Can concrete be carbon neutral?

Concrete's carbon impact

Some aspects of our economy are easy to decarbonize.

We are well on our way switching cars from internal combustion to electric. We are rapidly adding carbon-free electricity from solar panels and wind turbines. However, there are areas where it is not easy to decarbonize. At the top of that list is concrete.

According to Our World in Data, cement production is responsible for 3% of worldwide emissions—more emissions than aviation or landfills.

The world uses a lot of concrete. It is estimated at 30 billion tons are used each year. It is inexpensive, durable, strong and resilient. We cannot do without concrete. As the population grows, the amount we need is increasing. Global warming only makes this worse. Concrete plays a big role as we try to adapt to climate change, think of construction protecting communities from sea level rise.

Concrete is made of sand, gravel, water and cement, which is the binder that makes concrete harden and keeps it strong. While cement only makes up 15% of concrete, it is responsible for 80% of emissions. The fundamental problem today is how we make cement. Cement starts as limestone, which is crushed and then heated to1,450 C in a kiln to create lime.

Concrete can be “recycled,” where it is crushed and used to replace sand and gravel, but while that prevents concrete from overwhelming landfills, it doesn’t change the amount of greenhouse gases released in the production of cement.

Let’s take a look at two parts of this process, starting with heat.

The super high temperature needed to create lime from limestone is created using powdered coal, oil or gas (it is worth noting that in this context, gas is indeed a low emission fuel, releasing about 40% less CO2 than coal and oil). Electricity is poor at creating this kind of heat, and while it is possible to achieve these temperatures with concentrated solar power, fluctuations from nighttime and clouds remain a problem.

A study by the Canadian Energy Systems Analysis Research simulated using a mix of natural gas and alternative fuels to create cement, such as plastic waste or wood dust. The problem is those energy sources have a lower heating value and a higher moisture content. Because of these and other differences, a 50-50 mix of alternative fuel and natural gas requires a lot more oxygen and heating and pumping oxygen actually generated more CO2 than using gas alone by itself.

Now, let's look at the chemical transformation from limestone to lime. Limestone is mostly calcium carbonate and lime is calcium oxide. As the “carbonate” in the name suggests, limestone contains carbon which is released in the form of carbon dioxide during the high-temperature chemical reaction in the kiln. Sixty percent of the carbon emissions from cement come from this chemical reaction.

So cement has two problems—the high temperature needed to change limestone into lime and the chemical reaction that releases CO2 in that high temperature reaction. Is this hopeless? No. Project Drawdown, a collection of current-technology climate change solutions, takes aim at both the energy used generating the high temperatures and the limestone-to-lime CO2 emissions.

First, as with so many areas, they suggest beginning by upgrading to more energy efficient equipment. Then they suggest switching from lime as a binder. Natural products such as calcined clay can be used. More exciting is the possibility to use waste such as granulated slag (a by product of steel) or recycled glass. There are several small companies today that produce alternative cement such as CarbonCrete in Montreal or Brimstone in California.

So the carbon footprint of concrete can be reduced by energy efficiency. It can be reduced by switching from limestone to an alternate material. However, concrete can also be a carbon storage solution. One of the hottest areas of research is using concrete to lock away carbon emissions. There are companies doing this including CarbonCure (from Dartmouth Nova Scotia) and CarbonBuilt (from California). Both these companies collect CO2 and inject it into the concrete. The great thing about pumping carbon into concrete, is that it is permanent storage. You can store carbon by planting a tree, but trees can die, be chopped down or burned in a forest fire, releasing their stored carbon back into the atmosphere. Carbon injected into concrete is there to stay.

Concrete is irreplaceable in modern construction and there’s a lot of carbon emissions from how we create cement today. But there is a three prong solution: energy efficiency, alternatives to cement, and carbon capture and storage. We can update our cement manufacturing, taking energy efficiency steps to create high temperatures with less fuel. We can switch the binder from cement to alternatives that don’t release as much CO2. And finally we can integrate carbon storage in all concrete production.

Concrete’s problem is that it isn’t snazzy like solar panels or lovely like forests but it is literally the foundation of society. We have the tools, now let’s use them.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.


Potential environmental crises worse than global warming

Worse than global warming

For those of us who work in the field of climate change, it is some consolation to take a break and reflect there are crises worse than global warming.

Giant meteor: Sixty-six million years ago, a meteor impact triggered an extinction event that killed most of the dinosaurs. When the meteor hit, it was a double whammy. First, rock fragments triggered fires as far away as 2000 kilometres from the site. Those fires put carbon dioxide, methane and carbon monoxide into the air. Then the impact itself put microdust into the air, blocking sunlight and cooling the planet drastically. Winter-like conditions lasted for two full years and long-term effects lowered average temperatures by as much as 15 C over the next 15 years. Less sunlight means less plant life, which means less available food. Scientists estimate 75% of species went extinct. Don’t worry, a rock that size only hits Earth every 100 million years or so.

Death of the Sun: The Sun, our beloved yellow dwarf star, is critical to life on earth. Five billion years from now the sun will begin to run out of fuel. Currently it burns hydrogen, turning it into helium. When the supply of hydrogen gets low, it will start to burn helium creating carbon. Fusing helium creates much more heat and this heat will cause the outer layer of the star to puff up and get much larger. Our sun will expand, becoming a red giant, swallowing up Mercury, Venus, and Earth in the process.

Supervolcanos: Earthquakes have the Richter scale and volcanoes are measured by the “Volcanic Explosivity Index” (VEI). Vesuvius had a VEI of five and Kracatoa was a six, to name some familiar eruptions. During April 1815, Mount Tambora in Indonesia erupted, with a maximum VEI of seven on April 10. Approximately 10,000 people were killed as a direct result of the explosion. A further 50,000 in the vicinity of the explosion died of hunger and disease. However, the biggest impact came from worldwide changes in the weather. The year 1816 is known as “the year without a summer.” Many compounds (such as methane, carbon dioxide and water) increase the atmospheric greenhouse effect, making the earth warmer. However volcanoes release sulfur (in the form of sulfur dioxide and hydrogen sulfide) into the air, where it interacts with hydroxide and water to create sulfuric acid aerosols. These fine droplets reduce the Earth’s temperature by increasing the amount of sunlight reflected back into space. In 1816, so much sulfur was released into the atmosphere that the growing season was ruined—lower temperatures (including frost in June, July and August) destroyed crops and the crops that survived didn’t receive enough sunlight to thrive. Weather patterns were altered with some regions experiencing flooding and some drought due to changed monsoon patterns. It’s hard to estimate how many people died due to the world-wide knock on effects. Will this happen again? Yes but probably not soon. Some estimates suggest that VEI-seven explosions occur on the time scale of 200 to 400 years. Volcanoes to watch include Atitlan in Guatemala, Cerro Negro in Chile and Taal in the Philippines.

The Great Oxygenation Event: “The Great Oxygenation Event” took place 2.4 billion years ago during the Paleoproterozoic. Life on earth consisted of single cell organisms which were adapted to a life without oxygen. But then cyanobacteria started to take over. These were the first life forms capable of photosynthesis, (i.e., they could generate energy from sunlight) and photosynthesis took in carbon dioxide and created oxygen. Other life forms found the oxygen to be extremely toxic. It killed off 96% of the existing species. For the cyanobacteria photosynthesis was a powerful advantage and led to multi-celled organisms and eventually to the development of plants and animals. In addition to changing the makeup of the atmosphere, the Great Oxygenation Event changed the climate. The makeup of the atmosphere changed from methane (a strong greenhouse gas) to carbon dioxide (a weaker one) which probably triggered an ice age. It may be the most significant impact on the environment in the history of the planet.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.

Personal carbon emissions by the numbers

Impact of recycling

Are you interested in reducing your personal carbon footprint?

Have you ever wondered exactly how much recycling reduces global warming? In 2020, a meta-analysis paper was published by Diana Ivanova and her co-authors who reviewed studies covering a range of personal consumption options. The researchers started with a dataset of 6,990 studies from all over the world and used machine learning to winnow this down to the most relevant 53 studies.

The meta-analysis is great for two reasons—it gives a reliable average and it shows the uncertainty.

The data from the study is publicly available and I focused on two baskets, one with transportation choices and a second with common household actions like recycling.

Let’s look first at transportation options. The amount of carbon dioxide equivalent (CO2e) saved is measured in tonnes per person per year. Living car-free saves 2.1 tonnes of CO2e per person per year. (The average Canadian footprint is 15.2 tonnes of CO2e per person per year.) Driving a battery operated vehicle (BEV) saves two tonnes of CO2e per person per year.

In the global study, shifting to a smaller car generates a savings of 0.42, but I suspect that would be much greater in Canada where we drive the heaviest fleet in the world because we buy so many large pickup trucks.

Actions cause “backfire” or “rebound,” where a measure which is supposed to reduce carbon emissions actually increases them. You will notice this rebound effect in Figure 1 for “Shift to plug-in hybrid electric vehicles (PHEV)/hybrid electric vehicles (HEV)” and Figure 2 “Produce renewable energy.”

Some of the error bars are large. Should we be surprised at the size of error bars for BEVs or for installing renewable energy on your house? In both those cases, the amount of carbon you can save depends on how clean your electricity mix is.

Provinces with high-carbon electricity include Alberta, Saskatchewan and Nova Scotia. The Canadian Energy Regulator reports those provinces make about 85% of their electricity from fossil fuels. A really dirty electricity mix reduces the advantage of driving a BEV, but gives solar panels on your home a large positive impact. The authors commented in the paper the “electricity mix alone was found to explain almost 70% of the variability.”

If you are interested in solar panels or buying a BEV, you may be better off using an online calculator that factors in your local electricity mix.

People are often surprised that reducing or recycling stuff doesn’t reduce their carbon emissions by very much. Here, less packaging, fewer purchases, less plastic, recycle and less paper each have an impact of less than 0.2 tonnes of CO2e, approximately 1% of your total footprint. I do these things because they are sustainable (better for the planet) not because they reduce my overall carbon emission. I also expect better recycling technology will also increase the carbon savings.

As a numbers geek, I think this study is awesome. Having accurate numbers allows us to make meaningful choices. However, while people, especially in wealthy nations, need to reduce personal consumption, the spotlight shifts the focus from the political to the personal.

Are your personal consumption choices powerful enough to solve global warming? No. The largest amount of carbon emission in Canada comes from the oil and gas industry (28% in 2021, according to the Government of Canada), which is heavily subsidized by the government to the tune of $4.5 billion to $18 billion a year. Choosing to go car-free won’t make a dent in the state of the oil and gas industry. Other high-carbon subsidies support dairy, forestry and auto manufacturing.

The most powerful action I can take is to lobby the government (write, vote, protest) to make global warming and carbon reductions a priority. A close second is making the kind of lifestyle changes that significantly reduce carbon (for example, my family is saving for a BEV).

I reduce and recycle because it is the right thing to do, but I also acknowledge it doesn’t have a large effect on my family's carbon footprint.

If you are interested in seeing the full range of measures and their carbon impact, a summary of the results was published in Science Alert, These 5 Charts Show What You Can Do Right Now To Fight Climate Change, by Max Callaghan. Thanks to Callaghan for pointing me in the direction of the data.

You can read the full paper Quantifying the potential for climate change mitigation of consumption options at Environmental Research Letters.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.

Increased prices nullifying the advantage of rebates

Rebate inflation

It sounded like a great idea. Women need menstrual products once a month. These products are not discretionary, they are necessary, so why should people in the United Kingdom be forced to pay the Value Added Tax (VAT)?

Following this reasoning the “tampon tax” was repealed in 2021, lifting a 5% tax. However, the results were unexpected and disappointing—retailers responded by raising prices and consumers only experienced a savings of 1%.

The same thing is happening in the sustainability space. There’s a particularly distorted interaction between the auto industry quotas and government rebates. In the U.S., California (and eleven other states) set up a “zero emission” vehicle program, which requires automakers to sell an increasing percentage of electric vehicles (EVs). The U.S. also has state and federal incentives—$1,000 to $7,500 in state incentives and $7,500 in federal tax credits.

Automakers find it more expensive to build electric vehicles. Automakers, whose goal is to make a profit, comply with the requirements by selling the minimum number of EVs.

In the absence of incentives, how do automakers encourage more EV sales? They lower prices. Then, along comes state and federal incentives, which raise consumer demand for EVs. But, because it is still in the automakers best interest to produce fewer EVs, this allows companies to charge more.

Canada is in a similar situation. Nationwide, EV sales for light duty vehicle automakers are required to be 20% of the total by 2026, 60% of the total by 2030 and 100% by 2035. B.C. provincial incentives are $2,000 to $4,000 and federal incentives are $2,000 to $5,000. Here we have the same tradeoff. It is in the automakers best interest to only meet minimum sales targets, so the rebates—rather than increase the number of EV sales—raises the cost to the consumer.

We see a similar situation with heat pumps and rebates in B.C. Clean BC, BC Hydro and FortisBC are all offering rebates for heat pumps. The general rebates range from $1,000 to $9000 (in addition to federal rebates) and cover systems from “minisplits” to central forced air. There is anecdotal evidence that suggests when the rebates began, quotes for installing heat pumps went up.

It is harder to identify rebate inflation because most contractors don’t provide itemized quotes. Larry Whaley with Nanaimo Climate Action found, when he went to have a heat pump installed in his home, quotes were between $22,000 and $32,000.

He did his research on affordable and reliable heat pumps and found the cost of the pump was a small fraction of the total cost. He asked for contractors to break the quotes into two parts—the cost of the heat pump and the cost to install it.

Of more than 10 qualified installers, only two would provide a break down, and those quotes were significantly lower. He finally chose Supersave Heating, Plumbing and Cooling, which provided a quote of $11,400. Income-qualified rebates covered all but $1,400.

There are reasons why contractors, in general, don’t provide itemized quotes. Some find they result in an endless round of bargaining (“How much would it cost to leave this in and take that out?”). Some find clients try to swap quality parts with cheaper items that break, forcing the contractor to come back and replace them. However, one of the strongest forces preventing rebate inflation is transparency, which will require itemized quotes.

Geoff de Ruiter is also concerned about prices for heat pump systems—in this case the markup between the manufactures and the homeowners.

In October 2023, he put together a study: “Supply Chain Costing Spotlight for Central Forced Air Heat Pumps.”

Heat pumps are marked up at three points—when the manufacturer sells them to the wholesalers, when the wholesalers sell them to the installers and when the installers contract with the homeowner. The most commonly installed heat pump is 36,000 BTU/3.0 ton/11 kW and the average installation cost in B.C. is $19,000. However, if B.C. could make use of wholesale pricing, the cost to the consumer would come down as low as $13,100.

If B.C. could take advantage of wholesale pricing, we could afford to install many more heat pumps. That is actually being done for PEI, where heat pumps are purchased at wholesale prices in order to provide low-income households with free heat pumps.

We don’t have unlimited funding to throw at carbon reduction, so it is critical every dollar of taxpayer or utility-payer money is put to good use. Pricing transparency is needed for rebates to do their jobs.

Let’s spend smarter when it comes to carbon reduction.

More information on pricing heat pumps can be found at Nanaimo Climate Action here.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.

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About the Author

Kristy Dyer has worked in the sustainability field for more than 10 years, including work with solar energy in New Mexico and cleantech in Silicon Valley. After she moved to the Okanagan, she ran a small business, Teaspoon Energy, doing energy audits of large houses. Most recently, she worked for a B.C. business doing carbon footprints for tourism organizations.

She has written about sustainability since 2012. You can find her columns archived at TeaspoonEnergy.blogspot.com.

Dyer has a background in physics and astronomy, and has occasionally been caught trying to impersonate an engineer.

A long-time member of First Things First, Penticton’s local climate change group, whose goals are to educate and lobby for solutions to the climate crisis, Dyer is honoured to live, work and play in the unceded, ancestral and traditional territory of the Syilx Okanagan Nation.

You can contact her at [email protected]

The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet does not warrant the contents.

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