Biosolids Use in Marginal Land Conversion and Willow Plantation Establishment

The City of Calgary was seeking opportunities to beneficially manage dewatered biosolids from the Shepard Lagoons to augment and add diversity to their successful Calgro agricultural biosolids fertilization program. SYLVIS proposed a Marginal Land Conversion and Willow Plantation Establishment Program which would facilitate the use of large volumes of biosolids, providing the City of Calgary with program contingency and diversity. SYLVIS worked with Alberta Environment and Parks to obtain regulatory authorization as the program falls outside the purview of the Alberta Sludge Guidelines.

Since the program’s commencement in 2013, the program has accepted over 35,000 dry tonnes of biosolids for marginal agricultural land improvement and established three, even-aged willow stands spanning over 300 hectares. The three willow stands were designed to facilitate an annual biosolids fertilization, harvest, and re-growth occurring concurrently on a three-year rotation. In 2020, the program was accepted into the Government of Canada’s Low Carbon Economy Challenge. This has enabled SYLVIS and the City to expand the willow plantation by a further 300 hectares.

Biosolids use in short-rotation coppice willow system sequesters carbon in several ways including soil organic carbon from fine root turnover, litter-layer organic carbon from leaf/litterfall, and from the harvested aboveground biomass. Over time this system will act as a significant sink for carbon as soil organic matter accumulates, improving the overall productivity of marginal agricultural soils when they are returned to agricultural crop production after a period of approximately 25 years.

This program has demonstrated that afforestation with willows on marginal lands coupled with, organic residuals as soil amendments provide significant below ground carbon sequestration as well as a long-term source of carbon-neutral fibre feedstock. This innovative program has provided the groundwork for future afforestation and restoration projects realizing the benefits to an integrated approach to residuals management.