Purpose: The aim of this study was to investigate the effects of a maximal repeated-jumps task on force production, muscle activation and kinematics, and to determine if changes in performance were dependent on gender. Methods: Eleven male and nine female athletes performed continuous countermovement jumps for 60 s on a force platform while muscle activation was assessed using surface electromyography. Performances were videotaped and digitized (60 Hz). Data were averaged across three jumps in 10-s intervals from the initial jump to the final 10 s of the test. Results: No interaction between time and gender was evident for any variable; therefore, all results represent data collapsed across gender. Preactivation magnitude decreased across time periods for anterior tibialis (AT, P < .001), gastrocnemius (GAS, P < .001) and biceps femoris (BF, P = .03), but not for vastus lateralis (VL, P = .16). Muscle activation during ground contact did not change across time for BF; however, VL, G, and AT showed significant reductions (all P < .001). Peak force was reduced at 40 s compared with the initial jumps, and continued to be reduced at 50 and 60 s (all P < .05). The time from peak force to takeoff was greater at 50 and 60 s compared with the initial jumps (P < .05). Both knee fexion and ankle dorsifexion were reduced across time (both P < .001), whereas no change in relative hip angle was evident (P = .10). Absolute angle of the trunk increased with time (P < .001), whereas the absolute angle of the shank decreased (P < .001). Conclusions: In response to the fatiguing task, subjects reduced muscle activation and force production and altered jumping technique; however, these changes were not dependent on gender.

Orientador: Roberto Alves Oliveira / Resumo: A co-digestão de água residuária da bovinocultura leiteira (ARBL) e água residuária do beneficiamento do café (ARC) em reatores anaeróbios de fluxo ascendente com manta de lodos (UASB, R1 e R2), em série, é inédita e importante para o desenvolvimento dos setores envolvidos. Foram utilizadas proporções de 100:0; 85:15, 70:30 e 50:50 de ARBL:ARC no afluente dos reatores UASB e aplicados tempo de detenção hidráulica (TDH) de 2 (R1) e 4 (R2) dias. Isto proporcionou cargas orgânicas volumétricas (COV) de 11,9 (valor médio obtido nos testes 1 e 2, sem adição de ARC); 12,9 (teste 3); 14,0 (teste 4) e 21,3 (teste 5) g DQOtotal (L d)-1 no R1. As maiores produções volumétricas de metano, de até 0,89 L CH4 (L reator d)-1 foram obtidas com COV de 14,0 g DQO (L d)-1. As concentrações médias de fenóis totais no afluente variaram entre 6 e 132 mg L-1 e as eficiências médias de remoção nos reatores UASB, em dois estágios, foram de 35 a 52% com concentração de 50 mg L-1 para efluente do R2 após adição de ARC que contém elevadas concentrações de fenóis totais e apresentam toxicidade ao tratamento anaeróbio podendo afetar a estabilidade do processo. O sistema foi eficiente para remoção de ovos de helmintos. Os Domínios Bacteria e Archaea, as Ordens Methanobacteriales, Methanomicrobiales e Methanosarcinales e as Famílias Methanosaetaceae e Methanosarcinaceae se apresentaram de forma sincrônica e equilibrada na co-digestão anaeróbia dos resíduos estudados. / Abstract: The co-digestion of dairy manure wastewater (DMW) and coffee processing wastewater (CPW) in up flow anaerobic sludge blanket (UASB, R1 and R2) in series is unprecedented and important for the development of the sectors involved. Proportions of 100: 0; 85:15, 70:30 and 50:50 DMW:CPW were used in the UASB reactors influent and applied hydraulic retention time (HRT) of 2 (R1) and 4 (R2) days. This provided organic loading rate (OLR) of 11.9 (mean value obtained in tests 1 and 2, without addition of CPW); 12.9 (test 3); 14.0 (test 4) and 21.3 (test 5) g CODtotal (L d) -1 on R1. The highest volumetric methane yields of up to 0.89 L CH4 (L reactor d) -1 were obtained with OLR of 14.0 g COD (L d) -1. The mean concentrations of total phenols in the affluent ranged from 6-132 mg L-1 and the mean removal efficiencies in two-stage UASB reactors were 35-52% with 50 mg L-1 concentration for R2 effluent after addition of ARC containing high concentrations of total phenols and toxicity to anaerobic treatment may affect process stability. The system was efficient for removal of helminth eggs. The Bacteria and Archaea Domains, the Methanobacteriales, Methanomicrobiales and Methanosarcinales Orders, and the Methanosaetaceae and Methanosarcinaceae families were presented in a synchronic and balanced manner in the anaerobic co-digestion of the residues studied. / Mestre

Consumption of supplements and energy drinks is common among athletes; however, there is a lack of research on the efficacy of energy drink consumption before and during short-duration, intense exercise. The purpose of this research was to investigate the acute effects of a low-calorie, caffeine-taurine, energy drink (AdvoCare Spark®) on repeated sprint performance and anaerobic power in National Collegiate Athletic Association Division I football players. Twenty well-trained Division I football players (age: 19.7 ± 1.8 years, height: 184.9 ± 5.3 cm, weight: 100.3 ± 21.7 kg) participated in a double-blind, randomized crossover study in which they received the energy drink or an isoenergetic, isovolumetric, noncaffeinated placebo. The two trials were separated by 7 days. The Running Based Anaerobic Sprint Test (RAST), consisting of six 35-m sprints with 10 s of rest between each sprint, was used to assess anaerobic power. Sprint times were recorded with an automatic electronic timer. On average, there iv was no statistically significant difference between the placebo (15.06 ± 3.80 W·s-1) and beverage (15.3 ± 4.18 W·s-1) measurements of fatigue index. Neither were there statistically significant main effects of the beverage treatment on power F(1, 18) = 3.84, p = 0.066; or sprint time F(1, 18) = 3.06, p = 0.097. However, there was a significant interaction effect between caffeine use and the beverage for sprint times (F = 4.62, p = 0.045), as well as for anaerobic power (F = 5.40, p = 0.032), indicating a confounding effect. In conclusion, a caffeine-taurine energy drink did not improve the sprint performance or the anaerobic power of collegiate football players, but the level of caffeine use by the athletes likely influenced the effect of the drink.

Uncertainty about anaerobic digestion process stability is the main issue preventing more widespread use of the process as a source of energy recovery in wastewater treatment facilities. The overall objective of this research was to study the feasibility of enhancing biogas production inside wastewater facilities using co-digestion of municipal sludge with bakery waste. Another objective was to improve the stability index and a mathematical model that can be useful tools to predict the process stability of municipal sludge digestion alone, and when it is mixed with bakery waste, as a substrate for microorganisms. Experiments were conducted in three phases. In phase 1, a full-scale anaerobic digester at Central Weber Sewer Improvement District, Ogden, UT, receiving a mixture of primary and secondary sludge, was monitored for one hundred days. Chemical oxygen demand (COD), and volatile solids (VS) mass balances were conducted to evaluate the stability of the digester and its capability of producing methane gas. The COD mass balance accounted for nearly 90% of the methane gas produced while the VS mass balance showed that 91% of the organic matter removed resulted in biogas formation. Other parameters monitored included: pH, alkalinity, VFA, and propionic acid. The values of these parameters showed that the digester was running under stable steady state conditions. At mesophilic temperature, the stability index was determined and equal to 0.40 L (CH4)/ g(ΔVS) In phase 2, the feasibility of adding BW to MS was tested in batch reactors scale. The biogas production was enhanced and the digester was stable until the range of 37- 40% of BW to 63-60% of MS. The ADM1 coefficients were modified to accurately predict the digester performance. The modified model outputs (pH, VFA, and methane) were within acceptable ranges when compared with the observed data from the batch reactors. In phase 3, the feasibility of MS and BW were tested using an Induced Bed Reactor (IBR) with a 50:50% ratio of MS:BW (COD basis). The process was stable during different hydraulic retention times and the ADM1 was modified to predict the stability of the process in the IBR.

Whey permeate was anaerobically digested in laboratory scale upflow anaerobic sludge blanket reactors. Nine hydraulic retention times between 5 and 0.2 days were examined with a fixed influent concentration of 10.6 ± 0.2 g COD/L. Chemical oxygen demand removal efficiency ranged from 99.0 to 18.9% and maximum production rate of methane gas was 2.67 L/L/day at a hydraulic loading rate of 12.97 kg COD/m3/day. About 70% of the chemical oxygen demand removed was converted to methane. Both the nonlinear least square method with 95% confidence interval and linear regression were used to evaluate kinetic coefficients. The maximum substrate utilization rate, k, and half saturation coefficient, KL, were determined to be 1.269 ± 0.163 Kg COD/kg VSS/day and 1.000 ± 0.179 kg COD/kg VSS/day. The yield coefficient, Y, and biomass decay rate coefficient, Kd, were also determined to be 0.160 ± 0.012 kg VSS/kg COD and 0.027 ± 0.004 day-1, respectively.

The search for natural products which can increase animal productivity and reduce environmental impact has been intensified. Some plant extracts, such as essential oils, are used as feed additives able of improving ruminal fermentation by modulating the production of short chain fatty acids and inhibiting methanogenesis. The objective of this study was to evaluate the production of enteric and feces methane, as well as feeding behaviour, ruminal fermentation and kinetics of dairy and beef cattle fed with different essential oils. Eight non-pregnant, non-lactating and ruminally canullated cows were used: four were the dairy breed Holstein, and four were the beef breed Nellore. The diet was composed of 70% of roughage (corn silage) and 30% of concentrate (corn grain and soybean meal), the treatments differed only in relation to the essential oil added: CNT, a diet without any additive; EEO, a diet with 500 mg/kg of DM of eucalyptus (Eucalyptus citriodora) essential oil; PEO, a diet with 500 mg/kg of DM of Brazilian peppertree (Schinus terebinthifolius Raddi) essential oil, and LEO, a diet with 500 mg/kg of DM of lemongrass (Cymbopogon citratus Stapf) essential oil. The experimental design was the 4x4 contemporary latin square in a 2x4 factorial arrangement (referring to two specialized cattle breeds and four additives). The evaluation of the CH4 production of the manure was performed through experimental batch anaerobic digesters, in a completely randomized design. The beef cattle had lower DMI (P = 0.0413), they spent more time consuming, ruminating or chewing 1 kg of DM or NDF (min/kg), also had higher values for acetate, butyrate or total SCFA production than dairy cattle. The manure from dairy cattle had higher biogas production (L/gVS add) or CO2 (liters, percentage and L/gVS add) than the manure of beef cattle. The treatments with essential oils had on average 23% more rumination events per day than the control treatment (P = 0.0201). Diet containing essential oils decreased N2O production of feces from dairy cattle. The essential oils in the dosage used did not affect rumen fermentation and kinetics, as well as the emission of enteric methane and feces. / A busca por produtos naturais capazes de aumentar a produtividade animal e diminuir o impacto ambiental tem intensificado. Alguns extratos vegetais, como óleos essenciais, são utilizados como aditivos alimentares capazes de melhorar a fermentação ruminal, através da modulação da produção de ácidos graxos de cadeia curta e inibição da metanogênese. O objetivo deste estudo foi avaliar a produção de metano entérico e das fezes, bem como comportamento alimentar, fermentação e cinética ruminal de bovinos leiteiros e de corte alimentados com óleos essenciais. Foram utilizadas oito vacas não gestantes e não lactantes, fistuladas no rúmen, sendo quatro vacas com aptidão para produção leiteira e quatro para carne. A dieta base foi composta por 70% de volumoso (silagem de milho) e 30% de concentrado (milho grão e farelo de soja), os tratamentos diferiram apenas quanto ao óleo essencial adicionado: CNT: dieta sem nenhum aditivo; OEE: 500 mg/kg de MS do óleo essencial de eucalipto citriodora (Eucalyptus citriodora); OEA: 500 mg/kg de MS do óleo essencial de aroeira vermelha (Schinus terebinthifolius Raddi) e OEC: 500 mg/kg de MS do óleo essencial de capim cidreira (Cymbopogon citratus Stapf). O delineamento experimental utilizado foi o quadrado latino 4x4 contemporâneo em arranjo fatorial 2x4 (referente a duas diferentes aptidões e quatro dietas). Para avaliar a produção de CH4 dos dejetos utilizou-se biodigestores anaeróbios experimentais do tipo batelada, em delineamento inteiramente casualizado. Os bovinos de corte apresentaram menor ingestão de matéria seca (P = 0,0413) e levaram mais tempo para ruminar e mastigar 1 kg de MS ou FDN (min/kg). Eles também apresentaram maiores valores para produção de acetato, butirato e AGCC total. Os dejetos dos bovinos leiteiros tiveram maior produção de biogás e CO2 que os dejetos dos bovinos de corte. Os animais que receberam os tratamentos com óleos essenciais tiveram em média 23% mais eventos de ruminação por dia que animais do tratamento controle (P = 0.0201). Dietas contendo óleos essenciais diminuíram a emissão de N2O nas fezes de animais leiteiros. Os óleos essenciais na dosagem utilizada não alteraram a cinética e fermentação ruminal, bem como a emissão de metano entérico e das fezes.

A liquefação hidrotermal (HTL) é uma tecnologia muito utilizada para a conversão de diversos tipos de biomassa em Bio-óleo bruto; contudo, enquanto tal combustível é produzido uma fase aquosa (PHWW), rica em matéria orgânica e alguns compostos tóxicos, também é gerada, podendo ocasionar severos impactos ambientais negativos. O objetivo da presente pesquisa foi aplicar dois bio-adsorventes: in natura (BAA) e ativado quimicamente (BAAA), derivados da casca de amendoim, como pré-tratamentos da PHWW afim de melhorar sua biodegradabilidade anaeróbia. O carvão ativado granular (GAC) foi utilizado como adsorvente modelo para comparação. Os processos de adsorção foram otimizados com a utilização de desenhos compostos centrais rotacionais (DCCR), no quais as variáveis independentes foram: pH do adsorvato, temperatura e quantidade de (bio) adsorvente no meio. A porcentagem de remoção de DQO e do íon amônio foram as variáveis dependentes. Isotermas de adsorção foram obtidas em ensaios em batelada. Após realizado o estudo do processo de adsorção, o potencial metanogênico dos efluentes pré-tratados e do efluente in natura foi determinado. Esses ensaios foram conduzidos com três concentrações de PHWW (6,5%, 13% e 26%), com dois ensaios controle, um negativo e outro positivo. A pressão nos frascos reatores foi monitorada diariamente e a determinação da composição do biogás produzido foi realizada por cromatografia gasosa uma vez por semana. Os resultados para a processo adsortivo foram encorajadores, uma vez que cada bio-adsorvente testado foi otimizado para diferentes variáveis resposta: BAA (NH4+) e BAAA (DQO). Os ensaios anaeróbios mostraram que uma maior taxa de produção metanogênica, dos efluentes pré-tratados, pode estar ligada à modificação química da superfície nas cascas de amendoim. Foi possível concluir que a bio-adsorção se perfila como uma alternativa sustentável para o pré-tratamento de efluentes advindos da HTL de cianobactérias. / Hydrothermal liquefaction (HTL) is a technology widely used for the conversion of several types of biomass to bio-crude oil; however, while such a fuel is produced an aqueous phase (PHWW), rich in organic matter and some toxic compounds, is also generated and can cause severe negative environmental impacts. The objective of the present research was to apply two bio-adsorbents: peanut bio-adsorbent (PB) and activated peanut bio-adsorbent (APB), as pre-treatments of PHWW to improve their anaerobic biodegradability. Granular activated carbon (GAC) was used as an absorbent model for comparison. The adsorption process was optimized with the use of central rotational composite designs (DCCR), in which the independent variables were: pH of the adsorbate, temperature and amount of (bio) adsorbent in the medium. The percentage of COD removal and ammonium ion were the dependent variables. After the study of the adsorption process, the methanogenic potential of the pretreated effluents and raw PHWW was determined. These trials were conducted with three concentrations of PHWW (6.5%, 13% and 26%), with two control trials, one negative and one positive. The pressure in the reactor flasks was monitored daily and the composition of the biogas produced was determined by gas chromatography once a week. The results for the adsorption process were encouraging, and ach bio-adsorbent tested was optimized for different response variables: PB (NH4+) and APB (COD). The anaerobic assays showed that a higher rate of methanogenic production of pretreated effluents may be linked to the chemical modification of the surface in the peanut shells. It was possible to conclude that the bio adsorption is outlined as a sustainable alternative for the pretreatment of effluents coming from HTL.

This study wished to compare the same physiological responses of elite athletes to a typical intermediate term anaerobic capacity track running session with those of standing cycling of similar intensity and duration. Twelve well trained/elite male distance runners completed maximal running, standing cycling and strength testing sessions; and Intermediate Term Anaerobic Capacity Sessions (ITACS) in running and standing cycling; each comprising eight efforts of approximately 30 seconds duration at 90% maximal effort in each mode of activity, separated by 2 minutes rest. The experimental sessions took place from the end of November 1996 to the beginning of March 1997. The subjects were required to attend three maximal experimental sessions, which were performed on separate days and used for baseline data collection. On completing these they participated in both running and standing cycling ITACS, performed on separate days with at least 48 hours between each test protocol. There was complete randomisation of all test protocols. Descriptive statistics were determined for all the variables. Independent t-testing was used to determine if similar temperature and humidity readings were obtained during the maximal testing for each mode of activity. Paired t-testing was used to compare the differences in warmup heart rates between the maximal and ITACS, the differences in peak lactates obtained after each type of ITACS, draw comparisons between heart rate (HR) changes over time during the ITACS and determine if a difference existed between workloads for the two modes of activity. It was also used to draw a comparison between the peak BLa values and ascertain if pre-test creatine kinase (CK) levels were the same for each mode of activity. A repeated measures one way ANOVA was used to determine if workload reduced over time for each type of ITACS. A three way ANOVA with repeated measures on one factor (repetition) was performed on HR response. It was used to determine if there was a difference between the workload/recovery HR response; if workload/recovery HR values increased over the duration of each ITACS; and if the workload/recovery HR response over time was mode specific. A two way ANOVA with repeated measures on one factor (repetition) was performed on blood lactate (BLa) response. It was used to determine if there was a significant interaction between the mode of activity and time, if BLa increased over the duration of each ITACS and if there was an effect of mode on its own on the BLa response. A two way repeated measures ANOVA was used to ascertain whether there was a difference in CK levels between the two modes of activity, with Tukey's multiple comparison tests used in post hoc analyses to show the amount of difference. A linear regression analysis was performed to determine if BLa response was similar across the duration of each type of ITACS. The effects of temperature (22.3 ± 1.2 vs 21.1 ± 0.3 °C, run vs cycle, t = -0.94, n = 12, p = 0.36)) and humidity (57 ±4.2 vs 52 ± 1.7%, run versus cycle, t = -1.04, n = 12, p = 0.31) did not influence any of the results obtained during the ITACS. Nor did differing warmup intensities (as indicated by heart rate - HR) during the maximal (160 ± 5.7 vs 158 ± 3.1 beats per minute (bpm), run vs cycle, t = - 0.45, n = 9, p = 0.66) and ITACS (160 ± 3.6 vs 152 ± 3.1 bpm, run vs cycle, t = -2.81, n = 9, p = 0.02). An equal test preparation was confirmed by the warmup blood lactate (BLa) levels, which were not significantly different between the exercise modes for both the maximal (11.0 ±0.6 vs 11.8 ± 1.0 mmol-l1, run vs cycle, t = 2.26, ii n = 10, p =0.23) and ITACS (4.2 ± 0.7 vs 4.2 ± 0.6 mmol-1 ', run vs cycle, t = 0.27, n = 10, p = 0.796). A significantly higher workload was achieved during the running ITACS as compared to the standing cycling ITACS (105 ± 1.1 vs 89 ±2.9 %, run vs cycle, t = 10.45, n = 12, p<0.0005). The increase in workload/recovery HR response and their changes as each type of ITACS progressed was not mode specific [F(l,40) = 0.94, p > 0.05]. Those subjects who possessed high BLa concentrations performed less work on the cycle ergometer. There was a strong negative relationship for average workloads and BLa accumulation for the standing cycling exercise (Spearmans rho = -0.799, n = 11, p<0.005) suggesting that BLa accumulation was a limiting factor in work production. The increase in BLa levels was not mode specific F(l,20) = 1.36, p > 0.05]. The BLa response was comparatively similar because the rate of increase in BLa accumulation and peak BLa values (19.7 vs 16.9 mmol-l'1, cycle vs run, t = 2.1, n = 11, p = 0.06) were not significantly different between the modes of activity. Mode in conjunction with time affected standing cycling BLa response to a greater extent than running BLa levels [F(4.80) =3.929, p <. 0.05]. Standing cycling BLa concentrations were significantly negatively correlated with knee extension peak torque (Spearmans rho = - 0.771, n = 11, p < 0.01) and total work (Spearmans rho = - 0.802, n = 11, p < 0.01) measurements. In running they were negatively correlated with knee flexion total work measurements (Spearman rho = - 0.685, n = 11, p < 0.05) These findings suggest that BLa accumulation occurs from different muscle fibre recruitment patterns. Less work was performed in isokinetic knee extension following standing cycling as compared to running (2234 ± 68.4 vs 2462 ± 78.9 Nm, t = 2.23, n = 11, p < 0.05) suggesting that standing cycling is more fatiguing on the quadriceps than running. There was no difference in the knee flexion testing (1799 ± 89.6 vs 1785 ± 69.2, cycle vs run, t = 2.23, n = 11, p = 0.96). There was a significant difference in mean creatine kinase (CK) activity between the two modes 24 hours after completing the ITACS (450 ± 73.2 vs 320 ± 46.5 I/U, running vs cycle, F = 6.44, df = 1,17, p < 0.01). There was a significantly greater increase in CK activity and therefore muscle damage, following the running (mean increase of 190 I/U) as compared to the standing cycling session (mean increase of 44.0 I/U). In terms of reducing the risk of injury, achieving a similar cardiovascular response and achieving comparable BLa accumulation (even though mechanism/s of accumulation may be different) standing cycling appears to be is a satisfactory substitute for running during an ITACS. The results of this research strengthen the concept of utilising a simulated mode of activity as a substitute for the primary activity in order to maximise transfer effects, providing there is a careful balance between the specific training and the near specific training. The differing physiological responses between the exercise modes (ie- different muscle fibre recruitment patterns, different workload capacity, different CK measures) suggest that standing cycling cannot act as a total/comprehensive replacement for running. A training study is warranted to further investigate the findings of this research.

<p>In light of constant research regarding the development of alternate fuels, anaerobic digestion of grains diluted in process water from a wastewater treatment plant has been investigaed by starting biogas reactors to produce methane. The possibility of using the sludge from the reactors as fertilizer was also explored. The experiment ran for 90 days of which three days were used to collect samples over a 24-hour period. Variables monitored were associated to process stability, consistency and production. The results of the 24-hour periods show that volatile fatty acids concentrations increase immediately following feeding, peak a few hours later then decrease. Gas production is most efficient at the beginning of the period then stagers after about 20 hours. Results of the 90-day period resemble the 24-hour results; high volatile fatty acid (VFA) concentrations are often linked to low gas production and methane concentrations. The results indicate that certain types of process waters are better suited as dilution liquids than others i.e. digested sludge is better than centrifugation water, though overall gas production in all reactors averaged ca 650 ml/ g volatile solids loaded. With regards to fertilizer use, Cr was the only metal that was measured in unacceptable quantities. Fertilizing the land is not a problem seen from the heavy metals perspective. There is, however, a need for further research and process development before any full-scale digestion processes of this type are initiated.</p>

<p>Biogas, a mixture of methane and carbon dioxide, is produced in the anaerobic digestion of sewage sludge. After anaerobic digestion, the digested sludge is often allowed to degas for one or two days. This gas is seldom utilised, but if the degassing could be accelerated, utilisation would be easier. Ultrasound can be used as a pretreatment method for waste activated sludge. It has a disintegrating effect on the sludge and causes lysis of bacteria in the sludge. It also speeds up the hydrolysis; the limiting step of anaerobic digestion of waste activated sludge. Ultrasound can be used to degas waterbased liquids. Ultrasonic degassing of sewage sludge has not been examined previously. The present study aims to investigate the effect of ultrasound on waste activated sludge as well as the potential of ultrasound to speed up the degassing of digested sludge. A semi-continuous, lab-scale digestion experiment was performed with four reactors: two receiving untreated sludge and two receiving treated sludge. The effect of the sonicator was 420 W and the treatment time was 6 min, which corresponds to an energy input of 8.4 kWh/m³. Total solids (TS) of the waste activated sludge was ~3.5 %. The ultrasonic treatment caused an increase in gas production of 13 %. There was no difference in methane content. The concentration of filterable chemical oxygen demand (fCOD) increased 375 %, or from 2.8 % to 11 % of total COD. In terms of energy loss/gain the increase in gas production resulted in a loss of 2.7 kWh/m³, i.e. more energy is needed to treat the sludge than the potential energy of the increased gas production. However, if the sludge is thickened to a TS >5 %, a net energy gain should be reached. The effect of ultrasound on the degassing of digested sludge was examined in three barrels. The degassing was measured with and without circulation as well as with ultrasonic treatment. The digested sludge had a gas emission rate of 115 L/(m³ day). No direct burst of gas occurred due to ultrasonic treatment. Over two days more gas was emitted from the barrel equipped with ultrasound, probably due to an induced post-digestion. Thus, ultrasonic pretreatment of waste activated sludge increases the biogas yield. It is inconclusive, whether ultrasonic treatment of digested sludge effects the degassing or not.</p>