The role of energy as a stimulant for economic growth and environmental sustainabilityof any nation has made the focus on green fuels, including fermentative hydrogen (bioH2) andmethane (bioCH4), to be a priority for the World’s policy makers. Nigeria, as the most populousAfrican country, with worsening energy crisis, can benefit from the introduction of the bioH2 andbioCH4 technologies into the country’s energy mix, since such technologies have the potential ofgenerating energy from organic wastes such as fruit waste.Fruit waste was studied in detail in this work because of its great economic andenvironmental potential, as large quantities of the wastes (10–65% of raw fruit) are generatedfrom fruit consumption and processing. Meanwhile, bioH2 and bioCH4 productions involvinganaerobic microorganisms in direct contact with organic wastes have been observed to result insubstrate and product inhibitions, which reduce the gas yields and limit the application of thetechnologies on an industrial scale. For example, in this study, the first experimental work todetermine the effects of hydraulic retention times and fruit mixing on bioH2 production fromsingle and mixed fruits revealed the highest cumulative bioH2 yield to be equivalent to 30% ofthe theoretical yield. However, combining the fermentation process with the application ofmembrane encapsulated cells and membrane separation techniques, respectively, could reducesubstrate and product inhibitions of the microorganisms. This study, therefore, focused on theapplication of membrane techniques to enhance the yields of bioH2 and bioCH4 productions fromthe organic wastes.The second experimental work which focused on reduction of substrate inhibition,involved the investigation of the effects of the PVDF membrane encapsulation techniques on thebioH2 and bioCH4 productions from nutrient media with limonene, myrcene, octanol and hexanalas fruit flavours. The results showed that membrane encapsulated cells produced bioCH4 fasterand lasted longer, compared to free cells in limonene. Also, about 60% membrane protectiveeffect against myrcene, octanol and hexanal inhibitions was obtained. Regarding bioH2production, membrane encapsulated cells, compared to free cells, produced higher average dailyyields of 94, 30 and 77% with hexanal, myrcene and octanol as flavours, respectively. The finalpart of the study, which was aimed at reducing product inhibition, involved the study of theeffects of membrane permeation of volatile fatty acids (VFAs) on the bioreactor hydrodynamicsin relation to bioH2 production. The investigation revealed that low transmembrane pressure of104Pa was required to achieve a 3L h-1m-2 critical flux with reversible fouling mainly due to cakelayer formation, and bioH2 production was also observed to restart after VFAs removal.The results from this study suggest that membrane-based techniques could improve bioH2and bioCH4 productions from fermentation media with substrate and product inhibitions.

Sveriges avloppsreningsverk står inför ett antal utmaningar, där en av utmaningarna är minskning av växthusgaser. Lustgas är en av dessa växthusgaser, som bildas vid rening av avloppsvatten. Lustgas är 300 gånger skadligare för klimatet i jämförelse med koldioxid. Dessutom påverkar den nedbrytningen av ozonskiktet. I dagsläget är det svårt att mäta och uppskatta lustgasutsläpp, på grund av att det pågår flera samtidiga processer på stora ytor. För att driften av avloppsreningsverk ska ske på ett effektivt sätt och med en ytterst liten miljöpåverkan måste man kunna förstå hur lustgas uppstår och hur bildningsprocesserna samverkar med de andra reningsprocesserna och driftparametrarna.

Utsläpp av lustgas har studerats vid avloppsreningsverket i Göteborg. Syftet har varit att tillhandahålla resultat och mätningar från Gryaab AB reningsverk och fastställa vilka processer som ger upphov till störst eller minst lustgasemissioner. Utsläpp av lustgasemissioner har mätts från rejektrening med nitrifikation och denitrifikation process. Analyser på resultaten ska förhoppningsvist kunna hjälpa Gryaab AB med fortsatt studier om lustgas. Som mätningsmetod användes EPA-huvmätning som man mätte med ovanför vattenytan på bassängerna och mobilt extraktiv FTIR som åkte runt anläggningen.

Den dominerande källan för lustgas visade sig bildas allra mest i nitrifikationsprocessen. Där mätningarna med huv-mätning och stickprov visade totala utsläpp motsvarande 1,8 ton N2O/år. Den totala lustgasemissionen från biologiska reningsprocessen visade totala utsläpp motsvarande 3,5 ton N2O/ år.

Som en slutsats bör fler mätningar med olika mätningsmetoder och mer studier göras för att få en bättre överblick till varför och hur lustgas bildas. Samt vilka åtgärder som kan minska lustgasemission. Det finns ett behov av fortsatta studier med mätningar med olika mätningsmetoder på Gryaab AB.

Plastproduktionen och användningen av plast ökar varje år i hela världen och detta är ett av världens största problem. Plaster är ett svårnedbrytbart ämne och processen kan ta hundratals år. Detta leder i sin tur till att plastackumuleringen orsakar skadlig påverkan på klimat, miljö och människor. Ett av alternativen som har stor potential för hanteringen av detta problem är att minska användningen av plast och i stället öka produktionen och användningen av bioplastereller biopolymerer som är nedbrytbar.

Bioplaster har kortare nedbrytningstid än vanliga plaster och därför är bioplast ett bra alternativ istället för att använda vanliga plaster. Det finns tre olika grupper av bioplaster, nämligen dem som är biobaserade, bionedbrytbara och de som är både biobaserade och bionedbrytbara. Entyp av bioplast som är biologiskt nedbrytbar och biobaserad är polyhydroxialkanoater (PHA)som används i olika branscher då PHA är en av de biopolymerer som visar störst potential attersätta plast i framtiden.

Forskning pågår på Högskolan i Borås med målet av att bilda en ny process för produktion och återvinning av PHA. Processen baseras på produktion av PHA från flyktiga fettsyror som produceras från acidogen jäsning. Acidogen jäsning är en modifierad process av anaerobmatsmältning som används idag för produktion av biogas från avfall. Den kan vara den rättaprocessen för återvinningen av PHA-baserade avfall och för att producera ett billigt substrat, nämligen flyktiga fettsyror för PHA produktion. Det här projektet handlar om en del av processen, nämligen produktion av PHA med bakterier. Forskningsgruppen på Högskolan iBorås har en bakteriestam som inte har undersökts för produktion av PHA. Innan bakterien kan studeras för produktion av PHA från flyktiga syror behövs medelinnehållet optimeras för bakterietillväxt.

Syftet med detta arbete är att undersöka effekten av olika glukoskoncentrationer som kollkälla och olika mängder av ammoniumsulfat som används vid tillväxt av den bakterien Bacillusmegaterium för produktion av PHA. En jämförelse mellan det definierade mediet som användsi detta arbete och dess ersättning med nutrient broth, ett komplext medium som normalt används för bakterietillväxt genomfördes också för att utvärdera lämpligheten hos mediet underutveckling för att framgångsrikt stödja bakterietillväxt. Under detta arbete användes flera olika analytiska tekniker såsom pH mättning, Högupplösande vätskekromatografi (HPLC),Spektrometer (OD mättning), och Fourier-transform infraröd spektroskopi (FTIR) för att utvärdera bakterietillväxt och produktion av PHA samt analysera sammansättningen av PHAs. Mängden av ammoniumsulfat påverkade glukosförbrukningen, där koncentrationer av 3 g/Loch 7 g/L visades att leda till en snabbare glukosförbrukning jämfört med 5 g/L. Därför valdes3 g/L ammoniumsulfat då det innehåller mindre kemikalier användning och påverkar inte celltillväxten på ett negativ sätt. Under experimentet med användning av 3 g/Lammoniumsulfat med 10 g/L glukos, konsumerades glukosen fullständigt vid 72 timmar av bakterietillväxt och den maximala PHA-produktionen var på 13–14% baserad på torr cell vikt. Tillväxtmedelet som utvecklades i det här projektet visade att vara lämplig för bakterietillväxt eftersom användning av nutrient broth som används normalt för bakterietillväxt ledde till långsammare glukosförbrukning.

Initial glukoskoncentration (5, 10 och 20 g/L) påverkade inte glukosförbrukningen och får studerats vidare för att öka cellkoncentrationen och följaktligen produktionen av PHA. En av det mest studerade i PHA-familjen är polyhydroxibutyrat (PHB). Under detta arbete visade det sig att genom användning av FTIR att PHB framställdes.

Due to resource scarcity, current industrial systems are switching from waste treatment, such as wastewater treatment and biomass, to resource recovery (RR). Biofuels, manure, pesticides, organic acids, and other bioproducts with a great market value can be produced from wastewater and activated sludge (AS). This will not only help in the transition from a linear economy to a circular economy, but also contribute to sustainable development. However, the cost of recovering resources from wastewater and AS to produce value-added products is quite high as compared to conventional treatment methods. In addition, most antioxidant technologies remain at the laboratory scale that have not yet reached the level at industrial scale. In order to promote the innovation of resource recovery technology, the various methods of treating wastewater and AS to produce biofuels, nutrients and energy are reviewed, including biochemistry, thermochemistry and chemical stabilization. The limitations of wastewater and AS treatment methods are prospected from biochemical characteristics, economic and environmental factors. The biofuels derived from third generation feedstocks, such as wastewater are more sustainable. Microalgal biomass are being used to produce biodiesel, bioethanol, biohydrogen, biogas, biooils, bioplastics, biofertilizers, biochar and biopesticides. New technologies and policies can promote a circular economy based on biological materials.

Synthesis of polymers from renewable origin has been reported by many authors and it has been found out that it has enormous potential and can serve as alternative to conventional thermoplastics and thermosets in many applications. The use of these renewable resources will provide sustainable platforms to substitute fossil fuel-based materials. To date, efforts made to produce 100% bio-based thermosetting materials have yet to be achieved. Many studies have been reported on increasing the renewability ratio of thermoset materials produced.

A lot of reports have been made on the synthesis of thermoplastic resins from lactic acid for biomedical applications such as tissue engineering but only few reports have been made on composite applications. The issue of high melt viscosity of thermoplastic resins from lactic acid has been of paramount problem because of its difficulty in impregnation into fibre reinforcement. Bio-based thermoset resins have been produced for composite applications from plant oils and improved mechanical properties have been achieved.

In this thesis, an alternative route for synthesis of lactic acid based thermoset resins have been explored to solve the above problem. Thermoset resins were synthesized from lactic acid with different co-reactants and were characterized using NMR, FT-IR, DSC, DMA and TGA. Their rheological properties were also investigated. The resins were reinforced with natural and regenerated cellulose fibres in non-woven and woven form, and with different fibre alignment and fibre loading. The resulting composites were characterized by mechanical testing regarding tensile, flexural and impact strength, and by SEM analysis regarding morphology.

The results showed that these composites could possibly be used in automobile, transport, construction and furniture applications, particularly for interior purposes. The resins produced were found to be promising materials for composite production due to the good mechanical properties achieved.

The global food system is a major driver of many environmental impacts, particularly those related to climate change, biodiversity loss, and depletion of freshwater resources. These problems are aggravated by a substantial waste of food throughout the supply chain, where retailers are responsible for large quantities of waste. Although other parts of the supply chain account for relatively higher waste generation, retailers are particularly important because of their influence both downstream and upstream in the supply chain. 

This thesis aims to design and evaluate strategies for food waste prevention and valorisation, particularly for bread products, by analysing food waste quantities, identifying the causes and risk factors, and proposing and evaluating measures for preventing and valorising food waste.

This aim was achieved through a variety of approaches. First, food waste was quantified for one year in a typical mid-sized urban supermarket in Sweden. This information was used to identify hotspots at the product-level in relation to mass, environmental impacts, and cost. Bread was identified as a hotspot and also as a product with a high potential for waste prevention and valorisation measures. A second quantification was performed with the goal of estimating the quantity of surplus bread throughout the Swedish supply chain and to identify the risk factors for waste generation, particularly at the supplier–retailer interface. Finally, this thesis investigated current and future circular economy strategies for the prevention, valorisation, and management of bread surplus by evaluating the environmental performance of multiple strategies and comparing them with current waste management practices. 

The results from the first quantification indicated that bread was a category with significant contribution in all environmental impact categories analysed, with the greatest contribution in terms of the total mass of waste and the economic costs incurred by the supermarket. The second quantification estimated 80 500 tonnes of bread waste/year in Sweden, equivalent to 8 kg per person/year, which was mainly concentrated at household and retail levels, specifically at the supplier–retailer interface. The results provided evidence that the take-back agreement between suppliers and retailers is a risk factor for high waste generation. Therefore, current business models may need to be changed to achieve a more sustainable bread supply chain with lower waste generation. However, the currently established return system between bakeries and retailers enables a segregated flow of bread waste that is not contaminated with other food waste products. This provides an opportunity for alternative valorisation and waste management options that are not viable for mixed waste streams.

The results from the environmental assessment for the prevention, valorisation and waste management pathways supported a waste hierarchy, where prevention has the highest environmental savings, followed by donation, the use of surplus bread as animal feed, and for beer and ethanol production. Anaerobic digestion and incineration offer the lowest environmental savings, particularly in low impact energy systems. The results suggest that Sweden can make use of the established return system to implement environmentally preferred options for the management of surplus bread.

Sustainable development of society and industry is necessary for a safer future that is being challenged by environmental pollution, climate change, and scarcity of food and nutrition. Materials considered as waste can be converted into value-added products and energy, hence regained to the economy. Filamentous fungi are saprophytic microorganisms that show great potential for bioconversion of organic waste materials into a wide range of products, including ethanol, enzymes, fungal biomass, and organic acids. In this study, industrial residuals from bioethanol plants (thin stillage), agro-industrial residuals (oat husks), and fruit-processing residuals were considered as potential substrates for filamentous fungi. Different filamentous fungi species were investigated due to their edibility and ability to produce ethanol. The aim of this study was to investigate 1) the feasibility of a biorefinery concept and contribution of fungal products to the process economy, 2) the valorization of oat husks in the fungal biorefinery and its contribution to the process economy, and 3) the effect of bioactive compounds existing in fruit residuals on filamentous fungi in a synthetic medium.

Bioconversion of thin stillage into value-added products, e.g., additional ethanol produced by filamentous fungi and edible fungal biomass for various feed/food markets, improved the process economy of a conventional bioethanol plant. Techno-economic analysis was carried out with Aspen Plus® and Aspen Process Economic Analyzer®. The economy of the conventional bioethanol plant was improved to 76% and 5.6-fold higher net present value when the fungal product was sold as fish feed and human food, respectively. When the fungal product was sold as human food, Aspergillus oryzae was more advantageous than Neurospora intermedia. It is possible to integrate lignocellulosic material into the fungi-based biorefinery and produce additional products, e.g., lignin and fungal biomass as feed/food products. Several scenarios for integrating organosolv pretreatment into the biorefinery were investigated. When protein-rich biomass was sold as feed and food, 71% and 7.9-fold higher net present value was obtained, respectively, compared to the conventional ethanol plant. Similarly, other materials, e.g., fruit residuals, can be valorized through the fungal biorefinery. However, bioactive compounds in fruit residuals have antimicrobial effects; therefore, it is essential to assess the sensitivity of fungi toward them for efficient processes. In addition to the fungi species utilized in thin stillage and oat husk valorization, two other industrially important fungi, Rhizopus oligosporus and A. niger, were tested against 10 bioactive compounds with antimicrobial properties (octanol, ellagic acid, (-)-epicatechin, quercetin, betanin, ascorbic acid, limonene, hexanal, car-3-ene, and myrcene). The bioactive compounds were added to a synthetic medium to reach final concentrations of 2.4, 24 and 240 mg/L, within their natural concentration in fruit/fruit residuals. A. oryzae, A. niger and N. intermedia were inhibited by octanol, while the latter fungus was also inhibited by D-Limonene at 240 mg/L. On the other hand, R. oligosporus was resistant to inhibitory compounds and increased the biomass yield. The highest change in biomass yield was in the presence of ellagic acid with up to a 4-fold increase. Ethanol and lactic acid yields were increased 38% and 30% in the presence of ellagic acid and betanin, respectively. Similarly, the existence of quercetin and ellagic acid, ascorbic acid, and hexanal increased the biomass yield of A. niger up to 28%.

These studies can contribute to developing efficient and feasible biorefineries, in which filamentous fungi convert the industrial residuals into value-added products.

Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW), leading to renewableenergy production in the form of methane, is a preferable method for dealing with the increasing amountof waste. Food waste is separated at the source in many countries for anaerobic digestion. However, thepresence of plastic bags is a major challenge for such processes. This study investigated the anaerobicdegradability of different bioplastics, aiming at potential use as collecting bags for the OFMSW. Thechemical composition of the bioplastics and the microbial community structure in the AD processaffected the biodegradation of the bioplastics. Some biopolymers can be degraded at hydraulic retentiontimes usually applied at the biogas plants, such as poly(hydroxyalkanoate)s, starch, cellulose and pectin,so no possible contamination would occur. In the future, updated standardization of collecting bags forthe OFMSW will be required to meet the requirements of effective operation of a biogas plant.

Consumption of citrus fruits and citrus juice production creates wastes, which could be valorized by using it for cultivating fungi. Before cultivation, the medium needs to be sterilized though autoclavation. Larger volumes used when autoclaving requires longer heating cycles and therefore runs the risk of degrading the medium to a greater extent. This research examines the effects of the volume lemon waste medium used while sterilizing. The aim is to find the largest volume still providing good growth for the filamentous fungus used, Rhizopus Delemar. Lemon waste was provided by Herrljunga Musteri AB and was pre-treated at 45°C for 2h. The liquid was strained and autoclaved in different volumetric series ranging from 200 – 10 000 mL, that was then used in 200 mL shake flask cultivations.  A scale up in two 3,5 L bubble column reactors was also performed from the 10 000 mL autoclaved medium, after not observing severe impacts on growth. Testing was done by weighing biomass and HPLC analysis of sugars. The yield of the biomass in the shake flasks ranged from 0,11 – 0,14 g/g sugars and the biomass concentration ranged between 2,4 - 3,0 g/L. Overall, the volume of autoclavation seems to not too be of great concern when cultivating R. Delemar on lemon waste medium in the analyzed ranges.

The industrial production of bioethanol as a replacement to gasoline is well-established worldwide, using starch- or sugar-rich substrates. Additionally, the bioethanol plants produce animal feeds derived from fermentation leftovers. The biorefinery character of bioethanol plants can be enhanced via process diversification. This entails the production of more value-added products, which can be accomplished by including edible filamentous fungi as the second biocatalysts while taking advantage of the available equipment for cost-effective inclusion. The process diversification can be achieved either via valorisation of the process leftovers or via inclusion of other residual substrates.

In dry-mill biorefineries, baker’s yeast is unable to consume residual pentose sugars and other more complex substrates in the process leftovers so called whole stillage and thin stillage. Edible ascomycetes and zygomycetes fungi can be used to accomplish yeast and consume those residual substrates in stillage as well as from external substrates of lignocellulosic origin, e.g. spent sulphite liquor and wheat straw. The conversion of these substrates to ethanol, and biomass rich in protein, lipids, respective essential amino acids and fatty acids as well as chitosan was investigated in this thesis.

Among the filamentous fungi studied, Neurospora intermedia was the best ethanol producer from thin stillage. Process developments included primary shake-flasks experiments, followed by pilot scale-up using 26 L, 2.3 m³ and 80 m³ bioreactors. The 26 L bioreactor, as a bubble column led to similar performance as an airlift bioreactor, and also a continuous mode could be successfully used instead of a batch process. By using a dilution rate of 0.1 h^-1, around 5 g/L of ethanol and 4 g/L of biomass rich in protein, lipids, amino acids and fatty acids essential to humans were obtained. The inclusion of the process can potentially lead to a spent medium lower in solids and viscosity which may facilitate the energy-intensive evaporation and drying steps as well as the water recycling back to the process. By applying a two-stage cultivation with whole stillage, up to 7.6 g/L of ethanol could be produced using 1 FPU cellulase/g suspended solids and 5.8 g/L of biomass containing 42% (w/w) crude protein. In the first stage (ethanol production), N. intermedia was used, while Aspergillus oryzae was the biocatalyst in the second stage for further biomass production. Both strains were able to degrade complex substrates both in liquid and solid fraction of whole stillage. The extrinsic substrates included spent sulphite liquor and pretreated wheat straw slurry. When the former was used, up to around 7 g/L of Rhizopus sp. could be obtained in a 26 L airlift bioreactor. The biomass was rich in protein and lipids (30–50% and 2–7% on a dry weight basis, respectively). The monomers of the latter were continuously filtered for production of biomass under simultaneous saccharification fermentation and filtration. Biomass yields of up to 0.34 g/g of consumed monomeric sugars and acetic acid were obtained.

The inclusion of the process for valorisation of thin stillage can potentially lead to the production of 11,000 m³ ethanol and 6,300 tonnes of biomass at a typical facility producing 200,000 m³ ethanol/year.

Prevention of dramatic climate change and ensuring food and nutrition security for subsequent generations necessitates the reduction of greenhouse gas emissions and efficient use of the world’s resources, including efficient waste disposal. The agro-industrial sector generates a large amount of organic waste, that is currently underexploited owing to poor waste management practices. The circular bioeconomy model is expected to play an important role in the transition towards a sustainable future, and a group of microorganisms known as fungi can be part of the solution, owing to their ability to convert organic waste into useful products, including both materials and energy. These processes hold great potential to change waste materials into resources, leading to societal and environmental benefits. The versatility of various fungi, including their ability to grow in both submerged and solid states, enables the valorisation of liquid and solid streams such as ethanol plant residues ‘thin stillage’ and surplus bread. However, fungal strains need to produce marketable products and exhibit good growth characteristics to be considered suitable for industrial applications. An interesting candidate is the edible filamentous fungus Neurospora intermedia. This fast-growing fungus is able to grow on a wide array of substrates, in both liquid and solid states, and produce industrially relevant products, including its own nutrient rich fungal biomass and carotenoid pigments. 

Submerged fermentation by N. intermedia in semi-synthetic medium showed that the formation of carotenoids can be enhanced by modulating various factors such as light, low pH, high aeration, and the addition of Mg2+ and Mn2+. When cultivated in thin stillage, 6.3 g/L ethanol was produced, along with protein-rich fungal biomass with potential application as feed. However, an additional step was needed to promote pigment production in the fungal biomass. 

Inspired by the traditional use of N. intermedia for food production by solid-state cultivation, the fungal biomass obtained from cultivation in thin stillage was used as inoculum in a subsequent solid-state fermentation step on surplus bread. The fungal product obtained contained up to 33% proteins and 1.2 mg carotenoids/g total material dry weight. By further combining bread as substrate with brewer’s spent grain, a nutrient-rich fungal-fermented product with an attractive texture was successfully produced. The solid-state cultivation resulted in an improved ratio of essential amino acids, and an increase in dietary fibre, minerals, and vitamins, that added further value to the product. To scale up the process, a novel plug-flow bioreactor was developed and successfully operated semi-continuously, without the addition of an external inoculum. Furthermore, a techno-economic feasibility study of on-site solid-state fermentation in small-scale bakeries revealed that the implementation of this process to sustainably use surplus bread at bakery level is economically feasible. 

These studies lay the foundation for the development of N. intermedia as a tool to convert waste material into useful products, contributing to a fossil fuel-free future with positive impacts on the economy.

Rhizopus oryzae is a filamentous fungus, belonging to the order Mucorales. It can ferment a wide range of carbohydrates hydrolyzed from lignocellulosic materials and even cellobiose to produce ethanol. However, R. oryzae also produces lactic acid as a major metabolite, which reduces the yield of ethanol. In this study, we show that significant reduction of lactic acid production could be achieved by short (25nt) synthetic siRNAs targeting the ldhA gene. The average yield of lactic acid production by R. oryzae during the batch fermentation process, where glucose had been used as a sole carbon source, diminished from 0.07gm/gm in wild type to 0.01gm/gm in silenced samples. In contrast, the average yield of ethanol production increased from 0.39gm/gm in wild type to 0.45gm/gm in silenced samples. These results show 85.7% (gm/gm) reduction in lactic acid production as compared with the wild type R. oryzae, while an increase of 15.4% (gm/gm) in ethanol yield.

Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. A workshop was held in June 2015 in Leysin Switzerland to agree on common solutions to the conundrum of inconsistent BMP test results. A discussion covers actions and criteria that are considered compulsory ito accept and validate a BMP test result; and recommendations concerning the inoculum substrate test setup and data analysis and reporting ito obtain test results that can be validated and reproduced.

The application of anaerobic digestion (AD) as a sustainable waste management technology is growing worldwide, due to high energy prices as well as increasingly strict environmental regulations. The growth of the AD industry necessitates exploring new substrates for their utilisation in AD processes. The present work investigates the AD of two recalcitrant biomass: lignocelluloses and keratin-rich residues. The complex nature of these waste streams limits their biological degradation; therefore, suitable pre-processing is required prior to the AD process.In the first part of the study, the effects of organic solvent pre-treatments on bioconversion of lignocelluloses (straw and forest residues) to biogas were evaluated. Pre-treatment with N-methylmorpholine-N-oxide (NMMO) resulted in minor changes in the composition of the substrates, while their digestibility significantly increased. Furthermore, due to the high cost of the NNMO, the effect of pre-treatment with the recycled solvent was also explored. Since it was found that the presence of small traces of NMMO in the system after the treatment has inhibitory effects on AD, pre-treatments of forest residues using other organic solvents, i.e. acetic acid, ethanol, and methanol, were investigated too. Although pre-treatments with acetic acid and ethanol led to the highest methane yields, the techno-economical evaluation of the process showed that pre-treatment with methanol was the most viable economically, primarily due to the lower cost of methanol, compared to that of the other solvents.In the second part of the work, wool textile wastes were subjected to biogas production. Wool is mainly composed of keratin, an extremely strong and resistible structural protein. Thermal, enzymatic and combined treatments were, therefore, performed to enhance the methane yield. The soluble protein content of the pre-treated samples showed that combined thermal and enzymatic treatments had significantly positive effects on wool degradation, resulting in the highest methane yields, i.e. 10–20-fold higher methane production, compared to that obtained from the untreated samples.In the last part of this thesis work, dry digestion of wheat straw and wool textile waste, as well as their co-digestion were studied. The total solid (TS) contents applied in the digesters were between 6–30% during the investigations. The volumetric methane productivity was significantly enhanced when the TS was increased from 6 to 13–21%. This can be a beneficial factor when considering the economic feasibility of large-scale dry AD processes.

Enzyme immobilization on electrically conductive supports is necessary to improve their bioactivity and stability, for use and re-use in applications depending on bio-electrochemical response, such as in bioelectrodes, biosensors, or biofuel cells. However, the immobilization methods used are still facing many challenges in terms of health hazards and high environmental impact. Thus, it is important to find balanced and eco-friendly approaches to achieve efficient immobilization with minimum harmful consequences.

Hence, within the frame of this thesis, the use of eco-technologies such as cold remote plasma, a bio-compatible conductive (PEDOT:PSS) polymer coating, and a bio-based crosslinker “genipin” which has low toxicity, to immobilize glucose oxidase (GOx) enzyme on conductive carbon fiber-based nonwoven textiles was investigated. These carbon-based textiles, regardless of their hydrophobicity, are robust materials to be used as alternative for expensive rigid metals, since they possess good electrical conductivity and good resistance to corrosion in different media.

The results obtained showed that cold remote plasma treatment with nitrogen and oxygen gas mixture was efficient in functionalizing the surface of carbon felts and PEDOT:PSS coated felts. This increased carbon fiber surface energies, and facilitated the immobilization of GOx by physical adsorption with maintained bioactivity and improved reusability. Furthermore, immobilization of GOx using genipin as a crosslinking agent improved remarkably the stability of performance of bio-functionalized carbon felts. This crosslinker showed to be able to directly crosslink the enzymes without a matrix or hydrogel. Finally, the obtained bio-functionalized carbon textiles were primarily evaluated for use in sustainable applications for wastewater treatment such as Bio-Fenton (BF) and enzymatic Bio-Electro-Fenton (BEF). The results showed that bioactivity and bio-electro-activity of immobilized GOx was promising in color removal of Remazol Blue RR reactive dye and its partial degradation from solution in both treatments, which proved the success of the chosen immobilization methods in producing bioactive textiles that can be used as electrodes for power generation and pollution control.

In this paper, an overview of the bio-Fenton and bio-electro-Fenton processes for sustainable wastewater treatment is provided. These two methods have been used in recent years to treat many kinds of persistent pollutants while maintaining the sustainability in materials and power consumption compared to conventional methods, through efficient eco-designed systems. The different kinds of electrodes used for the bio-electro-Fenton are reviewed, along with the influencing factors affecting the efficiency of these methods, and the different designs used to construct the reactors. Moreover, the various organic pollutants from industrial sources, like effluents from textile and pesticides facilities, treated using these processes are also reported. However, the main challenge facing these technologies is to improve their performance, stability and lifetime to achieve more sustainable and cost-effective wastewater treatment on pilot and large scales. Hence, future perspectives and trends are discussed to overcome the drawbacks of these methods.

Lignocellulosic (or cellulosic) biomass derived ethanol is the most promising near/long term fuel candidate. In addition, cellulosic biomass derived ethanol may serve a precursor to other fuels and chemicals that are currently derived from unsustainable sources and/or are proposed to be derived from cellulosic biomass. However, the processing cost for second generation ethanol is still high to make the process commercially profitable and replicable. In this review, recent trends in cellulosic biomass ethanol derived via biochemical route are reviewed with main focus on current research efforts that are being undertaken to realize high product yields/titers and bring the overall cost down.

Dairy waste is a complex mixture of nutrients requiring an integrated strategy for valorization into various products. The present work adds insights into the conversion of fat-rich dairy products into biomass, glycerol, and fatty acids via submerged cultivation with edible filamentous fungi. The pH influenced fat degradation, where Aspergillus oryzae lipase was more active at neutral than acidic pH (17 g/L vs. 0.5 g/L of released glycerol); the same trend was found during cultivation in crème fraiche (12 g/L vs. 1.7 g/L of released glycerol). In addition to glycerol, as a result of fat degradation, up to 3.6 and 4.5 g/L of myristic and palmitic acid, respectively, were released during A. oryzae growth in cream. The fungus was also able to grow in media containing 16 g/L of lactic acid, a common contaminant of dairy waste, being beneficial to naturally increase the initial acidic pH and trigger fat degradation. Considering that lactose consumption is suppressed in fat-rich media, a two-stage cultivation for conversion of dairy waste is also proposed in this work. Such an approach would provide biomass for possibly feed or human consumption, fatty acids, and an effluent of low organic matter tackling environmental and social problems associated with the dairy sector.

Cellulose Solvent-And organic Solvent-Based lignocellulose fractionation (COSLIF) has been repeatedly shown to be a Cost-Effective and promising process to modify the structure of different lignocelluloses. It has been repeatedly reported to improve enzymatic hydrolysis and ethanol production from different lignocelluloses. In this study, COSLIF was used to improve biomethane production from pine (softwood), poplar (soft hardwood), and berry (hard hardwood) via solid state anaerobic digestion (SSAD). Feed to inoculum (F/I) ratio, which plays a major role in SSAD, was set to 3, 4, and 5. After the pretreatment, 39, 33, and 24% higher methane yield from pine was achieved for F/I ratios of 3, 4, and 5, respectively. However, the methane yield from the hardwoods was not improved by the pretreatment, which was related to overloading of the digester. Compositional analysis showed considerable reduction in hemicellulose and lignin content by the pretreatment. Structural changes in the woods, before and after the pretreatment, were examined by X-Ray diffractometer and scanning electron microscopy. The results showed that the crystallinity of cellulose was decreased and accessible surface area was drastically increased by the pretreatment.

Over the past few decades, a growing interest in the thermal conversion of alternative fuels such as biomass and waste-derived fuels has been observed among the energy-producing companies. Apart from meeting the increasing demand for sustainable heat and power production, other advantages such as reducing global warming and ameliorating landfilling issues have been identified. Among the available thermal conversion technologies, combustion in grate-fired furnaces is by far the most common mode of fuel conversion. In recent years, Fluidized-Bed (FB) technologies have grown to become one of the most suitable technologies for combustion and gasification of biomass and waste-derived fuels.In spite of the benefits, however, some difficulties are attributed to the thermal conversion of the alternative fuels. Ash-related issues could be a potential problem, as low-grade fuels may include considerable concentrations of ash-forming elements such as K, Na, S, Ca, Mg, P, Si and Cl. These elements undergo many undesirable chemical and physical transformations during the thermal conversion, and often cause operational problems such as deposition-related issues, slag formation in furnaces, corrosion of the heat transfer surfaces, and bed agglomeration of the fluidized-beds. Ash-related problems in the utility boilers are a major concern that may result in decreased efficiency, unscheduled outages, equipment failures, increased cleaning and high maintenance costs.This thesis investigated the ash behavior and ash-related problems in two different FB conversion systems: a Bubbling Fluidized-Bed (BFB) boiler combusting solid waste, and a Dual Fluidized-Bed (DFB) gasifier using biomass as feedstock. Full-scale measurements, chemical analysis of fuel and ash, as well as thermodynamic equilibrium modeling have been carried out for the BFB boiler (Papers I-IV), to investigate the impact of reduced-bed temperature (RBT) and also co-combustion of animal waste (AW) on the ash transformation behavior and the extent of ash-related issues in the boiler. For the DFB gasifier (Paper V), a thermodynamic equilibrium model was developed to assess the risk of bed agglomeration when forest residues are used as feedstock.The experimental results showed that the RBT and AW co-combustion could decrease or even resolve the ash-related issues in the BFB boiler, resulting in a lower deposit-growth rate in the superheater region, eliminating agglomerates, and a less corrosive deposit (in RBT case). Thermodynamic equilibrium modeling of the BFB boiler gave a better understanding of the ash transformation behavior, and also proved to be a reliable tool for predicting the risk of bed agglomeration and fouling. The modeling of the DFB gasifier indicated a low risk of bed agglomeration using the forest residues as feedstock and olivine as bed material, which was in good agreement following the observations in a full-scale DFB gasifier.

Bioreactors are designed to provide enabling conditions for the controlled growth of microorganisms, such as good heat and mass transfer, aeration, hydrodynamics, geometry for adequate gas holdup, pH and foaming control, conditions for optimal substrate consumption and product formation, as well as mechanisms for monitoring microbial conditions. Additionally, bioreactors are designed to handle stress that would be exerted on them by the weight of the fermenting media and by the high pressure used for sterilisation. Bioreactors are usually constructed with materials such as stainless steel, carbon steel and borosilicate glass, which must be suitable for growing the fermenting microbes, be inert and corrosion proof. In this thesis, a textile-based bioreactor was designed and developed for aerobic and anaerobic fermentation based production processes with emphasis on mixing, mass transfer, temperature control, rheology, hydrodynamics and stress containment in the bioreactor.

Temperature control was carried out using a heat control tubing either at the bottom of the bioreactor or as a heating jacket around its vertical height. The developed temperature control system was tested anaerobically and aerobically. Under anaerobic conditions with yeast it resulted in 200 % increase in ethanol productivity in comparison with the prototype without temperature control.

A mixing system was developed for flocculating microbes and tested for anaerobic fermentation processes such as ethanol and biogas production. The developed mixing system led to the elimination of mass transfer limitation even at 30 times less bulk flow conditions. The mixing system also favoured stable bed formation, and the possibility of operating the bioreactor at a dilution rate above 1/h for ethanol production using flocculating yeast. A mixing system was also developed for aerobic fermentation and it led to improved media rheological and hydrodynamic performance of the bioreactor for fungi fermentation. The improved performance could be seen from minimised foam formation and stabilisation at an aeration rate of 1.4 VVMon a viscous, integrated first- and second-generation ethanol substrate with an initial viscosity of 93 cP.

The stress that would be exerted on the bioreactor when used for large-scale applications was simulated and validated at laboratory scale. For 100–1000 m3 bioreactor, the tension per unit length that would be exerted on it would be between 300–20000 N/m.

In this thesis, it was found that the use of the developed textile bioreactor was effective in reducing the fermentation-associated investment cost by 21 % or more, introducing flexibility and addressing several technical problems associated with both anaerobic and aerobic fermentation-based production processes.

Global environmental concerns connected to the use of fossil fuels have forced the development ofalternative sustainable energy technologies. The application of anaerobic digestion, from waste streams thatcurrently have no use, can be utilized for bioenergy production. Due to the high protein and fat content,slaughterhouse waste has a high potential for biogas production. However, potential inhibitory compoundscan be formed during the degradation of the proteins and lipids, which can make the process sensitive andprone to failure. One of the ways to overcome these problems is co-digestion with carbohydrate-rich cosubstratesi.e., a mixture of agro-wastes with low protein/lipid content. This also leads to a better nutritionalbalance and enhanced methane yield due to the positive mixture interactions.

In this study, four different waste fractions, i.e., solid cattle slaughterhouse waste (SB), manure (M),various crops (VC), and the organic fraction of municipal solid waste (MSW) were investigated in monodigestionand co-digestion processes. Different mixture ratios were prepared, and the methane yield (YCH4),the specific methanogenic activity (SMA), and a kinetic parameter (k0) were determined using the batchdigestion assays at thermophilic conditions (55oC). The SB had a lower degradation rate and lower SMAcompared with those of the other samples. In order to investigate the effect of the temperature, a selectedmixture ratio was also digested at mesophilic conditions (37oC), which resulted in a decrease in YCH4 and inthe kinetic parameters, specific methane production rate (rsCH4), and k0, by up to 57% compared to thoseobtained at the thermophilic conditions. During the next part of the work, a four-factor mixture design wasapplied aiming to obtain possible synergetic or antagonistic effects. The performance of the process wasassessed using YCH4and rsCH4as the response variables. Mixing all four of the substrates resulted in a 31%increase in the YCH4compared to the expected yield calculated on the basis of the methane potential of theindividual fractions and 97% of the theoretical methane yield, clearly demonstrating a synergistic effect.Nevertheless, antagonistic interactions were also observed for certain mixtures. In order to maximize boththe response variables simultaneously, a response surface method was employed to find the optimalcombination for the substrate mixture.

The impact of the mixture interactions, obtained in the batch operation mode, was also evaluated undersemi-continuous co-digestion. Digestion of the SB as the sole substrate failed at an organic loading rate of0.9 gVS L-1d-1, while stable performance with higher loadings was observed for mixtures that displayedsynergy earlier during the batch experiments. The combination that showed the antagonistic effects resultedin unstable operation and poor representation of methanogens. It was proved that synergetic or antagonisticeffects observed in the batch mode could be correlated to the process performance, as well as to thedevelopment of the microbial community structure during the semi-continuous operation.

In the last part of the work, the response of the methanogenic biomass to the consecutive feeding applied inthe batch assays was evaluated regarding process parameters such as YCH4, SMA, and degradation kinetics.The objective was to examine whether there is a possibility to correlate these findings to the expectedprocess performance during the long-term operation. Digestion of the SB alone showed a total inhibitionafter the second feeding, which is in correlation with the failure observed during the semi-continuous mode.Furthermore, enhanced SMA was observed after the second feeding in those mixtures that showed synergyin the previous batch assays as well as a good process performance during the semi-continuous operation.

BACKGROUND: Several wastes from agro-industrial activities were mixed in different ratios to evaluate the co-digestion process. Methane yield (YCH4), specific methanogenic activity (SMA) and a kinetic parameter (k0) were determined. A second feeding was also performed to examine the recovery of bacterial activity after exhaustion. Mixture ratios of 1:1:1:1 and 1:3:4:0.5 (w/w) showed the best performance, with YCH4 of 664; 582 NmL CH4/gVSsubstrate, as well as SMA of 0.12; 0.13 gCODNmLCH4/gVSinoculum/d, respectively, during the digestion of the first feed. It was possible to relate synergetic effects with enhancement in YCH4 by up to 43%, compared with values calculated from YCH4 of the individual substrates. All batches started up the biogas production after an exhaustion period, when a second feed was added. However, long lag phases (up to 21 days) were observed due to stressed conditions caused by the substrate limitation prior to the second feed.

Global projections on the climate change and the dynamic environmental perturbations indicate severe impacts on food security in general, and crop yield, vigor and the quality of produce in particular. Sessile plants respond to environmental challenges such as salt, drought, temperature, heavy metals at transcriptional and/or post-transcriptional levels through the stress-regulated network of pathways including transcription factors, proteins and the small non-coding endogenous RNAs. Amongs these, the miRNAs have gained unprecedented attention in recent years as key regulators for modulating gene expression in plants under stress. Hence, tailoring of miRNAs and their target pathways presents a promising strategy for developing multiple stress-tolerant crops. Plant stress tolerance has been successfully achieved through the over expression of microRNAs such as Os-miR408, Hv-miR82 for drought tolerance; OsmiR535A and artificial DST miRNA for salinity tolerance; and OsmiR535 and miR156 for combined drought and salt stress. Examples of miR408 overexpression also showed improved efficiency of irradiation utilization and carbon dioxide fixation in crop plants. Through this review, we present the current understanding about plant miRNAs, their roles in plant growth and stress-responses, the modern toolbox for identification, characterization and validation of miRNAs and their target genes including in silico tools, machine learning and artificial intelligence. Various approaches for up-regulation or knock-out of miRNAs have been discussed. The main emphasis has been given to the exploration of miRNAs for development of bioengineered climate-smart crops that can withstand changing climates and stressful environments, including combination of stresses, with very less or no yield penalties.

Current biofuels face a noteworthy misfortune on commercialization because of its economiccomparison with low-cost fuel from the oil reserves. To compete with gasoline as a fuel, thebiofuels need to be economically feasible and demonstrated on a large-scale. Biogas and ethanolhave a great potential as commercial biofuels, even though it has difficulties, for example, highcapitalinvestment, absence of demonstrated innovations, and availability of raw materials and soforth. This thesis focuses on different application-driven bioprocess developments for improvingthe techno-economic feasibility of the biogas and ethanol industries.

The biogas industry was studied from three different perspectives:

1) Modeling approach in which a Process Simulation Model (PSM) model was developed forpredicting the biogas productions, as exploiting new substrates is vital for a biogas industrygrowth. The PSM model was created using Aspen Plus® which includes 46 reactions of differentphases in the Anaerobic Digestion (AD) processes. It also contains certain important processparameters, thermodynamics, rate-kinetics, and inhibitions involved in the AD processes. PSMwas a library model for the AD processes, which was validated against the laboratory andindustrial data. The validation showed that the PSM predicted the biogas production about 5% inexcess, which could ease the biogas industry to predict biogas from new substrates.

2) Simulation approach to study the imperative components affecting the profitability of theplant. For this purpose, a local municipality plant was studied under distinct situations. The choiceof upgrading method, capacity, cost of waste and its processing, number of digesters used, etc.were exploited. The results showed that the collection and transportation fee, landfilling fee, andthe reduced operation of a plant were the main considerations in influencing its profitability.Moreover, it was identified that for bigger cities the decentralization strategy could beat theexpense of collection and transportation of waste, and the plant could obtain a 17.8% return oninvestment.

3) Rethinking digester technology in which the cost of the digester was significantly lessenedusing a cutting-edge textile, which was principally intended for developing countries. The digestercost played an important role in consuming biogas for different applications. The textile digesterwas tested on a laboratory scale, followed by field tests in different countries including India,Indonesia, and Brazil. Textile digesters cost one-tenth of the conventional digesters, and thepayback was more or less between 1–3 years, when replacing the Liquefied Petroleum Gas (LPG)and kerosene as a cooking fuel for households.

When it comes to ethanol, the first generation ethanol production using grains was financiallypossible with a payback of about 13 years. Nonetheless, with the fluctuation of the oil prices, theethanol industries need to look for alternative sources of revenues. Different retrofits wereconsidered, including the effect of thin-stillage/whole-stillage to ethanol and biomass, in additionto the integration of the first and second generation ethanol production. The results revealed that4% additional ethanol could be obtained when the thin-stillage was converted into ethanol andfungal biomass, while the payback was reduced to 11.5 years. The integration of the first andsecond generation ethanol production revealed that it has a positive influence on the overalleconomics of the process with a payback of 10.5 years. This could help the ethanol industries toconsider a revamp for a better environmental, economic, and energy efficient process.

Biocomposites have been developed to address the sustainability issues of nonrenewableresource based materials. These composites are often produced by reinforcing natural fibres in petroleum based thermoset resins or thermoplastic polymers. Thermoplastic polymers from renewable resources are commercially available, whereas thermoset resins are predominantly derived from crude oil resources. Cellulose fibres have significant importance and potential for polymer reinforcement in lightweight composites. Natural fibres are chemically diverse and their properties vary largely which makes it difficult for them to be used in several applications. The natural fibre based products are limited by their characteristic odour emissions. These issues of natural fibres can be addressed by partly manmade fibres i.e. regenerated cellulose fibre which with little or no compromise in the environmental benefits of the natural fibres can be produced from biomass origin. Natural fibres and their composites have been observed and researched closely for many decades. Study of regenerated cellulose fibres and their composites is, on the other hand, relatively new. Regenerated cellulose fibres are prospective reinforcing material in the composite field due to their even quality and high purity. These fibres have good mechanical properties and also address the odour emission issue of the natural fibres. The development of biocomposites from regenerated cellulose fibre and thermoset resin synthesized from renewable resources has therefore been viewed with considerable interest.

This thesis describes the development of biocomposites from regenerated cellulose fibres (lyocell and viscose) and thermoset resins synthesized from renewable resources (soybean oil and lactic acid). The performance and the properties of the composites were evaluated. Chemical surface treatments, alkali and silane, were performed on the fibres in order to improve the performance of the composites. Hybrid composites were also produced by mixing of two types of reinforcement in order to complement one type of fibre with other. The developed composites were evaluated through mechanical, thermal, viscoelastic and morphological properties among others. The results showed that the regenerated cellulose fibre thermoset biocomposites have reasonably good properties. Fibres before and after treatment were studied in detail. The silane treatment on these fibres improved the mechanical properties of the composites as the silane molecules act as a link between the fibre and resin which gives the molecular continuity across the interface region of the composite.

In food industry, abundant fruit/vegetable byproducts (peel, seed, etc.) have been generated and released into the environment. These wastes can be considered as a largely available, low-cost source of value-added compounds. Among these, phenolic compounds are well-known for their beneficial effects on human health. Effective extraction methodologies are required for recovery of these phenolic compounds from agri-food wastes. These extracts can be used used as natural antimicrobials in pharmacology or disinfectants in food processing plants. In this work, pomegranate peel extracts were prepared by using different solvents to obtain high amount of phenolic-rich compounds. The pomegranate peel extracts were also tested against some important food pathogens to determine their antimicrobial and antibiofilm activities. Pomegranate peel extracts having high amount of phenolic compounds had higher antimicrobial and antibiofilm activities. As a result, phenolic-rich bioactive compounds can be recovered from food industry wastes and used as natural antimicrobial and antibiofilm agents. Thus, food industry wastes, especially fruit wastes, can be integrated into the extraction process and use in food, pharmacology, cosmetic and medicine industries. 

Enhancement of the desulfurization activities of Paenibacillus strains 32O-W and 32O-Y were investigated using dibenzothiophene (DBT) and DBT sulfone (DBTS) as sources of sulphur in growth experiments. Strains 32O-W, 32O-Y and their co-culture (32O-W plus 32O-Y), and Vitreoscilla hemoglobin (VHb) expressing recombinant strain 32O-Yvgb and its co-culture with strain 32O-W were grown at varying concentrations (0.1–2 mmol l^-1) of DBT or DBTS for 96 h, and desulfurization measured by production of 2-hydroxybiphenyl (2-HBP) and disappearance of DBT or DBTS. Of the four cultures grown with DBT as sulphur source, the best growth occurred for the 32O-Yvgb plus 32OW co-culture at 0.1 and 0.5 mmol l^-1 DBT. Although the presence of vgb provided no consistent advantage regarding growth on DBTS, strain 32O-W, as predicted by previous work, was shown to contain a partial 4S desulfurization pathway allowing it to metabolize this 4S pathway intermediate.

Crude oil and fossil fuels contain sulphur compounds. Consumption of these compounds could cause acid rain and environmental pollution. Dibenzothiophene (DBT) is considered as model compound for investigation of fossil fuel desulphurization. This compound is converted to 2-HBP following bio-desulphurization (BDS) by 4S pathway. This work aimed to investigate bacterial growth properties in the presence of 2-HBP which is a final product of DBT desulphurization. For this, two Paenibacillus strains (32 O-W and 32 O-Y) were incubated in 2-HBP (to give the final concentrations at 0.05, 0.1, and 0.2 mM) containing growth media. Although the OD600 value of the 32 O-W strain was low at all 2-HBP concentrations, the 32 O-Y strain could survive, and its OD levels were 3–4 fold higher than 32 O-W strain. As a result, it can be interpreted that the final products of DBT metabolism did not too toxic, and thus bio-desulfurization can be successfully completed by Paenibacillus strains. Acknowledgments: This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK, 118Y416).

Rapid industrialization has provided comforts to mankind but has also impacted the environment harmfully. There has been severe increase in the pollution due to several industries, in particular due to dye industry, which generate huge quantities of wastewater containing hazardous chemicals. Although tremendous developments have taken place for the treatment and management of such wastewater through chemical or biological processes, there is an emerging shift in the approach, with focus shifting on resource recovery from such wastewater and also their management in sustainable manner. This review article aims to present and discuss the most advanced and state-of-art technical and scientific developments about the treatment of dye industry wastewater, which include advanced oxidation process, membrane filtration technique, microbial technologies, bio-electrochemical degradation, photocatalytic degradation, etc. Among these technologies, microbial degradation seems highly promising for resource recovery and sustainability and has been discussed in detail as a promising approach. This paper also covers the challenges and future perspectives in this field.

Potato protein liquor (PPL), a side stream from the potato starch industry, is normally used as fertilizer. However, with more than 100 g/L of sugars, 20 g/L of Kjeldahl nitrogen and Chemical Oxigen Demand (COD) of 300 g/L, it represents serious environmental challenges. The use of PPL for fungal cultivation is a promising solution to convert this waste into valuable products. In this study, PPL was characterized and used to cultivate edible zygomycete Rhizopus oryzae, which is widely used in Southeast Asian cuisine to prepare e.g., tempeh. Moreover, it can be potentially used as a protein source in animal feed worldwide. Under the best conditions, 65.47 ± 2.91 g of fungal biomass per litre of PPL was obtained in airlift bioreactors. The total Kjeldahl nitrogen content of the biomass was above 70 g/kg dry biomass. The best results showed 51% reduction of COD and 98.7% reduction in the total sugar content of PPL.

Bread waste represents a significant portion of global food waste, necessitating innovative approaches for its valorization. This research project explores the utilization of bread waste through fermentation with Aspergillus oryzae to produce fungal film which could be used for textile applications. While previous studies have examined various applications of food waste, this project specifically targets the textile industry, aiming to mitigate pollution associated with conventional textile manufacturing. The objective of this project was to investigate the feasibility of creating fungal films derived from bread waste. Additionally, to analyze the material's properties through assessments of tensile strength, microscopic analysis, and the identification of an appropriate methodology for this investigation.

The biomass suspension was prepared using an ultrafine grinder, and a kitchen blender was subsequently employed to minimize the presence of remaining solids from the grinding process. Additionally, a range of strategies for film casting and wet laying were implemented and evaluated. Wet laying involved combining fungal biomass with tannin to mimic the characteristics of leather. On the other hand, casting utilized pre-treated biomass suspension to assess the formation and quality of the films. As the research progressed and different tannins were used to treat the biomass, a methodology was developed, and glycerol was introduced as a plasticizer. Furthermore, nanocellulose was later incorporated exclusively for the casting of the films to serve as a binder.

The films that were produced gave interesting results are observed in casted sheets containing nanocellulose and glycerol-infused biomass (3% BM + 2% Cellulose + 0.13 g Glycerol), exhibiting exceptional tensile strength (35.1 ± 3.42 MPa) and elongation (16.7 ± 5.98%). Wet laid biomass sheets treated with Tara and glycerol display tensile strength (19.9 ± 3.55 MPa) and elongation (6.66 ± 3.02%). These findings signify the potential for developing fungal films from bread waste, necessitating further research to refine methodologies. Overall, this research project paves the way for future advancements in fungal films derived from bread waste. By investigating the use of Aspergillus oryzae and employing wet laying and casting techniques, the project establishes a foundation for sustainable textile production. The successful utilization of bread waste not only addresses the issue of food waste but also contributes to reducing pollution in the textile industry.

One of the greatest challenges facing the societies now and in the future is the reduction of green house gas emissions and thus preventing the climate change. It is therefore important to replace fossil fuels with renewable sources, such as biogas. Biogas can be produced from various organic waste streams or as a byproduct from industrial processes. Beside energy production, the degradation of organic waste through anaerobic digestion offers other advantages, such as the prevention of odor release and the decrease of pathogens. Moreover, the nutrient rich digested residues can be utilized as fertilizer for recycling the nutrients back to the fields. However, the amount of organic materials currently available for biogas production is limited and new substrates as well as new effective technologies are therefore needed to facilitate the growth of the biogas industry all over the world. Hence, major developments have been made during the last decades regarding the utilization of lignocellulosic biomass, the development of high rate systems, and the application of membrane technologies within the anaerobic digestion process in order to overcome the shortcomings encountered. The degradation of organic material requires a synchronized action of different groups of microorganisms with different metabolic capacities. Recent developments in molecular biology techniques have provided the research community with a valuable tool for improved understanding of this complex microbiological system, which in turn could help optimize and control the process in an effective way in the future.

This article fully discusses the recent trends in the production of one the most attractive types of biofuels, i.e., biodiesel.with a focus on the existing obstacles for its large scale production. Moreover, recent innovations/improvements under three categories of upstream, mainstream, and downstream processes are also presented. Upstream strategies are mainly focused on seeking more sustainable oil feedstocks and/or enhancing the quality of waste-oriented ones. The mainstream strategies section highlights the numerous attempts made to enhance agitation efficiency including chemical and/or mechanical strategies. Finally, the innovative downstream strategies basically dealing with 1) separation of biodiesel and glycerin, 2) purification of biodiesel and glycerin, and 3) improving the characteristics of the produced fuel, are comprehensively reviewed.

Softwoodspruce (chips and milled), ricestraw and triticale (a hybrid of rye and wheat) straw, were pretreated with N-methylmorpholine-N-oxide (NMMO or NMO) prior to anaerobic digestion to produce biogas. The pretreatments were performed at 130 °C for 1–15 h, and the digestions continued for six weeks. The digestions of untreated chips (10 mm) and milled (<1 mm) spruce, ricestraw and triticalestraw resulted in 11, 66, 22 and 30 Nml CH4/g raw material. However, the pretreatments have improved these methane yields by 400–1200%. The best digestion results of the pretreated chips and milled spruce, ricestraw and triticalestraw were 125, 245, 157 and 203 Nml CH4/g raw material (or 202, 395, 328 and 362 Nml CH4/g carbohydrates) respectively, which correspond to 49, 95, 79 and 87% of the theoretical yield of 415 Nml CH4/g carbohydrates. Although the experiments were carried out for six weeks, one and a half weeks was enough to digest the materials.

Waste segregation at source, particularly at the household level, is an integral component of sustainable solid waste management, which is a critical public health issue. Although multiple interventions have been published, often with contradictory findings, few authors have conducted a comprehensive systematic synthesis of the published literature. Therefore, we undertook a systematic review to synthesize all published interventions conducted in any country in the world which targeted household-level waste segregation with or without additional focus on recycling or composting.

Following PRISMA guidelines, Web of Science, Medline, Global Health, and Google Scholar were searched using a search strategy created by combining the keywords ‘Waste’, ‘Segregation’, and ‘Household’. Two-stage blinded screening and consensus-based conflict resolution were done, followed by quality assessment, data extraction, and narrative synthesis.

8555 articles were identified through the database searches and an additional 196 through grey literature and citation searching. After excluding 2229 duplicates and screening title abstracts of 6522 articles, 283 full texts were reviewed, and 78 publications reporting 82 intervention studies were included in the data synthesis.

High methodological heterogeneity was seen, excluding the possibility of a meta-analysis. Most (n = 60) of the interventions were conducted in high-income countries. Interventions mainly focused on information provision. However, differences in the content of information communicated and mode of delivery have not been extensively studied. Finally, our review showed that the comparison of informational interventions with provision of incentives and infrastructural modifications needs to be explored in-depth. Future studies should address these gaps and, after conducting sufficient formative research, should aim to design their interventions following the principles of behaviour change.

Bio-based rhamnolipid production from waste streams is gaining momentum nowadays because of increasing market demand, huge range of applications and its economic and environment friendly nature. Rhamnolipid type biosurfactants are produced by microorganisms as secondary metabolites and have been used to reduce surface/interfacial tension between two different phases. Biosurfactants have been reported to be used as an alternative to chemical surfactants. Pseudomonas sp. has been frequently used for production of rhamnolipid. Various wastes can be used in production of rhamnolipid. Rhamnolipids are widely used in various industrial applications. The present review provides information about structure and nature of rhamnolipid, production using different waste materials and scale-up of rhamnolipid production. It also provides comprehensive literature on various industrial applications along with perspectives and challenges in this research area. 

The negative consequences of plastic pollution on both environmental and socio-economic aspects have motivated the development of sustainable and renewable materials to replace the petroleum-based plastic. Polyhydroxyalkanoates (PHAs), which are bioplastics, having an outstanding biodegradability and rather comparable thermal and mechanical properties, are potential alternatives for the replacement of conventional plastics. However, one of the hurdles on the way to PHA commercial production is the cost of conventional feedstock, which can constitute up to 50% of the production cost. In this regard, volatile fatty acids (VFAs) derived from acidogenic fermentation of organic waste can be a promising substrate to increase the cost-competitiveness of PHA production. Therefore, in this thesis, VFAs were utilized and developed to be a key carbon feedstock for the sustainable and economically feasible production of PHAs. The applicability of individual and mixed VFAs as potential substrates was initially investigated through the cultivation of two different PHA-bearing bacteria of Bacillus megaterium and Cupriavidus necator, providing an average PHA yield on biomass of 10 and 55%, respectively. Further thorough studies, in terms of VFAs loading and inhibition thresholds and operating parameters, were conducted to improve the conversion efficiency of VFAs by C. necator. Consequently, a biomass yield on VFAs of up to 82% was obtained, rendering a PHA accumulation of 1 g/L using actual waste derived VFA effluent. In addition, in order to tackle the inherent issue of low productivity in batch and/or fed-batch cultivations under high VFA containing feed, a novel approach of immersed membrane reactor (iMBR) was introduced and applied in this thesis. With the assistance of membrane filtration, the PHA production was conducted in semi-continuous mode (up to 128 h), yielding a maximum biomass and PHA production of 6.6 and 2.8 g/L, respectively. The outcomes achieved, furthermore, were 32.1 and 28.5%, respectively, higher than that from a continuous stirred tank (CSTR), in which the cultivation was affected by the washout effect. Moreover, considering the insufficiency of the current recycling methods of PHA-based products in terms of resource recovery, a novel attempt of acidogenic fermentation has been conducted to valorize the PHA-based composites through conversion into precursor VFAs. Afterwards, the recovered VFAs could be recirculated into PHA production, fulfilling the concept of a circular bioeconomy.

Approximately 1.3 billion tons of food waste is produced globally every year. In principle, all the resources in the supply chain are lost (e.g. land, energy, and water) when the food is not consumed as intended. Anaerobic digestion is an established biological technology to treat food waste, and is mainly employed for recovery of energy in the form of biogas. Volatile fatty acids (VFAs) are formed as intermediate products of the anaerobic digestion process, and can be applied as precursors for various essential biomaterials. The manipulation of the anaerobic digestion process to synthesize these intermediates instead of biogas is considered to recover more value from food waste. However, some bottlenecks that prevent large-scale production and application of VFAs still exist. Among the key issues to be addressed are the difficulty in recovering the VFAs from the fermentation medium and the overall low product yields. The goals of the present thesis were: 1) to investigate methods to boost the production of VFAs from food waste; 2) to continuously recover VFAs from food waste fermentation medium; 3) to determine the changes in the microbial structure during high organic loading of food waste in membrane bioreactors; and 4) to study a novel approach for applying food waste-derived VFAs for cultivating edible filamentous fungi.

For continuous product recovery at high yields, an immersed membrane bioreactor was constructed with robust cleaning capabilities to withstand the complex anaerobic digestion medium. The membrane bioreactor was first operated without pH control and a yield of 0.54 g VFA/g VSadded was achieved when an organic loading rate of 2 gVS/L/d was applied. Moreover, only a 16.4% reduction in the permeate flux during a 40-day operation period was recorded. In the second experimental work, the immersed membrane bioreactor system was subjected to high organic loading rates of 4, 6, 8, and 10 g VS/L/d as a tool of manipulating the anaerobic digestion process towards high VFAs and hydrogen production. The highest yield of VFAs was attained at 6 g VS/L/d (0.52 g VFA/gVSadded), while at 8 g VS/L/d, a maximal hydrogen yield of 14.7 NmL/gVSadded was obtained. An analysis of the microbial structure revealed that the presence of Clostridium resulted in high production of acetate, butyrate and caproate. On the other hand, the relative abundance of Lactobacillus was found to influence lactate biosynthesis.

Cultivation of edible filamentous fungi presents a novel possibility for application of food waste-derived VFAs. Due to the growing demand of single-cell protein, one of the potential uses for the fungal biomass is the production of animal feed. In this thesis, an edible filamentous fungus, Rhizopus oligosporus was grown solely on the VFAs recovered from the membrane bioreactors. It was revealed that high concentrations could inhibit fungal growth; thus, the dilution of the VFAs solution used as substrate was necessary. Furthermore, when a fed-batch cultivation technique was applied, a four-fold improvement in the biomass production relative to standard batch cultivation was realized. A maximum biomass yield of 0.21 ± 0.01g dry biomass/ g VFAs COD eq. consumed, containing 39.28 ± 1.54% crude protein, was obtained. With further improvements in the VFAs uptake and the biomass yield, this novel concept could be a fundamental step in converting anaerobic digestion facilities into biorefineries.