Capítulo 3 : las luchas por condiciones de producción

Syftet med detta examensarbete är att beskriva barns och pedagogers uppfattningar om lärande mellan barn på ett fritidshem. I studien intervjuades femton barn och tre pedagoger på ett fritidshem. Metoden för empiriinsamlingen utgjordes av kvalitativa intervjuer, där det insamlade materialet tolkades mot bakgrund av det sociokulturella perspektivet på lärande. Utifrån barns och pedagogers uppfattningar kring lärande mellan barn utkristalliserade sig fyra kategorier för lärande på arenan fritidshem: Lärande mellan barn utifrån vad man bör och inte bör göra, visade att lärandet mellan barnen kretsade kring regler. Lärande mellan barn via datorn som verktyg, visade att datorn utgjorde ett viktigt verktyg och en central plats för lärande mellan barnen. Lärande mellan barn när de utövar sina intressen, visade kopplingen mellan vad barn lärde sig av varandra och deras intressen. Lärande mellan barn utifrån olika syften, visade att barnen kunde ha olika syften med vad de lärde ut till andra barn

Vegetation on contaminated soil : how are plants affected and can their conditions be ameliorated? Proposals from soil contaminated by the historical mining industry in Falun

Falu koppargruva hade vid stängningen 1992 varit i drift i runt tusen år. Historiskt har gruvdriften och dess kringindustrier påverkat stadsklimatet i Falun negativt genom stora utsläpp av svavel och metaller. Restprodukter såsom slagg, varp och rödfärgsråvara ligger än i dag i stora stenhögar i tätorten närmast gruvområdet. Stora delar av detta gruvlandskap är sedan 2002 klassat som världsarv på grund av dess höga kulturhistoriska värde. Malmen som brutits, och som återfinns i restprodukterna, är av typen sulfidmalm, som lätt vittrar och lakar ur metaller till mark och vatten. Urlakningen gör att marken i Falun på vissa platser har ett innehåll av arsenik, bly, kadmium, koppar, kvicksilver, mangan och zink som överskrider Naturvårdsverkets generella riktvärden för förorenad mark. De ackumulerade utsläppen av svavel har under gruvans driftstid varit enorm stora, vilket är den största orsaken till markförsurningen i Falun. pH-värdet i humus är under 4 i ett stort område runt gruvan och också mineraljorden är försurad. Syftet med det här arbetet är att ta reda på hur markförhållandena i Falun påverkar biologiska och fysiologiska processer hos vegetationen och om befintlig mark är användbar för nyplantering. Syftet är också att titta på om växters förmåga att ta upp metaller kan användas för att rena mark från samma ämnen. Frågor som ställs i arbetet är: Är metaller i höga halter fytotoxiska, det vill säga giftiga för växter? Är befintlig mark i av gruvdriften förorenade områden i Falun användbara för plantering? Kan växter användas för att rena mark från metaller? För att besvara frågorna har en litteraturstudie gjorts. Resultatet visar att fytotoxiska symptom såsom hämmad tillväxt, kloros, nekros och missfärgningar kan förekomma vid höga halter av vissa av metallerna. Det största problemet med markförhållandena i Falun är att upptaget hos växter av de flesta metallerna ökar vid lågt pH. Vid lågt pH löses också aluminium ut i markvätskan, vilket hämmar upptaget av nödvändiga näringsämnen och kan leda till hämmad tillväxt. Försurning i kombination med höga metallhalter leder till näringsbrist och hämmad nedbrytning av förna i tallskog vilket i sin tur leder till dålig nybildning av humus. Vid plantering av parkvegetation i befintlig mark bör kalk, eventuellt i kombination med organiskt material, användas som jordförbättring för att höja pH och därmed hämma upptaget av metaller och höja näringstillgången. Att utnyttja växters egna fysiologiska processer för att rena mark kallas fytoremediering. Genom att använda växtmaterial som behöver växa, skördas och eventuellt nyplanteras är metoden långsammare men också billigare än konventionella reningsmetoder. Rätt val av växter för platsen är en förutsättning för att fytoremediering ska fungera. Mer forskning och försök behövs för att kunna svara på hur effektiv och tillämpbar metoden är på de markförhållanden som finns i Falun

Hydrothermal recycling of activated biochar

Emerging pollutants such as pharmaceuticals are of increasing concern in wastewaters. Carbon materials such as activated carbons prove to be effective filter materials for the removal of these pollutants, but regeneration of the adsorbents is necessary to improve their economic efficiency. However, common thermal regeneration methods using dry adsorbents and high treatment temperatures are expensive and hinder large scale applications in wastewater treatment plants 1. Novel adsorbents such as biochars are seen as an alternative due to their lower production costs 2. However, considering their generally lower adsorption capacity, costly regeneration will abolish the initial economic advantage of biochar. In contrast to fully regenerating the original adsorptive properties, we argue that a recycling step to prepare biochar for different subsequent applications can produce a higher value product. In this study we propose a method using hydrothermal treatment to decontaminate activated biochars. Two standard biochars from the UK Biochar Research Centre produced at 550°C from softwood and wheat straw were activated in CO2 at 800°C. Additionally, the same raw feedstocks were mixed with 5% Ochre, pyrolyzed and activated at the same conditions to produce two activated mineral biochar composites. The biochars were loaded with 10 pharmaceuticals commonly found in wastewaters and decontaminated in a hydrothermal reactor at temperatures ranging from 160 to 320°C for 4 hours at autogenic pressure. To avoid catalytic effects from the reactor walls, a novel experimental design based on standard borosilicate test tubes was developed. The sample is placed into a test tube, filled with water, flame sealed and placed into a hydrothermal reactor. The outer reactor is filled to the same level as the sample tube to counterpressure the glass and avoid bursting during the experiment. With this set-up, an inert and disposable reactor liner ensures comparable reaction conditions between runs and eliminates potential cross contamination. After the hydrothermal treatment, the biochars as well as the process water were analyzed by LC-MS/MS for remaining pharmaceuticals. Hydrothermal treatment was found to fully degrade 8 out of 10 investigated pharmaceuticals at a treatment temperature of 200°C, with almost complete degradation of the remaining pharmaceuticals at 320°C. The results show that hydrothermal treatment has the potential to recycle activated biochar and enable its use in subsequent applications such as gas filtration systems for the removal of H2S or as an additive for increased gas production in anaerobic digestion plants. Please click Additional Files below to see the full abstract

Synergies between BECCS and Biochar - Maximizing Carbon Sequestration Potential by Recycling Wood Ash

Bioenergy carbon capture and storage (BECCS) and biochar are key carbon-negative technologies. In this study, synergies between these technologies were explored by using ash from wood combustion, a byproduct from BECCS, as an additive (0, 5, 10, 20, and 50 wt %) in biochar production (wood pyrolysis at 450 °C). The addition of wood ash catalyzed biochar formation and increased the yield of fixed carbon (FC) (per dry, ash-free feedstock), i.e., the sequestrable carbon per spruce wood input. At the highest ash addition (50%), 45% less wood was needed to yield the same amount of FC. Since the land area available for growing biomass is becoming scarcer, our approach significantly increases biochar’s potential to sequester carbon. However, increasing the feedstock ash content results in less feedstock carbon available for conversion into FC. Consequently, the yield of FC per pyrolysis run (based on dry feedstock) in the 50% ash-amended material was lower than in the control. An economic analysis showed that the 20% ash-amended biochar brings the biggest cost savings over the control with a 15% decrease in CO₂-abatement costs. Biochar–ash composites increase the carbon sequestration potential of biochar significantly, reduce the CO₂-abatement costs, and recycle nutrients which can result in increased plant growth in turn and more biomass for BECCS, bringing synergies for BECCS and biochar deployment

Designing activated mineral biochar composites for the adsorption and degradation of emerging contaminants

The emergence of micropollutants such as pharmaceuticals in wastewaters presents a potential risk for human health as well as the aquatic environment. Current wastewater treatment plants are generally not capable of removing these pollutants without additional treatment steps. Adsorption on activated carbon is an effective way to remove these contaminants, however, the use of non-renewable feedstocks as well as low regeneration efficiencies increase the environmental costs of this method1. Biochar as an alternative carbon platform material can be specifically designed to overcome these drawbacks2. This study is aimed at designing activated mineral biochar composites with enhanced adsorption capacity for pharmaceuticals while simultaneously increasing its regeneration performance. Two standard biochars from the UK Biochar Research Centre produced at 550°C from softwood and wheat straw were activated in CO2 at 800°C. Mineral biochar composites were produced by the addition of ochre – a Fe-rich mining waste - in a wet mixing step prior to pyrolysis for both feedstocks. The activated biochars were analysed for their maximum adsorption capacity for two common micropollutants. Furthermore, to test their regeneration performance, the biochars were loaded with a mix of 10 pharmaceuticals covering antibiotics, fungicides and antidepressants. The loaded biochars were then subjected to a high pressure treatment in a hydrothermal reactor at temperatures ranging from 160 to 320°C to determine the degradation rate of pharmaceuticals loaded on the different materials. Hydrothermal treatment was found to successfully degrade the micropollutants across all biochars. The mineral biochar composites showed increased pollutant degradation, lowering the necessary treatment temperature to achieve full decontamination. The results show that while designing biochar for certain applications, a simultaneous focus on both the application as well as the regeneration of the material can give a more comprehensive picture of the overall requirements for further optimisation of biochar adsorbents. Please click Additional Files below to see the full abstract

Comparative characterisation and phytotoxicity assessment of biochar and hydrochar derived from municipal wastewater microalgae biomass

Microalgae, originating from a tertiary treatment of municipal wastewater, is considered a sustainable feedstock for producing biochar and hydrochar, offering great potential for agricultural use due to nutrient content and carbon storage ability. However, there are risks related to contamination and these need to be carefully assessed to ensure safe use of material from wastewater microalgae. Therefore, this study compared the properties and phototoxicity of biochar and hydrochar produced via pyrolysis and hydrothermal carbonisation (HTC) of microalgae under different temperatures and residence times. While biochar promoted germination and seedling growth by up to 11.0% and 70.0%, respectively, raw hydrochar showed strong phytotoxicity, due to the high content of volatile matter. Two post-treatments, dichloromethane (DCM) washing and further pyrolysis, proved to be effective methods for mitigating phytotoxicity of hydrochar. Additionally, biochar had 35.8–38.6% fixed carbon, resulting in higher carbon sequestration potential compared to hydrochar

Hydrothermal recycling of carbon absorbents loaded with emerging wastewater contaminants

Adsorption using carbon materials is one of the most efficient techniques for removal of emerging contaminants such as pharmaceuticals from wastewater. However, high costs are a major hurdle for their large-scale application in areas currently under economic constraints. While most research focuses on decreasing the adsorbent price by increasing its capacity, treatment costs for exhausted adsorbents and their respective end-of-life scenarios are often neglected. Here, we assessed a novel technique for recycling of exhausted activated biochars based on hydrothermal treatment at temperatures of 160–320 °C. While a treatment temperature of 280 °C was sufficient to fully degrade all 10 evaluated pharmaceuticals in solution, when adsorbed on activated biochars certain compounds were shielded and could not be fully decomposed even at the highest treatment temperature tested. However, the use of engineered biochar doped with Fe-species successfully increased the treatment efficiency, resulting in full degradation of all 10 parent compounds at 320 °C. The proposed recycling technique showed a high carbon retention in biochar with only minor losses, making the treatment a viable candidate for environmentally sound recycling of biochars. Recycled biochars displayed potentially beneficial structural changes ranging from an increased mesoporosity to additional oxygen bearing functional groups, providing synergies for subsequent applications as part of a sequential biochar system

Students’ attitudes towards forests

I denna studie undersöktes vad jägmästarstudenter och studenter ifrån Konstnärligt Campus i Umeå har för attityd till skog. Studien gjordes genom en enkätundersökning med en urvalsgrupp ifrån SLU och en ifrån Konstnärligt Campus. Studenterna delades in i två olika grupper för att kunna göra en jämförelse av svaren beroende på vilket universitet respondenten studerade vid. Resultaten visar att jägmästarstudenterna vistas oftare i skogen än vad studenterna ifrån Konstnärligt Campus gör och att skogsvistelsen är högre bland de som äger skog kontra de som inte äger skog. Andelen skogsägare är högre vid SLU än vad det är vid Konstnärligt Campus. Resultaten visade också att det finns en variation mellan studentgrupperna beroende på hur de använder skogen samt att det tänkta sambandet mellan önskad nytta och mest tilltalande skog inte finns.This study investigates students’ attitude towards the forest. This case study is based on answers from students at the Swedish University of Agricultural Sciences (SLU) and the Arts Campus in Umeå. The study was done through a questionnaire with a sample group from SLU and one from Arts Campus. The students were divided into two different groups in order to make a comparison of responses depending on which university the respondent attended. The results showed that forestry students more often visit the forest than students from the Arts Campus and that rate of forest visits is higher among those who own forest versus those who do not own forest. The results also show that there is a variation between the student groups depending on how they use the forest. The study also intended to show that there is a relationship between desired values of the forest and the most appealing forest site, but no relationship could be proven

Explanation and Dependence.

The deductive-nomological account, various causal accounts, and various unificationist accounts of explanation have all taken explanations such as the one of the motion of the planets by Newton’s theory of gravity and mechanics to be a paradigmatic example of explanation and of explanatory advancement within the sciences. Newton’s theory of gravity increased our understanding of a wide range of phenomena and nonetheless many were troubled by the notion of action at a distance that the theory postulates. Newton himself can be seen to take an ambivalent attitude towards the explanatoriness of his theory. On the one hand, he claims to have explained a range of phenomena from the law of gravity, but nonetheless he acknowledges the lack of a causal explanation. I think that this kind of situation is neither incredibly rare nor limited to peripheral cases in the history of science. In addition to the example from Newtonian gravity we can find this attitude towards certain quantum mechanical explanations that seem to require the acceptance of non-locality, and, in a somewhat different way, towards the role of spacetime in the explanation of inertial motion in general relativity. I argue that these cases pose a serious difficulty for the unificationist account and, in particular, for the causal account. Moreover, I take these cases to be illuminating as to the nature of explanation and I develop an account of explanation based on a notion of dependence that is broader than causal dependence that allows us to account for this attitude. Doing so opens up the possibility of rehabilitating the explanatory status of laws by providing a way of addressing the counter-examples to the deductive-nomological account that does not rely on replacing the role of laws as providing a relation that does explanatory work with causal relations or a relation of unification. Lastly, this allows us to understand the debates about explanatory status in Newtonian gravity, in quantum mechanics over EPR style cases, and over the role of spacetime in general relativity as arising from empirical issues rather than from conceptual disagreements about the nature of explanation.Ph.D.PhilosophyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/86273/1/ljansson_1.pd

Influence of hydrothermal carbonization conditions on the porosity, functionality, and sorption properties of microalgae hydrochars

Green microalgae is a possible feedstock for the production of biofuels, chemicals, food/feed, and medical products. Large-scale microalgae production requires large quantities of water and nutrients, directing the attention to wastewater as a cultivation medium. Wastewater-cultivated microalgae could via wet thermochemical conversion be valorised into products for e.g., water treatment. In this study, hydrothermal carbonization was used to process microalgae polycultures grown in municipal wastewater. The objective was to perform a systematic examination of how carbonization temperature, residence time, and initial pH affected solid yield, composition, and properties. Carbonization temperature, time and initial pH all had statistically significant effects on hydrochar properties, with temperature having the most pronounced effect; the surface area increased from 8.5 to 43.6 m(2) g(-1) as temperature was increased from 180 to 260 degrees C. However, hydrochars produced at low temperature and initially neutral pH generally had the highest capacity for methylene blue adsorption. DRIFTS analysis of the hydrochar revealed that the pH conditions changed the functional group composition, implying that adsorption was electrostatic interactions driven. This study concludes that un-activated hydrochars from wastewater grown microalgae produced at relatively low hydrothermal carbonization temperatures adsorb methylene blue, despite having low surface area