University of South-Eastern Norway Tittel i fet skrift - Tittel Faculty of Technology, Natural Sciences and Maritime Studies — Doctoral dissertation no. 93 2021 Navn Navnesen Navn Nirmal Ghimire Methane production from lignocellulosic residues Nirmal Ghimire Methane production from lignocellulosic residues A PhD dissertation in Process, Energy and Automation Engineering © 2021 Nirmal Ghimire Faculty of Technology, Natural Sciences and Maritime Studies University of South-Eastern Norway Porsgrunn, 2021 Doctoral dissertations at the University of South-Eastern Norway no .9 3 ISSN: 2535-5244 (print) ISSN: 2535-5252 (online) ISBN: 978-82-7206-598-9 (print) ISBN: 978-82-7206-599-6 (online) This publication is, except otherwise stated, licenced under Creative Commons. You may copy and redistribute the material in any medium or format. You must give appropriate credit provide a link to the license, and indicate if changes were made. http://creativecommons.org/licenses/by-nc-sa/4.0/ deed.en Print: University of South-Eastern Norway Nirmal Ghimire: Methane production from lignocellulosic residues Preface This dissertation is submitted to the University of South-Eastern Norway (USN) in partial fulfilment of the requirements for the degree of Philosophiae Doctor (Ph.D). This work has been carried out under the supervision of Associate Professor Wenche Hennie Bergland and Professor Rune Bakke. This dissertation consists of two parts. First part contains overview of the research project including literature review, method and materials, results and discussion and conclusion. Scientific articles, which are core part of the thesis, are included in the part II. This research was accomplished in collaboration with RISE PFI AS. The main task of the PhD work carried out at USN was anaerobic digestion (AD) of waste streams produced during biochar production at RISE PFI AS, which provided AD feeds for the experiments. Other external partners on this project were Norske Skog Saugbrugs, Ferroglobe, Cambi, Eramet Norway and Norwegian University of Science and Technology (NTNU). The work was done as a part of Norske Skog Saugbrugs innovation project Pyrogas co-funded by The Norwegian Research Council (EnergyX Programme). I participated in two international conferences during the study period. Planned third international conference “8th International Conference on Sustainable Solid Waste Management”, Greece, 17-20 June 2020, was moved to 2021 due to COVID-19. I was also involved in other projects taking place at USN and elsewhere. The review article (Paper 5) sent to Bioresource Technology has now been accepted and published. Courses (30 ECTS) I attended during the PhD periods are as following: • Theory of Science and Ethics (D0611), USN (Bø) (5 ECTS) • Process of Analytical Technology (D0110), USN (Porsgrunn) (5 ECTS) ___ I Nirmal Ghimire: Methane production from lignocellulosic residues • Microbial Ecology (BT8101), NTNU (Trondheim) (9 ECTS) • Sustainable Biomass Resources and Technology Pathways of Biogas and Biorefineries, Aalborg University (Esbjerg) (5 ECTS) • Advanced Environmental Biotechnology, Delft University of Technology (Delft) (3 ECTS) • Sustainability and Environmental Aspects in Biomass Production Systems, Swedish University of Agricultural Sciences (Uppsala) (3 ECTS) Nirmal Ghimire Porsgrunn, January 2021 ___ II Nirmal Ghimire: Methane production from lignocellulosic residues In the memory of Prof. Rune Bakke “When great trees fall, Great souls die and rocks on distant hills shudder, our reality, bound to lions hunker down in tall grasses, them, takes leave of us. and even elephants Our souls, lumber after safety. dependent upon their nurture, When great trees fall now shrink, wizened. in forests, Our minds, formed small things recoil into silence, and informed by their their senses radiance, eroded beyond fear. fall away. We are not so much maddened When great souls die, as reduced to the unutterable ignorance the air around us becomes of dark, cold light, rare, sterile. caves. We breathe, briefly. Our eyes, briefly, And when great souls die, see with after a period peace blooms, a hurtful clarity. slowly and always irregularly. Spaces fill Our memory, suddenly sharpened, with a kind of examines, soothing electric vibration. gnaws on kind words Our senses, restored, never unsaid, to be the same, whisper to us. promised walks They existed. They existed. never taken. We can be. Be and be better. For they existed.” - Maya Angelou (1928-2014) ___ I Nirmal Ghimire: Methane production from lignocellulosic residues Acknowledgements I am grateful to my main supervisor Associate Professor Wenche Hennie Bergland for her immense support, guidance and motivation throughout the journey. I must add that she has supported me more than I ever could have hoped for. I am deeply indebted to her personal kindness. I am equally grateful to my co-supervisor Professor Rune Bakke for his continuous support and guidance since my master’s degree. I will always be indebted to his trust on me which pushed me to do better. He had been my guardian on all fronts. I will always miss him. I also want to thank Associate Professor Carlos Dinamarca for his invaluable suggestions during difficult times. I am thankful to Eshetu Janka for his help in running experiments smoothly and update on African politics. I am also thankful to Hildegunn Hegna Haugen and Frank Aarvak for keeping labs well-functioning throughout the project period. I would also like to thank Cornelis van der Wijst, Øyvind Eriksen and Kai Toven from RISE- PFI for their valuable co-operations. I am also thankful to master thesis students Jitendra Sah, Vibeke Bredvold and Zahra Nikbakht Kenarsari for their collaborations. Finally, I am grateful to my parents who believed in me and motivated me to take this immense task. ___ II Nirmal Ghimire: Methane production from lignocellulosic residues Abstract Aims Biochar production by intermediate pyrolysis of renewable lignocellulosic biomass to replace traditional carbon material as a reducing agent and energy source in the metallurgical industries produces carbon rich waste streams viz., hemicellulose hydrolysate from hot water extraction (HWE) and aqueous pyrolysis liquid (APL) from pyrolysis requiring efficient treatment before discarding to enhance energy recovery and avoid environmental problems. Anaerobic digestion (AD), a robust biological process, was considered to treat these challenging organic waste streams individually or as co-digestion for enhanced energy recovery in the form of methane. AD of hydrolysate and APL, both individually and as co-digestion, was performed to study the effect of HWE and pyrolysis temperatures and biomass types on the methane yield. Effect of AD temperature and organic load (OL) on methane yield from Norway spruce hydrolysate was also studied. Materials and methods Air-dried wood chips of Norway spruce and birch were hot water extracted in two different conditions of 140 °C for 300 min and 170 °C for 90 min to produce hemicellulose rich hydrolysate to use as AD substrate. The wood chips (with or without HWE) were pyrolyzed at 550 °C or 400 °C to produce APL which was used as AD substrate. Both hydrolysate and APL were prepared and supplied by RISE-PFI, Trondheim, Norway. The hydrolysates from HWE and the APL from pyrolysis were tested for bio-methane potential (BMP) during batch AD in an Automatic Methane Potential Test System II (AMPTS II, Bioprocess Control® Sweden AB). Syringe batch reactors were used to study the effect of OL on methane yield. Simplified lab scale up flow anaerobic sludge bed (UASB) reactors of 345 mL working volume were used for mesophilic continuous AD of Norway spruce hydrolysates. ___ III Nirmal Ghimire: Methane production from lignocellulosic residues Results and discussions Hydrolysate of Norway spruce and birch showed good biodegradability (ranging from 69 to 79 %) in batch AD reactors. The HWE hydrolysates from pretreatment temperature of 170 °C gave a 13 % lower methane yield for birch compared to hydrolysates pretreated at 140 °C (not significant decrease for Norway spruce) in batch AD, while it was 9 % lower for Norway spruce in continuous AD compared to hydrolysates pretreated at 140 °C. This is due to higher concentration of inhibitors (furans and soluble lignin) and possible extraction and formation of higher concentration of recalcitrant compound (soluble lignin) at higher temperature. Birch (hardwood) hydrolysate pretreated at 140 °C resulted in higher methane yield (8 %) than Norway spruce (softwood) as hemicellulose extraction is better in hardwood. Hydrolysate of Norway spruce pretreated at 140 °C gave higher methane yield and improved production rate during mesophilic AD (35 °C) compared to thermophilic AD (55 °C) as thermophilic mixed cultures are more susceptible and sensitive to furan inhibitors. However, the result of hydrolysate pretreated at 170 °C was not consistent despite having higher concentration of furan inhibitors. Methane yield of hydrolysate pretreated at 170 °C decreased with increase in OL during the mesophilic AD while hydrolysate pretreated at 140 °C had similar methane yield at all OLs suggesting better performance of hydrolysate pretreated at 140 °C during higher OLs due to lower concentration of inhibitors compared to hydrolysate pretreated at 170 °C. During thermophilic condition, both hydrolysates pretreated at 140 °C and 170 °C were affected negatively with increasing OLs. APL of birch from pyrolysis temperature at 400 °C and 550 °C had a methane