The production of biopolymers for bioplastics using pulp and paper mill wastewater and residual fibre streams

MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 1 of 86. The production of biopolymers for bioplastics using pulp. and paper mill wastewater and residual fibre streams. Multibio Project - Work Package 2 - Final Report. Promiko Report 18-01-A, Revision 2:20-12-04. December 4, 2020 Lomma, Sweden.. Alan Werker and Simon Bengtsson, . Promiko AB, Lomma Sweden. . (alan.werker@promiko.se). . mailto:alan.werker@promiko.se. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 2 of 86. This is the final report of Mulitbio project work package 2 conducted by Promiko AB in. collaboration with the project partners. Multibio, Environmental services by multipurpose. biorefinery, was a VINNOVA sponsored project (reference number: 2017-03286) conducted. over the period from November 2017 to December 2020. The project coordinator was RISE,. Research Institutes of Sweden AB - Energi och cirkulär ekonomi, Borås. Further details with. thanks to contributing organizations and individuals are provided in the report. acknowledgements. This document is being published via the DiVA portal of RISE in. recognition of the public funding that supported the undertaking of the study presented herein.. Copyright Promiko AB (c) 2020:. Texts and figures from this report may only be reproduced with full acknowledgment and. citation of the source.. Disclaimer:. This publication has been compiled with the greatest of possible care. Nevertheless, the. authors and Promiko AB do not accept any liability for possible unintended oversights and. inaccuracies and/or possible consequences due to the interpretation or application of the. contents of this report.. Promiko AB Briggatan 16, 23442 23442 Lomma, Sweden. www.promiko.se info@promiko.se . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 3 of 86. Scenario 1 & 2: Summary flow diagrams depicting two feasible scenarios recommended as. steps to produce PHA from Skoghalls and Rottneros pulp and paper mill residual organic. streams and to produce collectively from 2400 (1) to 3600 (2) tons of PHA/yr. . . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 4 of 86. Sammanfattning på Svenska. Som en del av projektet Multibio har potentialen att producera biobaserade och biologiskt. nedbrytbara polymerer från organiska rester i processavloppsvatten utvärderats vid Stora. Enso Skoghalls och Rottneros pappers- och massabruk i Värmland, Sverige. Dessa polymerer. är termoplastiska polyestrar som produceras av naturligt förekommande bakterier och tillhör. gruppen polyhydroxyalkanoater (PHA). De kan formuleras som huvudingrediens i plaster,. funktionella kemikalier och kompositmaterial relevanta för vitt skilda sektorer inklusive. skogsindustrin. De kan också användas som ingrediens i fiskfoder för att åstadkomma en. pre/pro-biotisk effekt vid fiskodling. Kommersiellt relevanta mängder och kvaliteter av PHA. kan produceras som en bi-produkter vid den biologiska vattenrening som används för att. behandla industriella och kommunala processavloppsvatten. Målet med denna studie har varit. att bestämma de potentiella mängder av PHA som skulle kunna produceras som en integrerad. del av brukens hantering och behandling av restströmmar. Syftet med denna del av. Multibioprojektet har även varit att ge rekommendationer för en fortsatt stegvis utveckling.. Tillgängliga restströmmar vid Skoghalls och Rottneros bruk uppskattas motsvarar 70. respektive 15 ton per dag angivet som kemiskt syrebehov (COD, ”chemical oxygen demand”).. Siffrorna beräknades med en massbalans baserad på historiska data från bruken samt analyser. av stickprov från olika delar av reningsprocesserna. Restströmmarnas COD består av fiber,. överskottsbioslam och löst organiskt material. Detta organiska material skulle kunna. användas som råvara för att producera en mikrobiell biomassa rik på PHA med en återstående. mängd som kan förbrännas för värmeproduktion. Förbättrad slamavvattning kan antas. På så. sätt varje ton COD som används för PHA-produktion orsakar en minskning i värmeproduktion. som är mindre än vad som annars vore fallet.. Två scenarier presenteras. För att producera PHA behöver först den organiska råvaran. omvandlas till flyktiga fettsyror (VFA, ”volatile fatty acids”) genom acidogen fermentering. Om. alla tillgängliga organiska rester används för att producera VFA (Scenario 1), uppskattades att. ungefär 2 000 respektive 400 ton PHA per år skulle kunna produceras vid Skoghalls och. Rottneros bruk. De producerade mängderna skulle öka med ungefär 50 % (3 000 respektive. 600 ton PHA/år), ifall överskottsbioslammet från brukens processvattenrening kunde. utnyttjas för att producera PHA istället för att endast vara en råvara för VFA (Scenario 2).. Experimentella utvärderingar av överskottsbioslammen från respektive bruk visade att varken. Skoghall eller Rottneros producerar bioslam med tillräcklig potential för PHA-ackumulering. idag. Bioslammen kunde ackumulera PHA till ungefär 20 % av sin organiska vikt.. Massbalanserna baserades på bioslam med potential att ackumulera 60 % av sin organiska vikt. som PHA. Högre PHA-ackumuleringspotential i brukens överskottsbioslam bedöms möjlig att. åstadkomma men kräver beaktande av aspekter av bioprocesserna som kan skapa ett. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 5 of 86. selektionstryck som gynnar mikroorganismer i bioslammet som kan producera PHA. Dessa. aspekter behöver inte medföra omfattande uppgradering av befintlig infrastruktur för. processvattenrening. . Även om det vore fullt möjligt att göra ändringar för att öka selekteringen för förbättrad PHA-. potential, ansågs sådana förändringar inte vara av omedelbart intresse. En socialt, tekniskt och. ekonomiskt logisk utveckling vore att producera PHA genom att använda alla de identifierade. organiska restströmmarna som råvara för VFA (Scenario 1). Om en livskraftig produktion på. 2 000 och 400 ton PHA/år är möjlig, finns en tydlig motivation för att modifiera befintlig. processvattenrening för att förbättra bioslammets prestanda och därigenom öka produktionen. med 50 % från samma mängd råvaror.. En produktionsvolym av polymerer på 2 000 och 400 ton PHA/år är liten i förhållande till. huvudprodukterna vid Skoghalls och Rottneros bruk vilka är cirka 778 000 ton/år massa och. kartong respektive 170 000 ton/år massa. Å andra sidan innebär ett antaget pris för nisch-. polymerer på 5 €/kgPHA till potentiella intäkter på 12 M€/år vilket mycket väl kan vara. tillräckligt för en mindre, specialiserad tillverkning. Denna möjlighet innebär lägre risk. I det. korta perspektivet ska symbiosen av PHA-produktion som livnär sig på brukens restströmmar. inte skapa någon onödig börda för brukens kärnverksamhet. Tvärt om ska den förenkla. nuvarande verksamhet eller skapa andra fördelar.. Baserat på erfarenheter från liknande fall kan det förväntas att en liten produktion av. polymerer förankrar egna erfarenheter av materialen och deras produktion samtidigt som en. krok agnas för att fånga framtida vidare utveckling. Den framtida ekonomin för pappers- och. massabruk förväntas kräva en bredare affärsmodell med fiber såväl som andra biobaserade. produkter och tjänster. PHA kan även produceras från själva vedråvaran utifrån hemicellulosa. och cellulosa. Att starta en nisch-tillverkning av PHA kan vara ett sätt att möjliggöra. upptäckter som mycket väl kan motivera att vissa fraktioner av bruken huvudråvaror används. för nya material såsom PHA. . . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 6 of 86. Executive Summary. As part of the Multibio project, the potential for production of biobased and biodegradable. polymers, from organic residuals in process effluent streams, was evaluated for Stora Enso. Skoghalls and Rottneros pulp and paper mills in Värmland, Sweden. These biopolymers are. thermoplastic polyesters made by naturally occurring bacteria and are from the family of. polyhydroxyalkanoates (PHAs). They can be formulated as principal ingredients for plastics,. functional chemicals, and composite materials of interest to a diversity of sectors including the. pulp and paper industry. They can also be formulated into fish feed to impart pre/pro-biotic. benefits in aquaculture. Commercial quantities and qualities of PHAs can be produced as a. corollary benefit to biological wastewater treatment processes that are used to treat industrial. and municipal wastewaters for environmental protection. The goal of the present study has. been to determine the potential quantities of PHA that could be produced as an integral part. of the mill residual organics and effluent management. The aim of this Multibio work package. has also been to recommend steps forward.. It was estimated that Skoghalls and Rottneros mills manage 70 and 15 tons per day of residual. organic material on a chemical oxygen demand (COD) basis, and in relation to respective. production levels of about 778,000 and 170,000 ton/yr paper and board. These numbers were. calculated from mass balances using historical monitoring information provided by the mills. and with measurements made in this study on samples from selected locations of the treatment. processes. The residual COD is comprised of fibre and surplus activated sludge as well as. soluble dissolved organic material. This organic material is a resource to produce a microbial. biomass rich in PHA with remaining organic material being used for boiler heat production. . Improved sludge dewatering is expected such that COD used for heat production today could. be diverted to PHA without undue loss of heat production capacity in the balance.. Two process scenarios are presented (Scenario 1 & 2 Figure). PHA production requires that. the organic feedstock is first converted into volatile fatty acids (VFAs) through acidogenic. fermentation. If all the residual organic mass is used to produce VFAs (Scenario 1), it was. estimated that about 2 000 and 400 tons PHA per year could be produced at Skoghalls and. Rottneros mills, respectively. Production amounts would be increased (Scenario 2) by about. 50 % (3 000 and 600 tPHA/yr, respectively) if the residual mass flows of waste activated sludge. biomass from the mill aerobic biological wastewater treatment processes could be exploited. for a PHA storing potential rather than just being an organic feedstock to yield VFAs.. In experimental evaluations of the respective mill surplus activated sludge, it was found that. neither Skoghalls nor Rottneros generate activated sludge with sufficient PHA accumulation. potential today. The biomass could accumulate approximately 20 % of final organic weight as. PHA. The Scenario 2 mass balance evaluations were based on realistic expectation that such. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 7 of 86. a waste activated sludge could be made to accumulate PHA up to 60 % of final organic weight. . A higher accumulation potential in the mill waste activated sludge is possible but it requires. attention paid to details of bioprocess selective pressures that promote enrichment in presence. of PHA storing microorganisms in the waste activated sludge. Process changes to address such. details do not have to require complicated upgrades to the existing infrastructure and can be. made while still maintaining final effluent water quality discharge demands. . Even if it is in the realm of feasibility to manipulate selective pressures for improved PHA. potential for the waste activated sludge, such efforts were not considered to be strategic as a. first step. A logical initial low risk development would be to first produce PHA using all the. considered organic residuals just as an organic resource for VFAs (Scenario 1). Once an. economically viable production activity for 2000 and 400 tPHA/yr was established, then the. motivation to modify the existing wastewater treatment plants, to produce a better performing. PHA storing biomass, would be well-motivated. An ability to further exploit the surplus. activated sludge for its potential capacity to accumulate PHA rather than as just an organic. feedstock for VFAs, would upgrade by 50 % the PHA production supply from the same mass. flow of input material. . A polymer production activity for 2 000 and 400 tPHA/yr is small compared to the core. revenue generating outputs from Skoghalls and Rottneros mills, being approximately 778 and. 170 kton/yr pulp and board, or pulp, respectively. At the same time, assuming a niche polymer. market exploitation at 5 €/kgPHA, a product revenue of 12 M€/yr may well support a. worthwhile specialty industry. That is the lower risk opportunity to develop first. In the first. steps, the symbiosis of PHA production feeding on mill organic residuals management should. function with negligible if any burden on the mill daily routine in operations. At the same time,. it should simplify or create otherwise harder to achieve benefits or further efficiencies to the. current routine of mill operations. . A mill side-line of polymer production anchors in-house supply and experience with PHAs. while casting a net for evolving and capturing future interesting materials and business. . Future mill economies may foreseeably require standing on wider business footings including. fibre as well as from other cellulose derived biobased revenue generating products and. services. PHAs can naturally also be made using the prime input lumber starting with. hemicellulose and cellulose. Opening a PHA specialty industry first is a way to open the door. for discovery that may well motivate directing strategically separated mill upstream organic. fractions to successful large commercial revenues from PHAs in the future. . . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 8 of 86. Contents. List of acronyms ............................................................................................................................9. Introduction ................................................................................................................................ 10. Sourcing of volatile fatty acids from pulp mill organic residuals .............................................. 14. Skoghalls bruk - assessment of potential PHA production feedstocks ................................. 16. Rottneros bruk - assessment of potential PHA production feedstocks ................................. 21. Integration of PHA production at Skoghalls and Rottneros bruk ............................................ 24. Scenario 1 - Surplus activated sludge as just a feedstock for VFAs ....................................... 25. Scenario 2 - Surplus activated sludge as a PHA storing biomass ......................................... 26. Considerations for next steps ................................................................................................. 29. PHA accumulation potential of activated sludge from Skoghalls and Rottneros mills ............33. Outlook and recommendations ................................................................................................. 40. Acknowledgements .................................................................................................................... 43. Appendix A - Skoghalls bruk residual organic mass assessment .............................................. 53. Appendix B - Rottneros bruk residual organic mass assessment ............................................. 71. Appendix C - PHA accumulation potential (PAP) evaluations ................................................. 81. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 9 of 86. List of acronyms. BOD biochemical oxygen demand. COD chemical oxygen demand. sCOD soluble chemical oxygen demand. fCOD fibre suspended solids chemical oxygen demand. aCOD active COD (i.e. surplus activated sludge). vCOD VFA COD (soluble COD comprised of volatile fatty acids). xCOD COD of comprised of suspended solids. pCOD polymer COD (COD as polyhydroxyalkanoates). tCOD tons of COD. PAP PHA accumulation potential (an expressed content of PHA accumulated). PHA polyhydroxyalkanoates (a generic label for this family of polymers). tPHA tons of PHA. PHB polyhydroxybutyrate (a specific type of polymer in the PHA family). TOC total organic carbon. sTOC soluble total organic carbon . TSS total suspended solids. VSS volatile suspended solids. aVSS active VSS (i.e. surplus activated sludge). VFA volatile fatty acids. WWT wastewater treatment. bioWWT biological wastewater treatment. pcWWT physical-chemical wastewater treatment. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 10 of 86. Introduction. The Multibio project has had as a goal to establish methods and processes supporting a. multipurpose biorefinery involving a cascade of conversion of organic residuals, pulp and. paper mill industrial by-products, into renewable value-added biobased products. The. products under investigation have been 1) biohydrogen, 2) biopolymers and 3) meal. ingredients for fish farming. In so doing, an overall project aim has been to contribute to. activities at a pulp and paper mill that would also positively address 7 out of 10 nationally. identified environmental challenges. . This report presents the results from work package 2 that have dealt with the production of. biopolymers. The work was focused on production of polyhydroxyalkanoates, or PHAs1, that. are a naturally occurring family of polyesters produced by many types of bacteria. PHAs have. established commercial potential as ingredients for the bioplastics, biofuel and chemical. industries2. Applications include products and services that are directly linked to the forest. sector including film or latex based paper modifiers, and wood polymer composite materials3. . These biopolymers also have application in fish feed due to demonstrated pre/pro-biotic. effects as a control agent in aquaculture4. The specific type of PHAs produced within the. context of the present work are typically short chain length PHAs, namely poly(3-. hydroxybutyrate) (PHB) and/or co-polymer blends of poly(3-hydroxybutyrate-co-3-. hyroxyvalerate) or PHBV.. The integration of PHA production, using the surplus activated sludge from a pulp and paper. . 1 Laycock, B., Halley, P., Pratt, S., Werker, A., & Lant, P. (2014). The chemomechanical properties of microbial polyhydroxyalkanoates. Progress in Polymer Science, 39(2), 397–442.. 2 Chen, G.-Q., A microbial polyhydroxyalkanoates (PHA) based bio- and materials industry, Chemical Society Reviews 38(8) (2009) 2434-2446.. 3 Chan, C. M., Vandi, L. J., Pratt, S., Halley, P., Richardson, D., Werker, A., & Laycock, B. (2018). Composites of Wood and Biodegradable Thermoplastics: A Review. Polymer Reviews, 58(3), 444– 494.. Vandi, L. J., Chan, C. M., Werker, A., Richardson, D., Laycock, B., & Pratt, S. (2018). Wood-PHA Composites: Mapping Opportunities. Polymers, 10(751), 1–15.. 4 Defoirdt, T., Boon, N., Sorgeloos, P., Verstraete, W., & Bossier, P. (2009). Short-chain fatty acids and poly-β-hydroxyalkanoates: (New) Biocontrol agents for a sustainable animal production. Biotechnology Advances, 27(6), 680–685. . Gao, M., Du, D., Bo, Z., & Sui, L. (2019). Poly-β-hydroxybutyrate (PHB)-accumulating Halomonas improves the survival, growth, robustness and modifies the gut microbial composition of Litopenaeus vannamei postlarvae. Aquaculture, 500(October 2018), 607–612. . Boon, N., Defoirdt, T., De Windt, W., Van De Wiele, T., & Verstraete, W. (2013). Hydroxybutyrate and polyhyroxybutyrate as components of animal feed or feed additives (Patent No. US 8,603,518 B2).. De Schryver, P., Sinha, A. K., Kunwar, P. S., Baruah, K., Verstraete, W., Boon, N., De Boeck, G., & Bossier, P. (2010). Poly-β-hydroxybutyrate (PHB) increases growth performance and intestinal bacterial range-weighted richness in juvenile European sea bass, Dicentrarchus labrax. Applied Microbiology and Biotechnology, 86(5), 1535–1541. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 11 of 86. mill wastewater treatment process, is envisioned to contribute positively with the following. environmental goals: . • Reduced climate impact . • A non-toxic environment,. • Flourishing lakes and streams. • Sustainable forests. In addition, the development of activities for conversion of residuals into PHAs, is with the. intent to bring positive dividends to the mill and surrounding community by nurturing. regional economic diversity and development. This Multibio project work package, directed to. extending mill waste management and environmental protection practices, was as follows:. • the identification of streams that are promising for biopolymer production business case development and upscaling activities, and. • an evaluation for sourcing biomass with sufficient PHA accumulation potential that may be produced as part of the mill organic waste management activities.. Towards making these project milestones, two Swedish pulp and paper mills were considered,. namely, Stora Enso Skoghalls bruk, and Rottneros bruk, in Värmland.. Pulp and paper mills follow strict guidelines and regulations in the management and discharge. of process effluents. Advancements over the past 30 years in the understanding of biological. treatment, and potential for mill related acute as well as chronic contaminant environmental. fate and effects, has strongly influenced mill practices including upstream pulping and. bleaching technological developments, and downstream effluent treatment methods. The. mills must manage the removal of residues from process effluents before final discharge of. treated process water back to recipient environments. The process water contaminants will. include suspended solids rich in lumber related residues, cellulosic fibre slippage, chemical. reaction products, and other non-lumber materials that may have been introduced, or released. by mechanical, chemical and/or thermal processes in pulping and paper making. . Pulp mill effluent management practices often include the application of aerobic biological. treatment for the removal of soluble organic residuals from process effluents5. Aerobic. biological treatment transforms dissolved organic contaminants into carbon dioxide, water. and a waste of suspended solids comprising a microbial biomass. In the present report, this. residual biomass produced from the mill effluent treatment is referred to as a waste activated. . 5 Kamali, M., & Khodaparast, Z. (2015). Review on recent developments on pulp and paper mill wastewater treatment. Ecotoxicology and Environmental Safety, 114, 326–342.. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 12 of 86. sludge.. Waste activated sludge is an organic resource that does not have to be a waste. The sludge. organic matter has heating value, and it is itself fermentable into volatile fatty acids (VFAs). and biogas6. Waste activated sludge from treating pulp and paper mill wastewater can also be. made to exhibit significant capacity for PHA production7. Thus, waste activated sludge has. value either for its organic content, or for its inherent metabolic activity, or both. It is well. established that waste municipal and industrial activated sludges can be enriched, due to. imposed and relatively simple bioprocess principles, with capacity to accumulate at least its. organic weight in PHAs when fed VFA-rich fermented organic residues8. VFAs are the. principal feedstock leading to accumulation of PHA in such microbial biomass. . A production process to make commercial polymers requires that the PHA production yields. and productivities are robust, reliable and optimal. A recent pilot scale study suggests that. mixed culture processes can be relied upon to meet quality control demands for commercial. polymer production9. For the technical and economic justification of PHA production at a pulp. and paper mill, a reliable source of VFAs10 is also needed. The amount of VFAs that can be. supplied constrains the scale of production. PHAs are at an estimated current market value of. between 5 and 10 €/kg. The scale of production influences the production costs and, therefore,. scale is central to the techno-economics.. . 6 Meyer, T., & Edwards, E. A. (2014). Anaerobic digestion of pulp and paper mill wastewater and sludge. Water Research, 65, 321–349.. 7Bengtsson, S., Werker, A., Christensson, M., & Welander, T. (2008). Production of polyhydroxyalkanoates by activated sludge treating a paper mill wastewater. Bioresource Technology, 99(3), 509–516.. 8 Bengtsson, S., Werker, A., Visser, C., Korving, L., PHARIO. Stepping stone to a value chain for PHA bioplastic using municipal activated sludge, STOWA, The Netherlands, 2017.. Tamis, J., Lužkov, K., Jiang, Y., Loosdrecht, M.C.M.v., Kleerebezem, R., Enrichment of Plasticicumulans acidivorans at pilot-scale for PHA production on industrial wastewater, Journal of Biotechnology 192, Part A (2014) 161-169.. 9 Werker, A., Simon Bengtsson, S., Johansson, P., Magnusson, P., Gustafsson, E., Hjort, M., Anterrieu, S., Karabegovic, L., Alexandersson, T., Karlsson, A., Morgan-Sagastume, F., Sijstermans, L., Tietema, M., Wypkema, E., van der Kooij, Y., Deeke, A., Uijterlinde, C., and Korving, K. (2020). Production quality control of mixed culture poly(3-hydroxbutyrate-co-3-hydroxyvalerate) blends using full-scale municipal activated sludge and non-chlorinated solvent extraction. in Handbook of Polyhydroxyalkanoates, CRC Taylor & Francis.. 10 Nikodinovic-Runic, J., Guzik, M., Kenny, S. T., Babu, R., Werker, A., & O’Connor, K. E. (2013). Carbon-rich wastes as feedstocks for biodegradable polymer (polyhydroxyalkanoate) production using bacteria. Advances in Applied Microbiology, 84, 139–200. . Valentino, F., Morgan-Sagastume, F., Campanari, S., Villano, M., Werker, A., & Majone, M. (2017). Carbon recovery from wastewater through bioconversion into biodegradable polymers. New Biotechnology, 37, 9–23. . Laycock, B., Pratt, S., Halley, P., Werker, A., & Lant, P. (2014). Biodegradable polymers from pulp and paper wastewater streams - A critical review. Appita Journal, 67(4), 309–315. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 13 of 86. The present investigation was therefore directed to the assessment of the potential sources and. scale for VFA production using available organic residuals at the Skoghalls and Rottneros pulp. and paper mills. Given the input material supply, two plausible identified scenarios for PHA. production are considered. The first scenario evaluates production with waste activated sludge. utilized purely as an organic feedstock - i.e. on organic mass from which to convert and supply,. in part, some VFAs. The second scenario assumes that the waste activated sludge exhibits a. significant PHA accumulation potential (PAP). Data was provided by Skoghalls and Rottneros. mills from routine monitoring of the effluent treatment. Grab samples were also provided for. water quality analyses from selected locations along the effluent treatment line(s). A mass. balance evaluation was made of potentially available residual organic matter that could be. directed to a side stream PHA production process. Practical assessments of the present-day. PAP for the respective mill waste activated sludges were made as a benchmark. Based on the. mass balance and practical evaluations the strategic outlook was considered and. recommendations for next steps were made. Details in the mill assessments that were. estimated for residual organic flows are given in Appendix A and B, for Skoghalls and. Rottneros mills, respectively. Details in the materials and methods applied for the practical. experiments with PAP analyses are given in Appendix C. . . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 14 of 86. Sourcing of volatile fatty acids from pulp mill organic residuals. VFAs, the primary raw material for PHA, are short chain organic acids that occur in nature due. to many environments with anaerobic conditions where more complex organic molecules such. as polysaccharides, proteins and lipids are hydrolysed into simpler molecules such as sugars,. amino acids and long chain fatty acids. These simpler molecules are fermented, in turn, into. VFAs including acetic, propionic, butyric, and valeric acids. Other fermentation products may. include alcohols, longer chain fatty acids (hexanoic and heptanoic acids), and hydrogen. In. the Multibio project an acidogenic fermentation that produces predominantly acetic acid and. hydrogen was considered by means of the obligate anaerobic thermophile Caldicellulosiruptor. saccharolyticus11. Acidogenic fermentation is widespread in nature and single organisms as. well as syntrophic microbial communities are known to exist in many kinds of environments,. both in nature and in engineered bioprocesses12. The most common exploitation of acidogenic. fermentation is with methane biogas production. Notwithstanding the traditional and now. entrenched interest to produce biogas, the fermentation of organic residuals for VFAs as a. platform for other products and services higher on the value pyramid is ongoing and welling. up in both scientific and practical commercial activities and interests13.. . 11 Willquist, K., Zeidan, A.A., van Niel, E.W.J., Physiological characteristics of the extreme thermophile Caldicellulosiruptor saccharolyticus: an efficient hydrogen cell factory, Microbial Cell Factories 9 (2010) 89-89.. 12 Agler, M. T., Wrenn, B. A., Zinder, S. H., & Angenent, L. T. (2011). Waste to bioproduct conversion with undefined mixed cultures: The carboxylate platform. Trends in Biotechnology, 29(2), 70–78.. 13 Strazzera, G., Battista, F., Garcia, N. H., Frison, N., & Bolzonella, D. (2018). Volatile fatty acids production from food wastes for biorefinery platforms: A review. Journal of Environmental Management, 226(8), 278–288.. Garcia-Aguirre, J., Aymerich, E., González-Mtnez. de Goñi, J., & Esteban-Gutiérrez, M. (2017). Selective VFA production potential from organic waste streams: Assessing temperature and pH influence. Bioresource Technology, 244(August), 1081–1088.. Atasoy, M., Owusu-Agyeman, I., Plaza, E., & Cetecioglu, Z. (2018). Bio-based volatile fatty acid production and recovery from waste streams: Current status and future challenges. Bioresource Technology, 268(July), 773–786. . Tao, B., Passanha, P., Kumi, P., Wilson, V., Jones, D., & Esteves, S. (2016). Recovery and concentration of thermally hydrolysed waste activated sludge derived volatile fatty acids and nutrients by microfiltration, electrodialysis and struvite precipitation for polyhydroxyalkanoates production. Chemical Engineering Journal, 295, 11–19.. Lee, W. S., Chua, A. S. M., Yeoh, H. K., & Ngoh, G. C. (2014). A review of the production and applications of waste-derived volatile fatty acids. Chemical Engineering Journal, 235, 83–99. . Yin, J., Yu, X., Zhang, Y., Shen, D., Wang, M., Long, Y., & Chen, T. (2016). Enhancement of acidogenic fermentation for volatile fatty acid production from food waste: Effect of redox potential and inoculum. Bioresource Technology, 216, 996–1003. . Luo, L., Kaur, G., & Wong, J. W. C. (2019). A mini-review on the metabolic pathways of food waste two-phase anaerobic digestion system. Waste Management and Research, 37(4), 333–346. . Zhou, M., Yan, B., Wong, J. W. C., & Zhang, Y. (2018). Enhanced volatile fatty acids production from anaerobic fermentation of food waste: A mini-review focusing on acidogenic metabolic pathways. Bioresource Technology, 248, 68–78.. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 15 of 86. The research literature is filled with studies giving positive indications for the production of. VFA rich streams from cellulose rich sludges. Acidogenic fermentation of cellulose by a. mesophilic mixed culture has been suggested to give a soluble chemical oxygen demand (COD). yield of 0.35 grams of soluble COD per gram of cellulose added14. The hydrolysis and. fermentation of waste pulp and pulp and paper mill sludges have been investigated including. various pre-treatments15. Pre-treatment and retention times can influence the cellulose. crystallinity that ultimately needs to be broken towards the release of fermentable sugars16. . However, pre-treatments do not necessarily bring improved VFA yields, but may remove other. unwanted substances17. One may further consider that the pulping processes, through. thermal, chemical and mechanical processing are forms of inherent pre-treatments and will. influence cellulose crystallinity and the fermentability of the residual cellulosic solids ending. up in the mill waste sludge.. Enzyme activity influences the digestibility of cellulose rich sludges18. Thus, the type of. inoculum and reactor configuration may influence the hydrolytic activity in an acidogenic. bioprocess19. The co-fermentation of cellulose rich sludges with waste microbial biomass. sludges can bring synergistic potential due to the inherently rich spectrum of enzymatic activity. retained in the sludge. Co-fermentation of pulp cellulose rich residual streams with waste. . 14 Shang, Y. (2000). Cellulose mineralization in two-stage anaerobic digestion systems. In PhD. Thesis. Iowa State University.. 15 Veluchamy, C., & Kalamdhad, A. S. (2017). Enhancement of hydrolysis of lignocellulose waste pulp and paper mill sludge through different heating processes on thermal pretreatment. Journal of Cleaner Production, 168, 219–226.. Veluchamy, C., & Kalamdhad, A. S. (2017). Influence of pretreatment techniques on anaerobic digestion of pulp and paper mill sludge: A review. Bioresource Technology, 245(June), 1206–1219.. Bayr, S., Kaparaju, P., & Rintala, J. (2013). Screening pretreatment methods to enhance thermophilic anaerobic digestion of pulp and paper mill wastewater treatment secondary sludge. Chemical Engineering Journal, 223, 479–486.. 16 Fan, L. T., Gharphuray, M. M., & Lee, Y. H. (2013). Cellulose Hydrolysis. In Journal of Chemical Information and Modeling (Vol. 3). . Zhang, L., Gao, R., Naka, A., Hendrickx, T. L. G., Rijnaarts, H. H. M., & Zeeman, G. (2016). Hydrolysis rate constants at 10–25 °C can be more than doubled by a short anaerobic pre-hydrolysis at 35 °C. Water Research, 104, 283–291.. 17 Andrews, J., Smit, A. M., Wijeyekoon, S., McDonald, B., Baroutian, S., & Gapes, D. (2014). Application of hydrothermal treatment to affect the fermentability of Pinus radiata pulp mill effluent sludge. Bioresource Technology, 170, 100–107.. Park, N. D., Helle, S. S., & Thring, R. W. (2012). Combined alkaline and ultrasound pre-treatment of thickened pulp mill waste activated sludge for improved anaerobic digestion. Biomass and Bioenergy, 46, 750–756. . 18 Bonilla, S., Choolaei, Z., Meyer, T., Edwards, E. A., Yakunin, A. F., & Allen, D. G. (2018). Evaluating the effect of enzymatic pretreatment on the anaerobic digestibility of pulp and paper biosludge. Biotechnology Reports, 17(August 2017), 77–85.. 19 Gijzen, H. J., Zwart, K. B., Verhagen, F. J. M., & Vogels, G. P. (1988). High‐Rate two‐phase process for the anaerobic degradation of cellulose, employing rumen microorganisms for an efficient acidogenesis. Biotechnology and Bioengineering, 31(5), 418–425.. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 16 of 86. activated sludge streams have been considered20 resulting in up to 40 percent conversion of. the influent volatile solids. Shorter activated sludge solids retention time improves the yield. of fermentation products from the waste sludge and reduces the aeration energy demands in. the wastewater treatment21.. The applications of fermentation of cellulose rich sludges are considerably broadened to other. sectors by recent interests in resource recovery and energy capture in municipal wastewater. treatment processes22. Sieving technologies are well-developed for efficient capture of. cellulose sludges from wastewater. The sieved fibre solids create a dynamic filtration structure. which the sieving technology exploits for achieving a high degree of particulate matter capture. even from relatively diluted contaminated municipal wastewaters.. Skoghalls bruk - assessment of potential PHA production feedstocks. Stora Enso, Skoghalls bruk, is a pulp and paper mill in Värmland producing bleached and. unbleached sulphate pulp (370 kt/yr), and chemi-thermomechanical pulp (CTMP; 257 kt/yr),. for a total paper and board production of about 778 kt/yr23. A mass balance assessment was. made of selected process streams to estimate the availability of organic matter and the. potential for utilizing this for producing PHAs. Production methods for PHAs were to be. compatible with existing mill practices and infrastructure, and without disruption of the. . 20 Bayr, S., & Rintala, J. (2012). Thermophilic anaerobic digestion of pulp and paper mill primary sludge and co-digestion of primary and secondary sludge. Water Research, 46(15), 4713–4720. . Qi, B. C., Aldrich, C., Lorenzen, L., & Wolfaardt, G. W. (2005). Acidogenic fermentation of lignocellulosic substrate with activated sludge. Chemical Engineering Communications, 192(7–9), 1221–1242. . Lin, Y., Wu, S., & Wang, D. (2013). Hydrogen-methane production from pulp & paper sludge and food waste by mesophilic-thermophilic anaerobic co-digestion. International Journal of Hydrogen Energy, 38(35), 15055–15062. . Meyer, T., & Edwards, E. A. (2014). Anaerobic digestion of pulp and paper mill wastewater and sludge. Water Research, 65, 321–349. . 21 Hagelqvist, A. (2013). Sludge from pulp and paper mills for biogas production treatment and sludge management Sludge from pulp and paper mills for biogas production Strategies to improve energy performance in wastewater. Karlstad University Dissertation.. 22 Palmieri, S., Cipolletta, G., Pastore, C., Giosuè, C., Akyol, Ç., Eusebi, A. L., Frison, N., Tittarelli, F., & Fatone, F. (2019). Pilot scale cellulose recovery from sewage sludge and reuse in building and construction material. Waste Management, 100, 208–218. . Ruiken, C. J., Breuer, G., Klaversma, E., Santiago, T., & van Loosdrecht, M. C. M. (2013). Sieving wastewater - cellulose recovery, economic and energy evaluation. Water Research, 47(1), 43–48. . Ghasimi, D. S. M., de Kreuk, M., Maeng, S. K., Zandvoort, M. H., & van Lier, J. B. (2016). High-rate thermophilic bio-methanation of the fine sieved fraction from Dutch municipal raw sewage: Cost- effective potentials for on-site energy recovery. Applied Energy, 165, 569–582. . Ghasimi, D. S. M., Zandvoort, M. H., Adriaanse, M., van Lier, J. B., & de Kreuk, M. (2016). Comparative analysis of the digestibility of sewage fine sieved fraction and hygiene paper produced from virgin fibers and recycled fibers. Waste Management, 53, 156–164.. 23 miljodatabas.skogsindustrierna.org, 2017.. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 17 of 86. effluent management and the discharge water quality demands. Based on process information. provided by Skoghalls bruk, PHA production was evaluated based on residual fibre streams. and the microbial biomass (activated sludge) that is produced as a by-product in the existing. wastewater treatment process. . In 2018-2019 the wastewater treatment process received two principal streams (Appendix A). . One stream, significant in dissolved and suspended organic matter, was largely due to fibre. production with most significant inputs from CTMP pulping and the filtrate from the fibre. bleaching. The CTMP process water was pre-treated by sedimentation to remove suspended. solids dominated by sulphite impregnated cellulosic fibre24. Clarified CTMP effluent and. bleach mill filtrate were disposed to biological treatment. Other process streams included. condensates, sludge press waters, but these were not considered for the present evaluation.. The biological wastewater treatment process was a retrofitted aerated lagoon operated as an. activated sludge process with sludge sedimentation and return. From a two-year monitoring. record, the estimated average daily loading of organic matter was 15.1 tBOD/d with an average. influent flow rate of 26 720 m3/d. Given the reported process volume of 200 000 m3, the. theoretical process hydraulic retention time is 7.5 days. The process was operated as an. extended aeration activated sludge process25 with long solids retention time (SRT) of about 20. days. The suspended solids concentration in the lagoon was measured to be about 1 g/L, and. so the volumetric and specific organic loadings (0.08 kg-BOD/m3/d and kg-BOD/kgTSS/d). indicated the process as being low loaded25. The waste activated sludge was blended with waste. fibre sludge. The amount of active biomass produced was estimated from data of mean. biochemcial oxygen demand (BOD) removal across the bioprocess.. The second main effluent stream was largely due to paper machine operations. This fibre. effluent stream was of more significant hydraulic loading. It was dominated by suspended. solids (cellulosic fibres) and it had less significant content of dissolved organic matter. This. process effluent was also pre-treated by settling. The clarifier effluent was combined with the. final effluent coming from biological treatment. The combined effluent streams, from clarified. biological treatment and clarified paper machine process waters, were then polished by. chemical precipitation and suspended solids removal in two parallel clarifiers before final. effluent discharge to lake Vänern.. The combined sludge streams (gravity thickened surplus activated sludge, CTMP fibre sludge,. . 24 Environment Canada, The basic technology of the pulp and paper industry and its enivironmental practices, Training Manual EPS 6-EP-83-1. 25 Metcalf, & Eddy. (2003). Wastewater engineering: treatment and reuse (G. Tchobanoglous, F. L. Burton, H. D. Stensel, Metcalf, & Eddy (eds.); 4th ed.). McGraw-Hill.. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 18 of 86. paper machine fibre discharge sludge, and final chemical treatment sludge) were disposed to. dewatering presses wherein press water was returned to the biological treatment, and the. sludge cake went to incineration for steam production. . The detailed results supporting the mass balance evaluation are given in Appendix A. . Statistical analyses were made from influent and effluent data obtained from the mill routine. online monitoring (over 2 years of operations), and analyses from two events of grab sampling. in the summer and late autumn of 2018. Towards making this summary, grab samples were. found to be representative in water quality with respect to typical mean daily average values. from the two-year historical record. Therefore, grab sample measurements were used to. compliment with values necessary to complete the carbon mass flow estimations. The COD of. the suspended solids was expected to be cellulose dominated. Notwithstanding interpreted. sulphite impregnation of the CTMP fibre rich stream, a theoretical carbohydrate conversion of. 1.07 gCOD/gTSS was found to be a reasonable approximation of the organic content of the. suspended solids. Thus, reported COD values for the mass balance were meant to be indicative. of the material organic content only.. The mean daily loading for biological treatment was 15.1 tBOD/d with an estimated 95±3. percent reduction across the extended aeration process. Extended aeration processes are. robust, but energy use is typically relatively high. The high applied SRTs results in concurrent. aerobic digestion of the produced sludge with associated added oxygen demand, and as such,. additional aeration requirement. Reducing SRT reduces oxygen demand, while producing. more surplus biomass at the same time. Any additional biomass production was considered a. benefit if the biomass were to be utilized for polymer production. Today, additional biomass. production is avoided due to demands for sludge processing and dewatering. A conservative. sludge production yield25 of 0.5 kg volatile suspended solids (VSS) per kg BOD removed was. applied for the mass balance. Activated sludge suspended solids are typically represented with. an elemental composition C5H7O2N, giving a COD content with respect to produced volatile. suspended solids of 1.42 gCOD/gVSS. To distinguish between inert fibre suspended solids,. and metabolically active microbial biomass suspended solids (activated sludge), acronyms. fCOD and aCOD are used for fibre and active (biomass) suspended solids, respectively.. In excess of 50 tons COD residual cellulosic fibre is estimated to be captured on average per. day. Treatment of soluble organic matter further results in a potential production of about 10. tons COD per day of surplus activated sludge. Together, these two residual streams provide. the interpreted starting material supply and opportunity for side stream PHA production. . The residual fibre sludge is an important thermal energy source. Sludge dewatering of the. residual activated sludge is improved by admixing the waste biological sludge with fibre sludge. . At the same time, a lower degree of dewatering in the sludge press due to the presence of the. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 19 of 86. surplus activated sludge detracts from the heat production. . Diversion of a fraction of the residual organic matter, away from its conversion to heat. production, to biopolymer production is constrained by direct need for heat production for the. mill operations. However, it is considered that the permissible amount of diversion of organic. matter to PHA production will be larger if:. • energy demands for wastewater treatment operations are reduced, by, for example, reduced SRT giving reduced aeration energy demand. Reduced SRT will produce more. surplus activated sludge, and this higher yield is of synergistic benefit for biopolymer. production21, and/or. • a higher degree of dewaterability is achieved for the organic matter disposed to heat production due to a potential to improve overall sludge dewaterability from the sludge. fermentation26.. It was estimated that the gravity thickened fibre rich streams could supply a residual (fibre). organic mass of approximately 53.6 tCOD/day (fCOD). In addition, aerobic removal of 14.3. tBOD/d, may generate an estimated potential source of 10.1 tCOD/d as an active microbial. biomass (aCOD). In the fibre rich streams, before dewatering, an additional estimated carry. over of 6.3 tCOD/day (sCOD) was included. This fCOD, aCOD and sCOD represented organic. feedstocks available for a combination of PHA and boiler heat production (Figure 1). The. organic residual flow is estimated to be approximately 0.09 tCOD per kiloton of mill product. . . 26 Yu, L., Zhang, W., Liu, H., Wang, G., & Liu, H. (2018). Evaluation of volatile fatty acids production and dewaterability of waste activated sludge with different thermo-chemical pretreatments. International Biodeterioration and Biodegradation, 129(January), 170–178. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 20 of 86. Figure 1. Estimated (Appendix A) potential average daily flows of residual fibre, active. biomass, and soluble tons of COD (fCOD, aCOD, and sCOD respectively) discharged to. dewatering and incineration today at Skoghalls Bruk (above). Scenario considered in the. present investigation for integration of PHA production with these organic streams (below). . All numbers in units of tCOD/d.. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 21 of 86. Rottneros bruk - assessment of potential PHA production feedstocks. Rottenros AB, Rottenros bruk, is a pulp mill in Värmland producing CTMP (101 kt/yr), and. mechanical pulp (71 kt/yr)27. A mass balance assessment was made based on the main mill. effluent process streams in order to estimate the availability of residual organic matter and the. corresponding potential for utilizing this residual organic matter for producing PHAs. . Production methods for PHAs were to be compatible with existing mill practices and. infrastructure, and without disruption to meeting final effluent quality discharge demands.. Based on process information provided by Rottneros Bruk, PHA production was considered. from residual fibre streams and the microbial biomass (waste activated sludge) that is. produced as a by-product of the existing wastewater treatment process. . In 2018-2019 the wastewater treatment process comprised the management of one principal. effluent stream from the pulp mill (Appendix B). In additional, water from the lumber pre-. treatment (renserivatten) is present but this stream has not been included in the assessment. of potential PHA production feedstock as information was not available for considering the. suspended solids content of the renserivatten. Based on the soluble COD flows, it was. estimated that the renserivatten flow was about 9 percent of the total effluent flow. In the. main effluent stream, significant amounts of dissolved and suspended organic matter are. removed. Suspended solids (assumed as being fibre rich) were removed by two clarifiers. operated in series. Renserivatten was disposed to the second of these clarifiers. Primary. treated effluent was disposed to biological treatment which comprised a combination of. anaerobic and aerobic processes. An anaerobic expanded granular sludge bed (EGSB) process,. which was being commissioned at the time, was designed to take a flexible share of the organic. load. Thus, anaerobic treatment was in series before aerobic biological treatment, but the. anaerobic stage could also be by-passed to a selected degree. The aerobic treatment process. was operated with an estimated hydraulic retention time of 0.5 days and a high organic loading. (4 to 8 kgCOD/m3/d with respect to biodegradable soluble COD). . Monitoring data for the activated sludge effluent suggested loss of solids from the secondary. clarifier. Soluble COD removal across the whole biological treatment process indicated that. about a quarter of the biodegradable soluble organic loading was not removed. . Notwithstanding, the final chemical treatment process (precipitation and gravity separation). produced a final effluent to levels of interpreted complete removal of bioavailable soluble COD. . A greater degree of biological removal of the organic loading to the treatment process should. enable a reduction of the chemical demand for the effluent polishing. An anticipated. . 27 miljodatabas.skogsindustrierna.org, 2017.. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 22 of 86. additional significant organic loading due to colloidal biodegradable organic matter was not. considered implicitly in this work due to the selective nature of the soluble COD monitoring. data that was provided. Therefore, the mass balance for PHA production was conservative. . Treated final effluent was discharged to the Rottnan river. The sludge streams (gravity. thickened surplus activated sludge, fibre sludge, and final chemical treatment sludge) were. disposed to dewatering presses wherein press water was returned to the biological treatment,. and the sludge cake (estimated by the mill to be nominally 8000 dry tons per year) went to. land disposal. . The detailed results supporting the mass balance evaluation are given in Appendix B. . Statistical analyses were made from mill data obtained from the mill routine monitoring (over. 1 year of operations), and analyses from two events of grab sampling in the late autumn of 2018. and spring of 2019. Grab samples and batch assays were used to estimate a 78 percent. biodegradable fraction of the mill process effluent soluble COD. . The COD of the suspended solids was expected to be cellulose dominated. A theoretical. carbohydrate conversion of 1.07 gCOD/gTSS was used to give a reasonable approximation of. the organic content from the data of mill total suspended solids. . The potential to produce activated sludge biomass was based on the estimated optimal degree. of soluble COD removal across the biological treatment process. A conservative sludge. production yield25 of 0.2 kgVSS per kg COD removed was applied. As discussed for Skoghalls. bruk case, activated sludge was assumed with a COD content with respect to produced volatile. suspended solids of 1.42 gCOD/gVSS. Acronyms fCOD and aCOD are used for fibre and active. (biomass) suspended solids, respectively.. It was estimated that the gravity thickened fibre rich streams may supply a residual organic. mass of approximately 36.5 tCOD/day (fCOD). In addition, aerobic removal of 29.4 tCOD/d. soluble biodegradable organic matter, could generate an estimated potential source of 8. tCOD/d as active microbial biomass (aCOD). This fCOD and aCOD represent potential organic. feedstocks for PHA production, and are available to be diverted from disposal today (Figure. 2). Unconverted mass of suspended solids after the PHA production process may be dewatered. and sent for heat production, instead of land disposal as it was at the time of this study. The. estimated residual organic flow is approximately 0.09 tCOD per kiloton of mill product. Thus,. relatively speaking, organic residual mass flows were similar for both mills.. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 23 of 86. Figure 2. Estimated (Appendix B) potential average daily flows of residual fibre and active. biomass tons of COD (fCOD and aCOD) discharged to dewatering and land fill as performed. today at Rottneros bruk (above). Scenario considered in the present investigation for. integration of PHA production with these organic streams (below). All numbers in units of. tCOD/d.. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 24 of 86. Integration of PHA production at Skoghalls and Rottneros bruk. With reference to Figure 1 and Figure 2, estimations of mass balance on a COD basis were. undertaken to quantify scale of PHA production from the anticipated residual streams. comprised largely of cellulose rich residual fibre (fCOD) and waste activated sludge (aCOD). . From the fibre and active biomass flows, this section considers scenarios of estimated mass. flows of dissolved organic residuals (sCOD), VFAs (vCOD), PHA (pCOD), and mixed. suspended organic matter in general (xCOD).. Calculations for conversion of organic matter to polymer that are made on a COD basis remove. a dependency of the outcomes with respect to the type of polymer produced by the bacteria. . The composition of a VFA mixture, fed to a PHA accumulating biomass, will influence the. composition of the resulting PHA. Even number carbon chain length for the VFAs promote. formation of 3HB polymeric units, and odd number organic acids promote formation of 3HV. polymeric units. VFA mixtures will be converted typically into random co-polymer blends of. PHBV. The COD content of poly-3HB and poly-3HV is 1.67 and 1.92 gCOD/g, and for the. present work, the conversion factor 1.67 gCOD/g was used. Activated sludge biomass produced. in biological treatment processes is assumed to have a COD content of 1.42 gCOD/g. . Two similar process scenarios were considered for Skoghalls and Rottneros mills (Figure 3 and. Figure 4). The two scenarios that were considered are not mutually exclusive, and they could,. in the long term, represent a logical progression of development with steps of investment and. risk management towards establishing infrastructure and mass flows of diverting residual. organic mass to increasing production levels of biopolymers. The scenarios are 2 steps in. progression as follows:. Step 1. Surplus activated sludge is just an organic feedstock for VFA production. Step 2. Surplus activated sludge is a functional PHA storing biomass.. The first scenario (upper schematic in Figure 3 and Figure 4) assumes that the surplus. activated sludge from the wastewater treatment is not of a suitable quality to be able to. accumulate PHA to a sufficient level. This means that, when this microbial biomass is fed in a. controlled manner with VFA rich substrates, the bacteria do not accumulate PHA significantly. . In this regard, a biomass polymer content of 0.4 gPHA/gVSS has previously been considered. a threshold of enough polymer in the biomass towards making the downstream polymer. recovery practically and economically interesting8. Thus, in the first scenario, the "aCOD" is. not valued for its active microbial potential. It is simply an organic residual feedstock (sludge. or xCOD) that can be hydrolysed and fermented anaerobically to produce a VFA rich. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 25 of 86. effluent28,29. In the second scenario (lower schematic in Figure 3 and Figure 4), the aCOD. derived from the wastewater treatment process is of suitable quality to be exploited directly for. its activity of PHA storage. The following sections review and discuss the information of COD. balances presented in Figure 3 and Figure 4, as an outcome from the mill data assessments of. COD mass flows that have been summarized from Appendices A and B.. Scenario 1 - Surplus activated sludge as just a feedstock for VFAs. In this scenario, all the mill residual organic mass, including the waste activated sludge (WAS),. is disposed to acidogenic fermentation for VFA production. The ensuing active enzymatic. activity of the sludge may contribute positively to the hydrolytic levels and fermentation. performance. The literature suggests a yield of up to about 0.4 g of VFAs (as COD) per g of. COD6. The non-hydrolysed suspended solids can be separated from the VFA rich feedstock. . These suspended solids are dewatered, and incinerated. In the case of Skoghalls Bruk, this is. the same boiler heat as produced today. For Rottneros Bruk, boiler heat is considered as an. added value to the current fate of land disposal for the mill waste sludge today.. Boiler heat production is offset by the wet content of the waste sludge (xCOD) after. fermentation. Comparing the upper schematic diagrams Figure 1 and Figure 3, the organic. supply for incineration is reduced from 63.7 tCOD/d to 42.0 tCOD/d. While this may suggest. a 35 percent loss of potential heat production, it is anticipated that the fermentation producing. "xCOD" (Figure 3) will result in a dewatered sludge of lower moisture content. Activated. sludge is resistant to dewatering due, in part, to the extracellular polysaccharides that are. bridging the cells as a wet viscous mass by cations. Fermentation is expected to hydrolyse and. ferment much of this extracellular material resulting in a sludge structure that retains water. less firmly. In addition, the mill wastewater treatment process can be operated with a reduced. SRT. Reduction of SRT can be to levels where more biomass is produced with improved. fermentability for VFA production all the while treatment performance in effluent water. quality demands is still maintained. The SRT reduction will also decrease the biological. treatment oxygen demands resulting in energy savings. The organic supply for thermal. treatment may become reduced due to side stream PHA production, but any anticipated boiler. heat production losses will be significantly compensated for.. . 28 Luo, K., Pang, Y., Yang, Q., Wang, D., Li, X., Lei, M., & Huang, Q. (2019). A critical review of volatile fatty acids produced from waste activated sludge: enhanced strategies and its applications. Environmental Science and Pollution Research, 13984–13998.. 29 Zhang, L., Liu, H., Zheng, Z., Ma, H., Yang, M., & Liu, H. (2018). Continuous liquid fermentation of pretreated waste activated sludge for high rate volatile fatty acids production and online nutrients recovery. Bioresource Technology, 249(October 2017), 962–968. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 26 of 86. There is a potential for improved collective efficiency through intra-mill cooperation in PHA. production. Instead of disposing the fCOD and aCOD from Rottneros Bruk, the combined. sludge could be sent to a cooperative venture between both mills for boiler heat production. A. regional industrial symbiosis can be constructed, reducing the risks for any mill investment for. PHA, improving the collective economy of scale, and resulting in pro-rated win-win sharing.. The adjunct mass of polymers produced can still feed respective mill in-house proprietary new. materials, formulations, methods and processes leading to independent mill in-house product. and business developments.. The VFA rich stream (vCOD) separated from the anaerobic fermentation effluent is split into. two flows. Some of the vCOD is utilized for aerobically producing a microbial biomass that is. enriched with significant PHA storing potential10. Most of the vCOD is directed towards. accumulating PHA in biomass that is produced. The enrichment biomass PHA accumulation. potential was assumed to be 0.60 gPHA/gVSS. Conversions were assumed where nominally. 0.42 g-aCOD is produced per g-vCOD and 0.60 g-pCOD is produced per g-vCOD. The effluent. of the production process is a biologically treated wastewater yielding a PHA rich biomass. For. Skoghall and Rottneros this was estimated to be in the order of 9.4 and 2.0 tons of polymer as. COD (pCOD) per day, or about 2000 and 400 tons mass of PHA per year.. Scenario 2 - Surplus activated sludge as a PHA storing biomass. In this scenario, the surplus activated sludge produced during the effluent treatment is. anticipated to maintain a PHA accumulation potential of 0.60 gPHA/gVSS. Waste activated. sludge with significant PHA storing potential, from the biological treatment of industrial and. municipal wastewaters, has been repeatedly demonstrated in laboratory, pilot and full-scale. . Generally, activated sludge with PHA storing potential requires an influent wastewater with. readily biodegradable organic matter. The bacteria that dominate the activated sludge will. exhibit significant PHA storage potential if the bioprocess design and operating conditions. somehow favours more growth for those microorganisms that can store PHA. . One of the principles for enrichment of PHA storage entails exposing the microorganisms to. alternating conditions of high and low availability of readily biodegradable organic matter. (RBCOD) as part of the treatment process. When the RBCOD loading is high, bacteria will tend. to take up organic matter and store it in the form of PHA. When RBCOD is unavailable to the. bacteria, they will use most of the stored PHA for growth and survival. These bioprocess. conditions are often referred to as “feast and famine” conditions and will give PHA-storing. microorganisms a competitive advantage over those non-storing microorganisms. Feast and. famine conditions may be established in a treatment process with plug-flow or with several,. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 27 of 86. more or less well-defined, volumes in series with inherent changes in relative levels of organic. loading. A typical example is a process with a selector (smaller volume) to which recirculated. activated sludge and influent wastewater are directed causing local, high (feast) organic. loading conditions followed by lower (famine) organic loading conditions in the subsequent. process volumes.. Other factors that can favour presence of these naturally occurring PHA storing. microorganisms can be related to:. • the quality of the readily RBCOD,. • the presence of VFAs representing the RBCOD,. • the fate and management and relative amount of other biodegradable organic matter,. • the average quality, length, and frequency of feast and/or famine,. • the presence of essential nutrients (like nitrogen and phosphorus) relative to the RBCOD,. • the timing of nutrient addition,. • the SRT, and/or. • the perturbation of the microbial biomass with feast or famine in a side-stream.. The biological wastewater treatment plants at Skoghalls and Rottneros mills have not been. implemented with principles in mind to select for a PHA storing activated sludge. . Notwithstanding, some degree of enrichment for PHA storage is expected in almost all. biological treatment processes. The shift to a greater contribution of PHA storing organisms. can often be achieved by paying closer attention to these more subtle details in the engineering. of the process environments and dynamic conditions the biomass experience. Such details do. not necessarily require onerous or expensive upgrades to an existing process. They can be. related to small adjustments like:. • creating an optimal and well-defined contact zone for the return activated sludge with the influent wastewater, . • ensuring strategic addition in mass and timing of other nutrients to the process, application of an aerobic or anaerobic selector, . • promoting fermentation before aerobic treatment, and/or . • exposing the biomass to periodic conditions (perturbations) of feast or famine in a side stream.. Pulp mill wastewaters are nutrient limited for aerobic biological treatment and contain. fermentable RBCOD. CTMP effluents typically already contain significant levels of acetic acid. . Commonly the effluent management includes some form of aerobic biological process. To this. end both suspended and biofilm processes treating for COD removal at a pulp and paper mill. can result in a surplus activated sludge with significant presence of the PHA storing organisms. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 28 of 86. The lower schematic in Figure 3 and Figure 4 was developed to consider the potential for PHA. production at Skoghall and Rottneros given a realistic expectation in the future to obtain an. activated sludge biomass from the mill wastewater treatment expressing an accumulation. potential of 0.60 gPHA/gVSS.. As in the first scenario, fibre solids are fermented to generate a vCOD stream. Some surplus. activated sludge is also directed to anaerobic fermentation because fibre input alone with a. yield production, of up to about 0.4 grams of VFAs (as COD) recovered per input gram of fCOD. input, would not generate enough VFAs for the mass of available waste activated sludge. The. fermentation, furthermore, can be served by the inoculum of at least some added waste. activated sludge. The PHA accumulation process was considered as before with 0.60 g-pCOD. produced per g-vCOD. For Skoghall and Rottneros mills, this was estimated to result in the. order of 14.4 and 3.1 -tons polymer as COD (pCOD) per day, or about 3100 and 680 -tons mass. of PHA per year, respectively. A 50 % greater amount of polymer can be produced in this. scenario because directly exploiting the surplus activated sludge for its storage activity avoids. the Scenario 1 production of a separate PHA storing biomass.. For Skoghalls Bruk, the organic mass (xCOD) delivered for thermal treatment is reduced. (Figure 3) from 42 tCOD/d (upper schematic) to 37 tCOD/d (lower schematic). However, this. xCOD in Scenario 2 may also be anticipated to contain negligible amounts of surplus activated. sludge and, as such, would be expected to be most optimal in dewaterability. PHA production. in the second scenario results in the net export of most of the mill surplus activated sludge in. the form of an upgraded PHA rich biomass. Rottneros Bruk also could deliver 7.9 tons per day. of fibre dominated xCOD in this scenario (Figure 4). This fibre sludge could be directed. towards heat production instead of disposal as it is today.. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 29 of 86. Considerations for next steps. In this evaluation, a number of assumptions were made for yields and performance in PHA. accumulation. Validation of process and assumptions for Scenario 1 at pilot scale is the most. logical next step. Production of PHA with residual organic streams from either Skoghalls or. Rottneros mills enables an engagement of initial techno-economic and regional development. without necessitating changes to current mill operations. In pilot scale evaluations, the. experience would generate an appreciation of the technical and economic opportunities for. further developments. It would add to the understanding of utilizing by-products as resources. rather than treating them as wastes. At pilot scale, the impact on mill operations would be. negligible, so this would permit a comprehensive evaluation without risk to current operations. and practices.. It has been assumed based on the scientific literature, that VFA rich effluents will be generated. from the anaerobic fermentation of the selected feedstocks. Towards this end, the present. research experience is mostly with processes focused on methane production. VFAs can be. intermediary platform chemicals leading to either biogas or PHAs. Therefore, there should be. a range of robust bioprocess options, temperatures and conditions of implementation using. open mixed cultures or, where circumstances permit, specific organisms like. Caldicellulosiruptor saccharolyticus, depending on economic or technical requirements on. the fermentation bioprocess. Acidogenic fermentation can include more or less release of. hydrogen, where the yield of VFAs will decrease the more that hydrogen is produced. For the. case of Skoghalls bruk, diversion of organic matter for PHA production will reduce the flow of. organic matter to heat generation. Water content of sludge negatively impacts heat generation. . The literature suggests that reduced organic feedstock for boiler heat will be offset by improved. dewaterability of sludges sent for thermal treatment, and by lowering the mill biological. wastewater treatment SRT. For the case of Rottneros bruk, diversion of waste organic mass to. PHA production creates an opportunity for both polymers and heat generation, that the mill. does not practice today. . Due to the difference in amounts of residual organic streams managed by Skoghalls and. Rottneros mills, Skoghalls bruk is estimated to have about a 5-fold larger potential for PHA. production (2000 tPHB/yr with Scenario 1 at Skoghalls bruk). The investment for PHA. production infrastructure will be benefited by scales of economy. There is no necessity that. each mill should manage its own biopolymer production process. Scenario 1 feedstocks are. similar to both mills (residual fibre and waste sludges), suggesting that cooperation in. feedstock supplies, investments, and dividends in successful PHA production can reduce. individual company risks while generating better economy for mutually beneficial outcomes,. or win-win. Such industrial symbiosis is not a pre-requisite, but it may be worth to consider. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 30 of 86. seriously. Dewatered sludges can be transported, and the polymer production facility can be. located where the operations can fit most synergistically within the overall considerations of. process, economy and environmental performances. The polymers produced can be. distributed to participating companies based on respective financial and feedstock. contributions. Distributed polymers may serve distinctly different and respective company. interests, innovations and business developments.. The gains in PHA production capacity that comes with Scenario 2 motivate making changes to. a mill biological wastewater treatment process to improve the performance of the waste. activated sludge for its use directly for PHA accumulation. While such process changes do not. need to be complicated or major, they introduce (perceived or real) risk for the investment and,. as well, an increased dependency on the present-day mill operations. The activities of PHA. production operations will develop a greater vested interest and dependency on the effluent. management methods for environmental protection as well as novel products and services. . Therefore, Scenario 1 is considered a preferred first step as it permits the technology and. economy of PHA production to become established at first as relatively independent of the mill. daily operations. If Scenario 1 is viable economically, then Scenario 2 is motivated because the. required interdependencies will be with reduced risk, due, in part, to established viable. production experience and promise of significantly greater economic benefits. Towards future. developments of a Scenario 2, PHA accumulation potential of the surplus activated sludge was. evaluated for Skoghalls and Rottneros mills. This practical evaluation is the subject of the next. section of this report.. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 31 of 86. Figure 3. Two PHA production schemes at Skoghalls bruk with projections of mass balance. on a COD basis for fibre (fCOD), activated sludge biomass (aCOD), soluble organic matter. (sCOD), VFAs (vCOD), sludge (xCOD) and PHA (pCOD). The upper process scenario. considers the influent activated sludge as just a feedstock for VFAs, while the lower scenario. exploits the input aCOD for an assumed potential to accumulate PHA to 0.6 gPHA/gVSS. All. numbers in tCOD/d.. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 32 of 86. Figure 4. Two PHA production schemes at Rottneros bruk with projections of mass balance. on a COD basis for fibre (fCOD), activated sludge biomass (aCOD), VFAs (vCOD), sludge. (xCOD) and PHA (pCOD). The upper process scenario considers the influent activated sludge. as just an organic sludge source for VFAs, while the lower scenario exploits the input aCOD. for an assumed metabolic potential to accumulate PHA to 0.6 gPHA/gVSS. All numbers in. tCOD/d.. . MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 33 of 86. PHA accumulation potential of activated sludge from Skoghalls and Rottneros mills. The daily tons of mass of by-product surplus activated sludge that are produced at the mills. require management and, currently, some strategy and routine for its disposal. Skoghalls bruk. dewaters this waste activated sludge together with residual fibres and the dewatered organic. mass is disposed to thermal destruction for boiler heat production. Fibre addition to the waste. activated sludge improves the activated sludge dewaterability. Rottneros bruk similarly. dewaters a mix of fibre, bioprocess and chemical treatment residual sludges, and the. dewatered mass is disposed to landfill.. In the preceding mass balance evaluations, it was proposed that, at the very least, the mill. waste activated sludge could be considered as an organic sludge resource (upper schematic in. Figure 3 and Figure 4). The waste sludge may be fermented anaerobically to yield a volatile. fatty acid stream for PHA and a sludge stream for heat production. If the activated sludge. exhibits, or could be made to exhibit, a significant PHA storing potential, then the surplus. activated sludge could be exploited for its metabolic activity (Scenario 2), rather than "just" its. organic content (Scenario 1). In this way, it was estimated that Skoghalls and Rottneros PHA. production potentials could be increased by about 50 percent from 2000 to 3100 tPHA/yr, and. 400 to 680 tPHA/yr, respectively. Therefore, for the purposes of the Multibio, the extant PHA. accumulation potential of the surplus activated sludge from Skoghalls and Rottneros mills was. assessed to document the PHA storing capacity levels as it is today.. The PHA accumulation potential (PAP) of activated sludge grab samples were evaluated by. monitoring storage of PHA in the activated sludge in response to controlled feeding of acetic. acid for up to 30 h under aerobic conditions. Acetic acid is converted to PHB, the most. common type of PHA found in nature. The applied methods and materials for the PAP testing. are provided in Appendix C. . Acetic acid was fed by feed-on-demand. A feed-on-demand strategy entails dosing of substrate. to a respiring microbial biomass semi-continuously and in step with the concurrent rate of. substrate consumption. There should be no net build-up of the supplied substrate over time. . Aliquots of substrate are provided to the biomass to reach targeted peak concentrations in the. order of 100 mgCOD/L per pulse. The peak concentrations are intended to stimulate maximal. or near maximal substrate uptake rates. If the biomass is enriched with PHA accumulation. potential, these conditions favour polymer storage. The competition of substrate for polymer. storage instead of microbial growth can be made more stringent by limiting the availability of. nutrients such as nitrogen and/or phosphorus in the process.. The substrate should not be over supplied and thereby open the opportunity for active biomass. growth due to a build-up of a continuously available organic substrate with all other necessary. MultiBio - WP2 2020-12-04. Promiko AB REPORT 18-01-A Page 34 of 86. nutrients also present. It should also not be under-supplied and enable consumption of any. already accumulated PHA due to an onset of starvation conditions. So, the feeding rate needs. to be well-controlled to maintain a maximal or near maximal response that promotes polymer. storage without overshooting to bring an excess in substrate supply or undershooting to. starvation conditions. These principles can be applied readily in the laboratory but also in. scaled up process.. The substrate consumption rate during PHA accumulation is furthermore not necessarily. constant. As the biomass become saturated with polymer, and with some limitation of other. nutrients, the respiration (and substrate consumption) rates will decrease progressively. If the. substrate contains sufficient nutrients for growth, then an onset of selective growth concurrent. in and with the PHA storing biomass may result in a progressive increase in the volumetric. rates of respiration and substrate consumption. Substrate supply methods are part of the. technology and art for the PHA production process. Bioprocess conditions can be generated. for the selective growth of PHA storing bacteria while maintaining constant biomass PHA. content30,35.. In the present work, a hybrid control algorithm was used to apply feed-on-demand for PAP.

No results found