Earth Wise

A look at our changing environment.

You are here: Home / Archives for clay

clay

Self-healing concrete

By Leave a Comment

Concrete is the most widely used building material on Earth.  It has a dangerous and costly flaw:  it cracks easily.  Cracks in concrete can lead to inconvenient damage or to catastrophic structural failures such as collapses of buildings, bridges, or highways.

Concrete is made by mixing crushed stone and sand with powdered clay and limestone and adding water.  The mixture hardens and once set becomes extremely strong.  However, natural forces like freeze-thaw cycles, drying shrinkage, and heavy loads can cause cracks.  Even very tiny cracks can allow liquids and gases to seep into embedded steel reinforcements causing corrosion and weakness. 

For over 30 years, researchers have investigated microbe-mediated self-healing concrete.  It involves introducing microbial healing agents into cracks and injecting nutrients for the healing agents to produce repair materials.  It is not a very practical solution.

Researchers at Texas A&M University have developed a technique inspired by the behavior of lichen systems. Their system, like lichen, uses a combination of cyanobacteria which turns air and sunlight into food, and filamentous fungi, which produces minerals that seal the cracks. 

In lab tests, the paired microbes were able to grow and produce crack-filling minerals even in challenging environments such as concrete.  If it is possible to produce concrete that can heal itself, it would significantly reduce maintenance costs, extend its longevity, and even protect lives through increased safety.

**********

Web Links

Cracking the Code: Deciphering How Concrete Can Heal Itself

Photo, posted May 21, 2009, courtesy of DesignMag via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Restoring oil well sites with moss

By Leave a Comment

Researchers at the University of Waterloo in Canada have developed a method for restoring peatlands at tens of thousands of oil and gas exploration sites in Western Canada. 

A well pad is a prepared area used for drilling oil or gas wells, encompassing the site where drilling equipment, wellheads, and related facilities are located.  Preparing well pads involves burying native peatland vegetation under clay or sand, thereby eliminating the ability of the peatland to sequester carbon as well reducing available habitat for wildlife.

Restoring well sites has typically involved planting trees or grasses to eventually establish forests or grasslands.  The Waterloo method returns a well pad to its condition before drilling occurred and is part of ongoing efforts to restore peatlands, which are known to be even more effective for sequestering carbon than tropical forests.

The Waterloo technique involves lowering the surface of a decommissioned well site and transplanting native mosses onto it to effectively recreate a peatland.    They tested the technique to scale at an entire well pad and found that it results in sufficient water for the growth of peatland moss across large portions of the study site.

The results suggest that re-establishment of peatland vegetation on lowered well pads is possible.  The researchers plan to continue monitoring the ecosystem in the study’s well pads to confirm that the transplanted mosses will be self-sustaining over the coming decades.  They will focus on increasing the amount of water that flows from surrounding natural peatlands into the converted well pads to further optimize soil moisture. 

This work could represent an important milestone in ecological restoration.

**********

Web Links

Restoring oil wells back to nature with moss

Photo, posted November 6, 2014, courtesy of Chris Boyer / Kestrel Aerial Services via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A Huge American Lithium Discovery | Earth Wise

By Leave a Comment

Human history has often been described in terms of a succession of metal ages:  the copper age, the bronze age, and the iron age.  In many ways, we have now entered the lithium age.  The light metal goes into the batteries that power smartphones, electric vehicles, and massive storage banks for the power grid.  Lithium has become a critical strategic resource.

As it stands now, the U.S. gets most of its lithium from imports from Australia and South America.  Major lithium sources are not commonplace; in 2022 there were only 45 lithium mines in the world.  Many of the known deposits are not in North America but in Chile, Bolivia, Argentina, China, and Australia.  The current largest known lithium deposits lie beneath the salt flats of Bolivia.

Lithium Americas Corporation, a company dedicated to advancing lithium projects to the stage of production, funded research over the past decade that has identified vast deposits of lithium-rich clay in a dormant volcanic crater along the Nevada-Oregon border.  The McDermitt Caldera is estimated to hold between 20 and 40 million tons of lithium, which would make it the largest deposit in the world.

There are many questions still to answer.  It is not clear how easy it will be to extract lithium from the clay, in particular how expensive or carbon-intensive it will be.  There are also political complexities since the area where the lithium deposit was found is considered to be unceded ancestral land for both the Paiute and Shoshone tribes.

Apart from a dearth of domestic sources of lithium, the US also lags well behind China in lithium processing capabilities.  The country has catching up to do in the new lithium age.

**********

Web Links

America Just Hit the Lithium Jackpot

Photo, posted April 19, 2020, courtesy of Ken Lund via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

New York Is Sinking | Earth Wise

By Leave a Comment

The rising seas represent a threat to coastal cities across the globe.  Increasing that threat is the fact that most global cities are slowly sinking as the earth beneath them settles and groundwater is removed.   Another factor that has seldom been considered is that in major metropolises, the weight of large, concrete-and-steel skyscrapers may be hastening the sinking.

A new study by the U.S. Geological Survey published in the journal Earth’s Future estimated the weight of every building in New York City – 1.085 million of them – which they determined to add up to 1.68 trillion pounds – and estimated the downward force of those structures across the city.

The study found that buildings have a greater effect in areas that are rich in clay compared with those areas where sand or bedrock predominate.  The softer the soil, the more compression there is from buildings.  It wasn’t a mistake to build large buildings in New York, but it is important to understand that doing so pushes down the ground more and more.

The study determined that New York is sinking by around 1 to 2 millimeters each year, although some areas are sinking much faster.  The researchers say that cities must plan for future sinking, which will exacerbate the impact of rising seas. Sea levels are rising 1 to 2 millimeter each year, so the subsidence caused by the weight of buildings is equivalent to moving a year ahead in time with regard to rising ocean levels.  This is not a cause for immediate panic, but it is important to understand that this ongoing process only increases the risk of inundation from flooding.

**********

Web Links

New York City Sinking Under Weight of Skyscrapers

Photo, posted January 29, 2016, courtesy of Always Shooting via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Concrete And Carbon | Earth Wise

By Leave a Comment

After water, concrete is the world’s second most consumed material.  It is the cornerstone of modern infrastructure.  Its production accounts for 8% of global carbon dioxide emissions.  The carbon dioxide is a result of chemical reactions in its manufacture and from the energy required to fuel the reactions.

About half of the emissions associated with concrete come from burning fossil fuels to heat up the mixture of limestone and clay that ultimately becomes ordinary Portland cement.  These emissions could eventually be eliminated by using renewable-generated electricity to provide the necessary heat.  However, the other half of the emissions is inherent in the chemical process.

When the minerals are heated to temperatures above 2500 degrees Fahrenheit, a chemical reaction occurs producing a substance called clinker (which is mostly calcium silicates) and carbon dioxide.  The carbon dioxide escapes into the air.

Portland cement is then mixed with water, sand, and gravel to produce concrete.  The concrete is somewhat alkaline and naturally absorbs carbon dioxide albeit slowly.  Over time, these reactions weaken the concrete and corrode reinforcing rebar.

Researchers at MIT have discovered that the simple addition of sodium bicarbonate (aka baking soda) to the concrete mixture accelerates the early-stage mineralization of carbon dioxide, enough to make a real dent in concrete’s carbon footprint.  In addition, the resulting concrete sets much more quickly.  It forms a new composite phase that doubles the mechanical performance of early-stage concrete.

The goal is to provide much greener, and possibly even carbon-negative construction materials, turning concrete from being a problem to part of a solution.

**********

Web Links

New additives could turn concrete into an effective carbon sink

Photo, posted April 4, 2009, courtesy of PSNH via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Caterpillars And Light Pollution | Earth Wise

By Leave a Comment

Most of us are familiar with air pollution, water pollution, soil pollution, and even noise pollution.  But it turns out that light can be a pollutant as well, and it’s a consequence of industrial civilization.  In fact, nighttime light pollution now covers approximately 23% of the globe and over 80% of inhabited regions. 

Light pollution affects more than just our view of the stars.  For example, light pollution can alter our circadian rhythm, disrupting our sleep cycle.  In nature, light pollution can kill baby turtles by causing them to head inland instead of into the ocean, can cause birds to migrate during the wrong season, and can deter nighttime pollinators like bats.  And those are just a few of the examples.    

According to new research from scientists at Cornell University, moderate levels of artificial light at night – like a porch light – attract caterpillar predators and reduce the chance that caterpillars grow up to become moths. 

In the study, which was recently published in the journal Proceedings of the Royal Society B: Biological Sciences, the researchers placed 552 lifelike caterpillar replicas made of soft clay in a forest to measure predation rates compared to a control group.  They found that predation rates on clay caterpillars and the abundance of arthropod predators were significantly higher on the artificial light at night treatment plots.  In fact, of the 552 clay caterpillars deployed and glued to leaves to look authentic, 521 models were recovered and 249 of them- or 47.8% – showed predatory marks from arthropods during the summer-long nighttime study.

In addition to light pollution, caterpillars also face major threats from habitat loss, pollution, invasive species, and climate change.

**********

Web Links

Artificial light at night aids caterpillar predators

Photo, posted July 23, 2020, courtesy of Judy Gallagher via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The Bengal Water Machine | Earth Wise

By Leave a Comment

Over the past three decades, the owners of 16 million small farms in the Bengal Basin of Bangladesh have been pumping shallow groundwater during dry seasons to irrigate rice paddies.  By lowering groundwater levels in this way during the dry season, the ability of leakage from rivers, lakes, and ponds to replenish the groundwater was greatly enhanced.   Capturing surface water not only improved the recovery of groundwater levels but only helped to reduce flooding during monsoons.

The net result of this enormous collective groundwater pumping by millions of farmers has been the creation of vast natural reservoirs underground that are comparable to what is contained by many of the world’s largest dams.   This system of sustaining irrigation has transformed what was previously a famine-prone country into a food-secure nation.

The details of this remarkable transformation have been laid out in a study by University College London recently published in the journal Science.  According to the study, over the course of 30 years, more than 75 cubic kilometers of fresh water was captured by this process, which is equivalent to the combined reservoirs of China’s Three Gorges Dam and the Hoover Dam in the U.S.

The authors of the study described the water cycling process as “The Bengal Water Machine” and argue that it can be a sustainable alternative to conventional approaches to seasonal river flow storage for irrigation, which typically involve dams and reservoirs.  Such approaches are difficult to implement in densely populated alluvial plains where sand, silt, and clay are laid down by annual floodwaters. 

**********

Web Links

Millions of farmers “replumb” world’s largest delta

Photo, posted February 2, 2010, courtesy of Melanie Ko via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Reducing Emissions From Cement Manufacturing | Earth Wise

By Leave a Comment

Cement is the basic ingredient of concrete, which is the most widely used construction material in the world.  About 8% of global carbon dioxide emissions are associated with cement production.

More than half of these emissions come from making clinker, which is a major component of cement produced by heating ground limestone and clay to a temperature of over 2500 degrees Fahrenheit.  Some of the emissions come from burning fossil fuels to heat the materials, but much of them come from the chemical reaction that creates the clinker.

The Portland Cement Association, which represents 92% of US cement manufacturing capacity, has recently released its “Roadmap to Carbon Neutrality”, which lays out a plan to reach carbon net zero across the cement and concrete value chain by 2050.

The plan includes the greater use of alternative fuels to reduce emissions from energy use.  It also involves the adoption of newer versions of cement such as Portland limestone cement, which reduces CO2 levels.  The industry has already reduced emissions by some shifting to Portland limestone cement, but it still only represents a small fraction of cement production.

The most significant strategy would be the adoption of carbon capture, utilization, and storage (or CCUS) technologies.  The idea is to capture the CO2 generated in the production of clinker and inject it into the fresh concrete.  It would actually be permanently sequestered in the concrete and would not be released even if a structure is demolished in the future.

It will take a combination of technologies and initiatives for the cement industry to reduce its emissions.  Fortunately, the industry appears to be committed to that goal.

**********

Web Links

US cement manufacturers release their road map to carbon neutrality by 2050

Photo, posted March 26, 2014, courtesy of Michael Coghlan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Decarbonizing The Most Polluting Heavy Industries | Earth Wise

By Leave a Comment

The production of steel, cement, and ammonia accounts for about 20% of the carbon dioxide humans pour into the atmosphere.  Modern cities are largely constructed from concrete and steel and most of our food is grown using fertilizer made from ammonia. 

The most widely discussed solutions to decarbonizing these industries are green hydrogen and carbon capture and storage or CCS.

Steel manufacture is responsible for 11% of society’s emissions.  Most production starts by burning coal in a blast furnace. Using CCS could reduce emissions from burning the coal.  But the blast furnace could be eliminated entirely by the use of electrolysis to produce the pure iron needed to make steel.  This would be extremely energy-intensive but using a low-carbon source like green hydrogen could greatly reduce the emissions from making steel.

Ammonia is made by producing hydrogen from natural gas and then combining it with atmospheric nitrogen.  Both the hydrogen production and ammonia synthesis are energy intensive.  Using green hydrogen would eliminate emissions from the hydrogen production itself and new research on catalysts aims at lower-temperature, less-energy intensive ammonia synthesis.

Decarbonizing cement manufacturing is perhaps the toughest challenge.  Cement is made in a high-temperature kiln, typically heated by burning fossil fuels.  The process converts calcium carbonate and clay into a hard solid called clinker.  The main byproduct of that is even more carbon dioxide.  Burning green hydrogen and capturing carbon emission are about the best hope for reducing cement manufacturing emissions.

**********

Web Links

Can the World’s Most Polluting Heavy Industries Decarbonize?

Photo, posted June 30, 2009, courtesy of Portland Bolt via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Conspicuous Consumption

By 2 Comments

Human civilization consumes vast amounts of material.   The Circle Economy think tank actually puts some numbers on it.  According to their latest report, the amount of material consumed by humanity has passed 100 billion tons every year.  So, on average, every person on Earth uses more than 13 tons of materials per year.

That number has quadrupled since 1970, which is far faster than the population, which has only doubled during that time.  In the past two years alone, consumption has jumped by more than 8%.  While this has been going on, the proportion being recycled has been falling.

Of the 100 billion tons of materials, half of the total is sand, clay, gravel, and cement used for building, along with other minerals used for fertilizer.  Coal, oil and gas make up 15% and metal ores 10%. The final quarter are plants and trees used for food and fuel.  About 40% of all materials are turned into housing.  A third of the annual materials consumed remain in use, such as in buildings or vehicles.  But 15% is emitted into the atmosphere as greenhouse gases and a third is treated as waste.

The global emergencies of climate change and disappearing wildlife have been driven by the unsustainable extraction of fossil fuels, metals, building materials, and trees.  The authors of the report warn that if we continue to treat the world’s resources as limitless, we are heading for a global disaster.

The Circle Economy think tank promotes the idea of a circular economy in which renewable energy supports systems where waste and pollution are reduced to zero.  Some nations are taking steps towards circular economies, while others are not.  This is a problem we can’t allow to be unaddressed.

**********

Web Links

World Consumes 100 Billion Tons of Materials Every Year, Report Finds

Photo, posted March 13, 2015, courtesy of Joyce Cory via Flickr.

XXXXXXXXXXX

Emissions-Free Cement

By Leave a Comment

The production of cement – which is the world’s leading construction material – is a major source of greenhouse gas emissions, accounting for about 8% of global man-made emissions. 

Cement production produces carbon dioxide in two ways:  from a key chemical process and from burning fuel to produce the cement.  The process of making “clinker” – the key constituent of cement – emits the largest amount of CO2.  Raw materials, mainly limestone and clay – are fed into huge kilns and heated to over 2,500 degrees Fahrenheit, requiring lots of fossil fuel.  This calcination process splits the material into calcium oxide and CO2.  The so-called clinker is then mixed with gypsum and limestone to produce cement.

A team of researchers at MIT has come up with a new way of manufacturing cement that greatly reduces the carbon emissions.  The new process makes use of an electrolyzer, where a battery is hooked up to two electrodes in water producing oxygen at one electrode and hydrogen at the other.  The oxygen-evolving electrode produces acid and the hydrogen-evolving electrode produces a base.  In the new process, pulverized limestone is dissolved in the acid at one electrode and calcium hydroxide precipitates out as a solid at the other.

High-purity carbon dioxide is released at the acid electrode, but it can be easily captured for further use such as the production of liquid fuels or even in carbonated beverages and dry ice.  The new approach could eliminate the use of fossil fuels in the heating process, substituting electricity generated from renewable sources. 

The process looks to be scalable and represents a possible approach to greatly reducing one of the perhaps lesser known but nevertheless very significant sources of greenhouse gas emissions.

**********

Web Links

New approach suggests path to emissions-free cement

Photo, posted March 26, 2014, courtesy of Michael Coghlan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

WAMC Northeast Public Radio

WAMC/Northeast Public Radio is a regional public radio network serving parts of seven northeastern states (more...)