Protesters will challenge councillors when they visit the site planned for Gloucestershire's incinerator at Haresfield.
Gloucestershire County Council's planning committee will visit the Javelin Park site on March 14 to look at where the £500 million energy-from-waste plant would be built if they give it permission.
But campaign groups will descend on the area at 9.30am to let their views be known to decision makers.
The protest has been organised by campaign group GlosVain, which has an anti-incinerator campaign for several months.
But a decision will be made by Gloucestershire county councillors on March 21 at a public meeting at 10am at Kingsholm Stadium.