Helena Joyce
The leather industry has a significant impact on water pollution. The tanning process, which involves treating raw animal hides to make them more resilient, generates large amounts of wastewater and solid waste contaminated with various chemicals and organic pollutants. Chromium, a heavy metal used in the tanning process, is a major contaminant, with an estimated 170,000 tons of chromium waste discharged into the environment annually. In addition, the leather industry's high water consumption and chemical usage contribute to the pollution load, with an estimated average of 360.2 kg of chemicals consumed per ton of shaved leather. The pre-tanning and tanning operations are responsible for about 90% of the total pollution caused by the industry. With the volume of industrial wastewater expected to double by 2025, the environmental impact of the leather industry is a growing concern.
What You'll Learn
- The tanning process uses a lot of water and chemicals, creating liquid effluents with high pollution loads
- Chromium, a heavy metal used in leather tanning, is hazardous and contaminates water sources
- Pre-tanning and tanning operations contribute about 90% of the leather industry's total pollution
- The leather industry's wastewater contains organic pollutants and hazardous chemicals
- Animal agriculture, including leather production, is a leading contributor to climate change
The tanning process uses a lot of water and chemicals, creating liquid effluents with high pollution loads
The tanning process involves several mechanical and chemical operations in an aqueous medium, including acids, alkalis, chromium salts, tannins, solvents, auxiliaries, surfactants, metallorganic dyes, natural or synthetic tanning agents, sulfonated oils, and salts. The process uses a lot of water and chemicals, creating liquid effluents with high pollution loads.
A report supported by the European Commission found that tanning 1kg of leather uses up to 2.5kg of chemical substances and up to 250 liters of water, generating up to 6.1kg of solid waste. Another source states that to process one metric ton of wet salted hides, 40 cubic meters of water is required, and out of 452kg of process chemicals used, only 72kg of leather is produced while the remaining 380kg is discharged. The average water demand for the shaving process is 8.6 cubic meters per ton of shaved leather, with washing responsible for the highest consumption.
The pre-tanning operation causes differences in pH levels, thereby increasing the chemical oxygen demand (COD), total dissolved solids (TDS), chlorides, and sulfates in wastewaters discharged by tanneries. The lime and sulfide utilized during the dehairing process contribute 84% of biochemical oxygen demand (BOD), 75% of COD, and 92% of suspended solids (SS) from a leather manufacturing industry. The utilization of sulfides not only increases the negative consequences on the environment but also affects the efficacy of wastewater treatment plants. The post-tanning process also leads to significant modifications of COD, TDS, and heavy metal pollution.
The total quantity of effluent discharged by Indian tanneries is about 50,000 cubic meters per day and contains high concentrations of organic pollutants. Chromium is an important heavy metal used in the leather industry, and more than 170,000 tons of chromium waste are discharged into the environment worldwide each year. Chromium from leather tanning can make its way into air, soil, food, and water, and common forms of exposure include inhalation of dust or fumes and ingestion or contact with contaminated water.
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Chromium, a heavy metal used in leather tanning, is hazardous and contaminates water sources
The leather industry has a significant impact on water pollution, largely due to the high consumption of water and chemicals. The tanning process, in particular, contributes about 90% of the total pollution caused by the leather industry.
Chromium is a heavy metal commonly used in the leather tanning process. It is a crucial component in the conversion of raw hide to leather, giving the final product a very high quality. However, chromium is a hazardous substance, and its improper handling and discharge can lead to water contamination. During the tanning process, excess chromium salts are often applied to guarantee sufficient penetration and combination with the hide. This results in a high concentration of chromium in the wastewater. The wastewater, in turn, finds its way into surface water, contaminating sources used for bathing, cooking, swimming, and irrigation.
Chromium-contaminated water poses a serious threat to human health and the environment. Chromium waste in water can build up in aquatic animals, which are a common food source for humans. Additionally, chromium can seep into the soil, contaminating groundwater systems and posing health hazards to nearby communities. The toxic dust from chromium-contaminated soil can be inhaled by both people and livestock.
The potential health risks associated with chromium exposure are well-documented. Inhalation of chromium dust or fumes and ingestion or dermal contact with contaminated water are the most common forms of exposure. Workers in tanning facilities are particularly vulnerable to these risks. The negative health impacts of chromium exposure can be both short-term and long-term.
To address the issue of chromium contamination, various chrome-free tanning agents have been proposed to achieve a greener tanning process. These alternatives, however, come with their own set of challenges, such as low hydrothermal stability and pungent odors. As a result, the leather industry has been reluctant to adopt these chrome-free methods, opting instead for high-exhaustion chrome tanning technology to balance environmental sustainability and product quality.
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Pre-tanning and tanning operations contribute about 90% of the leather industry's total pollution
The leather industry is a significant contributor to water pollution. The pre-tanning and tanning operations alone contribute about 90% of the industry's total pollution. Pre-tanning operations cause changes in pH levels, increasing the chemical oxygen demand (COD), total dissolved solids (TDS), chlorides, and sulfates in wastewaters discharged by tanneries. The dehairing process utilises lime and sulfide, which contribute 84% of the biochemical oxygen demand (BOD), 75% of COD, and 92% of suspended solids (SS) from leather manufacturing. Sulfides also have negative consequences on the environment and affect the efficacy of wastewater treatment plants.
The tanning process involves the use of many chemicals, including acids, alkalis, chromium salts, tannins, solvents, and auxiliaries. The most common approach, chrome tanning, uses large amounts of basic chromium salts, which become a source of Cr pollution. For every ton of processed leather, more than 0.12 kg of Cr pollution is generated. Chromium is an important heavy metal used in the leather industry, and over 170,000 tons of Cr wastes are discharged into the environment annually.
The wastewater from the tanning process contains high levels of salinity and chrome, as well as sulfides and salts of ammonium and calcium, making it slightly alkaline. It is estimated that the global tanning industry generates about 50,000 m3/day of effluent, which contains high concentrations of organic pollutants. This includes heavy metals, toxic sludge, solvents, and high loads of suspended solids, organic nitrogen, and ammonia.
The leather industry's high consumption of water and chemicals results in liquid effluents with a high pollution load. The average water demand for the post-tanning process is 8.6 m3 per ton of leather processed, and the average chemical consumption is 360.2 kg per ton of shaved leather. The retanning and fatliquoring steps are the largest chemical consumers. The wastewater produced is poorly biodegradable and has high conductivity and elevated salt concentrations.
To address the issue of water pollution, the leather industry can adopt cleaner manufacturing practices, such as eco-friendly enzyme-assisted tanning processes, which have been shown to reduce pollution levels and improve leather quality. Additionally, emerging technologies like electrocoagulation offer a sustainable and cost-effective way to treat wastewater by using electrical currents to coagulate contaminants.
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The leather industry's wastewater contains organic pollutants and hazardous chemicals
The leather industry uses a lot of water and chemicals, and as a result, it generates a lot of liquid effluent with a high pollution load. The tanning process, in particular, generates large amounts of wastewater and solid waste. This wastewater contains organic pollutants and hazardous chemicals, which can contaminate nearby water systems and pose risks to human health and the environment.
The tanning process involves treating raw animal hides with a tanning agent to make them more resilient and strong for use in various products. Common tanning agents include chromium salts and vegetable tannins, with chromium being the most common. Chromium is a heavy metal, and its waste is considered hazardous by the US Environmental Protection Agency (EPA). Chromium waste can contaminate air, soil, food, and water, with inhalation and ingestion being the most common forms of exposure. It is estimated that over 170,000 tons of chromium waste are discharged into the environment annually.
In addition to chromium, wastewater from the leather industry contains other hazardous chemicals such as mineral salts, formaldehyde, coal-tar derivatives, oils, dyes, and finishes, some of which are cyanide-based. The pre-tanning and tanning operations contribute about 90% of the total pollution caused by the leather industry. The pre-tanning operation, which includes the dehairing and unhairing process, increases the chemical oxygen demand (COD), total dissolved solids (TDS), chlorides, and sulfates in wastewater. The high use of lime and sulfide during dehairing contributes significantly to the biochemical oxygen demand (BOD), COD, and suspended solids (SS) in wastewater.
The large volume of industrial wastewater generated by the leather industry is expected to double by 2025, leading to an increase in contaminated freshwater resources. This will have a significant impact on the environment and human health, as the pollutants in the wastewater are toxic and can cause ecological imbalances. To address this issue, some tanneries have implemented Zero Liquid Discharge (ZLD) systems, which treat and reuse wastewater while minimizing environmental impact. However, more efforts are needed to reduce the pollution caused by the leather industry and to transition to more sustainable alternatives.
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Animal agriculture, including leather production, is a leading contributor to climate change
The tanning process, in particular, contributes significantly to water pollution. Tanning accounts for about 90% of the total pollution caused by the leather industry. During the pre-tanning and tanning operations, there are increases in pH levels, chemical oxygen demand (COD), total dissolved solids (TDS), chlorides, and sulfates in wastewater. The use of lime and sulfide in the dehairing process further contributes to biochemical oxygen demand (BOD) and suspended solids (SS).
The post-tanning process also leads to modifications in COD, TDS, and heavy metal pollution. Chromium, a heavy metal used in leather tanning, is discharged into the environment, contaminating air, soil, food, and water. The presence of carcinogens and other hazardous pollutants in wastewater increases the need for effective treatment methods. While most tanning industries in developed countries have good pollution controls, abandoned factories and poorly managed tanneries in the developing world pose significant public health risks to local populations.
In addition to the direct impacts of leather production, animal agriculture as a whole contributes significantly to climate change. Raising animals for food and leather requires vast amounts of feed, pastureland, water, and fossil fuels. The methane and nitrous oxide emissions from animal agriculture are significant contributors to greenhouse gas emissions. Furthermore, the excrement produced by factory farms, without proper waste treatment, leads to water pollution and eutrophication, causing "dead zones" in water systems.
The fashion industry often markets leather as a byproduct of cow farming, claiming it is eco-friendly and sustainable. However, this is a misconception, as leather is a valuable co-product, accounting for a significant portion of slaughterhouses' earnings. The processing of cow skin and the subsequent tanning process result in even greater environmental harm. Therefore, it is essential to recognize the role of the leather industry in climate change and to explore sustainable alternatives to mitigate its environmental impacts.
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Frequently asked questions
The leather industry uses a lot of water and chemicals, and this generates liquid effluents with a high pollution load. The pre-tanning operation causes differences in pH levels, increasing the chemical oxygen demand (COD), total dissolved solids (TDS), chlorides, and sulfates in wastewaters discharged by tanneries.
The leather industry has significant environmental impacts. It contributes to land use, deforestation, and water pollution. The production of leather also hurts animals and the people who manufacture it.
Tanning leather generates a large amount of waste and water pollution. The tanning process involves treating raw hides with a tanning agent, and this generates liquid effluents with high levels of pollutants such as chromium, salt, lime sludge, sulfides, and acids.
Vegan leathers made from materials like recycled plastic, pineapples, cork, mushrooms, and polyurethane are alternatives to leather that contribute less to water pollution, water depletion, and greenhouse gas emissions.
Zero liquid discharge (ZLD) systems present a sustainable solution by efficiently treating and reusing wastewater while minimizing environmental impact. Other methods include using bone charcoal to remove chromium from water and vermiculture to remove chromium contamination from soil.
