The fleet has been overhauled in the past four years since the arrival of national fleet manager Larry Bannon and his team.
A total of 12 of the 15 centres around England and Wales will have bunkered biodiesel by the end of the year.
He said the decision to move from standard diesel was part of a strategy to improve the organisation’s environmental credentials.
He said: ‘We looked at LPG and it wasn’t a viable proposition, so we looked at ways of improving our environmental policy with diesel. One of the areas looked at was particulate traps, but because of the timing of our lease vehicles we felt it was cost prohibitive. That left biodiesel as our only option.’
The viability of biodiesel in each location depends on the availability.
Bannon said: ‘It will depend on the supplying contractors to make it cost effective – whether they have to transport the fuel longer distances.
‘In the areas where there’s no cost-effective supply we’ll be sticking with sulphur-free diesel, but where we can get biodiesel we’ll convert to it.
‘As a public sector organisation we need to be seen to be leading the way by example and trying to reduce emissions.’