Liberty Energy is committed to operating its energy facilities in a safe and environmentally sensitive manner. The Liberty Energy Centre will use modern technologies to ensure that air, water and noise releases will be kept well below provincial regulatory limits.
Biosolids in Ontario, which are recovered from sewage treatment and are commonly referred to as sewage sludge, are currently trucked to landfills or spread on farm land when land is available and weather is suitable. Some biosolids are further processed through heat drying and pelletization, producing a biosolids pellet that can be used as fuel or spread on farm land. Alternatively, biosolids can be mixed with an alkaline re-agent like cement kiln dust creating a material that can be used for fuel or spread on farm land.
The Liberty Energy Centre will use the latest generation of bubbling fluidized bed gasification technology to use biosolids as produced at wastewater treatment plants without additional processing or treatment. A syn gas is produced from biosolids that is burned in a boiler to produce heat, which in turn produces electrical energy with steam. Best Available Control Technology will be used to ensure that emissions are kept to a minimum. The heat of combustion will drive a condensing steam turbine coupled with a generator to produce electrical power for delivery to the grid.
Fluidized bed technology is a proven, reliable technology for the thermal reduction of biosolids and is well established in Ontario. The Lakeview wastewater treatment plant in Peel Region has relied on fluidized bed technology for thermal reduction of biosolids for 30 years and its four new fluidized bed units comprise the largest installed biosolids thermal reduction capacity in the world. The Duffin Creek wastewater treatment plant in Durham Region has operated two older fluidized bed units for many years and is currently installing two new fluidized bed units. The City of London relies on an older fluidized bed unit for thermal reduction, where waste newsprint is co-fired in order to reduce natural gas consumption. However, none of these successful facilities employ energy recovery and the renewable energy generation capability to the extent achieved by Liberty Energy Centre.
Thermal reduction is a sustainable biosolids management strategy which provides significant energy recovery. The Liberty facility features two state-of-the-art bubbling fluidized bed reactors that provide enhanced reliability and advanced emission control technologies with emissions far below required standards. Liberty Energy reduces the greenhouse gas footprint of biosolids management through the generation of renewable energy and by using fly ash, a byproduct, as a direct replacement for Portland cement in concrete production. LEC will co-fire some biomass along with the biosolids to ensure stable operation during variations of biosolids moisture or energy contents. This will eliminate the need for any fossil based auxiliary fuels, although a minimum amount of natural gas will be consumed for a few hours when a fluidized bed unit is first started or shut down.
The facility will include a fully enclosed fuel hall for biosolids and biomass and two identical power trains, each capable of continuously producing 4.5 MW (net) of electricity. The fuel hall will include two fully enclosed bays for reception of biosolids trucks and four fully sealed biosolids storage silos. Liberty Energy's biosolids thermal reduction service capacity will be 1,009 wet tonnes per day or 368,000 tonnes per year.
Liberty Energy's close-coupled gasification system will accommodate varying types of biosolids with differing heating values by co-firing with biomass. Co-firing is employed in order to maintain thermal process stability and avoid the cost and carbon footprint of supplemental fuel needed to sustain a thermal reduction process that is capable of firing well digested biosolids. The Liberty Energy Centre also accepts unstabilized biosolids for thermal reduction as well, potentially eliminating or reducing the need for digestion.
