The depletion of conventional fuel reserves, ambient conditions along with increased global warming and emission standards have emerged the research interests in utilisation of advanced combustion concepts on existing engines. This also made concern over the capability of using alternate energy sources along with conventional fuels. This research work indicates the results of analysis conducted to investigate the performance, exhaust emission and combustion characteristics of a VCR diesel engine fuelled with non-edible biodiesel at a rated speed of 1500 rpm with 300 bar injection pressure at three compression ratios. The test fuel was derived from Prosopis Juliflora seed oil methyl ester blends15% (B15) and 25% (B25) by volume. Biodiesel was produced by the transesterification process using methanol along with KOH as catalyst. The combustion characteristics investigated were rise in cylinder pressures, net heat release rate, cumulative heat release rate and mass fraction of fuel burned. The lower heat release rates, increased cylinder pressures were observed for both the blends compared to diesel. Increased brake thermal efficiency observed at higher compression ratio for B25 blend. It has also been observed that the emissions were decrease in trend with increase in compression ratios. © 2020 Institut za Arhitekturu i Urbanizam Srbije.