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The Bengal Water Machine | Earth Wise

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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. 

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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

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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.

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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

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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.

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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

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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.

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

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

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Emissions-Free Cement

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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.

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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.

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