More than 2 billion people – one out of every four people in the world – lack fresh water. For about 733 million of them, the situation is critical. There is no one solution to this grim problem; a multi-pronged approach will be needed, and technology will play a key role in, among other things, cleaning up polluted water. Salam Titinchi outlines the role of powerful nanotechnology: carbon nanomaterials.
Many futuristic novels and films have explored what the world might look like without water. But water scarcity isn’t a problem for the far-off future: it’s already here.
In its 2021 report UN Water outlined the scale of the crisis: 2.3 billion people live in water-stressed countries and 733 million of those people are in “high and critically water-stressed countries”.
In 2018 Cape Town, where I live and conduct my research, residents found themselves staring down “day zero”, when household water supplies would run dry. Good rains spared the South African city, but now other parts of the country face similarly dire predictions of empty taps.
This scenario is threatening to play out across Africa. In the Horn of Africa region, for example, large areas of Ethiopia, Somalia and Kenya have seen four consecutive rainy seasons pass without decent rains. The rise of “megacities” in Africa – with millions moving into city areas – puts further pressures on already limited infrastructure.
And the crisis extends far beyond the African continent. There is no one solution for this grim reality. A multi-pronged approach will be necessary, as Cape Town’s experience illustrated.
Technology will be a key part of solving the global water scarcity crisis. Technological solutions can run the gamut from the most basic, like water leak detectors for households, to highly sophisticated, like ways to pull moisture out of the air to produce clean drinking water, or convert the planet’s abundant salt water into fresh water.
In a recent paper colleagues and I outlined another potentially powerful technology: carbon nanomaterials, which have been shown to remove organic, inorganic and biological pollutants from water.
Contamination threatens water sources
Contamination is one of the factors putting strain on water sources. All water supplies contain some microbes and pathogens. But industrial waste is a huge problem: vehicles release heavy metal pollutants, for instance, and acid mine drainage seeps into water sources. This results in contaminated ground and surface water that cannot be safely used for most human activities, much less for drinking or washing food.
Some current technologies make the treatment of water too expensive. Others are simply not up to the job and are unable to remove microorganisms. In removing organic pollutants like pharmaceutical waste, organic dyes, plastics and detergents from wastewater, for instance, some conventional techniques such as membrane filtration have been found wanting.
That’s where carbon nanomaterials come in. With others, I am exploring their use and finding that they are more efficient and economically viable than conventional materials.
Nanomaterials
Nanomaterials are broadly defined as materials that contain particles of between 1 and 100 nanometres (nm) in size. One nanometre equals one-billionth of a metre. Different nanomaterials are composed of different atoms – some, like those I research, are made up of carbon atoms.
Carbon is, by mass, the second most abundant element in the human body after oxygen. It is also a common element of all known life. Carbon nanotechnologies are environmentally friendly because they hold less risk of secondary pollution than some adsorbents (solid substances used to remove contaminants from liquid or gas).
Engineered into nanomaterial form, carbon nanomaterials are being hailed by many scientists around the world for their superior physical and chemical properties. They are increasingly prized for their potential to remove heavy metals from water thanks to their large surface area and adsorption capabilities, their nano-scaled size and their chemical properties. Carbon nanomaterials have all been shown to be effective in the treatment of wastewater.
Tackling water scarcity
I work with carbon-coated magnetic nanomaterials. This blended composite plays a crucial role in decontaminating water. At the same time, it removes materials such as heavy metals. That makes it ideal for water treatment, as do its easy, fast recovery and recyclability, thanks to what’s known as magnetic filtration. In this process, the magnetic nanomaterials added to the contaminated water are recovered after treatment by an external strong magnet. The recovered materials can be regenerated and be reused again.
Carbon-based nanomaterials still have shortcomings. Nanomaterials tend to clump together into large particles, reducing their capacity to adsorb (attract and hold) pollutants. And nanoparticles are not always fully recovered from treated water, leading to secondary contamination. We’re still not sure how to separate exhausted – fully utilised – nanomaterials from treated water.
The work continues in our lab and others all over the world. Scientists dislike timelines, since breakthroughs rarely happen within set deadlines. But our hope is that more and more advances will be made with carbon-based nanonmaterials in the years to come, giving the world an important tool to tackle water scarcity.
The theme of this year’s Earth Day is “Planet vs. Plastics” – a theme chosen to raise awareness of the damage done by plastic to humans, animals and the planet and to promote policies aiming to reduce global plastic production by 60 percent by 2040.
As our chart shows, global plastics use has increased rapidly over the past few decades, growing 250 percent since 1990 to reach 460 million tonnes in 2019, according to the OECD’s Global Plastics Outlook, which projects another 67-percent increase in global plastics use by 2040 and for the world’s annual plastic use to exceed one billion tonnes by 2052. As our chart shows, packaging is the largest driver of global plastics use, which is why a rapid phasing out of all single use plastics by 2030 is one of the policy measures proposed under EARTHDAY.ORG’s 60X40 framework.
Other major applications of plastics include building and construction, transportation as well as textiles, with the fast fashion industry particularly guilty of adding to the world’s plastic footprint. “The fast fashion industry annually produces over 100 billion garments,” the Earth Day organizers write. “Overproduction and overconsumption have transformed the industry, leading to the disposability of fashion. People now buy 60 percent more clothing than 15 years ago, but each item is kept for only half as long.” Most importantly, the organization points out that 85 percent of disposed garments end up in landfills or incinerators, while just 1 percent are being recycled.
Felix Richter is a Data Journalist
This article was first published in the Statista.com.
Algeria’s Tassili N’Ajjer plateau is Africa’s largest national park. Among its vast sandstone formations is perhaps the world’s largest art museum. Over 15,000 etchings and paintings are exhibited there, some as much as 11,000 years old according to scientific dating techniques, representing a unique ethnological and climatological record of the region.
Curiously, however, these images do not depict the arid, barren landscape that is present in the Tassili N’Ajjer today. Instead, they portray a vibrant savannah inhabited by elephants, giraffes, rhinos and hippos. This rock art is an important record of the past environmental conditions that prevailed in the Sahara, the world’s largest hot desert.
These images depict a period approximately 6,000-11,000 years ago called the Green Sahara or North African Humid Period. There is widespread climatological evidence that during this period the Sahara supported wooded savannah ecosystems and numerous rivers and lakes in what are now Libya, Niger, Chad and Mali.
This greening of the Sahara didn’t happen once. Using marine and lake sediments, scientists have identified over 230 of these greenings occurring about every 21,000 years over the past eight million years. These greening events provided vegetated corridors which influenced species’ distribution and evolution, including the out-of-Africa migrations of ancient humans.
These dramatic greenings would have required a large-scale reorganisation of the atmospheric system to bring rains to this hyper arid region. But most climate models haven’t been able to simulate how dramatic these events were.
As a team of climate modellers and anthropologists, we have overcome this obstacle. We developed a climate model that more accurately simulates atmospheric circulation over the Sahara and the impacts of vegetation on rainfall.
We identified why north Africa greened approximately every 21,000 years over the past eight million years. It was caused by changes in the Earth’s orbital precession – the slight wobbling of the planet while rotating. This moves the Northern Hemisphere closer to the sun during the summer months.
This caused warmer summers in the Northern Hemisphere, and warmer air is able to hold more moisture. This intensified the strength of the West African Monsoon system and shifted the African rainbelt northwards. This increased Saharan rainfall, resulting in the spread of savannah and wooded grassland across the desert from the tropics to the Mediterranean, providing a vast habitat for plants and animals.
Our results demonstrate the sensitivity of the Sahara Desert to changes in past climate. They explain how this sensitivity affects rainfall across north Africa. This is important for understanding the implications of present-day climate change (driven by human activities). Warmer temperatures in the future may also enhance monsoon strength, with both local and global impacts.
Earth’s changing orbit
The fact that the wetter periods in north Africa have recurred every 21,000 years or so is a big clue about what causes them: variations in Earth’s orbit. Due to gravitational influences from the moon and other planets in our solar system, the orbit of the Earth around the sun is not constant. It has cyclic variations on multi-thousand year timescales. These orbital cycles are termed Milankovitch cycles; they influence the amount of energy the Earth receives from the sun.
On 100,000-year cycles, the shape of Earth’s orbit (or eccentricity) shifts between circular and oval, and on 41,000 year cycles the tilt of Earth’s axis varies (termed obliquity). Eccentricity and obliquity cycles are responsible for driving the ice ages of the past 2.4 million years.
The third Milankovitch cycle is precession. This concerns Earth’s wobble on its axis, which varies on a 21,000 year timescale. The similarity between the precession cycle and the timing of the humid periods indicates that precession is their dominant driver. Precession influences seasonal contrasts, increasing them in one hemisphere and reducing them in another. During warmer Northern Hemisphere summers, a consequent increase in north African summer rainfall would have initiated a humid phase, resulting in the spread of vegetation across the region.
Eccentricity and the ice sheets
In our study we also identified that the humid periods did not occur during the ice ages, when large glacial ice sheets covered much of the polar regions. This is because these vast ice sheets cooled the atmosphere. The cooling countered the influence of precession and suppressed the expansion of the African monsoon system.
The ice ages are driven by the eccentricity cycle, which determines how circular Earth’s orbit is around the sun. So our findings show that eccentricity indirectly influences the magnitude of the humid periods via its influence on the ice sheets. This highlights, for the first time, a major connection between these distant high latitude and tropical regions.
The Sahara acts as a gate. It controls the dispersal of species between north and sub-Saharan Africa, and in and out of the continent. The gate was open when the Sahara was green and closed when deserts prevailed. Our results reveal the sensitivity of this gate to Earth’s orbit around the sun. They also show that high latitude ice sheets may have restricted the dispersal of species during the glacial periods of the last 800,000 years.
Our ability to model the African humid periods helps us understand the alternation of humid and arid phases. This had major consequences for the dispersal and evolution of species, including humans, within and out of Africa. Furthermore, it provides a tool for understanding future greening in response to climate change and its environmental impact.
Refined models may, in the future, be able to identify how climate warming will influence rainfall and vegetation in the Sahara region, and the wider implications for society.
Edward Armstrong is a postdoctoral research fellow, University of Helsinki
A new draft text on global stocktake has been published at the UN climate summit, COP28 UAE, on Wednesday morning. While the draft text does not contain the words “phase out”, it includes reference to transitioning away from all fossil fuels to enable the world to reach net zero by 2050.
The text published by the UN’s climate body calls on parties to accelerate and substantially reduce non-carbon dioxide emissions worldwide with a focus on reducing methane emissions by 2030. “We all want to get the most ambitious outcome possible,” Majid Al Suwaidi, COP28 Director-General, said on Tuesday.
The text, published early Wednesday, does not specifically refer to oil, but mentions the need to ‘phase-down’ coal. It says that it recognises the need for ‘deep, rapid and sustained reductions in greenhouse gas emissions in line with 1.5C pathways and calls on Parties to contribute to global efforts.
Among those efforts it recognises the need to triple renewable energy capacity by 2030 and doubling the annual rate of energy efficiency improvements by the same date. It also recognises the need to accelerate the phase-down of coal and accelerate towards net zero energy systems, utilising zero or low carbon fuels by mid century.
While the document does not mention oil or combustion engines, it does recognises the need for accelerating the reduction of emissions from road transport on a range of pathways, including through development of infrastructure and rapid deployment of zero and low-emission vehicles. It also recognises the need to phase out inefficient fossil fuel subsidies that do not address energy poverty or just transitions, as soon as possible.
Finance specifics
On the subject of finance, the document said developed countries should continue to take the lead in mobilising climate finance from a wide variety of sources, instruments and channels, noting the significant role of public funds, through a variety of actions, including supporting country-driven strategies, and taking into account the needs and priorities of developing countries.
Such mobilisation of climate finance should represent a progression beyond previous efforts, the text said. It may provide small comfort to campaigners from developing countries who implored Parties to begin the phase out of fossil fuels and provide vastly improved access to funding for renewables.
The document highlights the persistent gap and challenges in technology development and transfer and the uneven pace of adoption of climate technologies around the world.
It further urges Parties to address these barriers and strengthen cooperative action, including with non-Party stakeholders, particularly with the private sector, to rapidly scale up the deployment of existing technologies, the fostering of innovation and the development and transfer of new technologies.
It also emphasizes the ongoing challenges faced by many developing country Parties in accessing climate finance and encourages further efforts, including by the operating entities of the Financial Mechanism, to simplify access to such finance, in particular for those developing country Parties that have significant capacity constraints, such as the least developed countries and small island developing States.
