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Doctoral thesis, 2013

Cost-effective cultivation of lodgepole pine for biorefinery applications

Backlund, Ingegerd

Abstract

The overall objective was to evaluate the scope for the cost-effective cultivation of lodgepole pine (Pinus contorta, PC) stands in a way that would enable early biomass harvesting to supply raw material for biorefineries. Commercial direct seeded PC stands were shown to produce 200 m3/ha of stemwood or 100 tons of d.w. biomass within 30 years despite one or two pre-commercial thinnings. Higher stand stem densities (≥3000 st/ha) yielded even more biomass (ca. 300 m3/ha) with only slight reductions in DBH (Study I). The effects of different silvicultural regimes on 20-year-old direct seeded PC stands were analyzed in a field experiment. A high biomass regime (no PCT) produced 144% more biomass and 134% more stem volume than the conventional regime (2200 st/ha). The diameter of the 1000 largest trees/ha did not differ between regimes. A regime with 4500 st/ha gave promising results in terms of both biomass and timber production. Importantly, producing large amounts of biomass early in the rotation period is compatible with a subsequent change of focus to emphasize pulp and timber production (II). To investigate the potential for using PC biomass in biorefineries to produce e.g. liquid biofuels, the chemical contents of wood samples from Scots- and lodgepole pine trials were compared. Heartwood had up to five times greater extractive contents than sapwood. 21 fatty and 10 resin acids were detected. It was estimated that ca. 150 kg of fatty acids and 1 ton resins/ha could be harvested from a mature boreal PC stand (III). The chemical compounds in the aboveground fractions of PC trees grown under a direct seeding-based regime were identified. The bark provided the highest extractive yields (16%) and the stemwood the lowest (1%). The extractive profiles of the needles differed strongly from the other fractions, being particularly rich in wax esters and fatty alcohols. It should be possible to harvest 2-3 tons of crude extractives/ha from a dense 30-year-old PC stand (IV). To estimate the commercial potential of different biorefinery products, a survey was performed. 95% of the respondents believed that the value of tree biomass will increase over the next ten years, mainly due to the replacement of oil-based products. Key product categories were: transportation fuels, special celluloses, materials and plastics, solid fuels and specialty chemicals. A strong correlation between the prices of electricity and wood fuel was identified, and electricity prices may play a key role in determining the future use of biomass (V). Overall, there is considerable but currently unrealized potential for the cost-effective cultivation of lodgepole pine in directly seeded dense stands using short rotation periods to produce substantial quantities of biomass for biorefineries within only a few decades.

Keywords

biomass production; goal-oriented forestry; biobased products; Fennoscandia; chemical extraction; direct seeding; short rotation

Published in

Acta Universitatis Agriculturae Sueciae
2013, number: 2013:81
ISBN: 978-91-576-7900-0, eISBN: 978-91-576-7901-7
Publisher: Institutionen för skogliga biomaterial och teknologi, Sveriges lantbruksuniversitet

Authors' information

Backlund, Ingegerd
Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology

UKÄ Subject classification

Renewable Bioenergy Research
Forest Science
Organic Chemistry

URI (permanent link to this page)

https://res.slu.se/id/publ/51918