The submission by CPCB came in the wake of the green panel's direction to set standards in this regard and ensure that the railway locomotive engines don't cause pollution.
The lawyer appearing for the MoEF, however, told a bench headed by NGT Chairperson Justice Swatanter Kumar that he would seek instructions on the issue and inform the tribunal on the next date of hearing.
The CPCB's interim report titled "Exhaust Emission Benchmarks for Diesel Locomotives on Indian Railways" aims to fix standards and protocols for the sector to achieve the targets submitted by India under the Paris climate change agreement.
The Railways contributed 9.7 per cent of this figure (24.7 million tonne). Globally, however, only 3.5 per cent of the emissions from the transport sector are attributed to the rail sector, CPCB's report said.
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"The changes in the energy sources allowed for a reduction of the share of rail transport CO2 emissions from 24 per cent in 1990 to less than 10 per cent in 2013, while rail activity doubled in the same period," the draft report by CPCB said.
However, when the matter came up for hearing, the Environment Ministry sought more time saying, "the standards are yet to be fixed and one year time is required for completion".
The Railways had earlier submitted international standards for emissions from diesel locomotive railway engines and filed a data sheet indicating the emissions from 30 railway engines.
According to the data sheet, the emission levels in the tested 30 railway engines were much above international standards.