What Is Black Carbon? - Sources, Impacts & Solutions

With an ever greater focus on climate change and global warming from politicians, journalists and the general public alike, scientists across the globe have turned a sharper spotlight on the major contributing factors to these phenomenon. In recent years, black carbon has emerged as a serious concern, with many claiming it to be the second biggest cause of global warming behind carbon dioxide.

But what exactly is this substance? Where does it come from and how does it find its way into our atmosphere? What are its negative impacts upon the natural world and upon human health? And how can we work to limit its concentrations and mitigate these undesirable outcomes? For those with an interest in the subject but a lack of familiarity with it, this introductory article will answer all of those questions and more.

What is black carbon?

Black carbon is a principal component of fine particulate matter (PM), which has led to the two terms being used interchangeably at times. However, black carbon is merely pure carbon present in several linked forms and just one component of PM, so technically they are not one and the same.

Black carbon is also one of the chief varieties of particle present in soot, which again leads to many commentators using the terms to mean the same thing. Although all soot contains black carbon, the specific dimensions and properties of the latter are not as easily defined as the former, making such an equivalence incorrect.

Where does black carbon come from?

Black carbon is produced through both natural and anthropogenic sources, though it is the proliferation of industrial activity over the last two centuries that has prompted a sharp increase in black carbon concentrations in the Earth’s atmosphere today. It is created through the incomplete combustion of fossil fuels such as oil, coal and gas, biofuels such as wood, peat and crops and other fuel sources.

Some of the biggest sources of black carbon emissions include diesel engines in vehicles, cooking stoves, wood-burning furnaces and forest fires. The chief culprit for black carbon emissions can vary from region to region around the globe. For example, the transportation industry is by far the largest emitter of black carbon in the developed world (including North America and Europe), but residential combustion of coal and biofuel accounts for a much bigger share of emissions in the developing world (including Asia and Africa).

What’s the difference between black carbon and carbon black?

Because of the similarity between their names, black carbon and carbon black are also often used by journalists, environmentalists or other commentators to refer to the same thing. But while they do share some similarities in their physical profiles and the processes via which they are generated, they are significantly different.

On the one hand, carbon black is a commercially produced commodity that is used for a variety of different applications, including as a colorant in inks, pigments and foodstuffs or as a filler in tyres and other rubber items. Black carbon, on the other hand, is an undesirable by-product of the combustion process that has no beneficial properties or applications.

Which countries emit the most black carbon?

Historically, developed countries such as the USA and those in Europe were the biggest emitters of black carbon. However, pollution control began to rise up the political agenda in the middle of the last century and precautions and protocols have since been implemented to limit its spread. America, for example, is responsible for over a fifth of the world’s CO2 emissions, but just 6.1% of its black carbon emissions.

Instead, the majority of black carbon in our atmosphere originates in developing parts of the world, especially in Asia, Africa and Latin America. Indeed, China and India together account for up to a third of the planet’s black carbon emissions, while other hotspots include equatorial Africa, southeast Asia and Indonesia and much of Brazil and Peru.

What impact does black carbon have on the environment?

While carbon dioxide may have hogged most of the headlines when it comes to greenhouse gases and environmental impacts in the mainstream media, scientists have long since looked past this headline contaminant to other contributing factors. Chief among them is black carbon, which negatively impacts the environment in two main ways.

Firstly, black carbon particles become suspended in the air and due to their dark colouring, they absorb the heat emitted by the sun’s rays. This contributes to a warming of the ambient temperature. Secondly, they can settle on the snow and ice in Arctic regions and reduce the ability of those surfaces to reflect the sun’s energy away from them. This increases the rate at which they become heated and melt, contributing to the loss of the polar icecaps, the raising of sea levels and potentially irreversible consequences for climate change.

Other, more indirect effects which black carbon can have on the environment include alteration of regional weather patterns, inhibition or encouragement of cloud formation and detrimental impacts on plant health and productivity. Clearly, there are a variety of ways in which black carbon affects the natural world – and none of them are positive or desirable.

What impact does black carbon have on human health?

As a chief ingredient in PM, black carbon can have devastating effects on the human body when inhaled. Most exposure occurs due to vicinity to the source of the emissions; in an indoor setting, this involves candle burning or biofuel combustion for heating purposes, while in an outdoor setting, it can refer to anything from traffic pollution to industrial incineration to forest fires.

Black carbon is a known carcinogen and in the most serious cases, it can cause lung cancer, lung disease, heart disease and stroke. In fact, it’s estimated that exposure to black carbon causes up to 4.9 million premature deaths each year. However, even relatively low concentrations of black carbon can interfere with blood pressure levels and cause or exacerbate more serious underlying health conditions in the bodies of those exposed to them.

Is black carbon worse than carbon dioxide?

Because it is a particle rather than a gas, black carbon is far more efficient at retaining heat than carbon dioxide, thus making it a much more serious contributor to global warming in the short term. Indeed, it’s thought that black carbon has an impact on global warming that is between 460 and 1,500 times greater than CO2.

Having said that, black carbon persists in the atmosphere for a miniscule amount of time compared to carbon dioxide. Whereas the latter can persist for well over a century, most black carbon biodegrades within two weeks – and it can sometimes disappear in as little as four days. That makes it not quite as serious a concern as carbon dioxide for the long-term ramifications of global warming, since any curbs on black carbon would yield much more immediate results and benefits.

How do we monitor black carbon concentrations?

Black carbon differs from many other pollutants in that it is a particle, rather than a gas. Traditionally, such ambient particulates have been monitored using gravimetrical methods which assess them by size.

However, it’s unclear whether black carbon differentiates significantly from other particulate contaminants (including carbon black, for example), leading the scientific community to question whether these analytical techniques are really the most effective for quantifying its concentrations.

What’s more, the fact that black carbon persists in the atmosphere for far less time than other climate change-contributors may be good news from an environmental perspective – but it merely creates more challenges when it comes to investigating ambient concentrations over time. As such, researchers have been working on revolutionary new methods for measuring particulates such as black carbon and PMx and have come up with some technologically advanced solutions for doing so.

The most cutting-edge of these solutions rely on collaboration between the leading players in the advanced stack sampling industry, using sophisticated optical instruments and advanced laboratory techniques to arrive at more precise and more reliable monitoring data than ever before.

How can we reduce black carbon concentrations?

The surest fire way to reduce black carbon concentrations in our atmosphere is to cut them off at source. This means transitioning away from combustion of fuel sources – be they fossil fuels, biofuels or any other – in favour of renewable means of power generation. Great advances in solar, wind and wave power have been made in recent years, making them more attractive to governments and private business interests.

However, there are still many parts of the world where the infrastructure and the investment capital is sorely lacking to put these sustainable technologies in place. It’s no coincidence that these regions are the very same ones which currently produce the lion’s share of black carbon emissions. As such, it will require concerted collaboration and substantial financial support from wealthy and developed nations to ensure their impoverished and developing counterparts can implement the technologies needed to bring down black carbon concentrations as much as possible, without negatively impacting upon the quality of life of their inhabitants.