Two highway sweepers have also been refurbished to run on hydro-treated vegetable oil.
The council said the reduced emissions would support its target to become carbon neutral by 2030. In June, Horsham council declared a climate and ecological emergency.
Cllr Jay Mercer, cabinet member for environmental health, recycling and waste, said: ‘Not only will they improve air quality, but they will also deliver a reduction in noise pollution which is especially important for residents in the town centre as they operate in the early hours of the morning.
‘It is another key step for us in achieving our vision for a greener, cleaner environment for the district.’