Science & Nature

Can the world’s most polluting heavy industries decarbonize?

This story was initially revealed by Yale Environment 360 and is reproduced right here as a part of the Climate Desk collaboration.

We know the right way to decarbonize vitality manufacturing with renewable fuels and land transportation with electrical autos. Blueprints for greening transport and plane are being drawn up. But what concerning the huge industrial processes? They look set to develop into decarbonization holdouts — the final and hardest CO2 emissions that we should get rid of if we’re to attain net-zero emissions by mid-century. In specific, how are we to inexperienced the three greatest globally-vital heavy industries: metal, cement, and ammonia, which collectively emit round a fifth of anthropogenic CO2? 

Our trendy city environments are largely constructed from concrete — which is comprised of cement — and metal. Most of our meals is grown via the applying of fertilizer comprised of ammonia. These most ubiquitous industrial supplies are produced at big expense of vitality and carbon dioxide emissions. 

Their staid industries have prospered for over a century utilizing largely unchanged manufacturing processes. But the pressing want to provide inexperienced ammonia, metal, and cement is beginning to shake them up. Research is offering new choices for elementary modifications to chemical processes. And in current weeks, main gamers have introduced main initiatives in every of those three crunch industries. 

Two rising applied sciences are promoting themselves because the “options” to decarbonizing drawback industries. One is carbon seize and storage (CCS), which goals to seize stack CO2 emissions and bury them in geological buildings corresponding to previous oilfields or salt mines. The different is “inexperienced hydrogen,” made by splitting water utilizing renewable vitality. Some see inexperienced hydrogen because the dream gas of the longer term, powering all the pieces from planes and energy stations to houses and heavy trade. 

U.S. Energy Secretary Jennifer Granholm stated in June that “clear hydrogen is a recreation changer,” as a result of it “will assist decarbonize high-polluting heavy-duty and industrial sectors.” 

But each applied sciences face technical criticism and accusations of hype. CCS is accused of being designed extra to extend the way forward for fossil-fuel industries than to decarbonize the world’s economic system. And even inexperienced hydrogen, which is basically a conveyor of renewable vitality, appears pointless for purposes the place the renewable vitality can be utilized straight — by plugging in electrical autos, as an illustration.

Yet every might have a job in sure industries, trade analysts say. “Primary metal and ammonia manufacturing are smart entry factors for inexperienced hydrogen,” Falko Ueckerdt of the Potsdam Institute for Climate Impact Research advised Yale Environment 360. Hydrogen could be very environment friendly at fueling high-temperature industrial processes, as an illustration, so inexperienced hydrogen might generally be the actual deal for heavy industries that presently require fossil fuels as a part of the method (metal), already use hydrogen (fertilizer), or want the excessive temperatures hydrogen is nice at producing (cement). 

Let’s take every of those industries. What do they should decarbonize?


Steel manufacture is presently chargeable for 11 p.c of anthropogenic CO2 emissions. Most manufacturing begins by burning coal with iron ore in a blast furnace. The coal generates warmth however is a part of the chemical course of within the furnace. It strips oxygen from the ore to make pure iron, referred to as pig iron, which is changed into metal in an electrical arc furnace. But the waste product — from combining carbon within the coal with the oxygen within the ore — is massive portions of carbon dioxide. The complete course of emits a mean 2.2 tons of CO2 for each ton of metal. 

So what will be achieved to scale back these emissions?

Two men, one wearing a red shirt with grey pants, and the other one a blue shirt and brown plants, use shovels to distribute fresh concrete over a street. They're also wearing construction boots.

Concrete being poured final October on the website of the Winthrop Center, a skyscraper underneath development in Boston.
DAVID L. RYAN/THE BOSTON GLOBE VIA GETTY IMAGES

More environment friendly use and recycling of the product ought to at all times be the primary avenue pursued. Recycling avoids the blast-furnace stage, with its heavy emissions. The scrap is fed into an electrical arc furnace, which generally produces solely 0.3 tons of CO2 for each ton of metal. Emissions might be decreased additional by switching away from fossil fuels to provide the electrical energy. But the potential good points from recycling are restricted, in keeping with analysts. Around 85 p.c of discarded metal is already collected for recycling. But metal’s lengthy in-service life implies that this recycled scrap nonetheless makes up solely round a 3rd of whole metal manufacturing, in keeping with the International Energy Agency (IEA).

Widespread adoption of CCS might probably additional scale back emissions. But greater good points might come up from abandoning the blast furnace altogether. The important various strategy for making pig iron is to run an enormous direct electrical present via the ore. This course of, referred to as electrolysis, is how bauxite ore is changed into aluminum. The vitality calls for are big, however with out the necessity for coal as a part of the method itself, that vitality might come from a low-carbon supply, corresponding to inexperienced hydrogen. So inexperienced hydrogen is seen as very important to inexperienced metal. 

This hydrogen route is presently being tried in Europe, underneath state subsidies, by each ArcelorMittal, the world’s second-largest metal producer, and in a undertaking introduced earlier this month within the Netherlands by India-owned Tata Steel.

It might catch on. An enticing strategy can be to make the hydrogen on the identical website because the metal. It represents a “big alternative” for Australia, which has each huge iron ore mines and plentiful photo voltaic vitality, in keeping with Jessica Allen and Tony Honeyands of the University of Newcastle, New South Wales, “It would increase our exports, assist offset inevitable job losses within the fossil gas trade, and go a protracted option to tackling local weather change,” they argued in a current weblog submit. 


The manufacture of ammonia fertilizer has been one of many fastest-growing industries worldwide over the previous half-century. It was the bedrock of the agricultural inexperienced revolution of the late 20th century and as we speak nourishes the crops that feed 40 p.c of the world’s inhabitants. Fertilizer is by far the primary use of the 176 million tons of ammonia produced yearly.

Ammonia is made utilizing the Haber-Bosch course of, invented by German chemist Fritz Haber in 1908. It gained him a Nobel Prize a decade later. The course of is in two levels. First it manufactures hydrogen, normally from pure fuel; then it synthesizes the hydrogen with atmospheric nitrogen. To do that requires breaking the tight bonds that maintain collectively molecules of nitrogen within the air, and that requires excessive pressures and temperatures of round 500 levels C.

Both hydrogen manufacturing and ammonia synthesis are energy-intensive. The complete course of, carried out in large industrial crops, emits roughly two tons of CO2 for each ton of ammonia and is chargeable for round 2 p.c of anthropogenic CO2 emissions.

Fertilizers are some of the wastefully used of all high-carbon merchandise. Less than half of what’s poured onto fields will get anyplace close to roots — a proportion that has been falling lately, in keeping with Xin Zhang, an environmental scientist on the University of Maryland. This not solely causes pointless CO2 emissions, but additionally floods the pure surroundings with nitrogen — creating algal blooms in rivers and lifeless zones within the oceans, and damaging biodiversity nearly in every single place. So utilizing fertilizer extra effectively must be a excessive precedence.

But past that, each levels of the fertilizer manufacturing course of have to be decarbonized. The first stage, making hydrogen, must be probably the most achievable. In April this yr, the world’s largest ammonia producer, CF Industries, introduced plans to “inexperienced” a part of the hydrogen manufacturing at its largest manufacturing advanced, in Donaldsonville, Louisiana. It is putting in German-made gear to make hydrogen by splitting water, utilizing renewable vitality.

Decarbonizing the second stage, ammonia synthesis, requires a serious enchancment on — or alternative of — the prevailing course of. Justin Hargreaves on the University of Glasgow, Scotland, says catalysts are key to the method. They are vital to interrupt the robust bond of the nitrogen molecule so the component can mix with hydrogen.

On a sunny day, a huge tractor sprays fertilizer on a green wheat field in England

A tractor sprays fertilizer on a wheat discipline in North Yorkshire, England.
STEVE ALLEN TRAVEL PHOTOGRAPHY / ALAMY STOCK PHOTO

The Haber-Bosch course of makes use of an iron catalyst. But ever since its invention, the sport has been on to seek out one thing that works effectively at decrease temperatures and pressures. “Tackling low-temperature ammonia synthesis is a kind of holy grails of chemistry,” says Levi Thompson, a chemical engineer on the University of Michigan. But the chemical vital to attain this has up to now eluded researchers. 

“Nature does it,” Hargreaves advised e360. “Nitrogen fixation by micro organism in plant roots occurs underneath ambient circumstances, with no excessive temperatures or pressures. But charges of manufacturing are too sluggish to be sensible for large-scale manufacturing.” The hope is that the precise catalyst might change that. “It is a giant prize, if we might do it,” Hargreaves stated.

Plenty of industrialists are within the recreation. A Japanese firm, JGC, has a trial plant at Fukushima combining photo voltaic vitality to make inexperienced hydrogen utilizing a brand new ruthenium catalyst that it has developed for ammonia synthesis. The firm claims to have minimize the strain wanted for manufacture by three-quarters. Another Japanese group, headed by Hideo Hosono on the Tokyo Institute of Technology, is championing a lanthanum-cobalt catalyst. He claims it cuts the temperature required to 400 levels C.

Some foresee future processes that ditch the traditional Haber-Bosch course of fully. In June, Doug MacFarlane and colleagues at Monash University in Australia, introduced success in creating an electrochemical course of for breaking the nitrogen bonds that might produce ammonia at room temperatures. They say the important thing was the addition of phosphonium salt, which dramatically sped up reactions.


The third carbon dinosaur — and probably probably the most tough to reform — is Portland cement, so named as a result of it resembles a constructing stone quarried on Portland, a peninsula in southern England. It was invented in 1824 by an English stonemason known as Joseph Aspdin. The manufacturing course of mixes chalk or limestone (calcium carbonate) with clay and cooks the combination in a kiln at 1450 levels C, triggering chemical modifications that create a tough strong, known as clinker, which is mixed with gypsum to make cement. The cement is then combined with aggregates and water to create concrete.

The excessive temperatures within the kiln require plenty of vitality, usually gained from burning fossil fuels that emit CO2. In addition, when the calcium carbonate is transformed within the kiln, the primary by-product is but extra carbon dioxide. When the kiln gas is coal, kilns emit round one ton of CO2 for each ton of cement manufactured.

Every yr greater than 4 billion tons of Portland cement are produced worldwide, greater than half a ton for each inhabitant on the planet. It makes our world of dams, roads, bridges, tower blocks, sea partitions, and parking tons. And it’s chargeable for round 8 p.c of anthropogenic CO2 emissions. 

How to alter this? While many of the world’s metal will get recycled, little or no of its concrete does. Buildings might be designed to be taken aside once more and their parts used once more. But few are. When wrecking-ball groups arrive, little of the rubble they create finds any future use, apart from landfill or as mixture. That wants to alter, says Brian Norton of the Dublin Institute of Technology. “Buildings … must be designed to be simply disassembled on the finish of their use.” Or we might use different development supplies, corresponding to sustainably sourced timber. 

But what of the cement manufacturing course of itself?

If the coal within the kiln had been changed by inexperienced hydrogen, that might minimize total CO2 emissions — however solely by a few third. So one thing must be achieved to do away with the CO2 generated by the manufacturing course of.

One means is CCS to seize the CO2 emissions. The IEA, in a current report on pathways to net-zero, noticed CCS contributing as much as 55 p.c of potential emissions reductions within the trade by 2050. Another manner is to seek out industrial makes use of for the CO2. Earlier this month, French cement producer Vicat introduced plans to divert 40 p.c of the CO2 from its kiln at Montalieu-Vercieu close to Lyon to fabricate methanol to gas new containers ships being constructed by the world’s largest transport line, Maersk.

A grey, almost castle-like -looking structure emits smog. Bhind,a mountain range emerges like a wall. In front of it, near to the lens, a green, calm river passes by. A few small trees, with red and green foliage, indicate that the photo was taken during the fall months.

Cement factories in China alongside the Yangtze River.
TIM GRAHAM / GETTY IMAGES

But there are additionally decarbonizing choices for altering the uncooked supplies of the cement manufacturing course of. The IEA says that probably as a lot as half the clinker in cement might be changed with different supplies, starting from uncooked limestone to fly ash from energy stations, discarded tires, and home refuse.

More radically, German researchers in a research revealed final month urged that at the very least half of the limestone within the kiln might be changed by alumina-rich clay, referred to as Balterra clay, that usually overlies geological reserves of bauxite, the uncooked materials of aluminum. Herbert Pollmann of the Martin-Luther-University in Germany says this calcium sulphoaluminate cement each avoids the CO2 emissions from firing calcium carbonate and cuts firing temperatures from 1450 levels C to 1250 levels C. “Our technique not solely releases much less CO2 through the chemical conversion, but additionally when heating the rotary kilns,” Pollmann says, probably lowering total emissions by two-thirds. 

Another potential answer, invented 20 years in the past by Australian industrial chemist John Harrison, replaces limestone with an identical rock, magnesium carbonate, typically referred to as magnesite, discovered within the mineral magnetite and in mixtures with calcium carbonate corresponding to rocks referred to as dolomite, which roast at a lot decrease temperatures, round 650 levels C, so requiring solely half the vitality. But Harrison says magnesium carbonate’s greatest profit is the power of the ensuing concrete to soak up atmospheric CO2 whereas in use.

This “carbonation” carries on so long as the fabric is uncovered to the air, probably recapturing all of the CO2 launched when it was made. Thus, he says, buildings fabricated from his “eco-cement” might act fairly like a tree — continually taking on CO2.

Regular cement additionally carbonates, however Harrison says his model continues for much longer. This competition was challenged 5 years in the past when a research urged carbonation of standard cement was larger than usually realized. Unnoticed by local weather scientists, the research discovered, “present cement shares worldwide take in roughly one billion tons of atmospheric CO2 every year.”

Still, Michael Taylor of the London-based Mineral Products Association believes Harrison’s invention has potential worth. Its important drawback, he suggests, stands out as the infamous conservatism of the cement trade. Initial prices for brand spanking new formulations are excessive, and offering the sturdiness of the completed product might take many years. “Innovators … expertise this conservatism as a substantial barrier, and will imagine it has been raised merely to frustrate their goals,” Taylor says.

It is a well-known drawback. But, as with metal and ammonia, political strain for greener processes might change that.


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