The project will generate electricity for homes and businesses as well as bringing permanent local jobs to Sefton, Liverpool and the wider Merseyside area, RES said.
The project will be between 100MW and 150MW in size, depending on the outcome of the initial feasibility studies.
RES project manager Johanna Doyle said: “We have chosen the Alexandra Dock site as it allows us to bring about 80% of the biomass fuel to the site by ship. This will help to ensure that road deliveries to the site are minimised, while using the skills and expertise that exist within the Port and local area. This project will contribute to wider regeneration and bring secure jobs to the region.
“The North West has a highly skilled workforce that we can draw upon and we will be using local contractors and service providers where possible.”
RES claimed that the proposed biomass power plant would generate clean electricity for the equivalent of 170,000 to 250,000 homes every year and cut emissions of carbon dioxide by 300,000 to 450,000 tonnes a year.