Wiltshire Council says some weeks it is seeing more than 500 missed appointments at recycling centres.
The organisation is urging people to cancel in advance any bookings they no longer need to free up capacity for other people who need to recycle items.
In the week commencing 15 March, 557 appointments were missed as people booked slots online that they then did not attend.
Director of Highways and Environment Parvis Khansari said the booking system was introduced in July last year to keep staff and residents safe.
He added: "It allows us to manage the number of people on site at any one time, enabling effective social distancing and also reducing queuing and the subsequent traffic issues that can cause."
But more than seven per cent of the total available bookings have not been used - meaning some people have been unable to attend at a time the council says demand is increasing.
Mr Khansari said: “Sites are now open for summer hours and we’ve worked closely with our contractors to ensure we provide as much capacity as possible, while still complying with the current social distancing requirements.
“We’ve made it as easy as possible to cancel a booking using the online system, so I’d urge anyone with a booking that they no longer need to log back in and cancel it, so someone else can make use of the slot."