Pulp and paper mill sludge (PPMS) is an organic residual generated from the wastewater treatments. PPMS management involves economic, environmental and social costs that will likely increase in the future as landfilling tends to be reduced or banned in certain jurisdictions. The reduction or the banning of landfilling may be considered as a climate change mitigation measure since organic waste disposal is normally associated with greenhouse gas (GHG) emissions. This critical review aims to (1) describe the variety of the current and emerging PPMS management practices that are alternatives to landfilling and (2) underline the crucial need for GHG emission assessments. The management practices of the three main PPMS types (primary, secondary and de-inking) comprised in this review are land application (agriculture, silviculture, land reclamation and composting), energy recovery (combustion, anaerobic digestion, pyrolysis, bioethanol, hydrogen production and direct liquefaction) and integration in materials (biocomposite, cement, asphalt and adsorbent-absorbent). Future research should focus to increase the comprehension of known GHG determinants from the PPMS management practices and reveal unknown factors. Life cycle analyses, based on direct GHG emission measurements, are needed to determine GHG emissions from current and emerging practices and plan a responsible future reduction or banning of landfilling. Such analyses will contribute to assist decision makers in implementing the best PPMS management practices with the least impact on climate change.

No abstract

No abstract

No abstract

Question Recent studies revealed by indirect evidence that lichen–spruce woodlands in the closed‐crown boreal forest are an alternative stable state of black spruce–feathermoss stands. This paper aims to demonstrate and quantify black spruce forest cover regression following successive wildfire events in the closed‐crown forest zone during the 20th century. A case study in north‐eastern North American closed‐crown forest zone is presented. Location The study area is at the centre of the closed‐crown boreal forest zone of eastern Canada (49°59′ N, 71°59′ W). Methods A burned area of 25 ha was selected in which three tree cohorts were visible. The first cohort contains partly buried trunks and stumps of a stand destroyed by a forest fire in 1920, the second contains standing dead trees from a 1995 forest fire and the third contains seedlings established after the 1995 fire. Fires were dated by scar analyses of living trees at the edge of the site. An array of sample plots was established in autumn 1997 to evaluate each cohort in terms of stocking and tree density. Results Black spruce stocking decreased significantly between cohorts, from 43.5% in Cohort 1 (all coniferous trees) to 25.6% in Cohort 2 and 11.5% in Cohort 3 (2011). Jack pine showed an inverse tendency, from 0% in Cohort 1 (not determined) to 0% in Cohort 2 and 3.8% in Cohort 3. Black spruce stems per hectare also dropped significantly from a minimum of 1322 in Cohort 1 to 1088 in Cohort 2 and 976 in Cohort 3. Conclusions This study is the first quantitative demonstration that lichen–spruce woodlands in the closed‐crown boreal forest zone are an alternative stable state of black spruce–feathermoss stands. Stocking levels and densities markedly declined after each of the two fires (1920 and 1995) that both occurred after spruce budworm outbreaks (1910 and 1980) and are most likely responsible for the shift from a closed‐crown to an open woodland.