As a steady renewable energy technology, biogas is a viable alternative to reduce our dependency to fossil fuels and to prevent severe climate change. Biogas potential can be improved through combining different types of substrate and inoculum, as well as through substrate pre-treatments. This study aims to observe and explore the potential of macroalgae Saccharina latissima as a promising new source in renewable energy technology. The biomethane potential of macroalgae in mixture with additional substrate of mixed waste paper will be studied as a mean to improve the biogas yield. It will also compare the biomethane results of the macroalgae and the mixed substrate (macroalgae plus waste paper) exposure to non-thermal and thermal pre-treatment. In the experiment, the ratio of 3 : 1 for gr VS inoculum : gr VS substrate is used in a quantitative BMP test up to 25 days of incubation. The substrate was pre-treated mechanically (blended) into slurry and thermally through pre-heating at high temperature (130°C, 45 minutes) before digested by the inoculum. In the end of incubation period at STP (0°C and 1 atm), the highest cumulative methane yield of 260.91 Nml CH4/gr VS substrate was achieved by sample in Var – I, while the control has cumulative methane yield of 50.52 Nml CH4/gr VS. Thermally pre-treated samples resulted in lower BMP yields than the ones which were not thermally pre-treated. Through the ANOVA t-test of the methane volume and biomethane potential (BMP) yields, it is concluded that the thermal pre-treatment and waste paper addition only give little effect to biomethane production from macroalgae.

The modernized world is over-consuming low-cost energy sources that strongly contributes to environmental stress. As a consequence, the interest for environmentally friendly alternatives has increased immensely. One such alternative is utilizing the diazotrophic nature of the heterocystous filamentous cyanobacteria Nostoc sp. as feedstock for biodiesel and hydrogen production using pulp and paper wastewater – a phosphorous and nitrogen deficient medium. In this work, biodiesel and hydrogen production was studied with respect to three main aspects: biodiesel quality properties, lipid content and hydrogen production coupled with a preliminary study investigating the luminous effects on the biomass and biodiesel quality properties when exposed to low (50 μEm-2s-1), medium (150 μEm-2s-1) and high light (300 μEm-2s- 1). The preliminary study showed that an increase of light intensity was associated with parabolic results for biomass following the 10-day cultivation period, with the medium light intensity showing an average dried weight of at the most 203% greater than the two other light intensities. When analysing the FAME- composition, similar results were demonstrated for the fatty acid constituents preferred for biofuel applications, C18:1 and C18:2 fatty acids, where the low, medium and high light showed an accumulative 34.65, 43.1 and 31.6 dwt % respectively. The strain could be of interest as feedstock for biodiesel when cultivated in pulp and paper wastewater, due to the positive results pertaining to the lipid content and biodiesel quality properties. Following the 10-day cultivation period the lipid content obtained was 35.9 dwt %. The biodiesel quality properties were tested to assess the strains suitability for biodiesel and were tested to ensure its accordance to the standards on commercial biodiesel quality; European Standard for Biodiesel as heating oil (EN 14213) and European Biodiesel Standard (EN 14214). The critical parameters tested were the regulated (iodine value, cetane number, density, viscosity, pour point, cold filter plugging point, oxidative stability) and unregulated (FAME-composition) fuel properties. Results obtained showed values within the regulated values set by the different standards. However, due to a high saturated fatty acid content, the strain showed inadequate low temperature flow properties (cloud point, pour point and the cold filter plugging point). This study shows that this strain has a low potential for hydrogen production, with a hydrogen production of 0.13 nmol/mg dry wt/h following the 10-day cultivation period. This low hydrogen production could be attributed to the among other things the current growth phase of the cyanobacteria. Chemical analyses were conducted for revealing the total nitrogen, total phosphorus and chemical oxygen demand (COD) content. Following the 10-day cultivation period, the samples showed a 22% decrease in phosphorous concentration, 11% decrease in COD concentration and 51% increase of nitrogen concentration. The probable causes for this increase is the Nostoc’s diazotrophic nature and the ammonium excretion nitrogen fixation entails, as well as the nitrogen release following the final algal growth phase – the death phase. In conclusion, the results showed great potential, however, further studies are recommended investigating the changes that occurs during cultivation period to further assess the strains potential as well as assessing the continuity of the results with a greater initial cellular concentration. Nonetheless, due to the positive results obtained regarding the nutrient uptake, biodiesel and hydrogen production, this study shows potential for further optimization for the use of Nostoc grown in pulp and paper wastewater for wastewater treatment, biodiesel and/or hydrogen production.

Fossil fuels are affecting our climate negatively and there is a limited amount of them in the world, which leads to the importance of finding alternative fuels. One alternative is biogas, which is produced though a digestion process of different organic materials in a biogasreactor. Organic substrate that comes from farms has the biggest potential to increase the production of biogas in Sweden. Primarily crops from farms, but also waste products like manure are of great importance. Today there is a calculated theoretical potential for biogasproduction of 14TWh per year, which is around ten times larger than Sweden’s production today. This potential depends on how much arable land that is used to produce crops for biogas though, and can be much larger. The biggest contributor to increase the biogasproduction is crops from farms and manure3. The reason for this is because sugar- and fodderbeets contain the highest amount of energy per hectare arable land for crops, and therefore it is interesting to study how to optimize the use of this energy. Usually the beets have to be stored after the harvest since the most of the beets cannot be used directly, and a consistent feed to the biogas reactors is favorable. The most common way to store the beets today is in covered storage or silage. The beets are usually in need of being co-digested together with another substrate since the amount of nitrogen that the beets contain are relatively low, and therefore the beets may be in need of co-digest with a substrate that contains a higher amount of nitrogen. For example are manure or slaughterwaste substrates containing high amounts of nitrogen, and therefore are co-digestion between beets and these kinds of substrates improving the ratio between carbon and nitrogen, which improves the digestion process. This is the reason why the beets were co-digested with manure from cattle during this study. The goal with this study were to compare newly harvested sugar- and fodderbeets potential for biogasproduction, with the production from beets that were placed in covered storage respectively silage. Another goal was to decide which type of beet, storage method and pre-treatment method that are the most optimal for co-digestion with manure from cattle. The tests showed that when newly harvested sugar- and fodderbeets were added the part size were a more important factor then when the beets had been stored or ensilaged. For newly harvested sugarbeets the biggest part size gave the highest production, while the newly harvested fodderbeets of the same size did not have time to digest properly, which resulted in that their production were the lowest. When the haulm from sugarbeets were added together with sugarbeets and co-digested with manure from cattle the results were more like the results from the fodderbeets. During the tests ensilaged beets had a higher production than the newly harvested and the beets that were stored covered. Even though the results from the ensilaged beets were modified since losses occurred from the ensilation process. Comparison between the groups showed no bigger differences in production for the sugarbeets, while for fodderbeets the second largest part size had a higher production than the others with fodderbeets. With ensilaged sugarbeets together with the haulm there was shown that the group with the second most amount of haulm gave a higher production than the rest of the groups that were co-digested with haulm. The tests can be concluded by that newly harvested and the sugarbeets that were stored covered are more suitable to be co-digested together with manure from cattle than fodderbeets when looking at these percentage admixtures and preconditions. When the beets have been ensilaged is it more favorably to use fodderbeets then sugarbeets together with manure from cattle. The part size was shown to have no bigger significance. To sum up ensilaged beets over all seem to be more favorably to co-digest with cattle manure than newly harvested or beets that were in covered storage. The production per gram VS were significantly higher although correction calculations. / Det används idag stora mängder av fossila bränslen som är av begränsad tillgång vilket påverkar vår miljö och omgivning negativt, vilket leder till att alternativa bränslen behövs1. Ett alternativ är biogas, vilket bildas genom en rötningsprocess av olika organiska material i en biogasrötningskammare. Organiskt material som kommer från jordbruket har störst potential att öka produktionen av biogas i Sverige. Främst odlade grödor, men även avfallsprodukter så som gödsel är av stort intresse. Idag har man en beräknad teoretisk potential för biogasproduktion på 14 TWh per år, vilket är omkring tio gånger så mycket jämfört med dagens produktion. Denna teoretiska potential beror dock på hur stor mark som kan avsättas för att odla grödor till biogas, och kan bli mycket större. De största bidragen till denna produktion av biogas skulle vara just odlade grödor och gödsel.3 I och med att socker- och foderbetor är de grödor som ger störst energimängd per hektar åkermark är det också ett bra alternativ till att undersöka hur man kan optimera produktionen ytterligare. Ofta används dock inte alla betorna direkt efter upptagningen till att producera biogas, utan större delen av betorna behöver lagras på något sätt för att kunna uppnå en jämn produktion i biogasreaktorn året om. Vanligast är idag att man lagrar betorna antingen i stuka eller som ensilage. Socker- samt foderbetor behöver dock samrötas med något annat material. Detta eftersom mängden kväve som betorna innehåller är relativt lågt, och det kan därför behöva samrötas med ett mer kväverikt material. Exempel på kväverika material är gödsel samt slakteriavfall, och genom att betorna samrötas med sådana material uppnås en bättre balans mellan kol och kväve i blandningen, vilket påverkar resultatet från rötningsprocessen positivt. Det är därför som testomgångarna med socker- samt foderbetor i denna rapport samrötats med nötflytgödsel. Målsättningen med denna undersökning var att jämföra färska socker- och foderbetors potential för biogasproduktion, med hur produktionen skiljer sig vid stuklagring respektive ensilering. Därefter var ytterligare en målsättning att bedöma vilken typ av beta, lagringsmetod och förbehandlingsmetod som lämpar sig bäst för samrötning med nötflytgödsel. Under de tre testförsöken som genomfördes visade det sig att när socker- samt foderbetorna tillsattes i färskt tillstånd, så spelade bitstorleken en större roll för resultaten, än när betorna lagrats eller ensilerats. För färska sockerbetor visade det sig att sockerbetor av den största bitstorleken gav högst produktion, medan för färska foderbetor av samma storlek hann betorna inte brytas ned ordentligt under loppet av testperioden, vilket resulterade i att dess produktion blev lägst. Vid tillsats av sockerbetsblast tillsammans med sockerbetor blev resultaten mer likt foderbetornas. Det visade sig under de tre testförsöken att ensilerade socker- samt foderbetor gav en högre produktion än vad färska samt stuklagrade betor gav. Detta trots att resultaten korrigerats enligt korrektionsformler för ensilerat material. Vid jämförelse inom själva testomgången visade det sig inga större skillnader i produktion för sockerbetorna. För foderbetorna gav gruppen med den näst största bitstorleken en lite högre produktion än de andra grupperna. För grupperna som innehöll sockerbetor tillsammans med sockerbetsblast visade det sig att gruppen innehållandes näst mest sockerbetsblast ge en förhöjd produktion jämfört med de andra grupperna innehållandes blast. De tre testomgångarna kan sammanfattningsvis beskrivas som att färska och stuklagrade sockerbetor är mer lämpade att samrötas tillsammans med nötflytgödsel än foderbetor är gällande dessa procentuella inblandningar och förutsättningar. När betorna ensilerats är det mer fördelaktigt att använda foderbetor än sockerbetor tillsammans med nötflytgödsel. Bitstorleken visade sig inte ha någon större betydelse. Ensilerade betor anses vara mer fördelaktigt att röta tillsammans med nötflytgödsel än färska samt stuklagrade betor då produktionen per gram VS var markant högre trots korrigeringsberäkningar.

This thesis is a part of a collaboration between Höganäs AB and Luleå University of Technology, aiming at replacing fossil process coal with bio-coal in their sponge iron process. The difference in gasification reactivity, i.e. reaction rate, between fossil coals and bio-coals is the major challenge in the endeavor to decrease the climate impact of the existing process. The goal of this thesis is to develop a model of reaction rate for bio-coals in relation to particle size distribution. Different particle size distributions were combined and tested to see how that affects the effective reaction rate. Within the scope of this work, gasification reactivities of different materials, including coal, cokes, and bio-coals, were determined. Three bio-coals were selected to study the effect of particle size distribution on reactivity. Kinetic parameters were determined by using thermogravimetric analysis in the temperature range of 770-850 °C while varying CO2 partial pressure between 0.1-0.4 atm. The effect of particle size on the reaction rate was investigated by using particles with diameter between 0.18 and 6.3 mm. The effect of particle size distribution on the reactivity of bio-coal in a packed bed was carried out in a macro thermogravimetric reactor with a constant bed volume of 6.5 cm3 at 980 °C and 40% (vol.) of CO2. The experimental investigation in three different rate-limiting steps was done for one bio-coal sample, i.e. Cortus Bark bio-coal. The activation energy of the bio-coal was 187 kJ mol-1, and the reaction order was 0.365. For the internal diffusion control regime, an increase in particle size resulted in low reaction rate. The effective diffusivity calculated from the Thiele modulus model was 1.41*10-5 m2 s-1. For the external diffusion control regime, an increase in particle size increased the reaction rate up to a certain point where it plateaued at >1 mm. By choosing two discrete particle size distributions, where a smaller average distribution can fit into a larger average distribution the reaction rate was lowered by 30% compared to only using a single narrow particle size distribution. This solution decreased the difference of apparent reaction rate in a packed bed between the bio-coal and anthracite from 6.5 times to 4.5 times. At the moment the model is not generalized for all bio-coals. However, the developed methodology can be routinely applied to assess the different bio-coal samples. One possible error can be that pyrolysis influences the gasification rate for bio-coal that is pyrolyzed below the temperature of the gasification test. There is a clear correlation between particle size distributions, bulk density, and apparent reactivity. By mixing two distributions the reaction rate of Cortus Bark was reduced from 6.5 times the reaction rate of anthracite to 4.5.

During combustion of biomass, particulate matter is emitted, which has severe health impacts on humans. The company ITK Envifront has developed a scrubber technology that cleans the flue gas while also recovering the flue gas energy, increasing the efficiency of the combustion plant. In this thesis, a simulation model was built in MATLAB according to the Finite Element Method. Validation of the model against 3 different facilities showed reasonable accuracy with a tendency to overestimate the scrubber heat recovery and a mean prediction deviation of approximately 7 %. The model was then used to make suggestions for process optimization. An increase of funnel height, and number of spray nozzles could increase the scrubbers heat recovery with up to 7 % and 8 %, respectively. Addition of moisture to the flue gas through evaporation of water droplets had the potential to increase scrubber efficiency with 10 %, and usage of the highest setting of the adjustable nozzle bank showed the potential to increase the efficiency with up to 5 % compared to the mid-setting. Furthermore, the process parameters of a scrubber with optimized running conditions, was compared to a scrubber with the current running conditions, through running of the developed model. The optimized running conditions showed an increase in scrubber efficiency with up to 14 %, resulting in an increase in scrubber heat recovery of approx. 90 kW at a boiler load of 3 MW. As a final conclusion, the developed model shows great potential to be used to as a toolbox to further investigate and optimize the scrubber design and operation. As a future work, it would be interesting to further model its performance regarding particle removal.

A big challenge within pulp and paper mills is the large quantities of waste activated sludge (WAS) that is produced during the wastewater treatment. The WAS is made up of biological cells and extra polymeric substances (EPS) and can bind a large amount of water causing difficulties to dewater the WAS. This study aimed to determine how to improve the dewatering properties of the WAS by using hydrolysis. Hydrolysis will cause the cells to disrupt and the bound water in the cells and the water trapped by the EPS can be released. Specifically, this study investigated what impact hydrolysis with heat, alkalis, and acids had on the WAS dewatering properties. In addition to the impact on the dewatering properties, the release of organic material and nutrients from the cells has also been important for biomethane production. In this study, it was specifically NH4-N, PO43- and COD that have been studied. WAS from paper mills have in general poor methane potential so it was of interest to see how the WAS was affected by hydrolysis and how hydrolysis could improve the methane production. To test the hypothesis of whether hydrolysis could affect the WAS and improve the dewatering properties, several experiments were performed. The experiments included thermal hydrolysis at temperatures of 70-90 °C, acidic hydrolysis with acids such as spent acid and acid water, and alkalis such as green liquor sludge and EOP. All acids and alkalis used in the study were chemicals that exist at the paper mills included in this study. To test the dewatering properties, methods such as TS analysis on the accept, CST-analysis, and a belt press were used. Analyses were also performed on the reject to measure the suspended solids and the nutrients NH4 – N, PO43– and COD in the WAS. This study did also determine what effect hydrolysed WAS had on the biomethane potential. In this study were the paper mills BillerudKorsnäs in Skärblacka and SCA in Östrand included. Hence was sludge from the two mills of interest to analyse. This study has shown better dewatering properties with an increase in the total solids (in the accept) after the thermal hydrolysis, the acidic hydrolysis with spent acid, and the alkali hydrolysis with green liquor sludge. Specifically did the acidic hydrolysis with spent acid improve the dewatering properties in terms of an increase in TS in %. The biggest increase in TS in % could be seen after using 10% spent acid ratio. The TS for the WAS from SCA Östrand increased in this experiment by 107 %. The thermal hydrolysis also showed promising results both in terms of dewatering properties and in the release of organic material. The biochemical methane potential test results showed a better and more rapid stabilized production of biomethane after hydrolysis of WAS compared to untreated WAS. The thermal hydrolysis both increased the rate of production and the total amount of methane produced. The thermally hydrolysed WAS from SCA Östrand improved the methane production from 77 Nml methane/g VS to 95 Nml methane/ g VS. The WAS from BillerudKorsnäs improved the methane production from 40 Nml methane/ g VS to 55 Nml methane/ g VS. These results, both from the methane potential tests and the results of the increased dewatering properties, show that the concept with hydrolysing should be evaluated further for improving the dewatering of the WAS.

Even though the Brazilian ethanol and sugar production system (based on sugarcane industry) have been providing large amounts of bioenergy, the extensive amounts of organic wastes generated cannot be ignored when it comes to sustainability. Using these biomasses to produce biomethane through anaerobic digestion has been proven as a promising way to tackle this issue. This study investigated the biomethane potential of the co-digestion of these biomasses: SF (sugarcane straw : filter cake = 8:2), SFV (sugarcane straw : filter cake : vinasse = 1:4:45), and D (digestate separated from AD of SFV). Three treatments autoclaving (AU), alkaline (AL) treatment using 6% (w/w) NaOH and the combination of these two (AUAL) were then conducted on SF and SFV as pre-treatments; on D as post- treatments. In the biomethane potential tests of untreated material, the highest methane yield was achieved by SFV with 275.28 ± 11 N ml CH4/g VS, followed by SF with 223.25 ± 10 N ml CH4 g-1 VS, substrate D also resulted in a methane potential of 144.69 ± 2 N ml CH4 g-1 VS. As pre-treatments, AL and AUAL both showed increase in methane yield (between 36.0% and 49.1%) and methane production rate. As post-treatments, AU, AL and AUAL showed distinctive results in methane production, with 33.8%, 99.8% and 128.8% increase, respectively. In comparison with pre-treatment, post-treatment showed a better performance in increasing methane production. The following feeding experiments performed in continuous stirred-tank reactors showed that AL treatment led to an average of 248% increase in methane yield. / Sugarcane waste: towards a zero C emission in the Brazilian bioenergy sector

Mellan 1960 och idag har världspopulationen dubblerats medan matproduktionen tredubblats. Det har möjliggjorts av kemiskt framställda gödsel som introducerades på mitten av 1900-talet. Sedan 1965 har användandet av kvävegödsel ökat sexdubblet. Kvävegödsel ökar lönsamheten och avkastningen men har stora koldioxdutsläpp och orsaker övergödning. Därför finns det en efterfrågan på andra alternativ. Ett alternativ skulle kunna vara en syntetsik föränding av rhizosfären. För att undersöka om det är möjligt kommer ett modellsystem för insulerat metaboliskt utbyte att skapas. Modellsystemet kommer att ha en kvävefixarande bakterie som fixerar kväve från atmosfären och producerar en kvävekälla till en kolfixerande bakterie, som kommer modellera en växt i system. Den kolfixerande bakterien kommer att fixera koldioxid from atmosfären och producera en kolkälla för den kvävefixerande bakterien att använda. I den här studien har olika produktioner av olika kvävekällor i Escherichia coli och Anabaena sp. undersökts. Fyra olika plasmider har skapats för produktionen av alanin, guanin och allantoin. Alla odlingar med plasmiderna växte bättre än kontrollodlingarna, men de har inte blivit analyserade för produktion av metaboliterna på grund av tidsbrist. Tilläggningsvis, två av tre replikat av Anabaena sp. med en plasmid för allantoin produktion i media med urinsyra verkar ha varit stressade för okända anledningar / Between 1960 and today, the world population has doubled while food production has tripled. This has been made through chemical fertilisers being introduced in the middle of the 20th century. From 1965, the usage of nitrogen fertilisers has increased by sixfold. Nitrogen fertilisers improve crop profitability and yield but have large carbon dioxide emissions as well as cause eutrophication. Thus, there is a demand for an alternative. One alternative would be to engineer the rhizosphere. To investigate whether this is possible, a model system for insulated metabolic exchange will be created. The model system will have a nitrogen-fixating bacteria that will fixate atmospheric nitrogen and produce a nitrogen compound to a carbon-fixating bacteria, that will act as a plant in the model system. The carbon-fixating bacteria will fixate carbon dioxide from the atmosphere and produce a carbon source for the nitrogen-fixating bacteria to utilise. In this study, different productions of different nitrogen compounds in Escherichia coli and Anabaena sp. have been investigated. Four different plasmids have been constructed for the production of alanine, guanine and allantoin, respectively. The strains containing the plasmids all grew better than the control cultures, however, they have not been analysed for producing the metabolites due to time constraints.

The urge for more sustainable living motivated the Stockholm Tiny House Expo. The project aims to build a floating, sustainable, man-made island for living and working outside of Stockholm. This paper proposes a waste management method with possible energy recovery for the island. It introduces a comprehensive system that integrates decentralized wastewater treatment with energy generation through anaerobic treatment. A by-product of the wastewater treatment process, the sludge, is combined with food waste to generate energy through biogas. The island’s organic waste (wastewater and food waste) is thereby managed sustainably. The results of this report require further research. The energy supply from the biogas reactor was calculated to be 52.19 MWh. The wastewater treatment process was designed with an objective of 90% reduction of BOD5, to comply with the Swedish regulations for wastewater discharge to natural bodies of water, including the ocean. The system's total volume proposed is 11.25 m3, which is the sum of the volumes of all the reactors, or tanks, needed to complete the treatment.

Följande rapport återspeglar ett examensarbete utfört hos Solör Bioenergi, examensarbetet har syftat till att utvärdera den höga andelen oförbränt som uppstår vid deras förbränning. Solör äger anläggningen i Nora och förser orten med fjärrvärme. Detta sker genom förbränning av biomassa och bränslet utgörs av sågspån och stamvedsflis. Under en stor del av eldningssäsongen blandas dessa bränslen med varandra men under säsongens varma perioder eldas enbart sågspån. För utvärderingen har information från kurslitteratur inhämtats, dessutom har studerande av forskningsrapporter hjälpt till att samla in kunskap för projektet och vilka faktorer som kan påverka en förbränning. Resultatet av litteraturstudien har jämförts med en utförd nulägesanalys tillsammans med flertalet intervjuer med drifttekniker, anläggningsansvarig och externa entreprenörer. Denna arbetsmetodik har skapat en samlad bild över förbränningen i pannan och har möjliggjort utformningen av en lista över åtgärdsförslag. Listan återfinns i ett, tillsammans med en ekonomisk kalkyl, eget avsnitt. Pålitligheten hos de rekommenderade åtgärderna har också kunnat bekräftats med en provkörning, där tillämpad teori har förbättrat förbränningen. En generell slutsats  som kan dras efter arbetet visar hur viktig en bra processtyrning är för ett ökat bränsleutnyttjande, detta kan förenklat sammanfattas med grundregeln för utformning av styrsystem: -Det som kan automatiseras, bör automatiseras. / The following report reflects a degree project carried out at Solör Bioenergi, the project has aimed to evaluate the high proportion of unburned that occurs during their combustion. Solör owns the plant in Nora and supplies the town with district heating. This is done by burning biomass and the fuel consists of sawdust and stemwood chips. During a large part of the heating season, these fuels are mixed with each other. But during the warm season, only sawdust is burned. For the evaluation, information from course literature has been collected. Together with studying of research reports, they have helped to gather knowledge for the project and what factors can affect an combustion. The results of the literature study have been compared with a performed current situation analysis together with several interviews with operating technicians, plant managers and external contractors. This working methodology has created an overall picture of combustion in the boiler and has enabled the design of a list of proposed measures. The list can be found in a separate section, together with a financial calculation. The reliability of the recommended measures has also been confirmed with a test run, where applied theory has improved combustion. A general conclusion that can be drawn after the work shows how important a good process control is for increased fuel utilization, this can be summarized with the basic rule for the design of control systems: -What can be automated, should be automated.