Poster exhibited at GPSC Student Showcase, February 24th, 2016, University of Arizona. / To make photovoltaics (PV) and concentrated solar thermal power (CSP) more practical forms of alternative energy, creative innovations to current solar energy methods must be employed. The PVMirror – a new technology – is our solution to that problem. The PVMirror combines PV and CSP technologies by splitting the spectrum of sunlight using a dichroic mirror film. Light that is not transmitted to the solar cell is to instead be reflected to a focus, by way of a curved mirror. This hybrid of technologies is competitive, as it is both efficient and affordable compared to many other innovations in renewable energy. The PVMirror is designed to be an easy and cost-effective replacement to the reflectors used in existing CSP plants. Ultimately, we hope to demonstrate this PVMirror technology on a large scale and market it. As validated from interviewing with industry professionals, this technology has the potential to impact the world of solar energy because many industrial companies and utility-scale CSP project developers are interested in pairing CSP and PV to increase efficiency. Currently, using an outdoor sun tracker, we are testing an 18 inch by 18 inch prototype with four solar cells.

Current concentrated solar power plants (CSP) use molten salt at 565°C as a heat transfer and energy storage fluid. Due to thermal energy storage (TES), these solar plants can deliver dispatachable electricity to the grid; however, the levelized cost of electricity (LCOE) for these plants is 12-15 c/kWh, about 2.5 times as high as fossil fuel electricity generation. Molten salt technology limits peak operating temperatures to 565°C and a heat engine efficiency of 40%. Liquid metal (LM), however, can reach >1350°C, and potentially utilize a more efficient (60%) heat engine and realize cost reductions. A 1350 °C LM-CSP plant would require ceramic containment, inert atmosphere containment, additional solar flux concentration, and redesigned internal receiver. It was initially unclear if these changes and additions for LM-CSP were technically feasible and could lower the LCOE compared to LS-CSP. To answer this question, a LM-CSP plant was designed with the same thermal input as a published LS-CSP plant. A graphite internal cavity receiver with secondary concentration heated liquid Sn to 1400°C and transferred heat to a 2-phase Al-Si fluid for 9 hours of thermal energy storage. Input heat to the combined power cycle was 1350°C and had 60% thermal efficiency for a gross output of 168 MW. The cost of this LM-CSP was estimated by applying material cost factors to the designed geometry and scaling construction costs from published LS-CSP estimates. Furthermore, graphite was experimentally tested for reactivity with liquid Sn, successful reaction bonds, and successful mechanical seals. The result is switching to molten metal can reduce CSP costs by 30% and graphite pipes, valves, and seals are possible at least at 400°C.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Most rural African villages enjoy high levels of sunlight, but rolling out solar power generation technology to tap into this renewable energy resource at remote rural sites in Africa pose a number of design challenges. To meet these challenges, a project has been initiated to design, build and test/evaluate a knock down 3 kW peak electrical stand-alone self-tracking dual-axis concentrating solar power system. This study focusses on the mechatronic engineering aspects in the design and development of a dynamic mechatronic platform and digital electronic control system for the stand-alone concentrating solar power system. Design specifications require an accurate automatic positioner and control system for a motorized parabolic solar reflector with an optical solar harnessing capacity of 12 kWt at solar noon. It must be suitable for stand-alone rural power generation. This study presents a conceptual design and engineering prototype of a balanced cantilever tilt-and-swing dual-axis slew drive actuation means as mechatronic solar tracking mobility platform for a ∼12 m2 lightweight parabolic solar concentrator. Digital automation of the concentrated solar platform is implemented using an industrial Siemens S7-1200 programmable logic controller (PLC) with digital remote control interfacing, pulse width modulated direct current driving, and electronic open loop/closed loop solar tracking control. The design and prototype incorporates off-the-shelf components to support local manufacturing at reduced cost and generally meets the goal of delivering a dynamic mechatronic platform for a concentrating solar power system that is easy to transport, assemble and install at remote rural sites in Africa. Real-time experiments, conducted in the summer of South Africa, validated and established the accuracy of the engineering prototype positioning system. It shows that the as-designed and -built continuous solar tracking performs to an optical accuracy of better than 1.0◦ on both the azimuth and elevation tracking axes; and which is also in compliance with the pre-defined design specifications. Structural aspects of the prototype parabolic dish are evaluated and optimized by other researchers while the Stirling and power handling units are under development in parallel projects. Ultimately, these joint research projects aim to produce a locally manufactured knock down do-it-yourself concentrated solar power generation kit, suitable for deployment into Africa. / AFRIKAANSE OPSOMMING: Landelike gebiede in Afrika geniet hoë vlakke van sonskyn, maar die ontwerp van betroubare sonkrag tegnologie vir die benutting van hierdie hernubare energie hulpbron by afgeleë gebiede in Afrika bied verskeie uitdagings. Om hierdie uitdagings te oorkom, is ’n projek van stapel gestuur om ’n afbreekbare 3 kW piek elektriese alleenstaande selfaangedrewe dubbel-as son-konsentreeder te ontwerp, bou en te toets. Hierdie studies fokus op die megatroniese ingenieurs-aspekte in die ontwerp en ontwikkeling van ’n dinamiese megatroniese platform en ’n digitale elektroniese beheerstelsel vir die alleenstaande gekonsentreerde sonkrag stelsel. Ontwerp spesifikasies vereis ’n akkurate outomatiese posisionering en beheer stelsel vir ’n motor aangedrewe paraboliese son reflekteerder met ’n optiesekollekteer- kapasiteit van 12 kWt by maksimum sonhoogte, en veral geskik wees vir afgeleë sonkrag opwekking. Hierdie studie lewer ’n konsepsuele ontwerp en ingenieurs-prototipe van ’n gebalanseerde dubbelas swaai-en-kantel swenkrat aandrywingsmeganisme as megatroniese sonvolg platform vir ’n ∼12 m2 liggewig paraboliese son konsentreerder. Digitale outomatisering van die son konsentreerder platform is geimplementeer op ’n industriële Siemens S7-1200 programmeerbare logiese beheerder (PLB) met ’n digitale afstandbeheer koppelvlak, puls-wydte-gemoduleerde gelykstroom aandrywing en elektroniese ooplus en geslote-lus sonvolg beheer. Die ontwerp en prototipe maak gebruik van beskikbare komponente om lae-koste plaaslike vervaardiging te ondersteun en slaag in die algemeen in die doel om ’n dinamiese megatroniese platform vir ’n gekonsentreerde sonkrag stelsel te lewer wat maklik vervoer, gebou en opgerig kan word op afgeleë persele in Afrika. Intydse eksperimente is gedurende die somer uitgevoer om die akkuraatheid van die prototipe posisionering sisteem te evalueer. Dit toon dat die sisteem die son deurlopend volg met ’n akkuraatheid beter as 1.0◦ op beide die azimut en elevasie sonvolg asse, wat voldoen aan die ontwerp spesifikasies. Strukturele aspekte van die prototipe paraboliese skottel word deur ander navorsers geëvalueer en verbeter terwyl die Stirling-eenheid en elektriese sisteme in parallelle projekte ontwikkel word. Die uiteindelike doel met hierdie groepnavorsing is om ’n plaaslik vervaardigde doen-dit-self sonkrag eenheid te ontwikkel wat in Afrika ontplooi kan word.

An experimental investigation is presented on a novel High Temperature Falling Particle Receiver for Concentrated Solar Power (CSP) to quantify the extent of erosion of the receiver structural materials by the flowing particulate matter. The current receiver design uses a series of metal wire mesh screens to slow down the particulate flow through the receiver in order to increase their residence time thereby achieving the desired temperature rise within the receiver without the need for particulate recirculation. The solid particulates are gravity fed through the receiver where they absorb the incident thermal energy before flowing to a high temperature storage bin upstream of a heat exchanger where the heat stored in the particulate material is transferred to the working fluid for the power cycle. To assess the effective life of the receiver, this experimental investigation is undertaken. This thesis includes the development of an apparatus to test wire meshes under high temperature and particle abrasion conditions, and the presentation and analysis of these results.

Les matériaux vitreux mous (émulsion concentrée, mousse, suspension concentrée...) présentent un comportement rhéologique entre solide et liquide. Aux petites contraintes le système reste élastique, mais au-dessus d’une contrainte seuil, le système s’écoule comme un liquide visqueux. Ce comportement se trouve dans de nombreux fluides industriels comme dans les cosmétiques, l’agro-alimentaire ou encore le béton. Une contrainte seuil n’apparait que au dessus d’une certaine fractions volumique. Au dessus de cette fraction les particules se bloquent entre elle, la relaxation n’est plus possible et l’écoulement devient fortement coopératif.Cette coopérativité influe sur la rhéologie à petite échelle, Quand le confinement devient de l’ordre de quelques particules, la viscosité ne dépend plus uniquement, comme habituellement, de la contrainte locale mais aussi de la contrainte au voisinage. C’est ce qu’on appelle rhéologie non-localeJ’ai étudié expérimentalement ce comportement en utilisant les outils de micro fluidiques. J’ai étudié une micro-émulsion concentrée s’écoulant dans un microcanal en observant directement l’écoulement des gouttes avec un microscope confocal. Les résultats sont comparés au model “Kinetic-Elasto-Plastic” de Bocquet et al. 2009 et à des simulations de dynamique moléculaire. / Soft glassy materials (concentrated emulsion, foams, concentrated suspension…) present rheological properties between solids and liquid. Under small stress they stay elastic but at stress higher than a yield stress they begin to flow as a liquid. Those fluids are used in cosmetics, food industry or building materials as concrete. The yield stress behavior only appears when the volume fraction is high enough, where the particles are blocked by their neighbors. So the systems cannot relax and the flow become highly cooperative.This cooperativity impacts the rheology at small scale. When the confinement is of the order of few particles, the viscosity does not only depend on the local stress as usually but also on the stress in the neighborhood. This is called non-local rheology.I studied experimentally this behavior by flowing concentrated emulsion in a microchannel and observing directly the flow of the droplet with a confocal microscopy. The results from these microfluidics experiments are compared to predictions of the Kinetic Elasto Plastic model of Bocquet et al. 2009 and molecular dynamic simulation of jammed soft particles.

Este trabalho teve por objetivo a utilização de xarope de milho na elaboração de cerveja super concentrada. Para atingir este propósito foram realizados ensaios em escala de 5 litros, testando três proporções quanto à relação de extrato de malte e de xarope de milho. Para seguir a legislação brasileira de acordo com o Decreto 6.871, de 2009, foram propostos para a realização dos experimentos as proporções de 70/30, 55/45 e 20/80 de malte:xarope de milho. Na proporção 20/80, definida pelo referido Decreto como cerveja de milho foram avaliadas diferentes variantes para obter diferentes concentrações alcoólicas, obtendo resultados inadequados. As fermentações foram conduzidas em regime descontínuo alimentado, com a adição do xarope por cargas, e foi utilizada uma levedura com alta eficiência fermentativa que tem demonstrado alta tolerância a concentrações de álcool, classificada como PPB - 01. Para comparar com os mostos experimentais, foram elaborados mostos padrões nas proporções 70/30 e 55/45. Em escala piloto foi elaborada uma prova de cerveja super concentrada, para as proporções 70/30 e 55/45, malte/milho. Foram avaliados os parâmetros cinéticos dos processos. As eficiências de formação de álcool e de consumo de extrato foram acima dos 90%, o que garantiu um bom processo fermentativo. As cervejas obtidas na escala piloto foram submetidas a análises sensoriais e comparadas com uma cerveja comercial, obtendo ótimos resultados. As duas proporções aprovadas proporcionaram economia de energia térmica e elétrica, quando comparadas com as cervejas padrões. Os resultados obtidos no projeto demonstraram que é possível a aplicação desta tecnologia, aumentando a produtividade utilizando os mesmos equipamentos e obtendo benefícios energéticos, econômicos e meio ambientais. / The aim of this project was the use of corn syrup to develop super concentrated beer. Accomplishing this purpose was made initially two repeat experiments on a scale of 5 liters and testing three variants as regards the relationship of malt extract and corn. Following the Brazilian law in accordance with the Decree 6.871, 2009, was proposed for the realization of experiments the proportions of 70/30, 55/45 and 20/80 from malt and corn. In the proportion 20/80, defined by Decree as corn beer, were evaluated different variants for obtaining different alcohol concentrations, obtaining inadequate results. Fermentations were conducted in fed batch regime with the addition of the syrup in pulses, and was used one yeast with high efficiency of fermentation and tolerating of alcohol high concentrations, classified as PPB - 01. To compare with the experimental worts, were prepared standards worts for proportions 70/30 and 55/45. In pilot scale, were made experiments of super concentrated beer to the proportions 70/30 and 55/45, malt/corn. The kinetic parameters of the processes were evaluated. The efficiencies of formation of alcohol and consumption of extract were above 90%, which ensured a good fermentation. The experimental beers obtained in pilot scale were subjected to sensory analysis compared with a beer sold in trade, getting great results. The two proportions approved had saving thermal and electrical energy, when compared with standards beers. The results obtained in the project demonstrated that it is possible to apply this technology, increasing equipment productivity and getting energy, economic and environmental benefits.

Vinte e quatro cordeiros machos não castrados, Santa Inês x Dorper, com aproximadamente 90 dias de idade e peso vivo médio inicial de 27,0 ± 4,4kg, foram alimentados com uma dieta com elevada proporção de concentrado com 20% de pelete proteico-mineral (Grano Entero®), 5% de feno de capim coast cross e 75% de milho, na forma de milho grão inteiro (MGI), milho grão moído (MGM) ou milho grão úmido (MGU). Os animais foram distribuídos em um delineamento em blocos ao acaso, de acordo com o peso vivo inicial, com três tratamentos e oito repetições. Os alimentos e as sobras foram pesados diariamente e os animais, a cada 14 dias, sem jejum de alimentos ou água. Após 65 dias de confinamento, os animais foram abatidos com peso vivo médio final (PVF) de 47,97 ± 5,13kg e obteve-se o peso de carcaça quente (PCQ), o pH (pH1h) e a temperatura (T1h). Após 24 horas de refrigeração, o peso de carcaça fria (PCF), o pH (pH24h) e a temperatura (T24h) foram novamente aferidos. As carcaças foram serradas entre a 12ª e 13ª costelas para a realização das medidas na carcaça de área de olho de lombo (AOL) e espessura de gordura subcutânea (EGS). Três amostras do músculo Longissimus dorsi de cada animal foram coletadas, para as análises de maciez, cor e perda por cocção (PAC). Os efeitos dos tratamentos foram analisados usando-se o procedimento GLM do SAS®. O ganho de peso médio diário e a eficiência alimentar (kg ganho/kg IMS) não diferiu (P>0,05) entre as dietas, com média de 0,33kg e 0,28kg, respectivamente. Não houve diferença (P>0,05) entre os tratamentos, quanto à ingestão diária de matéria seca em kg (1,20kg) ou em percentagem de peso vivo (3,17%). Em relação ao PCQ, animais que receberam MGM apresentaram diferenças de peso das carcaças (P<0,05) em relação aos animais que receberam MGU, e semelhança de pesos com os animais que receberam MGI com respectivas médias de 23,90 kg, 21,35 kg e 23,15 kg. O rendimento de carcaça quente (47,5%), rendimento de carcaça fria (46,25%), a AOL (15,6cm2) e EGS (2,7mm) também não foram afetados pelos tratamentos. Observou-se aumento (P<0,05) do PCF nos animais que receberam MGM e MGI, quando comparados aos animais que receberam MGU, com médias de 22,97kg, 22,84kg e 20,81kg. Não foram observadas diferenças (P>0,05) para as variáveis qualitativas de maciez, cor e PAC. O processamento dos grãos de milho não teve influência acentuada sobre as características de desempenho ou de carcaça, exceto para PVF, PCQ e PCF. No entanto, o MGI apresentou ganho de peso significativo em relação aos outros tratamentos, além de ser mais prático na sua utilização não apresentando despesas de processamento. / Twenty four Santa Inês x Dorper crossbred not castrated lambs, approximately 90 days old and average initial weight of 27.07 ± 4.36kg were fed a high concentrate diet 20% protein-mineral pellet (Grano Entero®), 5% coast cross hay and 75% corn as whole corn grain (WCG), grounded corn grain (GCG) or high moisture corn (HMC). The animals were assigned to a randomized block design. Feed and orts were weighted daily and each 14 days the animals were also weighed. After 65 days feeding the animals were slaughtered with an average final weight (AFW) of 47.97 ± 5.13kg and hot carcass weight (HCW), pH (pH1h) and temperature (T°1h) were measured. After 24 hours of chilling the cold carcass weight (CCW), pH (pH24h) and temperature (T°24h) were again measured, thus obtaining the hot carcass yield (HCY) and cold carcass yield (CCY). The carcasses were ribbed between 12th and 13th ribs to measure the loin eye area (LEA) and the subcutaneous fat thickness (SFT). Three samples of the Longissimus muscle of each animal were collected for analyzes of tenderness, color and weight loss due to cooking (WLC). Effects of treatments were analyzed using the GLM procedure of SAS®. The average daily weight gain and feed efficiency (kg gain/kg DMI) of the animals did not differ between diets (P>0.05), with an average of 0.33kg and 0.28kg, respectively. There was no difference between treatments (P>0.05) for DMI in kg (mean = 1.20) or when expressed as a percentage of live weight (mean=3.17 %). In relation to the CCW, animals that received GCG had greater carcass weight (P<0.05) compared to animals receiving HMC, and similar weights with animals receiving WCG with respective averages of 23.90kg, 21.35 and 23.15kg. Treatments WCG and HMC did not differ among themselves. HCY (mean=47.5%), CCY (mean=46.25%), LEA (mean=15.6cm2) and SFT (mean=2.7mm) were not affected by treatments. The same result was observed for cold carcass weight (P<0.05), averaging 22.97kg, 22.84kg and 20.81kg. There were no differences (P>0.05) for qualitative variables of softness, color and WLC. Corn grain processing had no influence on the performance or carcass characteristics except for AFW, HCG and CCY. However, whole corn showed significant weight gain compared to other treatments, since it has no processing expenses.

Há décadas a energia solar atrai pesquisadores de todo o planeta devido ao seu enorme potencial de aplicações como fonte de energia térmica. Com a crescente preocupação com o Meio Ambiente e a busca por fontes renováveis de energia, o interesse pelo aproveitamento da energia proveniente do Sol cresceu ainda mais. Apesar de desafios como a intermitência e a sazonalidade solares, e a dificuldade de transporte desta forma de energia, a busca por técnicas de armazenamento visa mitigar estes problemas. Uma alternativa termoquímica é a produção de combustíveis solares, ou seja, combustíveis obtidos por meio do uso da energia concentrada do Sol que possam ser estocados e transportados para onde e quando houver demanda de energia. Uma aplicação de destaque neste tema é a gaseificação de biomassa para a produção de gás de síntese (CO + H2). A gaseificação visa aumentar o potencial energético da biomassa sólida ou líquida ao realizar uma reação endotérmica que transfere a energia acumulada do Sol (por meio de concentradores) para as ligações químicas, com a recombinação dos átomos na forma de gás de síntese. Este gás, além do seu maior poder calorífico, é matéria-prima para muitos processos da indústria química. Desta forma, o objetivo desta reação é obter um combustível mais homogêneo e de fácil manuseio. A gaseificação é uma alternativa importante para o aproveitamento energético da biomassa, pois esta é normalmente bastante heterogênea. Sendo assim, o uso de gaseificadores viabiliza o uso de madeira, resíduos urbanos e agrícolas e outras matérias orgânicas como fontes de energia. Assim, este trabalho apresenta um estudo da utilização de concentradores solares para o processo de gaseificação de biomassa e a concepção de um reator químico solar para operação em escala laboratorial para a sequência dos estudos neste campo de pesquisa. Por meio de uma modelagem térmica, o trabalho destaca a viabilidade técnica da gaseificação solar de biomassa, comprovando um ganho energético e uma redução das emissões de gás carbônico em comparação com a queima direta da biomassa. Por fim, são apresentados os parâmetros de construção e operação de um gaseificador de pequena escala. / From decades, solar energy has instigated researchers worldwide due to its enormous potential. With raising concern for the environment and the search for renewable energy sources, the interest in using the Sun as a power supply grew even more. Despite challenges as the solar seasonality and intermittence, and difficulties transport its energy, innovative storage techniques aim to mitigate those issues. A thermochemical alternative is the production of solar fuels - fuels obtained from concentrated solar power (CSP) - which can be stocked and transported to the time and place there is demand. A forthcoming application in this field is biomass steam-gasification for syngas production (CO + H2). Gasification increases the thermal potential of liquid and solid biomass by means of an endothermic reaction that transfers solar energy (via radiation concentrators) to chemical bonds, re-combining the atoms as syngas (hydrogen and carbon monoxide). This gas mixture, besides its thermal potential, is a raw material for numerous processes in chemical industry. The purpose of this process is to obtain a fuel more homogenous and easy to manipulate. The gasification is an important alternative to biomass energy use, once it is generally heterogeneous. Thus, gasifiers enable the use of wood, algae, solid waste, agricultural byproducts, and other organic matter as power supplies. Therefore, this project presents the study of solar concentrators use in the steamgasification of biomass and the conception of a solar chemical reactor for laboratoryscale tests for the future steps of the research in this field. Models and bibliographic references points to the technical feasibility of solar steam-gasification of biomass, verifying a significant energy gain and carbon emission reduction comparing to direct burn of biomass. Ultimately, the dissertation presents the constructive and operational parameters of a small-scale gasifier.

Aditivos são amplamente utilizados em dietas ricas em concentrado para prevenir distúrbios metabólicos. A alga calcária, Lithothamnium calcareum, produto natural e renovável, fonte de carbonato de cálcio, pode ser uma alternativa na prevenção destes distúrbios. Este estudo foi desenvolvido para avaliar o efeito das fontes de cálcio, com ou sem monensina sódica na dieta, no controle da acidose ruminal de bovinos Nelore recebendo de forma abrupta uma dieta com elevada proporção (92,3%) de concentrado. Oito bovinos portadores de cânulas ruminais foram distribuídos em um delineamento quadrado latino (4x4) duplo. Os tratamentos foram a adição a dieta base com diferentes fontes de cálcio, calcário calcítico (CC) ou produto a base de alga calcária (AC), com (CMO) ou sem (SMO) a presença de monensina. A inclusão de CC, AC e monensina foi, respectivamente, de 7,1 g/kg, 7,4 g/kg e 30 mg/kg MS. Não houve efeito das fontes de cálcio e da monensina sobre o consumo alimentar e concentração total dos ácidos graxos de cadeia curta. Os tratamentos com AC resultaram em maior pH ruminal médio (P=0,039), menor tempo com pH ruminal abaixo de 5,2 (P<0,001) e um maior pH sanguíneo (P=0,006). Os tratamentos com monensina apresentaram menor tempo com pH ruminal abaixo de 5,2 (P=0.023). O produto a base de alga calcária pode ser uma boa alternativa para prevenir distúrbios metabólicos em animais submetidos a mudanças abruptas para dietas com elevada proporção de concentrado. / Additives are used in high concentrate diets in order to prevent metabolic disorders. Calcareous algae (Lithothamnium calcareum), a natural and renewable product, may be an alternative to prevent these disorders. This study was designed to evaluate the effect of calcium sources and monensin in the control of ruminal acidosis of Nellore cattle, abruptly fed a high (92.3%) concentrate diet. Eight cannulated steers were randomly assigned to a doubled 4x4 Latin square design. The treatments were the inclusion of different sources of calcium to the basic diet, limestone or calcareous algae, with or without the presence of monensin. The inclusion of limestone, calcareous algae and monensin was, respectively, 7.1 g/kg, 7.4 g/kg and 30mg/kg DM. There was on effect of calcium source (P=0.607) and monensin (P=0.294) on feed intake and in the short chain fatty acids concentration. Treatments with calcareous algae based product resulted in greater ruminal pH mean (P=0.039), lower time rumen pH remained below 5.2 (P<0.001) and better control of blood pH (P=0.006). Treatments with the presence of monensin also resulted in lower time of rumen pH below 5.2 (P=0.023). Calcareous algae may be an alternative to be used in pH control of beef cattle fed high concentrate diets.

Com o objetivo de estudar o uso de inóculo de fezes em substituição do conteúdo ruminal de bubalinos na técnica in vitro de produção de gases, este presente trabalho comparou as avaliações realizadas em três ensaios. Foram utilizados três bubalinos da raça Mediterrâneo, machos, adultos, castrados, fistulados no rúmen com média de peso vivo de 450 (± 18,7) kg. Estes animais receberam uma dieta basal, composta de silagem de milho (70%) e concentrado (30%). Estes animais foram os doadores dos 2 tipos de inóculos, que foram conteúdo ruminal (CR) e fezes. O primeiro ensaio realizado foi com alimentos concentrados: grão de milho, farelo de soja, farelo de trigo e farelo de algodão; o segundo ensaio foi com leguminosas forrageiras: alfafa (Medicago sativa L. ), estilosantes pioneiro (Stylosanthes macrocephala cv. Pioneiro), soja perene (Neonotonia wightii) e leucena (Leucaena leucocephala); e o terceiro e último ensaio foi realizado com gramíneas forrageiras: capim braquiarão (Brachiaria brizantha cv. Marandu), capim buffel (Cenchrus ciliaris L. cv. Biloela), estrela africana (Cynodon plectostachyus) e capim mombaça (Panicum maximum Jacq. cv. Mombaça). Os valores médios obtidos de produção potencial de gases em cada ensaio foram menores (P<0,05) para as amostras fermentadas com inóculos de fezes que com conteúdo ruminal, sendo respectivamente, para concentrados (140,23 e 194,08 mL.g-1MS), gramíneas (161,99 e 230,25 mL.g-1MS) e leguminosas (141,78 e 170,70 mL.gm-1MS). Conclui-se que inóculos de fezes não apresentam condições satisfatórias para substituição do inóculum com conteúdo ruminal para uso na técnica de produção in vitro de gases. / In order to study the use of faeces as inoculum as alternative for buffalo rumen contents in the in vitro gas production technique, the present work evaluations of three tests. We used three Mediterranean buffalos, male, adult, neutered, fistulated in the rumen, with an average live weight of 450 (± 18.7) kg. These animals received a basal diet composed of corn silage (70%) and concentrated (30%). These buffalo were the donors of the two types of inocula, rumen content (CR) and faeces. The first test was carried out with concentrate foods: corn grain, soybean meal, wheat bran and cottonseed meal, the second test was with legumes: alfalfa (Medicago sativa L. ), Pioneiro estilo (Stylosanthes macrocephala cv. Pioneiro) , perennial soybean (Neonotonia wightii) and leucaena (Leucaena leucocephala) and the third and last test was carried out with grasses: Marandu grass (Brachiaria brizantha cv. Marandu), buffel grass (Cenchrus ciliaris L. cv. Biloela), African Star grass (Cynodon plectostachyus) and Mombasa grass (Panicum maximum Jacq. cv. Mombasa). The average values of potential production of gas in each test were lower (P<0.05) for samples fermented with an inoculum of faeces with rumen contents, being respectively, for concentrates (140.23 and 194.08 mL.g-1MS), grasses (161.99 and 230.25 mL.g-1MS) and legumes (141.78 and 170.70 mL.g-1MS). It follows that fecal inoculum unsatisfactory condition for replacing the inoculum with rumen technique for use in the in vitro production of gases technique.