The main aim of this experimental work is to reduce engine-out carbon dioxide (CO2) emission of CI engine fuelled with Karanja oil methyl ester (K100). K100 emitted higher NO and CO2 and lower smoke in comparison to diesel as a result of high fuel borne carbon and oxygen. Various techniques namely 1. Low-carbon biofuel blending 2. Post-combustion carbon capture system (PCCCS) 3. Oxygenate blending 4. Pre-combustion treatment system was adopted to reduce CO2 emission. Equal volume blending of low-carbon biofuels namely eucalyptus oil (EU), camphor oil (CMO), pine oil (PO) and Orange oil (ORG) with K100 reduces CO2 emission. K50-O50 blend emitted minimum CO2, about 27% less in comparison to K100. PCCCS with zeolite, activated carbon and liquid mono ethanolamine (MEA) injection with K50-O50 reduced CO2 emission further. CO2 emission for K50-O50+zeolite is 13.5% less in comparison to K50-O50 at maximum load. CO2 is further reduced with oxygenate blending. Oxygenates namely methanol (M), ethanol (E), n-butanol (B), n-pentanol (P) and acetone (A) were blended 20% by volume (based on the knock limit) with K50-O50 and tested along with zeolite based PCCCS. Among the oxygenates, methanol blending with K50-O50 with ZPCCCS lessened CO2 emission by 65% in comparison to K100. Magnetic fuel reforming system based pre-combustion treatment system reduced CO2 emission further. The combination of all the techniques emitted 68.5% less CO2 in comparison to K100 at maximum load. The effect of the techniques on other emission and performance parameters were also discussed in detail.