In 2023, approximately 2.36 million metric tons of olive oil were produced globally. Olive pomace, a byproduct of the flesh and pits left after olive oil extraction, presents environmental challenges when used as landfill due to its high polyphenol and organic contents, or when combusted due to greenhouse gas emissions. Its potential as animal feed is limited, yet it holds promise for methane production via anaerobic digestion (AD), providing a source of renewable energy. However, the highly crystallized polysaccharides in olive pomace, such as cellulose, hemicellulose, and pectin, impede its conversion to methane, and the high polyphenol content inhibits methanogen growth. To address this, phenolics were extracted from olive pomace, producing a phenolics-extracted olive pomace (PEOP) and a phenolics-rich olive liquid. After further resin-based extraction of phenolics-rich olive liquid, approximately two-thirds of the phenolics were removed, yielding phenolics-extracted olive liquid (PEOL). Enzymatic hydrolysis was conducted on several olive byproduct streams: olive pomace with water, PEOP with PEOL, and PEOP with water, to convert insoluble polysaccharides into reducing sugars that are more readily utilized by methane-producing microorganisms. Various enzymes, including cellulase, hemicellulase, xylanase, and pectinase, were individually treated with olive pomace to determine the optimal hydrolysis time and enzyme concentrations. Response surface methodology (RSM) identified the optimal enzyme cocktail ratio (1.1% cellulase, db, and 0.9% pectinase, db) for achieving the highest reducing sugar contents (22.3 mg/mL), which had 79.1% increase when compared to the control sample (12.5 mg/mL). After 19 days of anaerobic digestion at 37 °C, olive samples before phenolics extraction (olive pomace with water) and olive samples after phenolics extraction (phenolics-extracted olive pomace with phenolics-extracted olive liquid), produced similar amounts of methane (~175 mL CH4/g VS). This indicated that in our experimental settings, the phenolics reduction did not significantly impact methane yields. Carbohydrate profiles may also influence biofuel yields, as hexoses (C6 sugars) are preferred over pentoses (C5 sugars) for end-product production during biotechnical conversion. To explore the effect of carbohydrate profiles on methane production from olive byproducts, two response surface methodology (RSM) coded enzyme cocktail-treated samples with different carbohydrate profiles underwent anaerobic digestion for 19 days at 37 °C, yielding similar amounts of methane (~156 mL CH4/g VS), comparable to the control sample. This suggested that anaerobic digestion can utilize different hexoses and pentoses at similar rates. These findings demonstrated that olive pomace can be used for biomethane production instead of being landfilled or combusted. While enzymatic hydrolysis increased reducing sugar contents, it did not enhance methane yields. Reducing phenolic contents of 2/3 did not improve biomethane yield, and the impact of greater reduction requires further assessment.

Thesis (Master of Environmental Management)--Cape Peninsula University of Technology, 2018. / Fresh water is a renewable resource, but it is also finite, especially given environmental impacts from anthropogenic activities. Globally, there are countless signs that untreated industrial discharge into fresh watercourses is one of the main causes of ecosystem degradation. Poultry slaughterhouse wastewater (PSW) amongst the main pollutants of fresh water sources. In recent years, the world’s pre-eminent researchers have developed innovative wastewater treatment processes to treat the large quantity of wastewater generated as well as to manage the environmental health concerns arising from PSW discharged into the environment. Furthermore, increasing wastewater treatment capital costs and the implementation of increasingly rigorous government legislation to mitigate environmental pollution whilst minimizing fresh water source contamination, requires that wastewater such as PSW, be adequately treated prior to discharge. In order to assist the small-scale poultry producers in South Africa (SA), process simulation for a small-scale poultry slaughterhouse wastewater treatment plant was proposed using Sumo Wastewater treatment plant (WWTP) simulation software. Sumo is an innovative and most versatile wastewater simulation package on the market. The simulator is capable of modelling treatment plants of unlimited complexity, focusing largely on Biochemical oxygen demand (BOD), Chemical oxygen demand (COD), nitrogen and phosphorus removal; with digester, and side streams design options, being available. Considering the possible advantages in modelling and ongoing studies of implementing wastewater treatment to increase water management, anaerobic digestion of high strength wastewater such as PSW, warranted this research study. Model development from the simulation included the evaluation of numerous design options to assist small scale poultry producers, to have a variety of designs to choose from in their PSW WWTP designs. With the aid of Sumo, two models were designed in this study, namely a single-stage and a two-stage anaerobic digestion without a recycle. The PSW used as feed was obtained from a local poultry slaughterhouse (Western Cape, South Africa). Both model designs predicted the reduction of the organic matter (COD, BOD5) total suspended solids (TSS), and volatile suspended solids (VSS) in the PSW. The digester for the single stage anaerobic digestion system modelled was set to operate at steady state for 150 days under mesophilic temperature (35 ˚C) with a solid retention time (SRT) of 25 days. The COD, TSS, VSS and BOD removal efficiencies reached a maximum of 64%, 77%, 84%, and 94%, respectively, at an organic load rate (OLR) of 143.6 mg COD/L/day. A minute increase in the ammonia (NH3) and phosphate (PO3- 4) concentration was observed once the simulation was completed. As for the two-stage anaerobic digestion system, both digesters were set to perform at mesophilic temperatures (35 ˚C) and a SRT of 13 days in the first digester and 25 days in the subsequent digester. The two-stage anaerobic digestion showed better performance in comparison to the single-stage anaerobic digestion system. The COD, TSS, VSS and BOD5 removal efficiencies reached a maximum of 69%, 79%, 85%, and 96%, respectively, at an at an OLR of 143.6 mg COD/L/day. A similar trend regarding phosphate and ammonia removal was noticed in the two-stage anaerobic digestion, suggesting a tertiary treatment system to be in place for further treatment. Although, the two-stage anaerobic digestion demonstrated adequate performance, for the purpose of this study, the single-stage was the process recommended for PSW treatment, as it is less costly and will be suitable for small scale poultry producers; albeit biogas production is much higher when digesters are connected in series. The PSW treatment modelling for this study was successfully employed with the resultant effluent being compliant with the City of Cape Town (CCT) wastewater and industrial effluent by-law discharge limits. Although, both the PO3- 4 and NH3 were suggested to require further monitoring. Therefore, the poultry slaughterhouse from which the PSW was obtained will be able to safely discharge the treated wastewater proposed in this research into local water bodies, i.e. rivers in the Western Cape, SA; however, the treated PSW will not be suitable for re-use as process water.

Denna rapport presenterar resultat och analys av prestandan i ett pilotförsök om temperaturstegsrötning (TPAD). Pilotförsöket genomfördes på uppdrag av Käppalaförbundet. Resultaten jämfördes med en nedskalad mesofil process som simulerade den nuvarande fullskaliga rötningsprocessen på Käppala  avloppsreningsverk. Syftet var att utvärdera om TPAD kunde erbjuda fördelar jämfört med det mesofila systemet. TPAD har tidigare visat stor potential i pilotstudier och till viss del i fullskaliga implementeringar på avloppsreningsverk runt om i världen. Då prestanda och beteende vid rötningsprocesser dock är starkt beroende av lokal slamkomposition och processparametrar, behövdes en skräddarsydd pilotstudie för att utvärdera TPADs applicerbarhet vid Käppala avloppsreningsverk specifikt. Sammanfattningsvis visade TPAD något bättre metanutbyte än det mesofila kontollförsöket (MAD), och VSD ökade markant. Dessa fördelar erhölls trots den lägre totala retentionstiden för TPAD. Kvävemineraliseringen ökade dock också märkbart vilket potentiellt kan medföra ökade kostnader associerade med rening av kväve i rejektvattnet för avloppsreningsverket. Avvattningsprov på labbskala visade ett omfattande utsläpp av TSS i rejektvattnet efter det termofila rötningssteget. Detta förbättrades dock avsevärt (om än inte i samma utsträckning som MAD) efter det mesofila skedet. Mycket preliminära resultat indikerade att TPAD hade en utmärkt inneboende hygieniseringsförmåga tack vare det termofila skedet, och resulterade i ett slutgiltigt rötslam som uppfyllde hygieniseringsriktlinjer enligt Revaq. TPAD verkade uppvisa hög robusthet, utan någon uppenbar syrakollaps trots hög belastning i det termofila steget. Framtida stresstester föreslås för att tvinga fram en termofil syrakollaps, vilket skulle kunna ge en syra/gas-fasad TPAD, med potentiellt ytterligare ökad prestanda enligt mycket av den befintliga litteraturen. / This report analyzes the performance of a pilot scale temperature phased anaerobic digestion process (TPAD) undertaken on commission from the Käppalaförbundet wastewater treatment plant. Results from the newly initiated TPAD pilot were compared to those of a scaled down mesophilic process simulating the current full scale digestion used at Käppala, to evaluate whether TPAD could provide benefits over the mesophilic system. TPAD had previously showed great promise at pilot and full scale at other plants around the world, but given that anaerobic digestion performance and behavior are highly dependent on local sludge composition and process parameters, a bespoke pilot was needed to evaluate TPAD at Käppala WWTP specifically. In summary, the TPAD exhibited slightly better methane yields than the mesophilic control, and showed better removal of volatile solids. Such benefits were seen despite the lower overall retention time of the TPAD. Nitrogen mineralisation however also increased, potentially imposing increased costs associated with sludge liquor nitrogen purification. Dewaterability tests showed the thermophilic stage of TPAD releasing large amounts of problematic colloidal material, which however was reduced by the subsequent mesophilic stage. Preliminary results indicated the TPAD had an excellent inherent hygienization ability owing to the thermophilic stage, producing a final digestate which fulfilled Revaq hygienization guidelines. The TPAD also seemed to exhibit great robustness, with no acid collapse in the thermophilic stage apparent despite high loads and short retention times. Future stress tests are proposed to test an acid-gas phased TPAD, with potentially further increased performance as per much of the existing literature.

Bacterial resistance to antibiotics has become a worldwide health problem, resulting in untreatable infections and escalating healthcare costs. Wastewater treatment plants are a critical point of control between anthropogenic sources of pathogens, antibiotic resistant bacteria (ARBs), antibiotic resistance genes (ARGs), and the environment through discharge of treated effluent and land application of biosolids. Recent studies observing an apparent resuscitation of pathogens and pathogen indicators and the widening realization of the importance of addressing environmental reservoirs of ARGs all lead toward the need for improved understanding of ARG fate and pathogen inactivation kinetics and mechanisms in sludge stabilization technologies. This research has investigated the fate of two pathogens, methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli, and various ARGs under pasteurization, anaerobic digestion, biosolids storage, and land application conditions. Pathogen die-off occurs at a rate specific to each pathogen and matrix in ambient and mesophilic temperature environments. Viable but nonculturable (VBNC) states are initiated by thermal treatments, such as thermophilic digestion and possibly pasteurization, and allow the persistence of pathogen cells and any ARGs contained therein through treatment and into the receiving environment where resuscitation or transformation could occur. Raw sludge ARG content does affect digester effluent quality, although the predominant mechanisms of ARG persistence may be different in mesophilic versus thermophilic digestion. In both thermophilic and mesophilic digestion, a correlation was observed between raw sludge and digester ARGs associated with Class 1 integrons, possibly as a result of horizontal gene transfer. ARB survival was shown to contribute to ARG content in mesophilic digestion, but not thermophilic digestion. Thermophilic digestion may achieve a higher ARG reduction because of reduced microbial diversity compared to mesophilic digestion. However, it is evident that horizontal gene transfer still does occur, particularly with highly mobile integrons, so that complete reduction of all ARGs would not be possible with thermophilic digestion alone. Surprisingly, the experiments that introduced various concentrations of antibiotic sulfamethoxazole and antimicrobial nanosilver did not induce enhanced rates of horizontal gene transfer. Finally, ARG concentrations in biosolids increased during cold temperature storage suggesting that there is a stress induction of horizontal gene transfer of integron-associated ARGs. / Ph. D.

Le processus de dégradation anaérobie de la matière organique est un phénomène naturel largement répandu sur terre (ex. marais, lacs, rizières, systèmes digestifs d'animaux et humains). Une très grande diversité microbienne est entretenue durant ce processus, traduisant une diversité de voies métaboliques impliquées. Lorsqu'elle est complète, la digestion anaérobie aboutie à la formation de biogaz (mélange de méthane et de dioxyde de carbone). En termes de biotechnologie, le traitement par voie anaérobie de pollutions organiques permet de réduire le volume de déchets en générant du méthane valorisable sous plusieurs formes (électricité, chaleur, gaz naturel, biocarburant). Cependant, les digesteurs industriels sont optimisés pour un fonctionnement à 35°C ou à 55°C, ce qui nécessite un apport exogène d'énergie de maintenance. Ainsi, les travaux de thèse se sont intéressés à l'étude de la capacité d'adaptation de divers écosystèmes anaérobies industriels couvrant une variété de procédés et de conditions opératoires à convertir l'éthanol en biogaz à différentes températures. La première phase de l'étude avait pour but le conditionnement, en réacteurs de laboratoire d'écosystèmes à leur température d'origine avec un substrat facilement biodégradable (éthanol). Ensuite, les performances des communautés microbiennes (le potentiel méthanogène maximal et la cinétique de dégradation) ont été estimées sur un gradient de température de 5°C à 55°C en fioles. La phase de conditionnement des écosystèmes en réacteur batch a montré que la production de biogaz avoisinait la production théorique et que cette production s'accompagnait d'une diminution de la durée de réaction avec ajout successif du substrat. De plus, les cinétiques de production de biogaz obtenues les variaient fortement d'un écosystème à l'autre. Des profils d'empreintes moléculaires (CE-SSCP) des communautés bactériennes et archées ont été réalisés au début et à la fin du conditionnement. Ces profils de communauté ont été comparés entre eux par analyse en composante principale (ACP). Les populations bactériennes qui assuraient une performance efficiente étaient différentes de celles qui garantissaient une bonne capacité d'adaptation. Par ailleurs, le potentiel d'adaptation dépendait de la présence de populations d'Archaea méthanogènes bien spécifiques. En plaçant ensuite les écosystèmes conditionnés dans des conditions de température éloignées de la température d'origine, seuls les écosystèmes mésophiles se sont acclimatés aux températures psychrophiles. Comme attendu, l'activé spécifique maximale des méthanogènes était toujours obtenue à la température d'origine de l'écosystème. L'analyse des communautés bactériennes et archées à la fin de la période d'acclimatation a révélé que l'acclimatation des écosystèmes thermophiles et mésophiles à des températures plus faibles ne modifiait que légèrement la structure des communautés microbiennes. En revanche, des changements plus importants étaient obtenus lorsque la température d'incubation était augmentée par rapport à la température d'origine de l'écosystème. En résumé, l'étude de l'effet de la température d'incubation (de 5°C à 55°C) sur l'activité fermentaire et sur la structure des populations microbiennes est un bon modèle d'étude au laboratoire pour appréhender l'impact d'un facteur abiotique sur la dynamique structurelle et fonctionnelle d'une communauté microbienne complexe. / The process of anaerobic degradation of organic matter is a natural phenomenon widespread on Earth (eg, marshes, lakes, rice fields, digestive systems of animals and humans). A high microbial diversity is maintained during this process, reflecting a diversity of metabolic pathways involved. When complete, the anaerobic digestion accomplished in the formation of biogas (methane mixture and carbon dioxide). In terms of biotechnology, anaerobic treatment of organic pollution reduces the volume of waste and generates methane recoverable in several forms (electricity, heat, natural gas, biofuels). However, industrial digesters are optimized for operation at 35 ° C or 55 ° C, which requires exogenous energy maintenance. Thus, the thesis is interested in the study of the adaptability of various anaerobic ecosystems covering a variety of industrial processes and operating conditions to convert ethanol into biogas at different temperatures. The first phase of the study was to the conditioning, in laboratory reactors ecosystems to their original temperature with a readily biodegradable substrate (ethanol). Then, the performances of microbial communities (the maximum methanogenic potential and degradation kinetics) were estimated on a temperature gradient of 5 ° C to 55 ° C in glass bottles. The conditioning phase of the ecosystems in batch reactor showed that the biogas averaged theoretical production and this production was followed by a decrease in reaction time with successive addition of the substrate. In addition, the kinetics of the biogas obtained varied greatly from one ecosystem to another. Molecular fingerprinting profiles (CE-SSCP) of bacterial and archaeal communities were performed at the beginning and at the end of conditioning. These community profiles were compared with each other by principal component analysis (PCA). Bacterial populations that ensured efficient performance were different from those that ensured a good adaptability. In addition, the potential for adaptation depended on the presence of very specific methanogenic Archaea populations. When placing ecosystems conditioned in temperature away from the original temperature, only mesophilic ecosystems adapted to psychrophilic temperatures. As expected, specific methanogenic activity was always obtained at the original temperature of the ecosystem. Analysis of bacterial and archaeal communities at the end of the acclimation period revealed that acclimation thermophilic and mesophilic ecosystems to lower temperatures only modified slightly the structure of microbial communities. On the other hand, more significant changes were obtained when the incubation temperature was increased in comparison to the original temperature of the ecosystem. In summary, the study of the effect of incubation temperature (5 ° C to 55 ° C) on the fermentation activity and microbial population structure is a good model for laboratory study to understand the impact of abiotic factor on the structural and functional dynamics of a complex microbial community.

Master of Agribusiness / Department of Agricultural Economics / Jeffery R. Williams / Anaerobic digestion is an alternative solution to organic waste management that offers economic and environmental benefits. The Kawangware open air market in Kenya generates approximately 10 metric tons of organic waste per day as a result of farm produce sold at the market. Fresh fruits and vegetables sold at the market account for more than 80 percent of the organic waste. This organic waste is left uncollected, piling up and therefore becoming pollution to the environment. Instead, this waste can be processed by anaerobic digestion to produce energy, organic fertilizer and greenhouse gas credits. The main objective of this project is to help investors and members of Kawangware Waste Utilization Initiative (a waste management community based organization in the Kawangware area) answer the following questions: (a) Is it economically profitable to invest in an anaerobic digestion system to convert the market organic waste to methane and fertilizer? (b) Is it economically profitable to burn the methane to generate electricity? To answer these questions, the study examines the costs and returns of producing methane, electricity, and fertilizer from organic waste under various scenarios using net present value, internal rate of return and payback period analysis techniques. Three production conditions under various scenarios using the anaerobic digester are examined. The conditions include: (a) Production of methane and organic fertilizer. (b) Production of methane, organic fertilizer, and carbon credits. (c) Production of electricity, organic fertilizer, and carbon credits. From these three production conditions examined, production of methane, organic fertilizer and carbon credits had the highest net present value of $332,610, internal rate of return of 21.4%, and the shortest payback period of 7.9 years. If carbon credits could not be sold the next best alternative would be production and selling of methane and organic fertilizer which has a net present value of $246,752, internal rate of return of 19%, and a payback period 9.2 years.

The production of pulp and paper is associated with the generation of large quantities of wastewater that has to be purified to avoid severe pollution of the environment. Wastewater purification in pulp and paper mills combines sedimentation, biological treatment, chemical precipitation, flotation and anaerobic treatment, and the specific combination of techniques is determined by the local conditions. Wastewater treatment generates large volumes of sludge that after dewatering can be incinerated and thus used for bio-energy production. Sludge is currently viewed as biofuel of poor quality due to its high water content, and some mills treat it solely as a disposal problem. Two strategies have been identified as feasible options to improve the energy efficiency of sludge management. One is drying using multi-effect evaporation followed by incineration. The other is anaerobic digestion of the wet sludge to produce methane. This thesis explores the energy balances of sludge management strategies in pulp and paper mills with special focus on anaerobic digestion. The first part consists of a system analysis, used to evaluate some wastewater treatment processes and sludge management, and the second part of empirical studies of anaerobic digestion of pulp and paper mill sludge. It was shown that the use of energy for aeration in aerobic biological treatment should be kept to the minimum required for acceptable quality of the processed water. Additional aeration for reduction of the generated sludge will only result in reduced energy generation in a subsequent methane generation stage. In the second part of the thesis, it is shown that anaerobic digestion is a feasible option for sludge management as it leads to production of high value biogas. Co-digestion with grass silage, cow/pig manure or municipal sewage sludge should then be used to counteract the low nitrogen content of pulp and paper mill sludge.

Surrogate organisms have been used to study highly pathogenic organisms, or organisms that cannot be cultured in the laboratory. Surrogates are selected based on multiple similarities to the pathogen, such as morphology, genome size and structure, and environmental characteristics. This dissertation utilized MS2 coliphage as a surrogate for norovirus and Ebola virus in three environments. MS2 is an icosahedral, single-stranded RNA bacteriophage. It is a male-specific coliphage that infects the bacteria Escherichia coli. Its properties, such as morphology and survival in the environment, have been likened to those of many enteric viruses. Because of this, it has been used as a surrogate for pathogenic enteric viruses for disinfection testing on surfaces, in water and in food; modeling the movement and survival of pathogens in different environments; and transfer properties from surfaces. This dissertation utilized MS2 as a surrogate in three different studies. In the first, MS2 is used as a surrogate for human enteric viruses in irrigation canals to predict the re-suspension of pathogenic viruses from bed sediment into overlying irrigation water using a flume to re-create field conditions in the laboratory. MS2 re-suspension into the overlying water was characterized at varying flow rates and velocities using two sediment types. Its overall re-suspension was not statistically significantly different (p > 0.05) between flow rates. The additional studies in this dissertation used MS2 as a surrogate for Ebola virus in human waste. Ebola virus is a BSL-4 organism that is spread through direct contact with bodily fluids. It is found in bodily fluids in concentrations between 10^5.5 and 10⁸ genome copies per milliliter. In the first study using MS2 as a surrogate for Ebola virus, efficacies of four disinfectants were tested using 10¹² PFU of MS2 in one liter containing 2.25% (w/v) organic matter at three contact times (1, 15 and 30 minutes). The purpose of this study was to assess the disinfectants on reducing virus in waste before toilet flushing. Peracetic acid and quaternary ammonium formulation were found to reduce the concentration of MS2 in the toilet bowl the fastest (within one minute) with the greatest reduction (2.26 and 1.99 log₁₀), when compared with the other disinfectants. Reductions observed from hydrogen peroxide were significantly less than those from peracetic acid and quaternary ammonium (p < 0.05). The contamination of restroom surfaces by MS2 was also evaluated after toilet flushing with and without disinfectant treatment. All four disinfectants were found to significantly reduce the viral concentrations on fomites after 15 minutes of contact (p < 0.05). Despite disinfectant use, three sites were contaminated in 100% of trials (N = 18). These were the toilet bowl rim, the toilet seat top and underside. The final study evaluated the inactivation of MS2 and several other viruses by thermophilic and mesophilic anaerobic digestion. Little information is available on the influence of the wastewater treatment process, specifically anaerobic digestion, on emerging viruses, such as Ebola virus. It is important to evaluate this process due to the environmental disposal and discharge of wastewater and solids into the environment. All viruses were recoverable after mesophilic digestion (reductions from 1.8-6.6 log₁₀ per mL), except the lipid-containing bacteriophage Φ6. Thermophilic digestion inactivated all viruses significantly (p = 0.0011) more than mesophilic digestion. The reductions by thermophilic digestion ranged from 2.8-7.1 log₁₀ per mL. The inactivation between the initial concentration and both digestion types was statistically significant (p = 0.007).

We initially studied the treatment of acid rock drainage using a sulfate-reducing bioreactor with zero-valent iron as the electron donor. The results demonstrate that this electron donor can serve as the sole exogenous slow-release electron donor to drive sulfate reduction over 400 operational days at short HRTs (1-3 days). The synthetic acid rock drainage contained high heavy metal concentrations (up to 50 mg/L of copper) and pH values ranging from 3.0 to 7.0. Treatment of this acid rock drainage efficiently removed Cu, Cd and Pb (>99.7%) and increased pH to circumneutral values (7.3-7.7). Elemental analysis indicated that formation of insoluble metal sulfides was responsible for the effective metal removal in the zero valent iron columns. In the second study, three inoculated columns containing anaerobic granular sludge were fed a synthetic medium containing H₂SO₄ and Cu²⁺ during the experimental period of 4 months. Algae biomass promoted 80% of sulfate removal (12.7 mg SO₄²⁻ d-1), enabling near complete Cu removal (>99.5 %), and alkalinity generation, raising the effluent pH to 6.5. In the algae amended columns Cu²⁺ was precipitated with biogenic H2S produced by sulfate reduction. Whole cell algae and lipid extracted algae biomasses were both shown to be effective e-donors in driving sulfate reduction of ARD, thus enabling the precipitation and removal of Cu²⁺. The precipitate retained in the columns was composed mostly of insoluble copper sulfide formed from the biogenic sulfide, as shown by sequential extraction and X-ray diffraction. In the third study, several pretreatments, i.e., thermal, chemical, sonication and combinations thereof, that enhance anaerobic biodegradability of Chlorella protothecoides biomass were evaluated. The results demonstrate that anaerobic digestion of pretreated Chlorella protothecoides biomass generates energy-rich methane and recovers nitrogen nutrients. Sonication of algal biomass under optimized conditions provided a significant increase in the methane yield (327 mL STP CH₄ g⁻¹ VS) compared to untreated algae (146 mL STP CH₄ g⁻¹ VS), as demonstrated in anaerobic digestion experiments incubated for 41 days. In contrast, thermal pretreatment provided only a moderate increase of the methane yield and alkaline treatment led to a decrease of the methane yield compared to the untreated algal biomass. Additionally, sonication treatment provided a 4.1-fold increase in the release of ammonia nitrogen during anaerobic digestion of the algal biomass. In the fourth study, the nutrient recovery and biogas generation from the anaerobic digestion of waste biomass from algal biofuel production was investigated. Anaerobic digestion of whole cell and lipid extracted Chlorella sorokiniana-1412 released 48.1 and 61.5% of the total algal nitrogen as NH₄⁺-N, and 87.7 and 93.6% of the total algal P as soluble P, respectively. The biochemical methane potential, quantified through the methane yield of whole cell algae and lipid extracted algae, was 0.298 and 0.253 L methane/g algal volatile solids, respectively. The conversion of lipid extracted algae and whole cell algae biomasses to methane was very similar (38 and 41% on a COD basis, respectively), indicating that the energy yield was not significantly lowered by extraction of the lipid fraction (which accounted for 9% of algal dry weight). Sonication improved the access of hydrolytic enzymes to algal biopolymers, compensating in part for the energy lost due to lipid extraction. The above results demonstrate that algal waste from the biodiesel industry has the potential to be recycled through anaerobic digestion into valuable nutrients and energy. These studies indicate that zero valent iron and algae biomass are promising reactive materials for the treatment of acid rock drainage in sulfate-reducing permeable reactive barrier systems. Additionally, to promote algae cultivation for the biodiesel industry, the anaerobic digestion of algae residues can generate nutrients and energy, making algae cultivation more fiscally attractive.

<p>All products will eventually end up as waste, which in a sustainable society has to be handled in an efficient and environment friendly way. This report focuses on waste fractions meant for combustion, often difficult to characterize. However, more homogeneous fractions that are treated biologically are also discussed.</p><p>The study concerns the region of Borås, Sweden, where the waste plant Sobacken has provided a good starting point. On this site, fuel to the Energy-from-Waste plant of Borås Energi is prepared and the biological waste is treated through anaerobic digestion.</p><p>One important part of the study has been to collect experience-based knowledge from the technical staff at Sobacken and Borås Energi. This information was compiled into an overview of wanted and unwanted fractions to the preparation plant and the boilers respectively. The purpose of this overview is to complement existing delivery terms and thereby facilitate an increased quality of the fuel from the suppliers.</p><p>A significant element of the analysis has been to characterize the content of the industrial waste sent to Sobacken for combustion. Chemical analyses of the prepared fuel as well as the conducted waste component analysis indicate a heterogeneous composition of the waste. A heterogeneous fuel often results in an uneven combustion, leading to higher emissions and an unwanted variation in the energy production.</p><p>Through the waste component analysis, a comprehensive picture of the waste composition was attained. Materials non-valid for delivery mostly consisted of wet domestic waste (biodegradable materials), but some hazardous waste was also found. The results of the waste component analysis were communicated to the involved suppliers and this has already resulted in a considerable reduction of the amount of biodegradable waste in the deliveries of industrial waste.</p> / <p>Förr eller senare blir alla produkter avfall, som i ett uthålligt samhälle måste hanteras på ett resurssnålt och miljövänligt sätt. Det här arbetet är främst inriktat mot de svåridentifierade fraktionerna som är ämnade för förbränning, men berör även de mer homogena fraktionerna som behandlas biologiskt genom rötning.</p><p>Arbetet har utförts i Boråsregionen där Sobackens avfallsanläggning, med beredning av avfallsbränsle till Borås Energis två FB-pannor och rötkammare, har utgjort en naturlig utgångspunkt.</p><p>Ett stort inslag i arbetet var sammanställning av erfarenhetsbaserade kunskaper hos driftteknikerna på beredningsanläggningen, liksom hos Anders Johnsson på Borås Energi. På detta sätt erhölls viktig information om både bra och dåliga fraktioner, för såväl avfallskross som för pannor. Dessa fakta har bland annat använts för att sätta samman en översikt över önskade respektive oönskade fraktioner. Översikten är tänkt som komplement till befintliga leveransregler, i syfte att förenkla för avfallsleverantörerna.</p><p>Stor vikt har lagts vid att försöka kartlägga sammansättningen av det verksamhetsavfall som kommer in till Sobackens beredningsanläggning. Både kemiska analyser av bränsleprov och utförd plockanalys visar på en heterogen sammansättning i avfallet. Ett heterogent bränsle brinner i många fall ojämt, vilket resulterar i högre emissionsnivåer samt en icke-önskvärd variation i energiproduktion.</p><p>I och med plockanalysen erhölls en övergripande bild av förbränningsavfallets sammansättning. Det icke leveransgilla materialet som påträffades utgjordes främst av blött hushållsavfall (biologiskt nedbrytbart material), men även av en del elektronik påträffades. Efter avslutad analys kommunicerades erhållna resultat med aktuella leverantörer, vilket hittills har resulterat i en betydande minskning av biologiskt nedbrytbart material i verksamhetsavfallet.</p>