CNG

Compressed natural gas is natural gas (primarily methane) squeezed to between 200 and 248 bar absolute pressure, stored in a gaseous state rather than liquefied. In mining and extraction operations, CNG serves as fuel for mobile equipment: haul trucks, loaders, drilling rigs, and support vehicles working in remote or underground sites where liquid fuel supply chains are impractical. The gas is stored onsite in high-pressure cylinders or in cascade systems that feed engine burners directly.

The pressure requirement distinguishes CNG from pipeline gas (which flows at much lower pressure) and from LNG, liquefied natural gas, which requires cryogenic cooling to around minus 161 degrees Celsius. CNG cylinders for mining vehicles are typically fabricated from seamless steel and undergo regular hydrostatic testing. A fully charged cylinder stores roughly 200 cubic meters of gas at standard temperature and pressure in a volume small enough to fit under a truck bed or alongside an engine compartment.

Mining sites, particularly in remote regions or underground operations, often lack reliable diesel supply infrastructure. CNG avoids the logistical cost of frequent fuel trucking and reduces fuel theft risk on isolated projects. Underground mining benefits from CNG engines because they produce lower carbon monoxide and soot than diesel equivalents, improving air quality in enclosed working environments. The fuel also burns more cleanly, reducing maintenance of particulate filters on equipment.

Drawbacks exist: CNG engines deliver less power per unit volume than diesel, requiring larger displacement or turbocharging to match performance. Range between refueling is shorter, typically 200 to 400 kilometers depending on load and terrain. Cold-climate performance degrades because gas density drops in freezing conditions. Onsite refueling infrastructure (compressors and storage) demands capital investment and qualified technicians to manage pressure systems safely.

CNG cylinders require certification, periodic inspection, and replacement at defined service intervals, typically 15 to 20 years depending on material and usage. Leakage from fittings or seals is a safety and emissions concern. Mining operators using CNG fleets must train personnel on pressure-system protocols and maintain compliance with transportation and storage regulations that vary by jurisdiction. The economics favor long-term operations at established sites rather than short-term or highly mobile projects.