The Edge

Lignin can improve phosphorus and nitrogen recovery from wastewater

By Tony Kryzanowski

Phosphorus, a fertilizer essential for plant growth, is a depleting, finite, natural resource derived from relatively few mines in the world. It’s estimated that 16 per cent of all mined phosphorus ends up in wastewater treatment plants.

Even though wastewater is treated to reduce the amount of nitrogen and phosphorus it contains, most of these nutrients end up being dispersed in the environment and not recovered.

Release of these nutrients into water bodies—whether from municipal wastewater or surface runoff of fertilizer and animal manure in farming operations—stimulates extensive plant growth such as blue-green algae, which may produce animal toxins and lead to fish death.

So, finding economical ways to recover more of these nutrients from wastewater will help ensure a sustainable supply of fertilizer for food production and reduce their negative impact on water resources.

Alberta Innovates (AI) is investing in research at the University of Alberta under the direction of Dr. Yang Liu, a professor in the Environmental Engineering Department who holds the NSERC Industrial Research Chair in Sustainable Urban Water Development and the Canada Research Chair in Future Community Water Services. Liu’s team has proven that adding small amounts of wood-derived lignin as part of the wastewater treatment process significantly improves the recovery of both phosphorus and nitrogen in a form known as struvite.

Researchers have shown that by adding only 0.1 gram of lignin per litre of wastewater as part of the treatment process, it is possible to achieve phosphorus recovery in the range of 98 per cent at a lower cost compared to less than 80 per cent recovery using conventional systems. In addition to its ability to improve recovery of fertilizers from wastewater, lignin is also a valuable soil amendment.

Lignin is a bioproduct and a byproduct of wood pulp manufacturing. The lignin used in this research project was sourced from the lignin recovery plant attached to West Fraser’s pulp mill in Hinton, Alberta, which has also received AI funding.

Having proven their concept, U of A researchers are now devising a process for lignin additive and nutrient recovery, which they hope to have developed within two years.

The researchers are also starting to evaluate how wood-derived cellulose nanocrystals (CNC) might assist in nutrient recovery from wastewater. The CNC is manufactured at a pilot plant located at InnoTech Alberta, an applied research subsidiary of Alberta Innovates.

In total, AI has provided $350,000 through its Alberta Bio Future research and innovation funding program toward these nutrient recovery research projects involving lignin and CNC.

“Dr. Liu’s research translates into real environmental solutions for local businesses and municipalities. The City of Devon is considering resource-recovery municipal wastewater alternatives, and the City of St. Albert and Sturgeon County are developing a community water service resource recovery demonstration site,” says Patrick Guidera, Director of Forest Technology at Alberta Innovates.

“Her work also provides a link to the forest sector and adds value to lignin, a previously undervalued waste stream in forestry.”

The current method for recovering nutrients from wastewater is a precipitation process that results in a fertilizer called struvite.

“It is very expensive to operate this type of process to adjust the pH so that it is high enough for the struvite to precipitate out,” says Liu.

The U of A researchers found that lignin aids in struvite crystal formation. And because lignin is already high in pH, it eliminates the need to adjust the pH of wastewater. Lignin, a natural compound in trees, is safe to use and there is also an unlimited supply as a renewable resource.

Liu says the economics of the recovery process still need to be studied in more detail, and the cost of lignin and phosphorus must be considered as part of the discussion. At present, the best economic scenario could be the use of lignin-derived struvite as a fertilizer in crop production close to where it is manufactured, perhaps by a municipal wastewater treatment plant, to save on transportation costs.

For more inforrmation about these nutrient recovery research projects involving lignin and CNC, contact Yang Liu at [email protected] and for more information about the Alberta Bio Future program, contact Julia Necheff at [email protected]

CWFC‘s Technical Development Group evaluates on-site wood processors for biomass recovery and chip production

By Tony Kryzanowski

The Canadian Wood Fibre Centre (CWFC) recently tested a variety of on-site and portable wood processors that could be used to produce custom pre-processed biomass feedstock captured from a variety of sources for use by communities—particularly in remote locations—and industry to generate both heat and power.

The South African-built Junkkari is a disc chipper. It has a 25 to 75 hp requirement and is powered by a tractor's PTO. This was the first time that this technology was demonstrated and evaluated in Canada.

This study is part of CWFC’s mandate to develop/evaluate effective biomass feedstock production systems, and was conducted in partnership with FPInnovations, CANMET, Alberta Innovates, and Drayton Valley, Alberta’s Biomass Innovation Inc.

Testing was conducted in two locations.

The North American-built Peterson 5900 whole tree chipper was tested in Nova Scotia, with chips blown directly into a walking floor trailer and delivered to the end user.

The first was at CWFC’s Ellerslie Short Rotation Woody Crop Technical Development site in Edmonton as part of its ongoing end-of-lifecycle research program.

Small diameter mixed woods located on private woodlots were also processed and evaluated in Nova Scotia using a large-scale system.

The Italian-built Pezzolato was equipped with a 2" screen. Chips were blown into a nearby chip wagon and then evaluated by CWFC to determine the unit's overall performance. This PTO-powered processor works at approximately 145 hp.

Three wood processors were evaluated, representing a range of technology with varying degrees of chip size production control and volume throughput. This provides potential adopters with a selection of production scale and practical options, so they can select one that is a good fit for their particular needs.

The three wood processors evaluated were the Pezzolato PHT700 drum chipper, the Junkkari HJ250 GT disc chipper and the Peterson 5900 disc chipper. They demonstrated the ability to produce wood chips ranging anywhere from 3 to 40 mm in size.