Pulp mill waste could find new use as fertilizer: study

Pulp mill waste destined for the landfill could instead be useful as an organic fertilizer to help reduce the environmental impact of using conventional fertilizers while improving soil and tree growth, University of Alberta research shows.

A two-year study conducted on a hybrid poplar tree plantation in northern Alberta showed that compared with using conventional fertilizers alone, adding biosolids – wood and other fibres left over from pulp and paper production – reduced harmful greenhouse gas emissions from the soil.

Conventional fertilizer, containing industrially produced urea, has been shown to stimulate nitrous oxide, a major contributor to global warming. Though pulp mill biosolids are generally rich in organic content and low in toxicity, it wasn’t known how they might also have an effect, says Scott Chang, the study’s lead author and a professor in the Faculty of Agricultural, Life & Environmental Sciences.

Combining biosolids and conventional fertilizer also improved soil fertility, the study showed.

The findings provide new insight into what effect biosolids could have if they were redirected for use on tree plantations that feed the forest industry.

The results of the study show the potential for developing a “win-win strategy” in managing pulp mill waste, he notes.

“Repurposing biosolids as an organic fertilizer, which may help reduce greenhouse gas emissions, could improve the sustainability of the pulp and paper industry.”

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