| Abstract | Invazivne biljne vrste sve su vidljivija prijetnja kako sa zdravstvenog tako i s ekološkog i ekonomskog aspekta. Ove vrste karakterizira laka prilagodljivost širokom arealu ekoloških čimbenika životnih staništa, izraženo zaraštavanje čime postaju dominantne nad nativnim vrstama, kao i specifičan sastav fitokemikalija. Svime navedenim, invazivne biljne vrste izgledna su prijetnja bioraznolikosti. U svijetu, pa tako i u Hrvatskoj sve veće površine kopnenih staništa, od šumskih do kultiviranih i ne kultiviranih površina pod pritiskom su invazivnih biljnih vrsta što dovodi do značajne destabilizacije ekosustava, a čime se postavlja potreba za uvođenjem mjera njihova suzbijanja i uklanjanja. No, s druge strane, s obzirom na karakteristiku invazivnosti, ove biljne vrste značajan su izvor biomase koja pokazuje potencijal daljnjeg korištenja. Naime, istraživanja dokazuju potencijal njihova korištenja kao obnovljivog izvora energije u procesima termo-kemijske oporabe i proizvodnje energije. Istovremeno, s obzirom na bogat sadržaj specifičnih fitonutrijenata, invazivne biljne vrste imaju i značajan potencijal u proizvodnji proizvoda dodane vrijednosti u npr. farmaceutskoj, kozmetičkoj, tekstilnoj industriji i dr. Svime navedenim, invazivne biljne vrste ukoliko se adekvatno koriste mogu biti prilika, a ne prijetnja biogospodarstvu i to kao vrijedan izvor zelene energije i fitonutrijenata.
Cilj ovog istraživanja bio je identificirati invazivne biljne vrste s područja Žumberačkog gorja, utvrditi energetski sastav i sadržaj fitonutrijenata vrsta te odrediti potencijalni način njihova korištenja. Istraživanje je uključivalo inventarizaciju flore prilikom čega su na 24 mikrolokacije ukupno determinirane 194 biljne vrste, a od kojih je prikupljeno i analizirano ukupno 12 iz kategorije invazivnih: tri drvenaste vrste (Ailanthus altissima, Rhus typhina i Robinia pseudoacacia) te devet zeljastih vrsta (Abutilon theophrasti, Amaranthus retroflexus, Ambrosia artemisiifolia, Datura stramonium, Erigeron annuus, Galinsoga ciliata, Reynoutria spp., Solidago gigantea i Sorghum halepense). Prosječno viši sadržaj svih fitonutrijenata (askorbinske kiseline, polifenolnih i fotosintetskih spojeva) te antioksidacijskog kapaciteta utvrđen je kod drvenastih invazivnih vrsta u odnosu na zeljaste. Vrsta Rhus typhina tako se izdvaja s najvišim sadržajem askorbinske kiseline (159,69 mg/100 g sv.t.) i ukupnih polifenola (2263,53 mg GAE/100 g sv.t.) od svih ostalih istraživanih vrsta. Nadalje, sve istraživane invazivne vrste ističu se i visokim antioksidacijskim kapacitetom i to drvenaste s prosječnom vrijednosti od 2150,48 μmol TE/L, dok zeljaste prosječno s 2002,90 μmol TE/L. Valja naglasiti kako kemijski profil istraživanih invazivnih vrsta značajno varira, a neovisno o podjeli na drvenaste i zeljaste vrste, visok funkcionalni potencijal pokazuju slijedeće: Ailanthus altissima, Amaranthus retroflexus, Erigeron annuus, Rhus typhina i Robinia pseudoacacia. Iz energetskog aspekta, drvenaste invazivne vrste ističu se višom energetskom vrijednošću s obzirom na viši udio: suhe tvari, vlakana, od kojih najviše lignina, fiksiranog ugljika i više ogrjevne vrijednosti te niže količine makro i mikroelemenata te teških metala u odnosu na zeljaste. Takve vrste poželjne su za proizvodnju energije izravnim izgaranjem, od kojih su se u ovom istraživanju posebno istaknule vrste Ailanthus altissima i Robinia pseudoacacia. Zeljaste invazivne vrste zbog prvenstveno visokog sadržaja vode i niskog udjela lignoceluloznih vlakana te niske ogrjevne vrijednosti imaju veći potencijal za proizvodnju bioplina postupkom anaerobne digestije, bioetanola fermentacijom ili u hidrotermalnim procesima, a posebice se izdvajaju vrste Amaranthus retroflexus i Ambrosia artemisiifolia.
Rezultati ovog istraživanja pružaju uvid u funkcionalnu i energetsku vrijednost istraživanih invazivnih biljnih vrsta te naglašavaju značajan potencijal ovih vrsta za proizvodnju zelene energije i fitonutrijenata široke primjene. Valorizacija biomase invazivnih vrsta ključan je segment u procjeni vrijednosti takve biomase, a s obzirom na krajnju upotrebu, u industriji proizvodnje energije ili proizvoda dodane vrijednosti. Takav pristup osigurava održiv odgovor na problem upravljanja i zbrinjavanja invazivnih biljnih vrsta kroz model kružnog biogospodarstva. |
| Abstract (english) | Invasive plant species pose an increasing threat to human health, ecology and the economy. These species are characterised by an unprecedented adaptability to various ecological conditions, including those that are detrimental to other species, pronounced successional behavior that renders them dominant over native species, and a distinctive array of phytochemicals with significant allelopathic properties. Consequently, invasive plant species significantly threaten biodiversity. Globally, including in Croatia, various terrestrial habitats - such as forests, agricultural and non-agricultural areas, areas with weedy and ruderal vegetation, industrial sites, and urban green spaces - are increasingly threatened by invasive plant species. This leads to considerable destabilisation of ecosystems, necessitating the implementation of measures for their suppression and eradication. On the other hand, due to their invasiveness, these plant species represent an important source of biomass with potential energy and functional applications. Various research show their potential as a renewable energy source in processes for the thermal utilisation of biomass and for energy generation. These processes include direct combustion (heat, steam, electricity), pyrolysis (biochar, bio-oil, biogas), gasification (synthetic gas, heat, electricity), anaerobic digestion (biogas - methane, electricity, heat), fermentation (bioethanol), torrefaction (torrefied biomass), hydrothermal carbonisation and liquefaction (hydrothermal coal; biogas - methane or hydrogen, biocrude - liquid, fuel similar to crude oil). At the same time, invasive plant species possess considerable potential for the production of value-added products in areas such as pharmaceuticals, cosmetics, textiles, etc. due to their high content of specific, specialised metabolites. If utilised effectively, invasive plant species can represent an opportunity rather than a threat, as they could make a significant contribution to the share of renewable energy and contain new or significant amounts of natural phytonutrients.
The aim of this study was to identify invasive plant species in the Žumberak highlands area that have sufficient biomass and to determine the energy composition and phytonutrient content of the species as well as a possible way of their utilisation and further use. The study included a flora inventory in which 194 plant species were identified at 24 sampling microlocations. Of these, 12 invasive species were collected and analysed, comprising three woody species (AILanthus altissima, Rhus typhina i Robinia pseudoacacia) and nine herbaceous species (ABUtilon theophrasti, Amaranthus retroflexus, Ambrosia artemisiifolia, Datura stramonium, Erigeron annuus, Galinsoga ciliata, Reynoutria spp., Solidago gigantea i Sorghum halepense). After sampling, all samples were were prepared for further analysis. Only the leaves of the collected invasive plant species were used to determine the functional value, while the entire collected, dried and ground biomass was used to determine the energy value. The functional value was determined using standard methods, while the analysis included dry matter content, L-ascorbic acid content, spectrophotometric total phenolic compound content, total flavonoid content, non-flavonoid content, pigment concentration (total chlorophyll and carotenoids) and antioxidant capacity determined using the ABTS method. To determine the energy value and the potential of the biomass for direct combustion processes, the biomass was analysed using standard methods. Dry matter, ash content, coke, fixed carbon, volatile matter, carbon, hydrogen, oxygen, nitrogen and sulphur were determined, lignocellulosic fibres, macroelements (Ca, K, Mg, Na), microelements (Fe, Zn, Cu, Mn, Co, Mo, Ni), heavy metals (Pb, Cr, Cd, Hg) and heating value were determined.
The woody invasive species exhibited a higher average content of all specialised metabolites (L-ascorbic acid content, total phenolic, flavonoid and non-flavonoid content, pigment concentration) and a higher antioxidant capacity compared to the herbaceous species. However, when functional value is the focus of research, it is justified to study a single species in relation to a specific specialised metabolite. Accordingly, the woody species Rhus typhina has the highest concentrations of L-ascorbic acid content (159.69 mg/100 g sv.t), total phenolic compound content (2263.53 mg GAE/100 g sv.t) and total
non-flavonoid content (2006.23 mg GAE/100 g sv.t) in this study, while the woody species Robinia pseudoacacia has the highest value of total flavonoid content (1159.13 mg GAE/100 g sv.t). While the mean concentrations of pigment compounds in woody species are 8-16 % higher than in herbaceous species, the highest concentrations of pigment compounds were found in the herbaceous species Galinsoga ciliata for chlorophyll A content (1.05 mg/g) and total chlorophyll content (1.81 mg/g), in the herbaceous species Solidago gigantea for chlorophyll B content (0.92 mg/g) and in the herbaceous species Amaranthus retroflexus for total carotenoids content (0.26 mg/g). The mean antioxidant capacity for the woody invasive plant species is about 7 % higher than for the herbaceous species; however, the highest antioxidant capacity was found for the herbaceous species Amaranthus retroflexus (2221.97 μmol TE/L). Consequently, the woody species Rhus typhina and Robinia pseudoacacia together with the herbaceous species Amaranthus retroflexus, Galinsoga ciliata and Solidago gigantea can be identified as promising sources of certain specialised metabolites for the pharmaceutical, cosmetic and textile industries, among others.
When evaluating the energy values of the biomass of invasive plant species, it is crucial to consider the full range of energy value parameters of each biomass species, as together they influence the heating value, which is the most significant factor in the evaluation of biomass for potential direct combustion applications. From the observed properties, it can be concluded that those species are desirable for the direct combustion process that have the highest concentrations of dry matter (Rhus typhina, Robinia pseudoacacia), fixed carbon (ERIgeron annuus), carbon (Rhus typhina), hydrogen (Robinia pseudoacacia) and structural fibres (AILanthus altissima, Robinia pseudoacacia, Erigeron annuus), while they have low levels of ash content (AILanthus altissima, Robinia pseudoacacia), oxygen content (Rhus typhina, Robinia pseudoacacia) and other components such as macro- and microelements and heavy metals (AILanthus altissima, Rhus typhina, Robinia pseudoacacia), which positively influence the heating value. The woody invasive species analysed in this study have, on average, higher total energy properties than herbaceous species when evaluated using a parameter that integrates most of the components affecting the energy value of the raw material. This study found that woody invasive plant species have around 12 % higher heating values compared to herbaceous species. It can be concluded that woody species such as Ailanthus altissima and Robinia pseudoacacia are best suited for energy production through direct combustion. Herbaceous invasive plant species have a greater potential for biogas production by anaerobic digestion, bioethanol production by fermentation or hydrothermal processes due to their high water content and low heating value, with particular emphasis on the species Amaranthus retroflexus and Ambrosia artemisiifolia.
This study highlights the considerable energetic and functional potential of the invasive plant species investigated and expands the existing knowledge about the possibilities of their use. These results serve as a basis for further research into the possible utilisation and further application of invasive plant species. They show that significant opportunities lie in the valorisation of the biomass of invasive plant species for the production of green energy and phytonutrients as value-added products across various industries, offering a sustainable solution to the problem of invasive plant species through a circular bioeconomy model. It is recommended that future research should focus on the development of advanced models to predict the properties of biomass and optimise their application through alternative utilisation methods. Special emphasis should be placed on an interdisciplinary approach that incorporates machine learning and regression analysis methods and takes into account the influence of climatic conditions and environmental factors. This would ensure greater efficiency of biomass utilisation in the bioeconomy with a focus on sustainability and environmental protection. |
