alkaline

Storing Carbon Dioxide In The Ocean | Earth Wise

May 11, 2023 By EarthWise 2 Comments

Reducing the amount of carbon dioxide entering the atmosphere means either shutting down emission sources (primarily curbing the use of fossil fuels) or capturing the CO2 as it is emitted. Capturing carbon dioxide from smokestacks and other point sources with high concentrations is relatively efficient and can make economic sense. Removing it from the air, which even at today’s dangerously high levels contains only 400 parts per million, is difficult and energy intensive. And even when it is removed, it then must be stored somewhere.

Researchers at Lehigh University have developed a novel way to capture carbon dioxide from the air and store it in what is effectively the infinite sink of the ocean. The approach uses an innovative copper-containing filter that essentially converts CO2 into sodium bicarbonate (better known as baking soda.) The bicarbonate can be released harmlessly into the ocean.

This technique has produced a 300 percent increase in the amount of carbon dioxide captured compared with existing direct air capture methods. It does not require any specific level of carbon dioxide to work. The filter becomes saturated with the gas molecules as air is blown through it. Once this occurs, seawater is passed through the filter and the CO2 is converted to dissolved bicarbonate. Dumping it into the ocean has no adverse effect on the ocean. It doesn’t change the salinity at all, and the stuff is slightly alkaline, which will help reduce ocean acidification.

Reusing the filter requires cleaning it with a sodium hydroxide solution, which can be created from seawater using electricity generated by waves, wind, or sun.

The filter, called DeCarbonHIX, is attracting interest from companies based in countries around the world.

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Path to net-zero carbon capture and storage may lead to ocean

Photo, posted March 10, 2007, courtesy of Gail via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Concrete And Carbon | Earth Wise

May 8, 2023 By EarthWise 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.

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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

Offsetting Reef Acidification | Earth Wise

August 13, 2021 By EarthWise Leave a Comment

The Great Barrier Reef is the world’s largest coral reef system. It is composed of nearly 3,000 individual reefs and 900 islands covering an area of more than 130,000 square miles. In recent times, it has been under unprecedented stress from ocean warming, tropical cyclones, sediment and nutrient runoff, marine pests, and ocean acidification.

Among these stressors, ocean acidification is one of the most significant threats to the long-term viability of the reef because acidification affects the ability of corals to rebuild and repair their structures and recover from bleaching events.

New research from CSIRO, Australia’s national science agency, studied the impact of artificial ocean alkalinization on the acidity of the waters in the Great Barrier Reef. The idea is to inject a source of alkalinity into the ocean, an accelerated version of a natural process that occurs from the chemical weathering of minerals under the sea.

The results of the study, published in the journal Environmental Research Letters, are that injecting an alkalinizing agent into the ocean along the length of the Reef would make it possible to offset ten years’ worth of ocean acidification based on the present rate of human-generated carbon emissions. Such an effort could use an abundant mineral resource like olivine, which is already mined near the Great Barrier Reef. Releasing 30,000 tons a day of the alkalinizing agent from an existing shipping line from a bulk carrier would reach almost the whole of the Great Barrier Reef.

In response to the declining health of coral reef ecosystems, many different intervention concepts and technologies are under consideration. The goal of these would be to minimize environmental pressures and enhance the resilience of the ecosystems.

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Projected acidification of the Great Barrier Reef could be offset by ten years

Photo, posted August 4, 2019, courtesy of Larry Koester via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Salt Cocktails Compromise Freshwater

August 1, 2018 By EarthWise Leave a Comment

Human activities are exposing US rivers and streams to a cocktail of salts, with consequences for infrastructure and drinking water supplies. Road salt, fertilizers, and mining waste – as well as natural weathering of concrete, rocks, and soils – all contribute to increased salt in waterways. When these different salt compounds combine, their harmful effects can amplify.