few seconds left in the game. The Pack had the ball, guarded by Reid Gettys of Houston. A tall guard, he was making it difficult on the shot. But, even with a foul to give, he did not foul intentionally prior to the shot. The player got off a desperation shot. Under the basket, in perfect rebounding position in front of the basket was Olajuwon. The Pack’s Lorenzo Charles was forced to occupy a less choice spot. The shot missed everything and fell into the hands of Lorenzo Charles. He gratefully dunked the ball and that was all she wrote. This was also the last time in the NCAA tournament that the winner did not produce the MVP. That award went to Olajuwon.

I was rooting for my hometown team Houston. So, dredging up these memories are not bereft of angst. But today, as a resident of the Triangle, I am rooting for the Pack. And that earlier game serves to remind that conventional wisdom does not always prevail. And who knows, maybe lightning will strike again*.

Vikram Rao

*Lightning is striking again, in Lightnin’ Strikes by Lou Christy (1966), written by Lou Christy and Twyla Herbert.

The UNC Cleantech Summit last week had a panel on this topic, on which I served. Here is one take on this rapidly accelerating trend in the decarbonization of industrial processes. But first some fundamentals.

Processes use fossil fuel in four different ways. The most common use is to produce heat to enable a process. An example in the hard to abate cement/concrete industry is the calcination of limestone in a rotary kiln together with other oxides such as silica to produce clinker. The clinker is blended with crushed rock, known as aggregate, and acts a binder for the aggregate particles. The clinker blend usually comprises about 15% of the concrete. The clinker is often combined with other cementitious materials such as fly ash from coal fired power plants and blast furnace slag, the primary purpose being to reduce the amount of clinker used. This purpose in turn is driven in part by the desire to reduce the carbon footprint, and in part because these other materials ought to be cheaper and but for utilization in means such as this, would be treated as wastes. States such as North Carolina have had to deal with environmental crises such as storm induced overflow of fly ash “lagoons”.

The rotary kiln calcination process causes about 0.9 tonne CO₂ per tonne clinker produced. About half of this is from the fossil fuel combusted to produce the 1500 C temperatures required. The rest is from the chemical reduction of CaCO₃ to CaO and CO₂. One remedy is to produce the heat with electric heating. But this addresses only half the problem. Another electricity-based approach, one that was presented at the cited conference, is by Sublime Systems. They electrochemically decompose silicate minerals to produce Ca(OH)₂, which may be used in place of Portland Cement.

Fossil fuel is also used as reactant in the process. An example is the use of coke in an iron blast furnace. The carbon is oxidized to CO, which then reacts with the iron oxide in the ore to produce metallic iron and CO₂. The molten iron, containing about 4% C, is sent to a Basic Oxygen Furnace, where it is lanced with oxygen. The combustion of the contained C produces heat and serves to reduce the C to the desired amount in steel, which is usually less than 0.3 % for mild steel. This too produces CO₂. Overall, steel has a CO₂ footprint of about 2 tonne CO₂ per tonne steel. One approach to electrification of the process is that of Boston Metals, where they electrochemically dissociate iron oxide to molten iron.

Fossil fuel may also be used as raw material for a process. Hydrogen is produced today dominantly by the process of steam methane reforming. Methane is the raw material and is reacted with steam to produce hydrogen and CO₂. Roughly 9 Kg CO₂ is emitted per Kg of hydrogen produced. This is classified as gray hydrogen. If the CO₂ is captured and stored, the color turns blue. Hydrogen produced by electrolysis of water is termed green if the electricity is carbon-free. Yet another electrolytic process in late-stage development uses microwave pyrolysis of methane to produce hydrogen and carbon.

Finally, we have the use of fossil fuel to drive an engine. This covers the gamut from internal combustion engines for road vehicles to aviation. Electric vehicles are the best example of fossil fuel replacement. A variant is the use of hydrogen in fuel cells to produce electricity on board electric vehicles. A further possible use is in aviation as engine fuel, although biofuel derived jet fuel is the more likely workhorse. Electric drive planes will be limited in size and scope.

Availability of Green Electricity

The electricity substitutions discussed above are carbon mitigating only if the electricity is carbon-free or substantially so. Carbon-free grids are still at least a decade away, more likely two. This is largely due to the fact that solar and wind are the new sheriffs in energy town. They are the low-cost source of energy in many jurisdictions, clean or otherwise. But they have monthly average capacity factors well below 25% and 40%, respectively. Grids want them for the low cost and renewable feature but must fill the gaps with other sources. The principal longer duration gap filler today, and for the next decade at least, is natural gas. Also, the last 40% is expensive to get carbon-free. Remedies are available, in the form of geothermal, small modular reactors and innovative storage means, but they will be a while getting to scale.

To make matters worse, according to a recent story in the NY Times, all electricity demand is expected to increase steeply over the next decade after being essentially flat over the last one. This is presumably due to the explosion in data centers, most recently compounded by generative AI, which is extremely compute intensive (read power hog). Adding to the demand is the up and down phenomenon of bit coin, also compute intensive. And, of course, electric mobility.

This is not to say that electricity substitution of fossil fuels is impractical*. It is to say that individual operations will find it difficult to get 24/7/365 clean electricity, and it is also to say that carbon-free grids need policy support to accelerate the gap fillers. At least this ought to come in the form of drastic reductions in the times of permitting.

Technology is necessary, but not sufficient.

*Do you believe in magic? From Do You Believe in Magic, by the Lovin’ Spoonful, written by John Sebastian.

Vikram Rao

A recent story in the New York Times describes what the author refers to as the first commercial plant in the US that captures CO₂ from the air. This is the class of operations known as Direct Air Capture (DAC). Costs are not disclosed except for noting that similar technologies elsewhere cost up to USD 600 per tonne CO₂ removed, and that this company intends to bring costs down to USD 100 per tonne. Corporations are buying carbon credits from the DAC operator and offsetting against their own generation. The federal 45Q legislation will also pay a subsidy which is as much as USD 85 per tonne, the amount depending on the permanence of the sequestration.

Clearly, therefore, declaring victory in the US in this atmospheric carbon mitigation sector involves some sort of subsidy, from a private or public source. In Europe, cap and trade legislation sets a penalty for emission, the avoidance of which would pay for the capture. That price has ranged from € 80 to 100 per tonne in 2023. In both cases, some sort of government legislation is defraying the cost of capture, and the business is not inherently profitable.

In contrast, many of the other carbon mitigation means are profitable in their own right. This certainly includes renewable electricity production by solar and wind, which are the lowest cost providers, at a profit, in many jurisdictions.  Electric vehicles, with zero tailpipe emissions, are also profitable. These two examples fall in the category of process change to minimize CO₂ emissions. Changing the process is the most effective, and usually involves using a fuel other than hydrocarbons (yes, we consider sunlight and wind as “fuels” in context).  But displacing incumbents is hard, in part because the capital being replaced may be far from being amortized. This is the future facing those other two major emitters after transportation, steel, and cement.

The two principal approaches to preventing emissions are changing the process or capturing in the output. The latter is alluded to as point source capture, and while still in commercialization infancy, CO₂ could be captured at source for under USD 40 per tonne. That figure could be expected to go down further, to about USD 30. Once captured, it must be stored or put to beneficial use. The highest value beneficial use in practice today is tertiary recovery of oil. Oil left behind after conventional recovery is swept with CO₂, which mixes with the oil, thus reducing viscosity and increasing mobility. Much of the gas is recovered on the surface and reused. Many efforts are also under way to mix the CO₂ with concrete. The most promising may be the mineralization of igneous rocks to form a stable carbonate, for use or disposal.

Carbon Capture

Capture is accomplished in one of two ways. In the most common process, a liquid such as an amine absorbs the CO₂ and the amine is regenerated by releasing the CO₂ in concentrated form, which is then disposed of. The other class of processes uses a solid to adsorb the CO₂, which is later released by pressure or temperature change, and the solid reused. Once again, the CO₂ is in concentrated form. Most DAC processes, including the one cited in the linked story, are some variants of the solid adsorbent method.

In either of the methods, the process is more efficient if the CO₂ concentration is higher. Accordingly, capture costs are roughly inversely proportional to the concentration. The cost per tonne captured will be lower for cement kilns, with CO₂ concentrations north of 25%, than for iron blast furnaces, with concentrations in the mid-teens. Costlier yet is capture from natural gas power plants, with concentrations in mid-single digits. And then we have DAC. The concentration of CO₂ in air is 0.04% (and rising!). There you have it, no wonder then that USD 100 per tonne is seen as a win.

Why DAC?

Why go after the costliest capture, and why not just double down on point source capture, low C electricity production and electric transportation? Many argue that capturing from the air gives a free pass for business as usual. But that argument could also be made for point source capture, albeit not as strongly.

The answer lies in how far behind we are in carbon mitigation. Point source capture will certainly involve retiring of assets, some of which may not be fully amortized. Acceleration of retirements may require policy support (read subsidies). Electric vehicles are being subsidized now. The key point is that even with an all of the above approach with emission prevention, we may fall short of reasonable 2050 atmospheric CO₂ targets unless we do something about the CO₂ already in the air.

So, yes, we need DAC. But it is indeed a subsidy play, and subsidies come and go, subject to the whims of the folks in power (look no further than the history of subsidies related to wind power) *.

*Drove my Chevy to the levy, but the levy was dry, from American Pie, written and performed by Don McLean (1971)

Vikram Rao

November 12, 2023

We now have the smoking gun

Eight of the ten largest wildfires ever in California occurred after 2017. The August Fire in 2020 burnt over a million acres. At the time, the next largest had been the Mendocino Complex in 2018, which burned 459000 acres. Then, the Dixie Fire in 2021was nearly as large as the record holder. Most, not all, scientists attribute this to climate change. But causality has been hard to establish. Then came the recent paper in The Proceedings of the National Academy of Sciences (PNAS) which was as close to a smoking gun as one could have when dealing with multiple variables. More on that later, but first some basics.

The severity of a fire season is often judged by the acreage burned, not the number of fires. This makes sense because that is the metric which is connected to the impact on society. The difference stands out when fire activity is examined over the last few decades. Shown in Figure 1 are US Environmental Protection Agency (EPA) wildfire figures for both metrics over three decades.

Courtesy US EPA 2019 (Wildland Fire Research Framework 2019-2022)

Figure 1. Time series of numbers of fires and area burned in the period 1988 – 2018.

The numbers of fires have no perceptible trend, although one can see a general progression downwards in the last decade. The acreage burned, on the other hand, has seen a gradual slope up, even though a regression line would show significant uncertainty due to the severe annual swings. Interestingly, the 2020 figure (not shown) is not that different from the 2017, even though five of the 10 largest fires ever were in 2020. A fire is considered large when the area burned is greater than 400 hectares (a hectare is roughly 2.47 acres). Acreage burned is dominated by the larger fires. Obviously, the impact on society is proportional to the area burned and the durations of the fires. One study showed that durations of large fire (>400 hectare) burns averaged 6 days in the period 1973-82 and was over 50 in 2003-12.

In attempting to unravel the distinction between the patterns in numbers and extents of fires, one statistic stands out. In recent years, ninety five percent of fires in California and the Mediterranean region have been caused by human activity (Syphard and Keeley, 2015). These activities include campfires, arson, equipment (such as chainsaws and mowers), vehicles, falling power lines, and controlled burns gone, well, uncontrolled. While human behavior can be influenced (the Smokey Bear program, for example), not surprising is the fact that the trend in the number of ignitions has been generally flat. Among natural ignition events lightning plays an interesting part. Depending on region, it ordinarily clocks in as the 4^th to 8^th most frequent contributor to ignition. The 2020 fire season changed all that. Cal Fire, a state agency reports that 4 of the 7 largest fires ever were triggered by lightning.

Effect of Climate Change

The progressively increasing severity of wildfires cannot really be in doubt. The data, such as in the figure above, speak for themselves. And, yes, the globe is warming incrementally. Also not seriously questioned is the observation that instances of severe weather have increased, ranging from droughts to floods, as have phenomena such as El Nino and La Nina, which are correlated with severity of weather. The western United States is a reasonable proxy for the relationship between climate change and wildfire severity. The states are arid and depend upon winter precipitation, primarily snowfall, for year-round water for consumption. An increasingly warming climate predicted reduced snowfalls, and earlier snowmelts. This latter statistic was shown to be strongly correlated with areas burned by wildfires. Other observations, such as climate change mediated drought conditions leading to more flammable matter (fuel), have added to the body of belief that climate change was increasing severity of wildfires. Yet, anything approaching causality had been elusive.

Then came the PNAS paper mentioned above.

Courtesy PNAS, Excerpted from Turco M. et al. (2023)

Figure 2. Time series of summer wildfire burn area (BA) and spring through summer monthly average maximum near-surface air temperature (TSmax) for the period 1971- 2021.

The authors used data from California to model area burned in wildfires (BA) against various parameters. Plotted in Figure 2 is burned area (on a log scale) against TSmax, which is the monthly mean of daily maximum near-surface air temperatures. The temperatures were in the period April – October, while the BA was in a smaller summer months subset of May – September. The temperature data are the open circles and black lines, while the BA are the filled circles and red lines.

 The most striking finding is that the single parameter of surface temperature correlated extremely well with area burned*. If there is one parameter that is indelibly linked to climate change, it is global warming, characterized by rise in ambient temperatures. The results of the model are a correlation of 0.84 between the two parameters, with a P-value (a parameter indicating statistical significance) <0.01. Statisticians will find that to be strong. Most of the rest of us can see that it passes the eyeball test. Without exception, the years in which the black circles rise or drop, so do the red ones.  Not all equally strikingly, but follow they do. The data from the first and last three years of the study are extraordinary in this regard. The authors also found that normalizing for precipitation did not make much difference.

            In the end, there is only one measure that will actively address severity of wildfires: slowing down the inexorable march of ever higher near-surface temperatures. Much is happening in that space. More is needed.

Vikram Rao

August 7, 2023

* Everybody look, what’s going down, in For What it’s Worth, by Buffalo Springfield, 1966, written by Steven Stills

References

Turco M. et al. (2023) Anthropogenic climate change impacts exacerbate summer forest fires in California. Proceedings of the National Academy of Sciences 120, e2213815120 https://doi.org/10.1073/pnas.2213815120

Syphard AD, Keeley JE (2015) Location, timing and extent of wildfire vary by cause of ignition. International Journal of Wildland Fire 24, 37–47. doi:10.1071/WF14024 

Steel is considered a “hard to abate” commodity because the production process uses a lot of fossil fuel and alternative processing methods are not readily available. The first step in the production is reducing iron ore (an oxide) to metallic iron. This is a continuous process performed in a vertical shaft furnace known as a blast furnace and the reducing agent is a form of processed coal known as coke. This is the primary culprit responsible for the high carbon footprint of steel, which is estimated to be about 2.2 tonne CO_2e per tonne steel. By comparison, that other hard to abate structural commodity, cement, has a footprint of about 1 tonne CO_2e per tonne cement.

The molten iron containing a few percent carbon is transferred from the blast furnace directly to a Basic Oxygen Furnace, where much of the carbon is oxidized to produce steel, which requires the carbon to be a fraction of a percent. This is known as primary steel. Steel produced from remelting scrap iron and steel is known as secondary steel, and has a very small carbon footprint, but is in relatively short supply.

A recent report from the Rocky Mountain Institute (RMI) provides a review of alternate ironmaking with lower carbon footprint. Their figure is reproduced below.

Courtesy RMI

They highlight the Direct Reduction Iron (DRI) process as the primary means to greener steel. This process has a vertical shaft variant which uses synthesis gas (syngas), a mixture of CO and H₂, as the reducing agent, instead of coke. The operating temperatures are also less than half that in blast furnaces. The result is a reduction of associated carbon to 0.8 tonne CO_2e per tonne steel, after the iron is converted to steel in an electric arc furnace (labeled EAF in the figure).

The report advocates a recent variant comprising substituting H₂ for the syngas, piloted by a Swedish entity Hybrit. This is straightforward because syngas can be reacted with water in what is known as the Water Gas Shift reaction to produce H₂ and CO₂, which, if sequestered, makes the hydrogen carbon free (although saddled with the color blue, rather than green). Alternatively, green hydrogen could be produced from electrolyzing water with carbon-free electricity. The report advocates this approach, and further estimates that if green electricity is used in the EAF as well, the carbon emissions associated with a tonne of steel drop to 0.1 tonne (see figure).

So, there you appear to have it. Switch to the DRI/EAF process and use green electricity for the EAF and to produce hydrogen as the reducing agent. The RMI report notes that the steel industry has vertically integrated to ensure supply of relatively scarce coking coal. It advocates that the new process do the same with respect to green electricity supply. This may well be necessary because grids will not be carbon-free for a long time (see  https://www.rti.org/rti-press-publication/carbon-free-power).  Captive supply will also have a lot of competition. But it could be done, certainly over time.

But there is a fly in that ointment. This is the fact that the DRI process can only use high grade iron ore, with over 64% iron, preferably over 67%. Those who don’t care why should skip the rest of this paragraph. In a blast furnace the mineral impurities such as silica and alumina are removed by combining with oxides of Ca and Mg to form a molten phase known as slag. This floats on top of the molten iron and both are removed continuously. In the DRI process the temperatures are too low for slag formation. Consequently, very small proportions of mineral impurities are tolerated. These small amounts are slagged in the EAF. Low impurities equate to high grade iron ore. Hence the requirement for the ore to be high grade.

Such high-grade ore is in very short supply. Most of the known reserves are in Brazil and Australia. The DRI process has been commercial for decades, but only about 7% of the steel supply comes from this source. The shortage of supply (and of world reserves, for that matter) and the higher cost of the high-grade ore are contributory factors.

Before we get into my opinion on the way forward, two other avenues to green(er) steel bear mention. A story in The Economist describes a way to clean up the blast furnace process. The CO₂ emitted is broken down into CO and oxygen using perovskites (essentially known science). The CO is used as the reducing agent in the furnace (instead of coke) and the oxygen is used in the steelmaking. There are practical issues in replacing the structural aspects of the coke. But the allure is that it modifies existing capital equipment. A complete departure from the blast furnace is electrolytic steel. The clever bit in a recent embodiment is their inert anodes. But the electricity must be carbon-free for the steel to qualify as green. And the process uses a lot of it: 4 MWh per tonne of steel. Scaling to anywhere close to the world usage of 2 billion tonnes per year means the need for a high fraction of all the power produced, leave alone the clean power. And as we noted earlier, carbon-free grids are not in the immediate future.

Where does that leave us? My favorite is the DRI/EAF with hydrogen, especially if we are not too choosy on the color of hydrogen; blue will do till green is feasible at scale. It is a tweak to an accepted process, essentially the same work force, so more easily acceptable. And that can be important for a staid industry such as iron and steel. The high-grade ore is the main hurdle to scale. Magnetite is the highest-grade variety, and it could be actively prospected. There will not be enough. We need another source.

One such is ultramafic rocks such as olivine, which are some of the most abundant minerals on earth and close to the surface. These are mixed silicates of iron and magnesium (in the main). Early-stage research offers the promise of extracting the Fe portion, and as luck (and thermodynamics) would have it, the Fe will be in a valence state making the oxide magnetite.

The CO₂ in blast furnace emissions can be captured and stored for under USD 50 per tonne of CO₂ with technology available today. This is well below the carbon penalty in Europe today. Partial use of hydrogen as a coke substitute would be minimally intrusive.

The two approaches above could handle the bulk of the decarbonization. They could be supplemented by electrolytic steel where captive carbon-free electricity could be arranged.

And don’t forget that Kermit the Frog said*, “It’s not easy being green”.

Vikram Rao

March 25, 2023

*Bein’ Green, Song by Kermit the Frog (Jim Henson), 1970, written by Joe Raposo

Direct air capture of CO₂ (DAC) is all the vogue in carbon capture, with considerable innovation occurring. Nature tried its hand at innovating in the passive DAC space a while back. The public is very familiar with the role of forests. To a lesser degree, also known is the role of oceans as carbon sinks.

But it may surprise many that there is a form of vegetation that does a far better job than trees. Five times better per square meter in places. These are plants in peat bogs, which capture CO₂ and transfer it over time to the organic layer below, which results in the material we know as peat. Peat may be classified as a very early form of coal, with as little as 40% carbon. Were it to be subjected to higher temperatures and pressures by being buried under sediment, it would eventually convert to lignite, and thence to bituminous and finally anthracite coal. The last clocks in at over 90% carbon and looks like a shiny black rock. Countries, such as Estonia, which are short of other hydrocarbons, have combusted peat for electricity. In other places, regular folks have retrieved buckets of peat from the bogs and burned them for fuel.

Source: Peat Bogs Wallpapers High Quality | Download Free (yesofcorsa.com)

Peat bogs comprise only 3% of the surface of the earth, but account for 30% of the land-based stored carbon, which is double that stored by all forests combined.  For comparison, forests cover about 31% of the earth’s surface. A recent paper compares carbon storage by trees and peat in boreal forested peatland (peatland that also has partial or complete tree canopy). They estimate that the organic storage is higher in the peat layers than in the trees and subsoil (11.0–12.6 kg m−2 versus 2.8–5.7 kg m−2) over a “short” period of 200 years.

And yet, saving rainforests gets all the ink. Save the peat bog does not have the same ring. And yet, it should. Admittedly, on imagery alone, a bog finds it hard to compete against a rainforest. Cuddly koala bears versus fanged Tasmanian Devils (mind you, as any Aussie knows, real-life koalas are not to be messed with either, and in a further nod to excellent promotion, they are not even bears, they are marsupials, as are kangaroos). And the comparison is not that straightforward, because forests provide other benefits over bogs.  In any case, the global warming situation is so dire that this is not an either/or proposition. The purpose of this discussion is twofold. One is to draw attention to peat bogs as at least just as important as forests for preservation and expansion, including the use in carbon offset programs. The other is to delve into the science of why peat moss is more effective than other plant matter in capturing and storing carbon.

Sphagnum mosses are the dominant species in peat bogs. They are specially adapted to thrive in low pH (acidic), anaerobic and nutrient poor waterlogged environments. The bog microbiome (defined as a mix of microbes) plays a critical role in the fate of the Sphagnum. The microbiome is dominated by bacteria, but also has fungi. The microbes are highly specific to the Sphagnum, indicating plant-microbe co-evolution. This specificity is believed to increase the carbon fixation efficiency, and to adapt to changing climatic conditions. An Oak Ridge National Laboratory investigation showed that heat tolerant microbes transferred heat tolerance to the Sphagnum.

A key feature of the low pH and anaerobic environment is that when the mosses die, they sink into the bog and do not decompose, thus retaining the carbon for incorporation into the peat layer. Meanwhile new moss grows above. This unique ecosystem carries on fixing carbon from the atmosphere in a manner far more effective than any other natural means. Yet, possibly through a failure to recognize the value, or through a desire to repurpose the land for commercial interests, many of the peatlands have been drained. In the state of North Carolina, nearly 70% of peatlands were drained, according to a Nature Conservancy report (Afield, Spring 2023), a reading of which was the impetus for this discussion. Drained peatlands cease to be carbon absorbers and become emitters. In the more spectacular instances, fires lit by lightning strikes have burned and smoldered for up to a year, spewing as much as 270 tons of CO₂ per day. This duration of a year is not surprising because the fire can go underground, where the fuel is plentiful.

Reforestation is a laudable goal. As is the support of the many ongoing investigations targeting passive and active capture of CO₂ from the air. But, equally, restoring peatlands and protecting existing ones ought to be a priority. Nature has already provided an efficient CO₂ sponge. We must feed it*. Adopt a bog.

Vikram Rao

* Sat on a fence, but it don’t work, from Under Pressure, by Queen and David Bowie (1981), written by Roger Taylor, Freddie Mercury, David Bowie, John Deacon and Brian May.