Tyres are used in everyday life for a variety of practical and recreational tasks. Frictional behaviour of tyres on any surface is important for vehicle safety and control; this behaviour becomes more important when that surface is snow. The interaction of rubber and a snow surface is complex and a deeper understanding of both is needed in order to help develop better tyres. Outdoor full scale tyre test results were compared to results from indoor laboratory tests using a linear tribometer and a surface of compacted artificial snow; these were in excellent correlation allowing a systematic and comprehensive study of rubber friction on snow to be conducted in the laboratory. Rubber samples of varied rubber compositions and geometries were used to gain an understanding of friction on snow. Samples with varying glass transition temperature (Tg), dynamic rigidity (G*) and Payne effect (dependence of the dynamic moduli on the amplitude of the applied strain) were investigated along with samples with and without sipes. The rubber friction coefficient (μ) was measured as a function of velocity and temperature. The siped samples exhibited a higher μ than those without sipes. FE simulations, rubber friction tests for varying contact pressures and steel blade force tests were performed to evaluate contributions from ‘surface’ friction and ploughing separately. The increased μ was attributed to the ploughing force from the front edges of the ‘subblocks’ created by the sipes. Although it is well known in the industry that siped tyres grip well, this is the first time it has been explained how sipes grip effectively through a combination of ploughing and rubber snow interaction. A comprehensive study of varying rubber properties (Tg, G* and Payne effect) was conducted to better understand their impact on snow friction. The findings were evaluated using the WLF shift factor to account for the running frequency of the rubber from the snow surface roughness. G* was found to be the dominant parameter for rubber μ when considering running frequency. Increased μ values were exhibited by rubbers with a lower G*. The decreased G* makes the rubber more compliant, thus increasing the contact area between the rubber and the snow, in turn increasing μ. A better knowledge of the surface roughness of snow will aid the understanding of the interaction between rubber and snow for tyres. A method was developed to characterise the artificial snow surface utilising sectioning and imaging of chemically stabilised snow samples. From images of the snow surface before friction testing the average indentor size can be found, this is used to analyse the running frequency of the rubber. Qualitatively comparing the surfaces before and after rubber friction testing shows a decrease in surface profile aggressivity after a test; this is attributed to melting of the snow from frictional heating and snow grain fracture. Friction tests were conducted to directly compare rubber friction on snow and ice using round edged samples. Again it was found that the rubber with the decreased G* exhibited higher friction; this was seen on both snow and ice confirming G* as the dominant rubber property for both surfaces, regardless of the surface roughness change. It was found that at low temperatures ice had a higher μ than snow, while at high temperatures snow exhibited a higher μ than ice. It is hypothesised that this intriguing switch is due to the surface roughness change leading to differing contact areas both with and without melt water. This switch is not seen when a simple heat transfer model is used, confirming the effect as a surface roughness change. The use of a modified Hertz model shows that indentation is the dominant mechanism at low velocities on snow. It is hypothesised that at high velocities melt water dominates on both snow and ice while adhesion may have a more significant role on ice at low velocities. These findings provide knowledge that can be used in the design of tyres for snow and ice in the future.

Understanding and predicting the way in which species interactions may change under the uncertain climatic future is imperative if the management of important resources is to be successful. Consumer – resource interactions underlie population dynamics and distribution, yet there is little known about how these interactions will respond to increasing temperature. Temperature increase can facilitate the movement and settlement of alien species into new ranges. Introduced species can often be ecologically damaging and unpredictable due to novel predator-prey interactions. Comparative functional response analysis has been used to gain insight into resource dependent behaviour and population dynamics. This study is an assessment of the way in which predicted temperature changes can affect resource consumption in three predators. The red lionfish Pterois volitans (Linnaeus, 1758) is a successful and hugely damaging invader in the Western Atlantic and sources point to an ongoing Mediterranean invasion. Through a series of laboratory experiments I assessed how temperature, habitat complexity, and light wavelength affect the functional response of lionfish towards a crustacean prey. I establish that lionfish have a persistent Type II functional response and that lower temperature decreased the magnitude of the functional response, suggesting that movement into the comparatively colder waters of the Mediterranean and British Isles could reduce the per capita response. Further, I found that red light reduced the maximum feeding rate of lionfish, compared to blue and white light, by dampening the attack rate. I assessed how temperature increase affects the proportional consumption of an amphipod prey by an intertidal predator, the bleniid, Lipophrys pholis (Linnaeus, 1758). Functional response analysis revealed that the shanny has a hump shaped relationship with increasing temperature wherein maximum feeding rate decreased at the highest temperature. Two prey supply models, where prey density was allowed to deplete, and where prey were replaced after consumption were compared and found to have differential results due to model choice. I used gut content data to assess the abundance, prey selection, degree of dietary overlap, in a commercial predator, cod (Gadhus morhua; Linnaeus, 1758) and a non-commercial predator, dogfish (Sycliorhinus canicula; Linnaeus, 1758) with regards to substrate type. While there were no significant conclusions to be made about habitat use, I found significantly larger populations of S. canicula and higher consumption of commercial invertebrates by S. canicula. I vi used this field data to inform further experiments, having highlighted S. canicula as a potential threat to commercial fisheries. A two-by-two experimental design was used to understand how differential acclimation of predator (S. canicula) and amphipod prey species (Echinogammarus marinus; Leach, 1815) affects the functional response of the predator. Increasing temperature concomitantly increased the magnitude functional response of S. canicula, however raised temperature caused a shift in functional response type, from Type II to Type III, conferring low prey density protection. Handling time was shorter when both predator and prey were acclimated to the raised temperature and as a result there was a significant interaction effect where maximum feeding rate was significantly higher when both predator and prey were acclimated. This increase in predation impact by S. canicula has the potential to affect valuable fisheries stocks due to the increasing populations of Scyliorhinus canicula and the additive effects of acclimation to raised temperature. Having highlighted the differential ways in which temperature can affect the per capita response of consumers I postulate a new metric wherein “Relative Impact Potential” of a consumer can be predicted under a set of environmental variables. This metric takes into account the per capita response, numerical response, and the potential change in predator and prey populations under the proposed conditions. I suggest the use of this metric as a rapid way of assessing and predicting potential threats to sustainability of fisheries under predicted climatic change. Overall, this thesis identifies species and scenarios wherein sustainability of important fisheries could be threatened. While this work focuses mainly on thermal responses, it demonstrates: (i) the utility of functional response analysis in assessing relative change in ecological impact under climate change scenarios; (ii) the species specificity of thermal responses and provides empiricle evidence of a hump shaped thermal response; (iii) the importance of considering both predator and prey when assessing ecological change, with reference to acclimation and population dynamics; and (iv) a metric with which to assess potential threats and ecological impact in a way that is standardized and easily accessible by managers and stakeholders alike.

This study examines the relationship between land use and temperature change in Dallas County, TX. The purpose of this research is to analyze the relationship between temperature and land use and to identify the primary factors contributing to the formation of urban heat islands based on different categories of land use. Specifically, this research analyzes the elements that contribute to the urban heat island effect in Dallas County using temperature data provided by remote sensing imagery and parcel-based land use data using Geographic Information System (GIS) technique and a correlation analysis method, which was employed to analyze the relationship between temperature and land use. The results of this study showed that every land use category has different temperature averages and those patterns were observed similarly in both 2000 and 2005. Parking, airport, commercial, industrial, and residential areas have relatively high temperatures. In contrast, water, undeveloped area and parks showed relatively low temperatures. Another major finding was ratio of land use composition affected the temperature of census tracts. Correlation analyses of land use and temperature in 2000 and 2005 indicate that various types of land use categories have significant relationships with temperature. Among them commercial, industrial, residential, parking, and infrastructure, are positively associated with temperature, while undeveloped, parks, water, and dedicated areas are negatively associated with temperature. Areas with a high ratio of commercial use showed the highest and undeveloped areas showed the lowest relationship. Furthermore, through the analysis of the relationship between land use and temperature change for five years (2000-2005), this study finds that temperature change depends on the ratio of each land use category change. The results of this study can help local planning and policy decisions which are related to urban land use planning concerning temperature change such as zoning, environmental regulations and open space preservation.

Magnetic refrigeration is an alternative cooling technology to vapour compression. Due to the large operating space of magnetic refrigeration devices, modelling is critical to predict results, optimize device parameters and regenerator design, and understand the physics of the system. Modeling requires accurate material data including specific heat, magnetization and adiabatic temperature change, . For a reversible material can be attained directly from measurement or indirectly through calculation from specific heat and magnetization data. Data sets of nine MnFeP1-xAsx alloys are used to compare calculated against measured . MnFeP1-xAsx is a promising first order material because of a tunable transition temperature, low material cost and large magnetocaloric properties. Because MnFeP1-xAsx alloys exhibit thermal hysteresis there are four possible calculation protocols for adiabatic temperature change; , , and . deviates the most from measured data and therefore it is assumed that this case is not representative of the material behavior. Results show and align with measured data as well as . The three protocols that align best with measured data have two consistent errors including a colder peak and a larger . With more data sets and analysis a preferred calculation protocol may be found. / Graduate

Therapeutic ultrasound is a deep heating modality often used to produce vigorous heating (≥4°C Δ) in tissues. The vigorous heating effects of 3 MHz therapeutic ultrasound have only been tested to a 2.5 cm depth, but its maximal depth of producing vigorous heating has yet to be established. Objective: To investigate the tissue temperature change produced by a 3 MHz ultrasound treatment at depths of 3 and 3.5 cm in the human triceps surae muscle group. Design: Randomized control design. Setting: Therapeutic modalities research laboratory. Patients or Other Participants: Twenty healthy college-aged participants (male = 13, female = 7; age = 23.4 ± 1.31; calf subcutaneous fat thickness= 0.6 cm ± 0.2 cm). Participants were randomized into treatment (n = 15) and sham (n = 5) groups. Participants were blinded to their group assignment. Interventions: Two MT-26/6 needle thermocouples were inserted into the left posterior triceps surae at depths of 3.0 ± 0.1cm and 3.5 ± 0.1cm from the skin's surface. Participants in the treatment group received a continuous 3 MHz ultrasound treatment at 1.4 W/cm2 for 8 minutes with 10mL of 100% ultrasound gel as a coupling medium. Participants in the sham group received the same treatment parameters, but the ultrasound device was not turned on. The Omnisound 3000 ultrasound device (ERA = 4.2cm2, BNR = 3.0:1) was used for all treatments. A 15 cm2 template was used to ensure a constant and proper treatment size. Baseline temperature (TB) was established by taking a mean of intramuscular tissue temperature (TIM)for five minutes before the treatment and TIM were recorded every 10 seconds throughout the experiment session. Participants marked a visual analog scale (VAS) indicating heat sensation at pre-treatment and post-treatment. Main Outcome Measures: A 2 x 2 x 2 (probe depth x condition x time) ANCOVA with TB used as a covariate analyzed the difference in TIM. We only used the time points of baseline and final TIM for our analysis as we are only interested in the change in TIM from beginning to end of the ultrasound treatment. Descriptive statistics for TIM and VAS for heat sensation were computed as post-treatment minus pre-treatment for each condition and probe depth. Results: There was a significant difference in TIM between the conditions at the different probe depths from the beginning and end of the ultrasound treatment (F1,15 = 7.35, p = 0.016). The mean changes in TIM for each condition at each probe depth were: sham 3cm = -0.4 ± 0.3°C, sham, 3.5cm = -0.2 ± 0.3°C, treatment, 3cm = 4.4 ± 0.2°C, treatment, 3.5cm = 3.5 ± 0.2°C. Mean VAS scores for each group were: sham = 0 ± 0mm and treatment = 71.8 ± 11.8mm. Conclusions: At 3cm deep into the posterior calf, the Omnisound 3000 using a 3 MHz treatment produced vigorous heating (≥4°C Δ). Moderate heating (2-3°C Δ) occurred at 3.5cm deep into the calf. Three MHz ultrasound may be used to heat tissues deeper than previously theorized, but it does, however, create a moderately high level of heat sensation for the patient.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: To predict the influence of temperature increases on organisms, and their capacity to respond to climate change, information on the upper thermal tolerance of organisms and its plasticity is required. However, various factors, such as rate of temperature change, may influence basal thermal tolerance and plastic responses, and consequently the vulnerability of organisms to temperature change. Although slower rates of temperature change might be more ecologically relevant, the majority of thermal tolerance studies feature rates of temperature change that are faster than those experienced by organisms in nature. Additionally, studies using slower rates of temperature change have been criticized as factors such as changes in body condition and accumulation of stress over time may confound results. This study determined the influence of fast and slow rates of temperature change and plasticity, induced by acclimation to different temperature conditions for 5 – 15 days, on the upper thermal tolerance of marine amphipod and isopod species from sub-Antarctic Marion Island and South Africa. Using congeners, intra- and inter-specific comparisons of the upper thermal tolerance and plasticity of these organisms were made across geographical regions (South Africa vs. Marion Island), across sites within regions (West coast vs. South coast of South Africa) and between tidal zones. Overall, lower rates of temperature change were found to be associated with lower values of upper thermal tolerance. At fast rates of temperature change, acclimation at high temperatures was associated with an increase in thermal tolerance, whereas at slow rates, acclimation to higher temperatures either had no effect or caused a decrease in thermal tolerance. Furthermore, microclimate recordings suggest that these organisms likely experience rates of temperature increase that are intermediate between the fast and slow rates employed in this study. Thus, in nature these marine invertebrates have upper thermal tolerances that are higher than mean environmental temperature and can likely mount plastic responses during short-term temperature variation. At slow rates of temperature change, however, the upper thermal tolerance of these organisms approximates environmental temperature and plasticity is reduced, likely increasing vulnerability to high temperatures. At the intra-specific level, upper thermal tolerance and plasticity response varied based on mass and sex, however, these effects were species-specific. Isopods inhabiting cooler but more variable microsites on the West coast of South Africa had a higher upper thermal tolerance, but similar magnitude of plasticity, than a population of the same species from the warmer, less variable South coast. Generally, Marion Island species had a lower upper thermal tolerance but higher magnitude of plasticity than South African species. The variability reported here at different hierarchical and geographical scales could be linked to the distinct thermal environments experienced, and the differing physiological and behavioural responses of populations and species to their thermal environments. This variation in thermal tolerance might be critical during environmental change and suggests that species composition may be altered in the future. / AFRIKAANSE OPSOMMING: Om die invloed van temperatuur verhogings op organismes, en hul vermoë om te reageer op hierdie verandering, te voorspel, word inligting oor hoë temperatuur verdraagsaamheid van organismes en die plastisiteit hiervan, benodig. Verskeie faktore, soos die tempo van verandering, kan egter basale termiese verdraagsaamheid en plastiese reaksies beïnvloed. Dus, mag dit die tasbaarheid vir temperatuur verandering beïnvloed. Alhoewel stadiger tempo van verandering meer ekologies relevant kan wees, fokus die meerderheid van warm verdraagsaamheid studies op temperatuur veranderinge wat vinniger gebeur as wat ervaar word deur organismes in die natuur. Boonop word studies wat fokus op stadige veranderinge in temperatuur, gekritiseer omdat faktore soos ‘n verandering in liggaamstoestand en die opeenhoping van stres, potentieël die resultate kan belemmer. Hierdie studie ondersoek die invloed van vinnige en stadige temperatuur veranderinge en die plastisiteit, geïnduseer deur akklimasie, met betrekking tot verskeie temperature vir 5-15 dae. Ons fokus spesifiek op die hoë temperatuur verdraagsaamheid van mariene amphipod- en isopod spesies van sub-Antarktiese Marion Island en Suid Afrika. Deur gebruik te maak van spesies wat aan dieselfde genus behoort, is vergelykings getrek tussen intra- en inter-spesies verbande met betrekking tot hul termiese verdraagsaamheid en plastisiteit. Die studie is oor geografiese streke (Suid Afrika vs. Marion Island), tussen areas binne ‘n geografiese streek (Weskus vs. Suidkus van Suid Afrika) en tussen gety sones voltooi. Oor die algemeen was stadige temperatuur veranderinge geassosieër met ‘n laer termiese verdraagsaamheid vir hoë temperature. Met vinnige veranderinge in klimaat, was akklimasie by hoë temperature geassosieër met ‘n hoër temperatuur limiet, maar by stadige temperatuur veranderinge het akklimasie by hoë temperature geen effek gehad nie, of het ‘n afname in termiese verdraagsaamheid veroorsaak. Verder het mikroklimaat opnames aangedui dat hierdie organismes waarskynlik temperatuur verhogings ondervind in hul natuurlike habitat, wat intermediêre is van die vinnige en stadige veranderinge wat in hierdie studie gebruik is. Dus, in die natuur, het hierdie mariene invertebrate `n boonste termiese toleransies wat hoër is as die gemiddelde omgewingstemperatuur en kan hulle waarskynlik van platiese reaksies gebruik maak tydens kort-termyn temperatuur variasie. Gedurende stadige temperatuur veranderinge toon hulle alhoewel hoë termiese verdraagsaamheid teenoor die omgewingstemperature en plastisiteit is verminder, wat heel waarskynlik toenemende kwesbaarheid vir hoë temperature tot gevolg het. Op die intra-spesifieke vlak was wisseling in hoë termiese verdraagsaamheid gebaseer op liggaams massa en geslag, maar hierdie veskille was spesie-spesifiek. Isopoda wat koeler areas bewoon, met meer variasie in hul mikroklimaat, soos ondervind in die Weskus van Suid Afrika, het `n hoër termiese verdraagsaamheid. Maar, soortgelyke mate van plastisiteit, as 'n populasie van dieselfde spesie van die warmer, minder veranderlike Suidkus. Oor die algemeen het Marion-eiland spesies 'n laer termiese verdraagsaamheid, maar hoër grootte van plastisiteit as Suid-Afrikaanse spesies. Die veranderlikheid wat hier geraporteer is, kan op verskeie hiërargiese en geografiese vlakke gekoppel wees aan die unieke termiese omgewings wat hierdie organismes ervaar en aan die verskillende fisiologiese- en gedrags reaksies van populasies en spesies tot hulle termiese omgewings. Die variasie in termiese verdraagsaamheid kan krities wees tydens omgewingsverandering en dui daarop dat spesie-samestelling kan verander in die toekoms. / The British Antarctic Survey for funding

The electricity system is particularly susceptible to climate change due to the close interconnectedness between not only electricity production and consumption to climate, but also the interdependence of many European countries in terms of electricity imports and exports. This study provides a country based relative analysis of a number of selected European countries’ electricity system vulnerability to climate change. Taking into account a number of quantitative influencing factors, the vulnerability of each country is examined both for the current system and using some projected data. Ultimately the result of the analysis is a relative ranked vulnerability index based on a number of qualitative indicators. Overall, countries that either cannot currently meet their own electricity consumption demand with inland production (Luxembourg), or countries that experience and will experience the warmest national mean temperatures, and are expected to see increases in their summer electricity consumption are found to be the most vulnerable for example Greece and Italy. Countries such as the Czech Republic, France and Norway that consistently export surplus electricity and will experience decreases in winter electricity consumption peaks were found to be the least vulnerable to climate change. The inclusion of some qualitative factors however may subject their future vulnerability to increase. The findings of this study enable countries to identify the main factors that increase their electricity system vulnerability and proceed with adaptation measures that are the most eective in decreasing vulnerability.

The attention for materials displaying high magnetocaloric effect (MCE) has grown during the past 30 years. One of the most important properties of MCE is the adiabatic temperature change ( ). The main aim of this work was to develop a method to measure the temperature change ( ) for magnetocaloric materials in a changing magnetic field.  A technique was developed where maximum reached  for Gadolinium was 1.19 K in a changing magnetic field of 1.3 T, however, this is lower value in comparison with previous studies (3.3 K in a changing magnetic field of 1 T, Bjørk, et al., 2010) which makes the developed method not sufficient enough to measure . Furthermore, finding novel materials displaying high MCE is of great interest. MnFePSiB alloys display promising MCE properties but processing method is expensive and time consuming. Therefore, a MnFePSiB compound was simply remelted several times and heat treated to enhance its properties. The MnFePSiB alloy was remelted 1, 2 and 3 times after initial casting. Melting the material 3 times resulted improvement in both the magnetic and magnetocaloric properties due to enhanced homogeneity. The material melted 3 times was further heat treated to improve its magnetic magnetocaloric properties. Heat treating the material for 5 hours at 1373K improved the magnetic entropy change more than 10 times compared to the as cast sample,  was moved closer to room temperature and maximum  of 0.71 K was obtained.

In this work over 200 temperature proxy data sets have been analyzed to determine if periodic and or quasi-periodic patterns exist in the data sets. References to the journal articles where data are recorded are provided. Chapter 1 serves an introduction to the problem of temperature determination in providing information on how various proxy data sources are derived. Examples are given of the techniques followed in producing proxy data that predict temperature for each method used. In chapter 2 temperature proxy data spanning the last 4000 years, from 2,000 BCE to 2,000 CE, are analyzed to determine if overarching patterns exist in proxy data sets. An average of over 100 proxy data sets was used to produce Figure 4. An overview of the data shows that several “peaks” can be identified. The data were then subjected to analysis using a series of frequency modulated cosine waves. This analysis led to a function that can be expressed by equation 3. The literature was examined to determine what mathematical models had been published to fit the experimental proxy data for temperature. A number of attempts have been made to fit data from limited data sets with some degree of success. Some other papers have used a sinusoidal function to best fit the changes in the temperature. After consideration of many published papers and reviewing long time streams of proxy data that appeared to have sine wave patterns, a new model was proposed for trial. As the patterns observed showed “almost” repeating sine cycles, a frequency modulated sine wave was chosen to obtain a best fit function. Although other papers have used a sinusoidal function to best fit the changes in the temperature, the “best fit” was limited. Thus, it was decided that a frequency modulated sine wave may be a better model that would provide a more precise fit. This proved to be the case and the more than 240 temperature proxy data sets were analyzed using Equation 3. In chapter 3 the time span for the proxy data was extended to cover the period of time 12,000 BCE to 2000 CE. The data were then tested by using the equation above to search for periodic/quasi-periodic patterns. These results are summarized under select conditions of time periods. In chapter 4 the interval of time is extended over 1,000,000 years of time to test for long period “periodic” changes in global temperature. These results are provided for overall analysis. The function f(x) as described above was used to test for periodic/quasi-periodic changes in the data. Chapter 5 provides an analysis of temperature proxy data for an interval of time of 3,000,000 years to establish how global temperature has varied during the last three million years. Some long-term quasi-periodic patterns are identified. Chapter 6 provides a summation of the model proposed for global temperature that can be expected if similar trends continue over future years as have prevailed for the past few million years. Data sets that were used in this work are tabulated in the appendices of this paper.

För att minska klimatpåverkan är energisnåla processer och användning av fossilfria bränslen viktigt. Vid stabilisering av avloppsslam vid reningsverk är en vanlig metod rötning som förutom att ta hand om slammet även producerar biogas, ett fossilfritt bränsle med låga växthusgasutsläpp. Processer som drivs inom det mesofila temperaturområdet har visat sig vara stabila och ger en jämn gasproduktion. Det mesofila området sträcker sig mellan 25–40°C men de flesta processer drivs mellan 35–40°C. Den här studien undersöker möjligheten att sänka temperaturen inom det mesofila området för att få en lägre energiförbrukning och en energisnålare process. Då det är viktigt att biogasproduktionen inte försämras av en sänkt temperatur har skillnad i utrötningsgrad, metanpotential och utrötningstid undersökts vid tre olika temperaturer (32, 34,5 samt 37,5°C) via satsvisa utrötningsförsök. Utöver påverkan på biogasproduktionen har en energibalansberäkning utförts för rötkamrarna vid Uppsala reningsverk. Detta ger ett mått på hur stora vinster i värmeenergi en sänkt temperatur kan leda till. En betydande kostnad vid reningsverk är avvattningen av slam och det är därför viktigt att den inte riskerar att försämras om temperaturen sänks. Ett filtreringsförsök som mäter CST (Capillary Suction Time) ger ett mått på slammets avvattningsegenskaper och har därför utförts vid tre olika temperaturer. Resultaten visade ingen försämring i biogasproduktion vid en sänkning till 34,5°C och en minskning i metanpotential med 11 % vid en sänkning till 32°C. Nedbrytningshastigheten försämrades inte vid en sänkt temperatur. Vinster i form av lägre värmeförbrukning uppgick till 14 % vid sänkning till 34,5°C och 27 % vid sänkning till 32°C. Avvattningsförsöket visade ingen försämrad avvattning vid lägre temperaturer. Den här studien visar att det finns en möjlighet att sänka temperaturen i rötkammaren vid reningsverket i Uppsala och på så sätt sänka energiförbrukningen. För att bekräfta resultaten bör även kontinuerliga försök utföras men denna studie visar att det är möjligt att få en lyckad nedbrytning även i lägre mesofila temperaturer. Resultatet öppnar upp för fortsatta undersökningar om temperaturförändringar inom det mesofila området och kan leda till en optimering av rötningsprocessen och möjlighet att få en effektiv och energisnål produktion av biogas. / Energy efficient processes and the use of fossil free fuels play an important role in order to reduce the impact of climate change. Anaerobic digestion is a common way for stabilizing sewage sludge at wastewater treatment plants (WWTP). One of the benefits with anaerobic digestion is that it also produces biogas, a fossil free fuel with low greenhouse gas emissions. An operational temperature within the mesophilic range has proven to give a stable process with an unfluctuating production of gas. The mesophilic temperature range between 25-40°C but most processes are operated between 35-40°C. This study investigates the opportunity to lower the temperature within the mesophilic range in order to reduce energy consumption. It is important to maintain the production of biogas with a lower temperature. Therefore, the reduction in VS-content (VS-volatile solids), methane yield and time for degradation was determined by a BMP-experiment (BMP-Biochemical Methane Potential) in three different temperatures (32, 34.5 and 37.5°C). In order to quantify the reduction in heat consumption with lower operational temperatures the change in heat balance for a full-scale WWTP in Uppsala was calculated. A major part of the operational cost is dewatering of sludge and it is therefore important that it does not deteriorate with a lower temperature. The effect on the dewaterability at different temperatures was examined by a filterability test measuring CST (capillary suction time). The results from the study showed no significant difference in methane yield between 37.5°C and 34.5°C. The methane yield at 32°C was 11 % lower compared to 37.5°C but the degradation kinetic was not affected by a temperature change. The reduction in heat consumption was 14 % when the temperature was reduced to 34.5°C and 27 % when it was reduced to 32°C. The filterability test did not show a deterioration with lower temperatures. The study showed that it is possible to reduce the operational temperature for anaerobic digestion at the WWTP in Uppsala in order to reduce the energy consumption. To confirm these results a continuously experiment should be done, but this study shows that it is possible to get a successful degradation in a lower mesophilic temperature. This leads the way for further investigations within the mesophilic range and could lead to optimizing anaerobic digestion and the opportunity to get an energy efficient production of biogas.