Finding optimal recycling strategies of wood ash, composted sludge, paper biosolids and lime slurry for plantation forestry in Quebec

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Thousands of tons of ash from forest biomass combustion are being produced each year in Quebec by paper mills and cogeneration power stations. In the coming years, ash production is bound to rise with the increasing use of forest biomass as a fuel in response to concerns over climate change, swelling oil prices, and energy security. Additionally, more than 700 wastewater treatment plants were built in Québec between the 1980s and 1990s following the adoption of a wastewater treatment law in 1978. Municipalities must manage the disposal of approximately one million tons of sewage sludge (municipal biosolids). The new Québec Government's law on the sustainable management of forested land, coming into effect in 2013, aims to intensify wood production on 15 to 20% of the forested land mass. On the other hand, Québec's environmental regulations for industrial and municipal waste disposal are becoming more stringent, resulting in large increases in disposal costs. These changes in legislation are creating a window of opportunities for forest industries and municipalities. Residual wastes such as ash, biosolids and composted municipal sludge are known sources of nutrients and organic matter and could be used as amendments for forest soils to increase forest productivity or to restore severely disturbed soils. Such practices could also give rise to carbon credits because they favor soil carbon sequestration. The proposal aims at strengthening Quebec's scientific expertise in the use of industrial and municipal wastes as forest soil amendments. The proposal regroups a number of independent trials that were or are currently being developed. They aim to assess the potential of wood ash, paper biosolids, lime slurry and N fertilizers in various combinations to correct nutrient imbalances and improve soil quality and growth of conifer and hybrid poplar plantations. A soil retoration study using fresh and composted municipal sludge is also conducted. The fate of trace metals and pathogens as a threat to the health of terrestrial and aquatic ecosystems (surface water quality) will also be a focus of this large project.