Karakterizacija biooglja za uporabo v kmetijstvu

Kapš, Špela (author), Žgajnar Gotvajn, Andreja (mentor)

V okviru magistrskega dela smo karakterizirali sedem različnih vzorcev biooglja, ki so bili pripravljeni z dvema metodama, s pirolizo ali uplinjanjem. Biooglju smo določali parametre za karakterizacijo, ki jih določa EBC standard. Biooglje je trdna, heterogena snov, z visoko vsebnostjo ogljika vezanega v aromatskih spojinah, ki jo pridobimo s termokemijsko pretvorbo biomase, v pogojih brez ali z zelo nizko koncentracijo kisika, najpogosteje s pirolizo. Namen magistrskega dela je bil karakterizacija biooglja, z namenom določitve ustreznosti uporabe v kmetijstvu. Biooglje se dodaja v tla z namenom izboljšanja kvalitete tal ter za sekvestracijo ogljika. Biooglje ima odličen potencial za zadrževanje ogljika in s tem blaženje podnebnih sprememb. Sekvestracija ogljika je proces, ki vključuje zajem in dolgotrajno vezavo oziroma skladiščenje CO2. Za sekvestracijo je pomembna dobra stabilnost biooglja in odpornost proti degradaciji v okolju. Eksperimentalno delo v laboratoriju je zajemalo pripravo vzorcev biooglja (sejanje, mletje), elementno (elemental) analizo, termično analizo biooglja, s katero smo določili okvirno (proximate) sestavo ter postavitev in modifikacijo metode za določitev policikličnih aromatskih ogljikovodikov (PAH). Metoda za določitev PAHov je zajemala Soxhlet ekstrakcijo ter kvantitatvno določitev PAHov v vzorcih z GC-MS/FID. Z elementno analizo smo določili vsebnost elementov C, H, N ter na podlagi vsebnosti teh elementov in pepela izračunali vsebnost O. Najvišje vsebnosti so bile določene za C (med 51,93 % in 94,45 %), medtem ko so bile vsebnosti za O in H nižje (od 1,78 % do 8,29 % za O in od 0,16 % do 2,62 % za H), vsebnosti N pa le v sledovih pri določenih vzorcih. S termično analizo smo pridobili podatke o vsebnosti štirih glavnih komponent biooglja: vlagi, vezanemu ali fiksnemu ogljiku (C-fix), hlapnih komponentah in pepelu. Vsa biooglja so imela visoke masne deleže vezanega ogljika (od 48,60 % do 93,20 %), predvsem to velja za biooglja iz lesne biomase, pripravljena s pirolizo. V okviru določanja PAHov v biooglju smo določali 16 EPA PAHov. Najbolj zastopan PAH je naftalen (15 – 76 %), ki se pojavi v vseh vzorcih. Na vsebnost PAHov ima največji vpliv način priprave biooglja, saj ima vzorec pripravljen z uplinjanjem bistveno višjo vsebnost PAHov. Vsebnost PAHov se je izkazala za ključni izločilni kriterij. Ugotovili smo, da zaradi vsebnosti PAHov EBC standardu ustreza samo en preiskovani vzorec.

• Language: Slovenian
• Keywords: biooglje, piroliza, elementna analiza, termična analiza, PAH
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-132838
• COBISS.SI-ID: 89743363
• Publication date in RUL: 04.11.2021

Secondary language

• Language: English
• Title: Characterization of biochar for agricultural use

Abstract

The aim of the master's thesis was to characterize seven different biochar samples, which were prepared by pyrolysis or gasification. The characterization of biochar was performed according to the parameters determined by the EBC standard. Biochar is a solid, heterogeneous substance, with a high content of carbon bound in aromatic compounds, obtained by thermochemical conversion of biomass, under conditions without or with a very low concentration of oxygen. The most common technology is pyrolysis. The aim of the work was to characterize biochar, in order to determine the appropriateness of use in agriculture. Biochar is added to the soil in order to improve soil quality and to sequester carbon. Biochar has excellent potential for carbon sequestration and thus climate change mitigation. Carbon sequestration is a process that involves the capture and long-term binding or storage of CO2. Good stability of biochar and resistance to environmental degradation are important for carbon sequestration. Experimental work in the laboratory included the preparation of biochar samples (seeding, grinding), elemental analysis, proximate analysis and determination of polycyclic aromatic hydrocarbons (PAH). The method for the determination of PAHs included Soxhlet extraction and quantification of PAHs by GC-MS / FID. Content of elements C, H, N were obtained by elemental analysis. Content of O was calculated based on the content elements C, H, N and ash. The highest contents were determined for C (between 51,93 % and 94,45 %), while the contents for O and H were lower (for O from 1,78 % to 8,29 % and for H from 0,16 % to 2,62 %), and the N contents only in traces at certain samples. Thermogravimetry provided data on the content of four main components of biochar: moisture, fixed carbon (C-fix), volatile organic components (VOC) and ash. All biochar had high weight fractions of fixed carbon (from 48,60 % to 93,20 %), especially biochar from wood biomass prepared by pyrolysis. As part of the determination of PAHs in biochar, 16 EPA PAHs were determined. The most common PAH is naphthalene (15 – 76 %), which occurs in all samples. The method of preparation of biochar has the greatest influence on the content of PAHs, as the sample prepared by gasification has a significantly higher content of PAHs. The content of PAHs proved to be a key exclusion criterion. We found that due to the content of PAHs, only one sample corresponds to the EBC standard.

• Keywords: biochar, pyrolysis, elemental analysis, thermal analysis, PAH