What is methane gas ?

The Story of Marsh Gas

Centuries ago, people living in rural, damp areas began noticing strange features in ponds and marshlands. At night, small, invisible flames would occasionally appear on the water’s surface—a phenomenon people attributed to spirits or mysteries of nature. These sudden blue flames, flickering with every breeze, often filled them with fear.

However, centuries later, with scientific advancements, scientists discovered that these flames were caused by the combustion of a gas known as methane, which came to be popularly known as marsh gas. Today, this gas is not only utilized in various industries and energy production, but it also draws significant attention due to its environmental impacts. From “marsh gas” to one of the primary drivers of global warming, methane has traveled a long journey through history, remaining a vital yet challenging element in the modern world.

The Molecular Structure of Methane Gas

• The methane molecule (CH₄) has a tetrahedral structure, with a carbon atom at the center connected by four covalent bonds to four hydrogen atoms. This structure provides methane with high stability.
• The angle between the C-H bonds in a methane molecule is 109.5 degrees, contributing to the molecule’s symmetry and stability.
• Due to the even distribution of electrons around the carbon atom and the tetrahedral symmetry, methane is a nonpolar molecule that does not dissolve in water and tends to interact with other nonpolar molecules.
• The bond enthalpy (or bond energy) of the carbon-hydrogen (C-H) bond in the methane molecule is approximately 413 kJ/mol.

Physical Properties

Chemical Properties

Applications of Methane Gas:

• Energy and electricity generation: Fuel for power generation plants and household uses such as heating and cooking.
• Fuel for compressed natural gas (CNG) vehicles: Especially for cars and heavy-duty vehicles.
• Hydrogen production: Used as a raw material in the steam methane reforming (SMR) process to produce hydrogen.
• Ammonia production: Used in the chemical industry for the production of fertilizers and other compounds.
• Methanol production: Used as a base material in the production of plastics, chemicals, and fuels.
• Methane mixed with propane is used as fuel under the name “liquefied gas (LPG)” in the petrochemical industry for energy production. This gas mixture provides the necessary energy for various industrial processes, and due to its flammability and high heat production, it is an efficient and common option in the petrochemical industry.

Storage and Preservation of Methane Gas
Today, activated carbon is used for storing and preserving methane at low pressure. Due to its vast surface area and high porosity, activated carbon retains methane within its structure through adsorption. This method, known as Adsorbed Natural Gas (ANG) storage, allows tanks to store methane without needing high pressure, which is both safer and reduces compression costs. For this reason, ANG is an appropriate and cost-effective option for small-scale methane storage, such as in compressed natural gas (CNG) vehicles.

Transportation

For gas transportation, the higher the boiling point, the easier it is to liquefy the gas to reduce its volume, facilitating transportation. However, methane has a low boiling point, making its transportation costlier compared to gases like isobutane. Here are various methods for transporting methane gas:

Pipeline Transportation

In this method, methane gas is transported through a network of pipelines, with pressure booster stations along the way that maintain gas flow and pressure, enabling continuous and uninterrupted transport. This method requires extensive infrastructure and investment but is one of the most efficient and cost-effective options for domestic methane transport due to low operational costs.

Liquefied Natural Gas (LNG) Transportation

Transporting methane as liquefied natural gas (LNG) is an efficient way to move it over long distances and to areas without access to pipeline networks. In this method, methane is cooled to around -162°C, converting it to a liquid state that reduces its volume by up to 600 times, making it easier to transport in specialized LNG tanks. These tanks have advanced insulation to maintain low temperatures and prevent gas evaporation. LNG transportation is a cost-effective and safe option for international gas export and transport to remote areas, though it requires specialized equipment and significant costs for liquefaction and maintenance.

Compressed Natural Gas (CNG) Transportation

CNG transport involves compressing methane gas to high pressures (about 200 to 250 bars) and storing it in sturdy, specialized cylinders. This method is suitable for transporting methane over shorter distances and for use in gas-powered vehicles and supplying gas to areas without pipeline access. Since the gas occupies less volume in this state than in regular gaseous form, its transport becomes more economical; however, it still takes up more space compared to LNG. CNG transport does not require cooling but demands high-pressure-resistant tanks and adherence to strict safety standards.

Gas-to-Liquids (GTL) Transportation

Transporting methane as gas-to-liquid (GTL) products involves converting methane through chemical processes into liquid fuels like diesel, naphtha, and other liquid hydrocarbons. This method enables easier and safer transport and storage, as GTL products can be readily handled in standard tanks and with existing liquid fuel infrastructure. GTL is a suitable and profitable option for long-distance transport or for areas lacking pipeline infrastructure, although it requires advanced equipment and high initial investment.

Petrochemical Products Transportation (such as Methanol and Ammonia)

Transporting methane as petrochemical products, such as methanol and ammonia, is an effective and economical method for indirect methane transportation. In this method, methane is converted at the production site into valuable petrochemical materials like methanol and ammonia, which, due to their liquid state and greater stability, allow for easier and safer transport. Methanol and ammonia have wide applications in various industries, including fertilizers, plastics, and industrial chemicals, and can be easily transported to domestic and international markets with simpler transport infrastructure compared to natural gas. This method not only facilitates methane transportation but is also economically profitable for producers, creating additional added value.

Methane: A Greenhouse Gas

Methane (CH₄), as a greenhouse gas with high warming potential, is released into the atmosphere through natural and human processes and significantly impacts global temperature rise. Methane’s warming potential is approximately 25 times that of carbon dioxide (CO₂) over a 100-year period, though it has a shorter atmospheric lifespan. This gas is primarily emitted from human activities such as agriculture (especially livestock farming), waste management, and fossil fuel extraction processes. Reducing methane emissions is a key priority in climate policies due to its high effectiveness in mitigating short-term global warming.

Comparison of Methane Gas with LPG

Methane gas and LPG are both widely used fuels in various industries and for household purposes, but they have important differences in terms of transportation, usage, and physical properties.

In terms of transportation, LPG can easily be transported and stored in compressed cylinders due to its ability to liquefy under relatively low pressure, making it easier for LPG transport companies. This feature also allows LPG to be used as a fuel source in remote areas and locations without natural gas pipeline infrastructure. In contrast, methane, due to its low boiling point, requires extreme cooling (around -162°C) and specially insulated tanks to liquefy, which increases cost and complexity. Therefore, methane is typically transported on a large scale through pipelines rather than in liquid form.

In terms of usage, LPG, which is primarily composed of propane and butane, has a higher energy content than methane and can be used as a heating and cooking fuel in homes and industries. Methane, on the other hand, is more commonly used as fuel for power plants, urban heating systems, and as a raw material in the petrochemical industry.

Overall, while both gases have their unique characteristics, LPG, due to its ease of transport and wider range of applications, is a more suitable option for household use and areas without pipeline networks, while methane is more frequently supplied to industrial areas through infrastructure networks.