Biomass Burning: Air Pollution And Its Hazards

Biomass, derived from organic matter synthesized by green plants, is one of the most abundant resources on Earth. It is frequently depicted as a clean and carbon-neutral energy source. However, burning biomass, including wood, charcoal, and other biological materials, releases harmful pollutants and contributes significantly to air pollution, particularly in indoor environments. The extent of air pollution from biomass burning depends on various factors, such as fuel type, combustion temperature, and pollution controls. Incomplete combustion can lead to the release of toxic compounds, including carbon monoxide, particulate matter, and hazardous air pollutants (HAPs), posing serious health risks to vulnerable populations.

Burning biomass emits large amounts of pollutants, including hazardous air pollutants

Biomass burning emits a range of hazardous air pollutants, including organic HAPs such as styrene, acrolein, and formaldehyde, as well as acid gases like hydrofluoric and hydrochloric acid. Even the burning of “clean wood,” derived from forestry, emits these chemicals. In addition, biomass burning releases heavy metals such as lead, mercury, and chromium, which are known to have highly harmful health and environmental effects. These metals are considered HAPs, and their emissions from biomass burning can be significant, as seen in the example of China, where Cd, Hg, Cr, As, and Pb emissions from biomass burning were measured in 2014.

The incomplete combustion of biomass also produces polycyclic aromatic hydrocarbons (PAHs), which are recognized as highly toxic organic pollutants. PAHs are known to damage a wide range of human organs and are considered a priority for control by the US Environmental Protection Agency (EPA). Biomass burning is the second-largest source of residential PAHs, contributing to 32.1% of their emissions. Furthermore, biomass burning emits volatile organic compounds (VOCs), which are major gaseous pollutants with adverse effects on the climate, environment, and human health.

The impact of biomass burning on air quality is not limited to indoor spaces but also affects the ambient air severely. Globally, biomass burning contributes significantly to the emissions of primary PM2.5, black carbon, and organic carbon. These emissions have been estimated at about 51, 4.6, and 29 Tg, respectively, accounting for a large proportion of the total emissions from all sources. The residential sector and open fires are major sources of these emissions, with open fires contributing to nearly 70% of primary PM2.5 emissions.

To summarize, burning biomass releases a range of hazardous air pollutants, including organic compounds, acid gases, heavy metals, PAHs, and VOCs. These emissions have severe impacts on both indoor and outdoor air quality, with subsequent effects on human health and the environment. While biomass is considered an important energy source, particularly in developing regions, it is crucial to recognize the associated pollution and health risks and work towards cleaner alternatives.

Biomass is a major source of indoor air pollution, especially in low-income countries

Despite being considered a "clean" and renewable energy source, biomass is a significant contributor to air pollution, especially in low-income countries. Biomass fuel, which includes wood, dung, charcoal, and crop residues, is used by one-third of the world's population for cooking, heating, and lighting. In low-income countries, biomass can account for up to 95% of domestic energy usage. The burning of these organic materials releases various pollutants, including hazardous air pollutants (HAPs) and particulate matter, which have severe health and environmental consequences.

Biomass is a major source of indoor air pollution, particularly in low-income households. The incomplete combustion of biomass fuels in simple stoves results in high levels of indoor air pollution, affecting women and children the most. Indoor air pollution from biomass smoke has been linked to an increased risk of respiratory tract infections, exacerbations of inflammatory lung conditions, cardiac events, stroke, eye disease, tuberculosis, cancer, and other serious health issues. The health impacts of indoor air pollution are more severe among vulnerable populations, including the poorest and those living in developing countries.

Biomass burning emits hazardous air pollutants (HAPs), which are known to have detrimental effects on human health and the environment. These HAPs include organic compounds such as styrene, acrolein, and formaldehyde, as well as acid gases like hydrofluoric and hydrochloric acid. Even the burning of "clean wood" releases these toxic chemicals and heavy metals. Carbon monoxide, a product of incomplete combustion, can accumulate in closed spaces, posing additional risks to human health.

The impact of biomass burning on indoor air pollution is particularly prominent in low-income countries due to the high reliance on biomass fuels as a primary energy source. In these countries, the transition to cleaner fuels is challenging due to various barriers, including poverty and limited access to alternative technologies. However, initiatives and interventions are being implemented to address this issue, such as improved biomass cookstoves, which aim to reduce exposure to harmful pollutants.

While biomass burning has negative consequences, it is important to recognize its role in socioeconomic development, especially in areas with abundant biomass resources. The challenge lies in adopting more efficient and sustainable practices to minimize the impact on air pollution, particularly in low-income communities that are most vulnerable to its health and environmental effects.

Incomplete combustion of biomass releases carbon monoxide, a harmful pollutant

Burning biomass releases a range of pollutants, including hazardous air pollutants (HAPs). Incomplete combustion of biomass, in particular, releases carbon monoxide, a harmful and toxic pollutant.

Incomplete combustion occurs when there is a shortage of oxygen in the combustion chamber, or when the temperature is not high enough. This can happen due to poor combustion conditions, such as low temperature, limited oxygen availability, and short residence times. Incomplete combustion can also occur when the burn happens too quickly, not allowing enough time for all the carbon monoxide to finish reacting and escape as exhaust.

Carbon monoxide is a highly dangerous product of incomplete combustion. When inhaled, it interferes with oxygen absorption in the blood. It does so by taking the place of oxygen and combining with hemoglobin in the blood, rendering it incapable of transporting oxygen. This can lead to serious health issues, including respiratory infections, exacerbations of inflammatory lung conditions, cardiac events, stroke, and eye disease.

The release of carbon monoxide from biomass boilers generally increases with fuel moisture. To control carbon monoxide emissions, "good combustion practices" are recommended, which involve ensuring optimal combustion conditions and minimizing the emission of carbon monoxide.

In addition to carbon monoxide, incomplete combustion of biomass can also produce other harmful pollutants, such as formaldehyde, acetaldehyde, benzene, and acrolein. These pollutants contribute to indoor and outdoor air pollution, adversely affecting human health and the environment.

Biomass burning contributes to outdoor air pollution and adversely affects human health

Despite being considered a carbon-neutral and renewable source of energy, biomass burning, especially in developing countries, contributes to outdoor air pollution and adversely affects human health. About one-third of the world's population burns biomass fuel for cooking, heating, and lighting. The burning of biomass, including wood, charcoal, dung, and crop residues, accounts for over half of domestic energy in most developing countries and up to 95% in low-income countries. The incomplete combustion of biomass releases harmful pollutants, such as carbon monoxide, particulate matter, volatile organic compounds (VOCs), and hazardous air pollutants (HAPs). These emissions negatively impact both indoor and outdoor air quality, with outdoor air pollution carrying more severe consequences.

Biomass burning is a significant contributor to outdoor air pollution, with emissions from residential sectors and open fires being major sources. The global consumption of biomass, including natural and anthropogenic sources, was approximately 7900 Tg in 2019, with developing countries like China experiencing notable increases in biomass consumption over time. The burning of biomass emits large amounts of pollutants, including organic HAPs such as styrene, acrolein, and formaldehyde, and acid gases such as hydrofluoric and hydrochloric acid. Even the burning of "clean wood," derived from forestry, emits these harmful chemicals.

The type and level of emissions from biomass burning depend on various factors, including the completeness of combustion, fuel type, and combustion temperature. Incomplete combustion releases higher levels of harmful pollutants, while complete combustion minimises air pollutants. However, achieving complete combustion can be challenging, especially in manual systems, due to the complexity of maintaining ideal combustion conditions. Modern wood-burning stoves, pellet stoves, and fireplace inserts can help reduce particulate emissions from burning wood, but they may not always be accessible or affordable for those who rely on biomass fuel.

The adverse health effects of biomass burning are well-documented. Air pollution from biomass burning has been linked to respiratory infections, including pneumonia, tuberculosis, and chronic obstructive pulmonary disease (COPD). It also increases the risk of respiratory tract infections, exacerbates inflammatory lung conditions, and contributes to cardiac events, stroke, eye disease, cancer, and hospitalisations. The pollutants released during biomass burning can lead to increases in fibrinogen, plasma viscosity, platelet activation, and the release of endothelins, which are potent vasoconstrictor molecules, posing a significant risk to cardiovascular health. Additionally, biomass burning has been associated with birth defects, neurodegenerative diseases, and even death.

In conclusion, biomass burning, particularly in developing regions, significantly contributes to outdoor air pollution and has detrimental effects on human health. The release of harmful pollutants during incomplete combustion and the subsequent impact on air quality underscore the urgency of implementing effective interventions to reduce biomass burning emissions. Addressing this issue is crucial to mitigate the adverse health consequences faced by vulnerable populations, especially in low-income countries where biomass fuel usage is prevalent.

The type and level of emissions from biomass heating depend on complete or incomplete combustion

The burning of biomass, including wood, animal dung, charcoal, and crop residues, is a significant source of air pollution, particularly in developing countries. While biomass is often considered a "clean" and renewable energy source, data reveals that it is a heavily polluting technology, comparable to coal in terms of emissions. The type and level of emissions from biomass heating depend on whether complete or incomplete combustion occurs in the heating system.

During complete combustion, biomass is converted into carbon dioxide (CO2) and water vapour (H2O). However, if the conditions for complete combustion are not met, incomplete combustion occurs, resulting in the release of various gaseous and particulate pollutants. These include volatile organic compounds (VOCs), biomass char, soot, and tars, and carbon monoxide (CO). Incomplete combustion can also lead to the emission of hazardous air pollutants (HAPs), such as heavy metals, hydrochloric acid, and formaldehyde.

The level of emissions from biomass heating varies depending on the type of heating system, the fuel used, and the operating conditions. Open fireplaces and simple log stoves tend to produce higher emissions and are discouraged in urban areas. Modern, high-efficiency biomass boilers can significantly reduce particulate emissions, especially when combined with high-efficiency filters like ceramic filters. However, these technologies may not be economically feasible for residential-scale systems.

To minimize emissions from biomass heating, "good combustion practices" are essential. This includes proper fuel ignition, precise fuel quantity, and adequate combustion air supply. Secondary measures, such as catalytic converters and electrostatic precipitators, can also be employed, although they may not always be effective due to inappropriate combustion conditions.

It is important to note that the combustion of biomass can release toxic substances, impacting human health. Incomplete combustion products, such as carbon monoxide, can interfere with oxygen absorption in the blood and lead to serious health issues, including respiratory infections, cardiovascular diseases, and even death. Therefore, proper combustion and ventilation are crucial to mitigate the harmful effects of biomass heating on air quality and human health.

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