Internal combustion engines are extensively used in every field of life in today's world. Diesel engines being more efficient are preferred in the industrial and transportation sector in comparison to spark ignition engines for their higher efficiency, versatility and ruggedness. The major emissions of diesel engines are oxides of nitrogen (NOx), particulate matter (PM), carbon dioxide (CO2), carbon monoxide (CO). Among these emissions, oxides of nitrogen (NOx) and the particulate matter are the reasons of serious concern. For reduction of oxides of nitrogen (NOx) and particulate matter simultaneously, the use of Homogeneous Charge Compression Ignition (HCCI) have provided a sustainable solution in the present scenario. Further, the use of CNG in HCCI engine along with pilot diesel injection; the emissions have been decreased drastically. Homogeneous mixing of fuel and air leads to cleaner combustion and lower emissions. As peak temperatures are significantly lower than in typical CI engines, NOx levels are supposed to reduce significantly. The premixed lean mixture reduces soot particles. Natural Gas for Vehicles (NGV) is composed of methane gas and, unlike gasoline, does not contain lead because of its high octane rating (120-130), reducing exhaust gas emissions by 80%. The exhaust gases expelled by using natural gas as a fuel being less corrosive than those in case of diesel being used as a fuel increase the durability of the exhaust system. A methodology using a small pilot quantity of diesel fuel injected during the compression stroke to improve the power density and operation control is carried out for an HCCI engine based on a stationary, constant RPM, air cooled diesel engine. Significant technological improvements are still required to make HCCI engines competitive in the stationary power generation market.