Alberta pulp mill proposes biomass plant

By Lisa Gibson | August 22, 2011

Millar Western Forest Products Ltd., a market pulp mill in Whitecourt, Alberta, Canada, hopes to build a 5.2-megawatt biomass power plant that would use its mill wastewater. The mill produces pulp that is sold to paper mills.

The $35 million ($35.6 million) Bioenergy Effluent Project would use an anaerobic hybrid digester (AHD), according to Louise Riopel, Millar Western communications manager. The process differs from traditional AD in that it has a two-zone system, according to the company. It includes an upflow sludge blanket, where effluent will be mixed with micro-organisms to remove organic pollutants, and an upflow filter, where largely soluble organics and biological solids will be retained. The hybrid process offers a number of benefits, Riopel said, including increased wastewater contaminant removal because of the longer solids retention time; reduced waste sludge production; enhanced adaptability to influent variation arising from pulp grade differences; and the ability to use any type of anaerobic sludge for initial seeding and propagation.

Where traditional anaerobic digesters use a granular sludge bed requiring maintenance via internal circulation reactor, AHD can use other sludges, including flocculants, for seeding and propagation. Furthermore, maintenance of an inventory of sludge seed stock is not required, because biomass wash-out does not occur in the hybrid digester.

The pulp mill currently has an aerobic system to treat the effluent and the project will add the anaerobic element to recover more organic material to fuel two reciprocating engines, Riopel said.

The project recently received $17.5 million from Alberta’s $155.9 million share of the Canada ecoTrust for Clean Air and Climate Change, which distributed $1.5 billion among all the provinces and territories to assist with clean air and climate change initiatives.

“We’re some ways away from moving ahead with the project, but this brings us closer to realizing it,” Riopel said. Millar Western is working on permitting the plant and anticipates a two-year construction period once proper approvals are in place.