Animal Waste: Nitrogen Pollution's Unseen Threat

Animal waste is a significant contributor to nitrogen pollution, which is one of the most pressing pollution issues facing humanity today. Nitrogen pollution has severe impacts on human health, the economy, and the environment. Animal waste, including manure from cows, pigs, and chickens, contains high levels of nitrogen and phosphorus, which can contaminate surface and groundwater if not properly managed. Improper disposal of animal waste can lead to increased nitrogen runoff into waterways, affecting water quality and ecosystems. Additionally, the burning of animal waste and the combustion of fossil fuels release nitrogen into the atmosphere, contributing to climate change and air pollution. With the increasing concern over the environmental and health impacts of nitrogen pollution, there is a growing global effort to reduce nitrogen waste and improve nitrogen management practices.

Animal waste and water pollution

Animal waste is a significant contributor to water pollution. Animal wastes predominantly include manures from cows, pigs, and chickens, and can contaminate both surface and groundwater. The burning of animal waste also contributes to air pollution. Animal waste application on pasture lands is a convenient method of waste disposal and is an economical and commonly used fertilizer in some places, such as Louisiana. However, the recent growth of Concentrated Animal Feeding Operations (CAFOs) presents an increased risk to water quality due to the larger volume of waste and the presence of contaminants.

Animal agricultural wastes can be divided into two production types: range and pasture production, and confined or concentrated animal production. In range and pasture systems, the concentration of wastes is generally much more diffuse or dispersed than when large numbers of animals are confined to small areas. Range and pasture systems have two principal effects on surface water quality:

• Increased turbidity through the movement of soil particles into streams, rivers, and lakes;
• Increased fecal coliform counts in areas of heavy animal use.

The impact of CAFO waste on aquatic communities is not well understood, but it can include the spread of fecal bacteria and other microbial pathogens, antibiotic-resistant bacteria, pesticides, heavy metals, and other pollutants. These contaminants can have additive or synergistic effects on aquatic life, and CAFO waste spills can result in high densities of pathogenic microorganisms in sediments for weeks to months.

Additionally, animal waste contributes to gaseous nitrogen emissions, which, when deposited back into the landscape, can be a significant source of nitrogen in coastal marine ecosystems. Meat production is inefficient in terms of nitrogen, and the consumption of meat protein is of particular concern regarding nitrogen pollution. For example, it requires 100 kg of nitrogen in corn to produce 5 kg of edible nitrogen in beef, with a protein conversion efficiency of only 5%. The remaining 95 kg of nitrogen enters the environment as metabolic wastes from the animals or their carcasses. Increased meat consumption also leads to more nitrogen excretion into the environment.

To address these issues, best management practices should be implemented to prevent or minimize the release of contaminants into the environment. Educational materials should also be developed and distributed to agricultural producers to raise awareness about pollution prevention and best practices.

Nitrogen in animal manure

Animal waste is a growing environmental concern due to its potential to contaminate both surface and groundwater. Animal waste, including manure from cows, pigs, and chickens, can contribute to nitrogen emissions, which can have significant impacts on coastal marine ecosystems.

Nitrogen is a crucial element in manure, and its management is essential for maintaining soil fertility and preventing environmental pollution. Fresh farmyard manure (FYM) from cattle and sheep typically contains an estimated ammonium-nitrate content of 20% of total nitrogen, while pig and duck FYM contain slightly higher levels at 25%. The availability of nitrogen in duck manure is generally lower than that of other poultry manures.

The nitrogen content in manure can vary depending on factors such as the type of animal and the storage time. For example, old FYM, which has been stored for three months or more, tends to have lower nitrogen content, with cattle and sheep FYM containing approximately 10%, and pig and duck FYM containing 15%.

Properly managing animal manure is crucial to minimise environmental impacts. In the past, cow manure was often treated and sold as fertiliser for agricultural purposes or spread on agricultural lands. However, stricter environmental regulations now control odour, surface and groundwater pollution, soil contamination, and nutrient management.

Converting agricultural and animal wastes into biochar through pyrolysis is an efficient waste management strategy that reduces environmental challenges. This approach not only improves waste management but also offers the added benefit of decreased transportation costs and production volumes.

Environmental impact of animal agriculture

Animal agriculture has a significant environmental impact, contributing to various forms of environmental degradation. By 2050, the world's population is expected to reach 10 billion, requiring a 70% increase in global food production, which will further exacerbate the environmental harm caused by animal agriculture.

One of the most significant impacts of animal agriculture is its contribution to greenhouse gas emissions. Animal agriculture is responsible for 18% of all greenhouse gas emissions worldwide, with livestock producing the majority of agricultural greenhouse gases. Cows, sheep, and other ruminants have a complex digestion process that produces methane, a greenhouse gas 30 times more potent than carbon dioxide over 100 years. Animal agriculture also produces 65% of the world's nitrous oxide emissions, which have a global warming impact 296 times greater than carbon dioxide.

Animal agriculture is a major driver of deforestation, with meat production being the single greatest cause. It encompasses 83% of farmland and uses 70% of agricultural land, contributing to habitat alteration and biodiversity loss. The high land usage also impacts water resources, with animal agriculture polluting freshwater sources and accounting for a significant proportion of water consumption. For example, processing one pound of beef uses 2,500 gallons of water.

Animal waste is a significant pollutant, contaminating both surface and groundwater. It contributes to water pollution through the release of toxins, excess fertilizers and pesticides, leading to increased phosphates, nitrates, and decreased dissolved oxygen in water bodies. The concentration of wastes is particularly high when large numbers of animals are confined to small areas, further exacerbating the issue. Additionally, the use of antibiotics in livestock husbandry can lead to antibiotic resistance, impacting human, animal, and environmental health.

To mitigate the environmental impact of animal agriculture, a shift towards a plant-based food system is often suggested. Adopting a plant-based diet, supporting farmers practicing regenerative agriculture, and reducing meat consumption can help reduce greenhouse gas emissions and alleviate the pressure on natural resources caused by animal agriculture.

Nitrogen pollution and climate change

Nitrogen is an essential component of the air we breathe, but human activities have led to the creation of chemically reactive nitrogen forms that are dangerous and costly pollutants. Animal waste is one of the most common sources of nitrogen pollution, which can contaminate both surface and groundwater. When animal waste enters waterbodies, it increases nitrate levels, which can be fatal to infants who consume it and can increase the risk of cancer in adults. Animal waste also contributes to gaseous nitrogen emissions, which can be deposited back into the landscape and significantly impact coastal marine ecosystems.

Agricultural activities are a major contributor to nitrogen pollution. The use of nitrogen-based fertilisers in agriculture has increased globally, with consumption rising from 12 Tg in 1960 to 113 Tg in 2010. If current trends continue, even more fertiliser will be needed to sustain global food production and provide food for an additional 2 billion people by 2050. The application of fertilisers to fields leads to microbial reactions that release nitrous oxide, a gas 300 times more potent than carbon dioxide in warming the atmosphere. Fertiliser run-off can also cause algal blooms in lakes and waterways, which emit greenhouse gases.

The burning of agricultural wastes, such as rice husks, wheat straw, and soybean stover, results in air pollution and the emission of greenhouse gases. Animal agricultural wastes can be divided into two production types: range and pasture production and confined or concentrated animal production. In range and pasture systems, animal waste is more dispersed, leading to increased turbidity in streams, rivers, and lakes, as well as higher fecal coliform counts in areas of heavy animal use. In contrast, confining large numbers of animals in small areas results in a higher concentration of wastes.

To address the pervasive impact of nitrogen pollution on society, urgent action is needed. The UNEP #BeatPollution campaign advocates for rapid, large-scale, and coordinated efforts against air, land, and water pollution. Additionally, the UNEA resolution on Sustainable Nitrogen Management aims to significantly reduce nitrogen waste globally by 2030 and beyond. Scotland has also taken steps to address nitrogen pollution by including a nitrogen budget in its 2019 Climate Change Bill, with the goal of achieving net-zero greenhouse gas emissions by 2045.

Animal waste and air pollution

Animal waste is a significant contributor to air pollution. Animal agricultural wastes can be categorized into two production types: range and pasture production, and confined or concentrated animal production. In recent times, the latter has become more common as agriculture becomes more industrialized. Concentrated animal feeding operations (CAFOs) are characterized by large numbers of animals being raised, and often confined, in relatively small areas. This results in the production of massive amounts of animal waste, which emits around 400 different harmful gases into the atmosphere. These gases include nitrous oxide, ammonia, particulate matter, endotoxins, and hydrogen sulfide.

Ammonia emissions from animal waste are of particular concern, with animal waste contributing 50 to 85% of ammonia emissions in the United States, according to EPA estimates. When ammonia gas is released into the atmosphere, it can combine with other pollutants to form nitric acid. This nitric acid then returns to the Earth's surface as acid rain, causing harm to soil, forest habitats, and water ecosystems. Additionally, ammonia emissions can have detrimental effects on human health, including dizziness, eye irritation, respiratory illness, and nausea.

The burning of agricultural wastes is another source of air pollution, resulting in the emission of greenhouse gases. Animal waste from CAFOs is often sprayed onto crop fields, leading to environmental contamination over large regions. This practice, along with the use of animal husbandry-related products such as feed, pesticides, antibiotics, and hormones, contributes to the release of hazardous emissions into the environment. These emissions include microorganisms, endotoxins, air pollutants, and malodorous compounds.

To mitigate the air pollution caused by animal agriculture, it is essential to reduce the consumption of meat and dairy products. By choosing more plant-based foods, individuals can lower their carbon footprint and help reduce the demand for industrial animal agriculture. However, the lack of regulation and reporting requirements for farms and ranchers contributes to the challenge of addressing air pollution from animal waste.

Frequently asked questions