Natural Drying and Chemical Characteristics of Hybrid Poplar Firewood Produced from Agricultural Bioenergy Buffers in Southern Québec, Canada

Abstract

Implementing bioenergy buffers on farmland using fast-growing tree species could reduce firewood harvest pressure in woodlots and increase forest connectivity, while improving carbon sequestration, phytoremediation, stream habitats, soil stabilization and hydrological regulation. The objective of the study was to evaluate the natural drying and chemical characteristics of hybrid poplar firewood produced from bioenergy buffers, and to compare these characteristics with those of native species harvested in adjacent woodlots. In Trial A, 110 cm-long unsplit logs (a feedstock for biomass furnaces) were produced to evaluate the effect of log diameter class on firewood quality. In this trial, hybrid poplar firewood characteristics were also compared with Populus tremuloides, Acer rubrum and Fraxinus americana. In Trial B, the effect of hybrid poplar genotype and cover treatment was evaluated on the moisture content of short split logs (40 cm long). Firewood of satisfactory quality was produced on a yearly cycle for short split logs, and on a biannual cycle for long unsplit logs. Covering short split log cords with metal sheeting lowered the final moisture content (from 20.7% to 17.3%) and reduced its variability, while genotype did not significantly affect final moisture content. In Trial A, larger-diameter logs from hybrid poplar had lower element concentrations, but slightly higher moisture content after two years. A two-fold variation in N concentration was observed between diameter classes, suggesting that burning larger poplar logs would minimize atmospheric N pollution. Heating value, carbon and calcium concentrations increased following the seasoning of hybrid poplar firewood. After the first seasoning year outdoors, hybrid poplar had the highest moisture content (33.1%) compared to native species (24.1–29.5%). However, after the second seasoning year in an unheated warehouse, the opposite was observed (14.3% for hybrid poplar vs. 15.0–21.5% for native species). Heating value, carbon and nitrogen concentrations were similar between tree species, while high phosphorus and base cation concentrations characterized hybrid poplar, suggesting higher ash production. Poplar bioenergy buffers could provide a complementary source of firewood for heating in the fall and in the spring, when the heat demand is lower than during cold winter months.

Growth and Development of Short-Rotation Woody Crops for Rural and Urban Applications

“…Fortier et al [2] conducted a study in Canada on the use of hybrid poplars in forest buffers to reduce firewood harvest pressure in woodlots while improving ecosystem services related to soils, water, and carbon. They evaluated the natural drying and chemical characteristics of hybrid poplar firewood produced from bioenergy buffers and then compared those results to Populus tremuloides Michx., Acer rubrum L., and Fraxinus americana L. from adjacent woodlots.…”

“…There are a total of 20 papers in the Special Issue representing 13 countries and four genera (Phalaris L., Populus L., Robinia L., Salix L.) (Figure 1; Table 1). In addition to the development and management of a Salix cultivar database [1], rural and urban applications represented in the Special Issue include: (a) forest buffers [2], (b) forest health screening [3,4], (c) phytoremediation [5][6][7], (d) short rotation coppice [8][9][10][11][12][13][14][15], (e) volume production [16][17][18], and (f) wastewater reuse [19,20] (Table 1). There were >130 genotypes from 27 genomic groups tested across all studies (Table 2), representing the importance of phyto-recurrent selection and other methods to choose clones for local and regional biomass production systems whose methodologies and approaches are relevant worldwide.…”