Background

Caldicellulosiruptor saccharolyticus is an attractive hydrogen producer suitable for growth on various lignocellulosic substrates. The aim of this study was to quantify uptake of pentose and hexose monosaccharides in an industrial substrate and to present a kinetic growth model of C. saccharolyticus that includes sugar uptake on defined and industrial media. The model is based on Monod and Hill kinetics extended with gas-to-liquid mass transfer and a cybernetic approach to describe diauxic-like growth.

Results

Mathematical expressions were developed to describe hydrogen production by C. saccharolyticus consuming glucose, xylose, and arabinose. The model parameters were calibrated against batch fermentation data. The experimental data included four different cases: glucose, xylose, sugar mixture, and wheat straw hydrolysate (WSH) fermentations. The fermentations were performed without yeast extract. The substrate uptake rate of C. saccharolyticus on single sugar-defined media was higher on glucose compared to xylose. In contrast, in the defined sugar mixture and WSH, the pentoses were consumed faster than glucose. Subsequently, the cultures entered a lag phase when all pentoses were consumed after which glucose uptake rate increased. This phenomenon suggested a diauxic-like behavior as was deduced from the successive appearance of two peaks in the hydrogen and carbon dioxide productivity. The observation could be described with a modified diauxic model including a second enzyme system with a higher affinity for glucose being expressed when pentose saccharides are consumed. This behavior was more pronounced when WSH was used as substrate.

Conclusions

The previously observed co-consumption of glucose and pentoses with a preference for the latter was herein confirmed. However, once all pentoses were consumed, C. saccharolyticus most probably expressed another uptake system to account for the observed increased glucose uptake rate. This phenomenon could be quantitatively captured in a kinetic model of the entire diauxic-like growth process. Moreover, the observation indicates a regulation system that has fundamental research relevance, since pentose and glucose uptake in C. saccharolyticus has only been described with ABC transporters, whereas previously reported diauxic growth phenomena have been correlated mainly to PTS systems for sugar uptake.

Background: The members of the genus Caldicellulosiruptor have the potential for future integration into a biorefinery system due to their capacity to generate hydrogen close to the theoretical limit of 4 mol H2/mol hexose, use a wide range of sugars and can grow on numerous lignocellulose hydrolysates. However, members of this genus are unable to survive in high sugar concentrations, limiting their ability to grow on more concentrated hydrolysates, thus impeding their industrial applicability. In this study five members of this genus, C.owensensis, C. kronotskyensis, C.bescii, C.acetigenus and C.kristjanssonii, were developed to tolerate higher sugar concentrations through an adaptive laboratory evolution (ALE) process. The developed mixed population C.owensensis CO80 was further studied and accompanied by the development of a kinetic model based on Monod kinetics to quantitatively compare it with the parental strain. Results: Mixed populations of Caldicellulosiruptor tolerant to higher glucose concentrations were obtained with C.owensensis adapted to grow up to 80 g/L glucose; other strains in particular C. kristjanssonii demonstrated a greater restriction to adaptation. The C.owensensis CO80 mixed population was further studied and demonstrated the ability to grow in glucose concentrations up to 80 g/L glucose, but with reduced volumetric hydrogen productivities (QH2) and incomplete sugar conversion at elevated glucose concentrations. In addition, the carbon yield decreased with elevated concentrations of glucose. The ability of the mixed population C.owensensis CO80 to grow in high glucose concentrations was further described with a kinetic growth model, which revealed that the critical sugar concentration of the cells increased fourfold when cultivated at higher concentrations. When co-cultured with the adapted C.saccharolyticus G5 mixed culture at a hydraulic retention time (HRT) of 20 h, C.owensensis constituted only 0.09–1.58% of the population in suspension. Conclusions: The adaptation of members of the Caldicellulosiruptor genus to higher sugar concentrations established that the ability to develop improved strains via ALE is species dependent, with C.owensensis adapted to grow on 80 g/L, whereas C.kristjanssonii could only be adapted to 30 g/L glucose. Although C.owensensis CO80 was adapted to a higher sugar concentration, this mixed population demonstrated reduced QH2 with elevated glucose concentrations. This would indicate that while ALE permits adaptation to elevated sugar concentrations, this approach does not result in improved fermentation performances at these higher sugar concentrations. Moreover, the observation that planktonic mixed culture of CO80 was outcompeted by an adapted C.saccharolyticus, when co-cultivated in continuous mode, indicates that the robustness of CO80 mixed culture should be improved for industrial application. © 2021, The Author(s).

Background: Current EU directives demand increased use of renewable fuels in the transportation sector but restrict governmental support for production of biofuels produced from crops. The use of intercropped lucerne and wheat may comply with the directives. In the current study, the combination of ensiled lucerne (Medicago sativa L.) and wheat straw as substrate for hydrogen and methane production was investigated. Steam-pretreated and enzymatically hydrolysed wheat straw [WSH, 76% of total chemical oxygen demand (COD)] and ensiled lucerne (LH, 24% of total COD) were used for sequential hydrogen production through dark fermentation and methane production through anaerobic digestion and directly for anaerobic digestion. Synthetic co-cultures of extreme thermophilic Caldicellulosiruptor species adapted to elevated osmolalities were used for dark fermentation. Results: Based on 6 tested steam pretreatment conditions, 5 min at 200 °C was chosen for the ensiled lucerne. The same conditions as applied for wheat straw (10 min at 200 °C with 1% acetic acid) would give similar sugar yields. Volumetric hydrogen productivities of 6.7 and 4.3 mmol/L/h and hydrogen yields of 1.9 and 1.8 mol/mol hexose were observed using WSH and the combination of WSH and LH, respectively, which were relatively low compared to those of the wild-type strains. The combinations of WSH plus LH and the effluent from dark fermentation of WSH plus LH were efficiently converted to methane in anaerobic digestion with COD removal of 85-89% at organic loading rates of COD 5.4 and 8.5 g/L/day, respectively, in UASB reactors. The nutrients in the combined hydrolysates could support this conversion. Conclusions: This study demonstrates the possibility of reducing the water addition to WSH by 26% and the phosphorus addition by 80% in dark fermentation with Caldicellulosiruptor species, compared to previous reports. WSH and combined WSH and LH were well tolerated by osmotolerant co-cultures. The yield was not significantly different when using defined media or hydrolysates with the same concentrations of sugars. However, the sugar concentration was negatively correlated with the hydrogen yield when comparing the results to previous reports. Hydrolysates and effluents from dark fermentation can be efficiently converted to methane. Lucerne can serve as macronutrient provider in anaerobic digestion. Intercropping with wheat is promising.

Copper (Cu) and zinc (Zn) with their unique propertiesare central for economic growth, quality of life and creation of new jobs. The base-metalproducing sector is, however, under growing public pressure in respect toenergy and water requirements and needs to meet several challenges, includingincreased demand and lower ore grades generally associated with larger resourceuse. The development of technologies for metal production from secondarysources is often motivated by increased sustainability and this paper aims to providefurther insights about one specific aspect of sustainability, namely climatechange. The paper presents a review of carbon footprints (CF) for Cu and Znproduced from primary and secondary raw materials, by analyzing data taken fromscientific literature and the Ecoinvent database. Comparisons are carried outbased on the source of data selected as reference case. In the case of Cu,reduced CF of secondary production is indicated, although there is large datavariation. As for Zn, production of this metal from secondary sources seems to bebeneficial but the number of data and cases to be compared is much smallercompared to Cu. The general variation of data suggests that standardization ofcomparison is needed when assessing the environmental benefits of production inline with the principles of waste valorization, zero waste approach andcircular economy.

Vanadium exists as a mobile and toxic trace metal in many alkaline residue leachates. Its removal and recovery not only reduces a global environmental risk but is also critical to the emergence of innovative technologies and the circular economy. In parallel, the use of treated biomass feedstock is receiving increased attention as a low cost adsorbent for toxic metals in wastewater. This study investigated the adsorption of Vanadium (V) from aqueous solution by KOH modified seaweed (Ascophyllum nodosum) hydrochar (HCKOH). The results showed that HCKOH is an effective V(V) adsorbent, achieving maximum uptake of 12.3 mg g-1 at solution pH 4, 60 min contact time and temperature 293 K. The kinetics followed a pseudo second order model with film diffusion controlling the overall adsorption rate. The type I adsorption isotherm was well fitted to a Langmuir model (qm = 12.3 mg g-1, R2 = 0.970, RMSE = 0.66) and a thermodynamic study indicated that the V(V) adsorption was both exothermic and spontaneous. The low enthalpy change (-10.97 kJ mol-1) indicated a weak binding of V(V) to HCKOH pointing to the possibility of V recovery. The impact of co-existing cations on V(V) uptake was negligible for Na(I) and Ga (III) but was reduced slightly for Al(III). Desorption and re-adsorption results (3 cycles) indicated that HCKOH has reusable potential to remove and recover V(V) from waste leachates. © 2020 The Author(s).

Owners of stables and owners of zoos have difficulty finding an economically sustainable deposition of their produced manure. More than two million tons of horse manure are produced in urban environments in Sweden every year. If the manure cannot be used as fertilizer on farm land it is classified as a waste fraction and should be handled according to current regulations. The manure is a valuable waste fraction that contains both energy and nutrients. If the manure cannot be spread on farm land more applications need to be identified, where the energy and nutrients in the manure can be used. The focus in this study is to investigate possible applications for the usage of horse and zoo manure within Borås municipality where, among other things, a waste water treatment plant and a combined heat and power plant are available. Horse and zoo manure have been investigated in the following applications: co-digestion with sewage sludge at a waste water treatment plant (lab experiments), co-digestion with food waste (theoretical), co-incineration with waste (full scale) and co-incineration with biomass (theoretical). Potential quantity of manure and economical and legal aspects have been studied as well. There is no compilation of the number of horses in the country which makes it hard to estimate the true quantity of manure. The quantity of manure from the zoos are somewhat easier to estimate since the zoo owners are fewer and have knowledge of their manure production. The co-digestions experiments in this study showed that addition of horse manure to digestion can be of interest in many ways, among other things it can give a more stable biogas production and a possible decrease in the Cd/P-ratio in the end product. Horse manure turned out to have a faster degradation rate compared to zoo manure, however the degradation rate was lower than that of sewage sludge. Zoo manure gave a relatively low biogas production compared to horse manure at thermophilic conditions. The co-incineration trial with waste and manure gave no negative effect with regard to emissions and operation. However, the amount of manure added to the incineration trial was low. The theoretical studies regarding the co-incineration with biomass, showed two potential alternatives that need to be investigated further. Interesting aspects to look further upon, based on this study, are for example: • Laws and regulations in the EU regarding manure. • Co-digestion of manure and sewage sludge in a larger scale. • Laws and regulations and costs regarding incineration of manure with biomass.

Sverige har som mål att ha 100% förnybar kraftproduktion år 2040. Detta skall uppnås genom attbl.a. kraftigt bygga ut den intermittenta kraftproduktionen med t.ex. vindkraft. En ökad andel vindkraftställer dock krav på en ökad tillgång av energilagring och balans- och/eller reglerkraft. Detfinns också andra svenska högt uppsatta miljö- och klimatmål samt ambitioner såsom fossiloberoendetransportsektor 2030, ett koldioxidneutralt samhälle 2045 och att Sverige skall bli ledande påatt ta hand om och återanvända sitt avfall i en cirkulär ekonomi.Kombinationen power-to-gas och biogasproduktion kan på olika sätt bidra till att nå samtliga ovanbeskrivna mål genom att göra det framtida elsystemet flexiblare samtidigt som tillgänglig biomassa,t.ex. gödsel och biologisk nedbrytbart avfall, utnyttjas mer effektivt för ökad produktion avförnybara drivmedel och/eller kemikalier från samma mängd biogassubstrat. Konceptet bygger påatt omvandla billig förnybar el, via elektrolys, till vätgas (dvs. power-to-gas) som tillåts reagera vidaremed koldioxiden i rå biogas via s.k. elektrobränsleprocesser.Det finns idag både termokemiska och biologiska elektrobränsleprocesser för metanproduktion.Det finns också biologisk gasfermentering för produktion av flytande elektrobränslen, t.ex. bioalkoholer.Bland biogasproducenter finns idag ett växande intresse för de olika elektrobränsleprocessernaeftersom de på sikt skulle kunna ge mer lönsamma, produktflexibla och mindre marknadskänsligabiogasanläggningar. Den allmänna uppfattningen hos den svenska biogasbranschen ärdock att det är svårt att på ett lättillgängligt sätt få grepp om vad den teknoekonomiska prestandanoch mognadsgraden för de olika elektrobränsleprocesserna idag är, särskilt vad gäller de biologiska.Denna kunskapssyntes syftar till att tillgodose detta behov och innefattar elektrobränsleprocessernain-situ och ex-situ metanisering samt biologisk gasfermentering, samt med termokemisk metaniseringsom referensprocess. Möjligheten att kombinera elektrobränsleprocesserna med och/ellerersätta konventionell biogasuppgradering undersöks och diskuteras också. De huvudsakliga slutsatsernai studien summeras nedan.Genom att utnyttja billig el och elektrobränsleprocesser i kombination med koldioxidöverskott frånbiogasproduktion kan metanproduktionen från en och samma mängd substrat öka upp till det dubbla.Samtidigt kan konventionell biogasuppgradering för biometanproduktion slopas under förutsättningatt tillräcklig mängd vätgas finns tillgänglig. Den stora utmaningen för denna process ärdock kostnaden och det finns behov av fortsatt FoU inom området för att elektrobränsleprocessernaskall kunna bli ett kostnadsekonomiskt alternativ för svenska biogasproducenter.Av de undersökta elektroprocesserna är termokemisk metanisering den mest mogna tekniken(Technology Readiness Level, TRL=7-8). Processen bygger på termokatalytisk omvandling och äreffektiv, generar högvärdig värme och kan ersätta konventionell biogasuppgradering förutsatt tillgångpå tillräcklig mängd vätgas. Processen är dessutom snabb och reaktorerna som placeras nedströms(ex-situ) biogasreaktorn är kompakta. En primär utmaning med processen är dock att katalysatorernaär känsliga för vanligt förekommande biogasföroreningar (t.ex. svavel), vilket gör attuppströms gasrening krävs. En annan utmaning är att processen sker vid hög temperatur (300-700°C) och tryck (vanligtvis ≤20 bar) vilket medför att uppstartstiden från kallt tillstånd blir relativtlång (timmar). Processen har slutligen relativt låg tolerans mot svängningar i gaskvalité (H2:CO2)och variationer i temperatur vilket medför att uppströms vätgaslager behövs vid intermittent drift.Vid biologisk metanisering (in-situ och ex-situ) omvandlas koldioxid och vätgas till metan medhjälp av mikroorganismer. Ingen katalysator behövs och mikroorganismerna är självproducerande.Reaktionen sker vanligtvis vid atmosfärstryck och låg temperatur (37-60°C). Tack vare den lågadrifttemperaturen är uppstartstiden från kallt tillstånd snabb (minuter). Processerna har, i motsatstill termokemisk metanisering, också mycket hög tolerans mot gasföroreningar (sulfider) och ingeneller mycket begränsad uppströms gasrening krävs.I likhet med termokemisk metanisering är ex-situ biologisk metanisering effektiv och kan ersättakonventionell biogasuppgradering. Till skillnad mot termokemisk metanisering är processen tolerantmot svängningar i gassammansättning (H2:CO2) och kan köras intermittent utan uppströmsvätgaslager. Processen är däremot långsam och kräver betydligt mer voluminösa reaktorer (10-1000 ggr större än vid termokemisk). Ex-situ biologisk metanisering är mindre mogen än termokemiskmetanisering (TRL=6-7).Vid In-situ metanisering tillförs vätgasen direkt till rötningskammaren och önskvärd metaniseringsker parallellt med biogasprocessen. Detta innebär att inte behöver investera i någon separat kostsammetaniseringsreaktor. Nackdelen är att det finns begränsade möjligheter till att ändra och optimeradriftbetingelserna (T, p, omrörning) mot metaniseringsprocessen utan att störa rötningsprocessen.Omvandlingseffektiviteten blir därför betydligt lägre än för ex-situ metanisering (från 52till 75% metanhalt har som bäst demonstrerats) och processen kan inte ersätta konventionell biogasuppgradering.En annan utmaning är att processen är känslig för vätgasinhibering vilket innebäratt vätgaslager behövs uppströms rötningskammaren vid intermittent drift. Mognadsgraden är lägreän för både termokemisk och ex-situ biologisk metansiering (TRL=4-5).Biologisk gasfermentering ökar flexibiliteten hos en biogasanläggning och kan minska risken avinvesteringen eftersom processen kan anpassas till marknadsdrivkrafter. Flexibiliteten begränsasdock av kostnaden för produktuppgraderingen där etanol t.ex kräver dyrare och en annan typ avuppgradering än vad t.ex långa fettsyror gör. I jämförelse med metanisering är det en fördel medproduktion av flytande bränslen när en anläggning ligger långt från en existerande gasinfrastruktur.Idag produceras främst etanol kommersiellt, men forskning och utveckling för produktion av långafettsyror och butanediol pågår. Dessa produkter har ett högre marknadsvärde och medför en merkostnadseffektiv uppgradering. Teknikutvecklingen och kommersialiseringen har utgått från fermenteringav syngas från förgasning och koldioxid från stålindustrin. Produktionen av koldioxidfrån svenska biogasanläggningar uppskattas vara ca en tiondel för låg för att en kostnadseffektivetanolproduktion skall kunna vara möjlig. Processen bedöms därför vara den minst mogna av deundersökta alternativen (TRL=2-4). I övrigt är gasfermentering en biologisk process som inneharliknande fördelar och utmaningar som beskrivits ovan för biologisk ex-situ metanisering.

The use of straw for biofuel production is encouraged by the European Union. A previous study showed the feasibility of producing biomethane in upflow anaerobic sludge blanket (UASB) reactors using hydrolyzed, steam-pretreated wheat straw, before and after dark fermentation with Caldicellulosiruptor saccharolyticus, and lucerne. This study provides information on overall microbial community development in those UASB processes and changes related to acidification. The bacterial and archaeal community in granular samples was analyzed using high-throughput amplicon sequencing. Anaerobic digestion model no. 1 (ADM1) was used to predict the abundance of microbial functional groups. The sequencing results showed decreased richness and diversity in the microbial community, and decreased relative abundance of bacteria in relation to archaea, after process acidification. Canonical correspondence analysis showed significant negative correlations between the concentration of organic acids and three phyla, and positive correlations with seven phyla. Organic loading rate and total COD fed also showed significant correlations with microbial community structure, which changed over time. ADM1 predicted a decrease in acetate degraders after a decrease to pH ≤ 6.5. Acidification had a sustained effect on the microbial community and process performance. © 2020 by the authors.

MultiBio project aimed to establish and demonstrate a novel multipurpose biorefinery cascade concept, producing three renewable biobased products: 1) biohydrogen, 2) biopolymers and 3) protein rich meal ingredients for fish farming. The cascade concept exploits the ability of a bacterium (Caldicellulosiruptor saccharolyticus) to transform nutrients present in low-value waste process waters of the pulp and paper industry, to high-value products hydrogen gas, organic acids and microbial biomass. The organic acid rich effluent will then be managed in an open culture microbial process used to achieve discharge water quality objectives and to produce polyhydroxyalkanoate (PHA) biopolymers. Moreover, since C. saccharolyticus protein content is more than 63% of cell dry weight, their potential in formulation of fish feed was evaluated. 

A fiber sludge containing, CTMP residual stream was found to be a possible feedstock for the MultiBio process concept. Due to safety risks the demo-scale experiments of biohydrogen gas technology were moved from Biorefinery demo plant (Örnsköldsvik) of 40 m3 capacity to ATEX classified pilot-scale facility with 0.4 m3 capacity. Hence, bacterial biomass enough for the large-scale fish feed ingredient could not be produced. Lab-scale experiments with Caldicellulosiruptor cells as fish feed ingredient showed promising results as a protein-rich, sustainable fish feed ingredient. In addition, PHA biopolymer also showed favourable results as fish food ingredient for experiments at Gårdsfisk AB. Lab-scale experimental tests showed that the surplus activated sludge from the mills wastewater treatment could currently accumulate PHA to about 20 % of its dry weight. Mass balance evaluations based on realistically achievable expectations indicated a PHA biopolymer production potential of 3 600 tons of PHA per year from available organic residuals and for the two evaluated mills combined. 

The MultiBio concept has a positive climate impact in comparison with current treatment and moves developments in a positive direction to achieve 7 of the 10 Swedish environmental goals. Through a detailed feasibility analysis, a natural progression in next steps in scenarios were suggested for PHA production. The MultiBio cascade process can be implemented with further necessary development with good business potential and a positive effect on climate change. However, biohydrogen technology needs further developments before this cascade process concept can be implemented. Alternatively, a scenario with only biopolymer technology shows already a significant business potential and even larger positive effect on climate change. A successful next step in demonstration of the PHA biopolymer production scenario may lead to it being implemented within the next few years. Furthermore, MultiBio has attracted a lot of attention regionally and nationally but also internationally with a total of 65 media listings. A licentiate thesis and three university degree projects linked to the project have been completed. Overall, the MultiBio project has successfully achieved its goals and objectives.

With an increasing number of low-grade primary ores starting to be cost-effectively mined, we are at the verge of mining a myriad of low-grade primary and secondary mineral materials. At the same time, mining practices and mineral waste recycling are both evolving towards sustainable near-zero-waste processing of low-grade resources within a circular economy that requires a shift in business models, policies and improvements in process technologies. This review discusses the evolution towards low-grade primary ore and secondary raw material mining that will allow for sufficient supply of critical raw materials as well as base metals. Seven low-grade ores, including primary (Greek and Polish laterites) and secondary (fayalitic slags, jarosite and goethite sludges, zinc-rich waste treatment sludge and chromium-rich neutralisation sludge) raw materials are discussed as typical examples for Europe. In order to treat diverse and complex low-grade ores efficiently, the use of a new metallurgical systems toolbox is proposed, which is populated with existing and innovative unit operations: (i) mineral processing, (ii) metal extraction, (iii) metal recovery and (iv) matrix valorisation. Several promising novel techniques are under development for these four unit-operations. From an economical and environmental point of view, such processes must be fitted into new (circular) business models, whereby impacts and costs are divided over the entire value chain. Currently, low-grade secondary raw material processing is only economic and environmentally beneficial when the mineral residues can be valorised and landfill costs are avoided and/or incentives for waste processing can be taken into account. © 2020 The Author(s)

BACKGROUND: Caldicellulosiruptor saccharolyticus has the ability to produce hydrogen (H2) at high yields from a wide spectrum of carbon sources, and has therefore gained industrial interest. For a cost-effective biohydrogen process, the ability of an organism to tolerate high partial pressures of H2 (PH2) is a critical aspect to eliminate the need for continuous stripping of the produced H2 from the bioreactor.

RESULTS: Herein, we demonstrate that, under given conditions, growth and H2 production in C. saccharolyticus can be sustained at PH2 up to 67 kPa in a chemostat. At this PH2, 38% and 16% of the pyruvate flux was redirected to lactate and ethanol, respectively, to maintain a relatively low cytosolic NADH/NAD ratio (0.12 mol/mol). To investigate the effect of the redox ratio on the glycolytic flux, a kinetic model describing the activity of the key glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), was developed. Indeed, at NADH/NAD ratios of 0.12 mol/mol (Ki of NADH = 0.03 ± 0.01 mM) GAPDH activity was inhibited by only 50% allowing still a high glycolytic flux (3.2 ± 0.4 mM/h). Even at high NADH/NAD ratios up to 1 mol/mol the enzyme was not completely inhibited. During batch cultivations, hydrogen tolerance of C. saccharolyticus was dependent on the growth phase of the organism as well as the carbon and energy source used. The obtained results were analyzed, based on thermodynamic and enzyme kinetic considerations, to gain insight in the mechanism underlying the unique ability of C. saccharolyticus to grow and produce H2 under relatively high PH2.

CONCLUSION: C. saccharolyticus is able to grow and produce hydrogen at high PH2, hence eliminating the need of gas sparging in its cultures. Under this condition, it has a unique ability to fine tune its metabolism by maintaining the glycolytic flux through regulating GAPDH activity and redistribution of pyruvate flux. Concerning the later, xylose-rich feedstock should be preferred over the sucrose-rich one for better H2 yield.

This hypothesis testing project has been with aim to validate potential for a novelmultipurpose cascading biorefinery, producing four principal platform productswithin a Kraft pulp mill: cellulose, lignofuels, biohydrogen and biopolymers.Cellulose and lignin product lines are presently well characterized at commercialscale. The project was, therefore, focused on evaluating and identifyingopportunities and challenges in processes for biohydrogen and biopolymersproduction from mill hemicellulose residuals.The project undertaking comprised three phases: determining the hemicelluloserich stream (HRS) to use, fermentation of sugars to hydrogen gas and organicacids, and conversion of organic acids to PHA by activated sludge. A literaturesurvey and discussions with the experts at various pulp and paper industries in theKarlstad region, as well as the developers of LignoBoost technology at Innventiaclearly mark the challenges of using black liquor directly as the HRS. Thesechallenges can be avoided by pre-extraction of the hemicellulose residual massvia ‘autohydrolysis’ of wood before the Kraft process. Hence, the residualhemicellulose before it enters the black liquor was the selected HRS.The HRS contained about 19 g/L of organics comprising of mainly pentose sugarsand organic acids along with some soluble lignin. A number of batch experimentswere performed in flasks that confirmed potential for H2 production by anosmotolerant strain (CSG5) of Caldicellulosiruptor sacchrolyticus. Experimentswere also performed in a fed-batch bioreactor. Here practical advancement wasmade with respect to process developments for industrial applications. However,no significant growth or H2 production was observed when permeate was added tothe reactor. This outcome was considered in hindsight to be due to an unforeseenoutcome of headspace partial pressure generated by the experimental set up.Nevertheless, given the HRS strategy and first positive indicators from batchexperiments, next steps to establish the industrial methods for conversion ofautohydrolysis hemicellulose residuals to H2 were recommended based onadaptation of the strain to the feed and/or application of co-culture bioprocessengineering.The effluent from biohydrogen production feeds a biopolymer production process.Two distinct sludge samples were sourced from municipal water treatment atSjölunda to evaluate polyhydroxyalkanoates (PHA) accumulation potential. Themixed cultures naturally accumulated a moderate level of more than 25% ofgPHA/gVSS. The conversion of the organic matter in the HRS stream into PHAwas successfully observed thus supporting the project hypothesis. Similarly to thebiohydrogen outcome, next steps will entail the development of an acclimatedenrichment PHA producing biomass from Kraft mill industry wastewaterbiological treatment.Through this work steps were made that strengthened the ideas as well as thestrategy forward which are to be implemented through the forthcoming proposedproject – HyPer.

The process of biogas upgrading with ionic liquids, i.e. pure 1-butyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)imide ([bmim][Tf2N]), aqueous choline chloride/urea (ChCl/Urea), and aqueous 1-allyl-3-methyl imidazole formate ([Amim][HCOO]), was simulated in Aspen Plus and compared with the conventional water scrubbing upgrading technique. The comparisons of the performances on the amount of recirculated solvents and energy usage show the following order: aqueous [Amim][HCOO]<aqueous ChCl/Urea<[bmim][Tf2N]<water. Six different co-digestion plants (anaerobic digestion, AD, plants) were surveyed to acquire data for comparison. The selected plants had different raw biogas production capacities and produced gas with differing methane content. The data confirmed the simulation results that the type of substrate and the configuration of AD process are two factors affecting energy usage, investment cost, as well as operation and maintenance costs for the subsequent biogas upgrading. In addition, the simulation indicated that the energy usage of the ionic liquid-based upgrading was lower than that of the conventional upgrading techniques in Scandinavian AD plants. The estimated cost including investment, operation and maintenance for the ionic liquid technology showed to be lower than that for the water scrubbing upgrading process.