At our Slave Lake Pulp mill in Alberta, we make energy from the by-products of our pulping process, namely the pulp mill effluent (wastewater) that many people think of as a waste product.
After we have refined wood chips and recovered the pulp, what is left over from our process is wastewater. It’s a mix of water, organic matter and other substances left over from the pulping process. This material is typically treated in large ponds to settle solids suspended in the water. At our Slave Lake mill, we have introduced a new technology to make biogas from it before we treat and return the water to the environment.
So, what is biogas, and how do we produce it?
We pump our wastewater from the mill into Slave Lake Pulp’s industrial pond, which is about three football fields in size. This is where the waste-to-energy action happens: tiny organisms in the pond digest the solids suspended in the wastewater (a process called biomethanation). They produce methane biogas by breaking down the organic matter in the pulp mill’s wastewater into gas.
As the organisms generate biogas, a membrane covering our pond collects it. We then clean it and use it to power three large reciprocating engine generator sets (gensets). The gensets can produce up to 6 megawatts of electricity using biogas – that’s roughly the same amount of power consumed by 4,300 homes for a year!
Slave Lake Pulp’s waste-to-energy plant reduces greenhouse gas emissions by approximately 37,000 tonnes annually by reducing our use of coal-generated electricity. BCTMP mills are high consumers of electrical energy as a result of the refining process used to generate BCTMP pulp. By producing some of our energy needs from mill waste, we are reducing the use of fossil fuel-based energy sources.
Read more about how Slave Lake Pulp makes energy from wastewater here.