Even if it is running on bio-diesel, it causes similar amounts of pollution as normal diesel locos. Not much difference on that front. Also all bio-diesel locos in IR run on a mixture of diesel land bio diesel, usually 95% or 80% diesel and 5% or 20% Bio diesel. Pollution levels are not really different. Use of bio-diesel is mainly to reduce diesel ( non-renewable resource) consumption.
Most probably this loco is due for maintenance soon.