Boosting the usefulness of hybrid aspen:from tailored biomass to a versatile feedstock for use in the chemical industry

Abstract The hybrid aspen tree (Populus tremula L. × P. tremuloides Michx.) is a fast-growing tree species with the potential to produce biomass in an enhanced manner for industrial needs. Research has shown that by breeding hybrid aspen clones, tree properties (e.g., growth ability, resistance to disease, energy density and cellulosic pulp properties) can be influenced. However, there is a gap in the research on how clonal breeding affects the chemical composition of bark and whether this information can be used in the production of added value according to the cascading use principle. In this dissertation, chemical determinations were used to calculate variations in the chemical composition of the barks of different clonal trees and to evaluate the possibilities of clonal selection to produce added value to the bark. The results were also used to select the highest potential bark biomass for cascade use studies. Cascade use was investigated by linking the methods of extraction of bark and the torrefaction of extraction residue. The added value of the extract was evaluated experimentally by producing rigid foam and activated carbon. Applicability of pyroligneous acid was tested in herbicidal and fungicidal applications. This current study produced three key results: 1) clonal variation in the chemical composition of bark indicated that bark quality varies between clone types, and this has an impact on the added-value potential of bark-derived raw material, 2) by using hot water extraction, it is possible to separate an extract suitable as a precursor for producing rigid foam and activated carbon, and 3) hemicellulose of hybrid aspen bark can be converted into herbicidal and fungicidal active pyroligneous acid by torrefaction. In summary, clone selection can affect the bark quality of hybrid aspen in a situation in which bark pulp is collected from trees grown in certain growth areas. This information has value when the goal is to produce added value for hybrid aspen in the chemical industry via the cascading use of bark.Tiivistelmä Hybridihaapa (Populus tremula L. × P. tremuloides Michx.) on nopeasti kasvava puulaji, josta on mahdollista muodostaa tehostetusti biomassaa teollisuuden raaka-aineeksi. Hybridihaapakloonien jalostuksella tiedetään olevan vaikutusta puun ominaisuuksiin, kuten kasvukykyyn, taudinkestävyyteen, energiatiheyteen ja selluloosamassan latuun. Ei ole kuitenkaan tutkittu sitä, miten kloonijalostus vaikuttaa puun kuoren kemialliseen koostumukseen, ja voidaanko koostumuksellisia kloonivariaatioita hyödyntää kuoren käyttöarvon parannuksessa noudattaessa biojalostuksen kaskadikäyttöperiaatteita. Tässä väitöskirjassa määritetään erilaisten kloonipuiden kuorien koostumuksellisia vaihteluja ja arvioidaan kloonityyppien valinnan tuomia mahdollisuuksia tuottaa kuorelle uutta käyttöarvoa. Kloonivaihtelujen perusteella valitaan kiinnostavin kuorimassa biojalostustutkimuksiin, jonka jälkeen kuoren hyödyntämistä tarkastellaan ketjuttamalla kuoriuutteiden erotusmenetelmät sekä kuoren uuttojäännöksen termokemiallinen konversio, torrefiointi. Kuoriuutteen käyttöarvoa selvitetään valmistamalla uutteista hiilivaahtoa ja aktiivihiiltä, sekä tutkimalla torrefikaatiolla tuotettavan konversiotisleen käyttöä rikkakasvien ja sienitautien torjunta-ainekemikaalina. Tutkimuksen keskeisimmät tulokset ovat: 1) kuoren koostumuksellinen laatu vaihtelee kloonityypeittäin, ja tällä arvioidaan olevan merkitystä arvopotentiaaliin, 2) kuoriuute soveltuu hiilivaahdon ja aktiivihiilen valmistukseen, ja 3) kuoren uuttojäännöksen konversiotisleellä on herbisidi- ja fungisidiaktiivisuutta. Yhteenvetona todetaan, että kloonivalinnalla voidaan vaikuttaa hybridihaapapuun kuoren koostumukselliseen laatuun tilanteessa, jossa kuorimassa kerätään tietyllä kasvualueella kasvaneista kloonipuista. Tuloksilla nähdään olevan arvoa, kun tavoitteena on tuottaa kuoribiomassalle lisäarvoa kemianteollisuuden käyttöön ketjuttamalla menetelmiä kaskadikäyttöperiaatteen mukaisesti

Applicability of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) bark extract as a precursor of rigid carbon foam and activated carbon

Abstract Hybrid aspens have long attracted scientific interest, but the research on their use as feedstocks for chemical applications are still very limited. The bark biomass of the poplar species contains many valuable extractives that can be utilized as value-added products. This paper examines the applicability of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) bark extract as a precursor of rigid carbon foam and activated carbon. To explore this, the study considers 1) the basic chemical composition of the bark in terms of added value potential, 2) the basic chemical composition of the bark extract and the effect of its pretreatment on the extract composition, 3) the production of rigid carbon foam, and 4) the chemical activation of carbon foam with different impregnating agents. The study determines that the bark extract of the hybrid aspen can be used as a precursor for rigid carbon foam and further processed into an activated carbon product. Therefore, the bark extract of Populus tremula L. × P. tremuloides Michx. can be assessed as a potential value-added product that increases the use value of the hybrid aspen biomass

Clonal variation in the bark chemical properties of hybrid aspen:potential for added value chemicals

Abstract This study aims to promote comprehensive utilization of woody biomass by providing a knowledgebase on the utility of aspen bark as a new alternative source for fossil-based chemicals. The research focused on the analysis of clonal variation in: (1) major chemical components, i.e., hemicelluloses, cellulose, and lignin; (2) extraneous materials, i.e., bark extractives, and suberic acid; (3) condensed tannins content and composition; and (4) screening differences in antioxidative properties and total phenolic content of hot water extracts and ethanol-water extracts of hybrid aspen bark. Results of this study, the discovery of clonal variation in utilizable chemicals, pave the way for further research on added-value potential of under-utilized hybrid aspen and its bark. Clonal variation was found in notable part of chemicals with potential for utilization. Based on the results, an appropriate bark raw material can be selected for tailored processing, thus improving the resource efficiency. The results also indicate that by applying cascade processing concepts, bark chemical substances could be more efficiently utilized with more environmentally friendly methods

Pyroligneous acids of differently pretreated hybrid aspen biomass:herbicide and fungicide performance

Abstract The pyroligneous acids (PAs) of woody biomass produced by torrefaction have pesticidal properties. Thus, PAs are potential alternatives to synthetic plant protection chemicals. Although woody biomass is a renewable feedstock, its use must be efficient. The efficiency of biomass utilization can be improved by applying a cascading use principle. This study is novel because we evaluate for the first time the pesticidal potential of PAs derived from the bark of hybrid aspen (Populus tremula L. × Populus tremuloides Michx.) and examine simultaneously how the production of the PAs can be interlinked with the cascade processing of hybrid aspen biomass. Hybrid aspen bark contains valuable extractives that can be separated before the hemicellulose is thermochemically converted into plant protection chemicals. We developed a cascade processing scheme, where these extractives were first extracted from the bark with hot water (HWE) or with hot water and alkaline alcohol (HWE+AAE) prior to their conversion into PAs by torrefaction. The herbicidal performance of PAs was tested using Brassica rapa as the test species, and the fungicidal performance was proven using Fusarium culmorum. The pesticidal activities were compared to those of the PAs of debarked wood and of commercial pesticides. According to the results, extractives can be separated from the bark without overtly diminishing the weed and fungal growth inhibitor performance of the produced PAs. The HWE of the bark before its conversion into PAs appeared to have an enhancing effect on the herbicidal activity. In contrast, HWE+AAE lowered the growth inhibition performance of PAs against both the weeds and fungi. This study shows that hybrid aspen is a viable feedstock for the production of herbicidal and fungicidal active chemicals, and it is possible to utilize biomass according to the cascading use principle