Oxygen

Oxygen is a vital chemical element, denoted by the symbol O and possessing the atomic number 8. It is one of the most abundant and essential elements on Earth, indispensable for sustaining life and supporting numerous industrial processes. In its diatomic molecular form (O₂), it constitutes about 21 per cent of the Earth’s atmosphere. Oxygen plays a crucial role in respiration, combustion, and various chemical reactions that underpin both biological and technological systems. Beyond its natural significance, oxygen holds immense importance in modern industry, medicine, and the global economy.

Physical and Chemical Characteristics

Oxygen is a colourless, odourless, and tasteless gas at room temperature and pressure. It liquefies at −183°C and solidifies at −218.8°C. Oxygen supports combustion but is not itself flammable. It readily forms compounds, particularly oxides, by combining with most other elements. The high reactivity of oxygen stems from its strong electronegativity and its ability to form stable bonds. In nature, it exists primarily in molecular form, but other allotropes such as ozone (O₃) also play significant environmental roles, notably in filtering ultraviolet radiation from the Sun.

Biological and Environmental Role

In biological systems, oxygen is essential for aerobic respiration, a metabolic process through which organisms derive energy from food molecules. It acts as the final electron acceptor in cellular respiration, enabling the conversion of glucose into carbon dioxide, water, and energy (ATP). Aquatic life depends on dissolved oxygen, and its concentration serves as a key indicator of water quality.
In the environment, oxygen participates in the biogeochemical cycles that regulate the Earth’s atmosphere and biosphere. The oxygen cycle links photosynthesis and respiration, maintaining equilibrium between oxygen production and consumption. Photosynthetic organisms such as plants, algae, and cyanobacteria release oxygen as a by-product, replenishing atmospheric levels.

Industrial Applications

Oxygen has widespread applications across diverse industrial sectors. It is integral to processes involving combustion, oxidation, and synthesis.

• Metallurgical Industry: Oxygen is used extensively in the production and refining of metals. In steelmaking, the basic oxygen furnace (BOF) process employs oxygen to oxidise impurities such as carbon, silicon, and phosphorus, resulting in purer steel. Similarly, non-ferrous metals like copper and zinc are refined using oxygen-based processes.
• Chemical Manufacturing: The chemical industry utilises oxygen for synthesising various compounds, including nitric acid, hydrogen peroxide, and ethylene oxide, all of which serve as raw materials for plastics, fibres, and detergents. Controlled oxidation reactions rely heavily on oxygen for their efficiency and precision.
• Glass and Ceramics: Oxygen-enriched combustion improves furnace temperatures and fuel efficiency in glass and ceramic production. It enhances product quality by providing more uniform heating and reducing impurities.
• Pulp and Paper Industry: Oxygen is applied in bleaching processes as an environmentally friendly alternative to chlorine-based chemicals. Oxygen delignification reduces the environmental impact of pulp bleaching while maintaining paper quality.
• Energy and Power Generation: In industrial energy systems, oxygen enrichment improves the combustion efficiency of fuels, reducing emissions and energy costs. Emerging technologies such as oxy-fuel combustion are being explored for carbon capture and storage (CCS) applications to mitigate greenhouse gas emissions.

Medical and Healthcare Uses

In medicine, oxygen is indispensable for sustaining life and treating respiratory disorders. Medical-grade oxygen is administered in hospitals and clinics to patients with conditions such as asthma, pneumonia, chronic obstructive pulmonary disease (COPD), and hypoxaemia. Oxygen therapy helps maintain adequate blood oxygen levels when natural respiration is impaired.
In anaesthesia and intensive care, oxygen is mixed with other gases to support patients during surgical procedures. Portable oxygen cylinders and concentrators are also used in home healthcare for chronic patients. Furthermore, hyperbaric oxygen therapy (HBOT)—where patients breathe pure oxygen in pressurised chambers—is employed to treat decompression sickness, carbon monoxide poisoning, and certain wound-healing disorders.

Economic and Industrial Significance

Oxygen production and supply form a significant segment of the global industrial gas market. It is primarily obtained through cryogenic distillation of air or by pressure swing adsorption (PSA) methods. The demand for industrial oxygen is closely linked to economic activity in sectors such as steel, energy, chemicals, and healthcare.
Major industrial gas companies, including Linde, Air Liquide, and Air Products, operate large-scale oxygen production facilities worldwide. The market for industrial oxygen continues to expand, driven by increasing urbanisation, infrastructure growth, and medical needs. The cost of oxygen is influenced by factors such as energy prices, production technology, and transportation logistics, as oxygen is often delivered via pipelines or in liquid form to major industrial consumers.

Everyday Applications

In everyday life, oxygen’s influence is profound, though often unnoticed. It supports the fundamental process of breathing, enabling life for humans and animals. Oxygen is also crucial in combustion, making it essential for cooking, heating, and transportation. In household and recreational contexts, oxygen cylinders are employed in scuba diving, mountaineering, and emergency situations to assist breathing at high altitudes or underwater.
Furthermore, oxygen is used in water treatment plants to improve aeration and degrade pollutants. In aquaculture, oxygenation enhances fish health and productivity. Even in modern technology, oxygen plays roles in semiconductor manufacturing and space exploration, where liquid oxygen (LOX) serves as an oxidiser in rocket propulsion systems.

Environmental and Sustainability Considerations

While oxygen itself is non-polluting, its industrial production and utilisation can have environmental implications. The generation of oxygen through energy-intensive cryogenic processes contributes indirectly to carbon emissions, depending on the energy source used. Efforts to integrate renewable energy into oxygen production are gaining momentum, particularly in the context of the hydrogen economy, where oxygen is a valuable by-product of water electrolysis.
In environmental management, oxygen plays a pivotal role in mitigating pollution. Aerobic treatment systems rely on oxygen to decompose organic waste in wastewater. Similarly, oxygen injection into contaminated soils accelerates bioremediation by stimulating aerobic microbial activity.

Role in the Future Economy

Oxygen is expected to play an increasingly significant role in future energy systems. As industries transition towards green hydrogen production, large-scale water electrolysis will generate both hydrogen and oxygen. This will not only reduce dependency on fossil fuels but also create opportunities for integrating oxygen utilisation into circular industrial systems.
Moreover, as healthcare demands rise globally, oxygen supply infrastructure is being prioritised as a critical component of public health preparedness, a lesson underscored by the COVID-19 pandemic. The continuous development of energy-efficient and decentralised oxygen production technologies is vital for both economic resilience and environmental sustainability.