The lowland areas of the southern part of Rio Grande do Sul are predominantly cultivated with border irrigated rice in the continuous flooding system. This irrigation method is characterized by low water use efficiency and high greenhouse gas emissions. Given the current scenario of climate change and water scarcity, the seek for alternative irrigation methods and/or systems that are efficient in the water use, that promote high yield and quality of the grains produced, as well as provide a reduction in gas emissions greenhouse effect has been a constant challenge to research and the productive sector. In this sense, border irrigation methods in intermittent flooding and sprinkler systems emerge as alternatives to traditional flood irrigation, aiming to reduce water use and lessen environmental impact. Although these irrigation methods can promote a reduction in water use, plants can be affected by the reduction in water availability. When associated with conditions of high evapotranspiration demand, they can cause morphophysiological changes in rice plants, promoting a reduction in their growth and development, with effects on the yield and quality of the crop's grains. Thus, the present study aimed to evaluate the agronomic performance and morphophysiological modifications of rice varieties subjected to different irrigation methods and systems, as well as their influence on irrigation water productivity (Chapter I); evaluate yield components and grain quality of rice varieties subjected to irrigation methods and systems (Chapter II), as well as the influence of irrigation methods and systems on methane and nitrous oxide emissions, global warming partial potential and the relation with grain yield of irrigated rice varieties (Chapter III). For this, experiments were carried out in the 2019/20 and 2020/21 growing seasons in the lowlands didactic-experimental area at the Federal University of Santa Maria. As the main results obtained, it was verified that intermittent irrigation provides a reduction in the use of water without harming the productivity and quality of rice grains. However, due to the intensity of the intermittence used, the emission of methane and nitrous oxide were not affected, being the PAGp/PG similar to that verified by continuous irrigation. Sprinkler irrigation promotes reduced water use, however, with a reduction in shoot and root dry matter accumulation, nutrient accumulation, parameters related to photosynthesis, number of grains per panicle and grain yield. In addition, sprinkler irrigation had a higher percentage of opaque and plastered grains and reduced whole grain rice yield. As for the emission of greenhouse gases, the sprinkler provided a reduction in the emission of methane from the soil in rice cultivation, however, it increased the emissions of nitrous oxide. Variety IRGA 431 CL provides reduced water use and higher irrigation water productivity, without harming grain yield with lower percentage of opaque and plastered grains and higher whole grain rice yield than variety IRGA 424 RI. The fluxes and total emission of methane and nitrous oxide, as well as the partial global warming potential were not influenced by rice varieties, containing similar values of PAGp/PG. | As áreas de terras baixas da metade Sul do Rio Grande do Sul são predominantemente cultivadas com a cultura do arroz irrigado por superfície no sistema de inundação contínua. Esse método de irrigação se caracteriza pela baixa eficiência do uso da água e elevada emissão de gases de efeito estufa. Diante do atual cenário de mudanças climáticas e escassez de água, a busca por métodos e/ou sistemas de irrigação alternativos que sejam eficientes quanto ao uso da água, que promovam elevado rendimento e qualidade dos grãos produzidos, bem como proporcionem redução da emissão de gases de efeito estufa tem sido um desafio constante à pesquisa e ao setor produtivo. Nesse sentido, a irrigação por superfície no sistema de inundação intermitente e por aspersão surgem como alternativas à tradicional irrigação por inundação, visando a redução do uso de água e menor impacto ambiental. Embora esses métodos de irrigação possam promover redução do uso da água, as plantas podem ser afetadas negativamente pela redução da disponibilidade hídrica. Quando associada a condições de elevada demanda evapotranspirativa, a redução na disponibilidade de água provocada por práticas alternativas de irrigação, podem provocar alterações morfofisiológicas em plantas de arroz, promovendo redução do seu crescimento e desenvolvimento, com reflexos sobre o rendimento e a qualidade de grãos da cultura. Dessa forma, o presente estudo teve como objetivo avaliar o desempenho agronômico e as modificações morfofisiológicas de cultivares de arroz submetidas a diferentes métodos e sistemas de irrigação, bem como sua influência sob a produtividade da água de irrigação (Capítulo I); avaliar os componentes do rendimento e a qualidade de grãos de cultivares de arroz submetidas a métodos e sistemas de irrigação (Capítulo II), bem como a influência de métodos e sistemas de irrigação sobre as emissões de metano e de óxido nitroso, o potencial de aquecimento global parcial e a relação com a produtividade de grãos de cultivares de arroz irrigado (Capítulo III). Para isso, foram conduzidos experimentos nas safras 2019/20 e 2020/21 na área didático-experimental de terras baixas da Universidade Federal de Santa Maria. Como principais resultados obtidos, verificou-se que a irrigação intermitente proporciona redução do uso de água sem prejuízo a produtividade e a qualidade de grãos de arroz. Todavia, devido a intensidade da intermitência utilizada, a emissão de metano e óxido nitroso não foram afetadas, sendo o PAGp/PG semelhante ao verificado pela irrigação contínua. A irrigação por aspersão promove redução do uso de água, no entanto, com redução do acúmulo de matéria seca da parte aérea e de raiz, do acúmulo de nutrientes, dos parâmetros relacionados à fotossíntese, do número de grãos por panícula e da produtividade de grãos. Além disso, a irrigação por aspersão obteve maior percentual de grãos opacos e gessados e reduziu o rendimento de grãos inteiros de arroz. Quanto a emissão de gases de efeito estufa, a aspersão proporcionou a redução da emissão de metano do solo em cultivo de arroz, porém, potencializou as emissões de óxido nitroso. A cultivar IRGA 431 CL proporciona redução do uso de água e maior produtividade da água de irrigação, sem prejuízo a produtividade de grãos, com menor percentual de grãos opacos e gessados e maior rendimento de grãos inteiros quando comparado a cultivar IRGA 424 RI. Os fluxos e a emissão total de metano e óxido nitroso, bem como o potencial de aquecimento global parcial não foram influenciados pelas cultivares de arroz, contendo valores semelhantes de PAGp/PG.

Resumen El propósito de este trabajo fue analizar la viabilidad técnica y económica del uso de un calentador comercial que funciona con biogás para obtener el agua caliente necesaria en el saneamiento del área de ordeño o para calentar la leche que alimenta a los becerros en establos de La Comarca Lagunera, México. Es una alternativa económica y sostenible a la práctica generalizada de usar resistencias eléctricas o gas licuado de petróleo (GLP) que genera un gasto de aproximadamente $300 000.00 pesos por año. Las características del calentador comercial adquirido se determinaron utilizando diversas ecuaciones de transferencia de calor. El análisis económico de la inversión se realizó a un plazo de cinco años utilizando indicadores que toman en cuenta el valor del dinero a través del tiempo como el valor presente neto, la tasa interna de retorno y la relación beneficio-costo. En las corridas experimentales se mantuvo la energía necesaria para el calentamiento del agua y una combustión eficiente. Se mostró la viabilidad técnica de la propuesta al no rechazar la hipótesis nula de igualdad de medias (p> 0.05) de las 45 muestras lo que implica una consistencia en los tiempos de calentamiento. El análisis financiero, en sus diferentes indicadores VAN, TIR y R B/C, mostró valores en rangos de aceptación del proyecto. Con esta solución se reduce la emisión de gases efecto invernadero y los costos de producción en las operaciones. La opción del empleo del biogás, es viable técnica y económicamente. | Abstract The purpose of this work was to analyze the technical and economic feasibility of using a commercial heater that works with biogas to obtain the necessary hot water in the sanitation of the milking area or to heat the milk that feeds the calves in stables of the Comarca Lagunera, Mexico. It is an economic and sustainable alternative to the widespread practice of using electrical resistors or liquefied petroleum gas (LPG) that generates an expense of approximately $300 000.00 pesos per year. The characteristics of the commercial heater acquired were determined using various heat transfer equations. The economic analysis of the investment was carried out over a period of five years using indicators that take into account the value of money over time such as the net present value, the internal rate of return and the cost-benefit ratio. In the experimental test, the energy required for water heating and efficient combustion was maintained. The technical feasibility of the proposal was shown by not rejecting the null hypothesis of equality of means (p> 0.05) of the 45 samples, which implies a consistency in the heating times. The financial analysis, in its different indicators NPV, IRR and R B/C, showed values in project acceptance ranges. This solution reduces the emission of greenhouse gases and production costs in operations. The option of using biogas is technically and economically viable.

Proper management of irrigation in flooded rice contributes to high levels of grain quality and yield. However, the flood irrigation system, which is predominant in Rio Grande do Sul, by the volume of water used, provides low water use efficiency and due to the long period of flooding causes a great methane emission. In this context, an early irrigation withholding can be an alternative for saving water in the crop season and reduce greenhouse gas emissions. Likewise, post-harvest management of the area affects environmental impact, such as greenhouse gas emissions as well as contamination of water sources. Thus, the present study aims to evaluate the physical and physiological quality of seeds and grains, as well as the physicochemical properties of water (Article I), besides to evaluate greenhouse gas emissions and water quality in function of drainage periods after post-harvest management (Article II). The experiment I was conducted in a field in two municipalities of Rio Grande do Sul. In Cachoeira do Sul at the Estação de Pesquisa do Instituto Riograndense do Arroz (2017/18 and 2018/19 crop season), and in Santa Maria (2018/19 crop season) in the lowland experimental area of the Federal University of Santa Maria (UFSM). The treatments were composed by irrigation withholding moments (R4, 7, 14, 21, 28 and 35 days after R4), in an experimental randomized complete block design with four replications. Experiment II was conducted in Santa Maria after rice harvest, with an experimental randomized complete block design and with different water drainage moments after the knife roller (0, 3, 6, 9 and 12 days) and a treatment with harvest in dry land. Based on the main results achieved, we can observe that irrigation withholding at 14 days after flowering does not affect the physiological quality of seeds, as well as the physical quality and grain yield, and in the case of drainage, it reduces nutrient loss and total solids. During off-season, drainage performed for three days after the use of the knife roller reduces potassium loss and soil particle through drainage water, the shorter period of flooding reduces CH4 emission as well the global warming potential. The rate of decomposition of plant residues is accelerated by the incorporation of straw into the soil, but it is harmed by high rainfall volumes. | Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES | O manejo adequado da irrigação da lavoura de arroz contribui para elevados níveis de produtividade e qualidade de grãos. No entanto, o sistema de irrigação predominante no Rio Grande do Sul apresenta baixa eficiência do uso da água. Neste contexto, a supressão antecipada da irrigação pode ser uma alternativa para economia de água e redução da emissão de gases de efeito estufa. Da mesma forma, o manejo pós-colheita da área influencia no impacto ambiental, pela emissão de gases de efeito estufa e pela contaminação de mananciais hídricos. Assim, o presente trabalho tem como objetivo avaliar a qualidade física e fisiológica de sementes e grãos, bem como as propriedades físico-química da água em momentos de supressão da irrigação (experimento e artigo I), além de avaliar a emissão de gases do efeito estufa e a qualidade da água em função do momento de drenagem após manejo pós-colheita (experimento e artigo II). O experimento I foi conduzido a campo em dois municípios do Rio Grande do Sul. Em Cachoeira do Sul, na estação de pesquisa do Instituto Riograndense do Arroz (safras 2017/18 e 2018/19) e em Santa Maria (safra 2018/19), na área didático-experimental de várzea da UFSM. Os tratamentos foram compostos por momentos de supressão da irrigação (R4, 7, 14, 21, 28 e 35 dias após R4), em delineamento experimental de blocos ao acaso, com quatro repetições. O experimento II foi conduzido em Santa Maria após a colheita do arroz, com delineamento experimental de blocos ao acaso com quatro repetições, e os tratamentos utilizados foram momentos de drenagem da água após passagem do rolo-faca (0, 3, 6, 9 e 12 dias) e um tratamento com colheita no seco. A supressão da irrigação realizada aos 14 dias após a floração não prejudica a qualidade fisiológica de sementes bem como a qualidade física e o rendimento de grãos e, em caso de drenagem, esta realizada aos 14 dias após R4 reduz a perda de nutrientes e sólidos suspensos totais na água. Durante a entressafra, a drenagem realizada aos três dias após a utilização do rolo-faca reduz a perda de potássio e partículas de solo via água de drenagem menor período de permanência de lâmina reduz a emissão de CH4 e o potencial de aquecimento global. A taxa de decomposição de resíduos vegetais é acelerada pela incorporação da palha no solo, no entanto é prejudicada por altos volumes de precipitação.

Resumen El propósito de este trabajo fue analizar la viabilidad técnica y económica del uso de un calentador comercial que funciona con biogás para obtener el agua caliente necesaria en el saneamiento del área de ordeño o para calentar la leche que alimenta a los becerros en establos de La Comarca Lagunera, México. Es una alternativa económica y sostenible a la práctica generalizada de usar resistencias eléctricas o gas licuado de petróleo (GLP) que genera un gasto de aproximadamente $300 000.00 pesos por año. Las características del calentador comercial adquirido se determinaron utilizando diversas ecuaciones de transferencia de calor. El análisis económico de la inversión se realizó a un plazo de cinco años utilizando indicadores que toman en cuenta el valor del dinero a través del tiempo como el valor presente neto, la tasa interna de retorno y la relación beneficio-costo. En las corridas experimentales se mantuvo la energía necesaria para el calentamiento del agua y una combustión eficiente. Se mostró la viabilidad técnica de la propuesta al no rechazar la hipótesis nula de igualdad de medias (p> 0.05) de las 45 muestras lo que implica una consistencia en los tiempos de calentamiento. El análisis financiero, en sus diferentes indicadores VAN, TIR y R B/C, mostró valores en rangos de aceptación del proyecto. Con esta solución se reduce la emisión de gases efecto invernadero y los costos de producción en las operaciones. La opción del empleo del biogás, es viable técnica y económicamente. | Abstract The purpose of this work was to analyze the technical and economic feasibility of using a commercial heater that works with biogas to obtain the necessary hot water in the sanitation of the milking area or to heat the milk that feeds the calves in stables of the Comarca Lagunera, Mexico. It is an economic and sustainable alternative to the widespread practice of using electrical resistors or liquefied petroleum gas (LPG) that generates an expense of approximately $300 000.00 pesos per year. The characteristics of the commercial heater acquired were determined using various heat transfer equations. The economic analysis of the investment was carried out over a period of five years using indicators that take into account the value of money over time such as the net present value, the internal rate of return and the cost-benefit ratio. In the experimental test, the energy required for water heating and efficient combustion was maintained. The technical feasibility of the proposal was shown by not rejecting the null hypothesis of equality of means (p> 0.05) of the 45 samples, which implies a consistency in the heating times. The financial analysis, in its different indicators NPV, IRR and R B/C, showed values in project acceptance ranges. This solution reduces the emission of greenhouse gases and production costs in operations. The option of using biogas is technically and economically viable.

El Centro Integrado de Tecnologías del Agua (CITA), le invita a participar en el V Taller Nacional de Promoción de Tecnologías para el abasto de agua y el uso de las Fuentes Renovables de Energía, a celebrarse en el Hotel Gran Club Santa Lucia, Camagüey, del 26 al 29 de Septiembre de 2017.

In this work the physicochemical characteristics of the residues of the market place, sludge of the sewage treatment plant and pruning residues of the municipality of Guachené of the department of Cauca were analyzed. According to the characterization of the municipal solid waste, it was found that the waste in the market place is generated in greater proportion, with a monthly quantity of 326.08 kg, followed by PTAR sludge with 135.47 kg, and finally the pruning residues that generate every month 61.8 kg. The results of the elementary analysis of the residues showed that the residues of market place have a greater potential to generate methane individually; however, in all cases it is always important to keep in mind the amount of waste to be used; that is, as the elementary analysis of the waste showed that for the solid waste of market places 0.35 m3 of CH4 can be obtained per 1.0 kg of waste, for PTAR sludges 0.14 m3 of CH4 can be obtained per 1.0 kg of sludge and for pruning residues 0.29 m3 of CH4 can be obtained per 1.0 kg of treated pruning. Based on the analysis of the general context of the municipality, a strategy was formulated for the exploitation of the residues, using the anaerobic digestion of the residues by means of an anaerobic digester , where it was obtained as market place residues can present a methane production around 0.98 m3 CH4 /day, pruning of 0.77 m3 CH4 /day and PTAR sludge a production of 0.13 m3 CH4 /day. Finally it was found that when performing a Co-digestion of the residues the production of methane is 4.33 m3 CH4 /day, which indicates that the production increases if the mixture of the residues is performed, allowing the conclusion that the waste management strategy of the municipality of Guachené, can represent a significant reduction of the problems associated with solid waste management in the municipality and the costs associated with the operation, transport and final disposal of waste | En este trabajo se analizaron las características fisicoquímicas de los residuos de plaza de mercado, lodos de la planta de tratamiento de agua residual y los residuos de podas del municipio de Guachené del departamento del Cauca. Según la caracterización de los residuos sólidos del municipio, se encontró que los residuos de la plaza de mercado se generan en mayor proporción, con una cantidad mensual de 326.08 kg, seguido de los lodos de la PTAR con 135.47 kg, y por último los residuos de podas lo cual generan cada mes 61.8 kg. Los resultados del análisis elemental de los residuos mostraron que los residuos de plaza de mercado presentan un mayor potencial de generar metano de manera individual; no obstante, en todos los casos siempre es importante tener presente cual será la cantidad de residuos a utilizar; es así, como el análisis elemental de los residuos mostró que para los Residuos sólidos de plazas de mercado se puede obtener 0.35 m3 de CH4 por cada 1.0 kg de residuo, para los Lodos de PTAR se puede obtener 0.14 m3 de CH4 por cada 1.0 kg de lodo y para los residuos de poda se puede obtener 0.29 m3 de CH4 por cada 1.0 kg de poda tratada. A partir del análisis del contexto general del municipio, se formuló una estrategia de aprovechamiento de los residuos, utilizando la digestión anaerobia de los residuos por medio de un digestor anaerobio, donde se obtuvo como los residuos de plaza de mercado pueden presentar una producción de metano alrededor de 0.98 m3 CH4 /día, las podas de 0.77 m3 CH4 /día y los lodos de la PTAR una producción de 0.13 m3 CH4 /día. Por último se encontró que al realizar una Co-digestión de los residuos la producción de metano es 4.33 m3 CH4 /día, lo cual indica que la producción se incrementa si se realiza la mezcla de los residuos, permitiendo concluir que la estrategia de aprovechamiento de los residuos del municipio de Guachené, puede representar una reducción significativa de los problemas asociados al manejo de los residuos sólidos en el municipio y los costos asociados a la operación, transporte y disposición final de los residuos | Pasantía institucional (Ingeniero Ambiental)-- Universidad Autónoma de Occidente, 2019 | Pregrado | Ingeniero(a) Ambiental

In most cases, the current strategies to treat swine effluents in Mexico are not efficient, resulting in the discharge of partially treated wastewater, wasting an energy resource. This study aimed to evaluate the impact of the solid-liquid separation of swine wastewater on methane production using granular (GS) and disperse sludge (DS), under three concentrations. The COD concentration in the raw effluent (RE) was 13,640 mg/L, which corresponds up to 69 % to the solid fraction (SF) and the remaining to the liquid fraction (LF). The results indicate that the cultures with the SF produced the higher cumulative methane, increasing 1.47-, 1.31-, and 1.22-times in retaliation to the RE, at 3, 6, and 9 g VSS/L of DS. The solid-liquid separation strategy resulted in a higher methane production, evidenced by the amount of methane obtained by the SF and LF, which was 2.14- and 2.28-times higher than the obtained by the RE. The application of anaerobic processes to treat solid and liquid wastes will allow to recovery efficiently the energy from the transformation of organic matter into methane. | Las estrategias actuales de tratamiento de efluentes porcinos en México son en muchos casos poco eficientes, que se traduce en la descarga de aguas tratadas parcialmente y no tratadas, así como el desaprovechamiento de un recurso energético. El objetivo de este estudio fue evaluar el impacto de la separación sólida-líquida del agua residual porcina sobre la producción de metano, utilizando lodo granular (LG) y lodo disperso (LD), bajo tres concentraciones. La concentración de DQO en el efluente crudo (EC) fue de 13,640 mg/L, con 69 % correspondiente a la fracción sólida (FS) y el resto para la fracción líquida (FL). Los resultados indican que los cultivos con la FS produjeron una mayor cantidad de metano, incrementándose 1.47, 1.31 y 1.22 veces en comparación al EC, para las concentraciones de 3, 6 y 9 g SSV/L de LD. La estrategia de separación sólida-líquida resultó en incrementos en la producción de metano, evidenciado porque la suma del metano acumulado por la FS y FL fue entre 2.14 y 2.28 veces mayor que la cantidad obtenida por el EC. La aplicación de procesos anaerobios para tratar residuos sólidos y líquidos permitirá recuperar de manera más eficiente la energía a partir de la transformación de la materia orgánica a metano.

This study investigates the occurrence of greenhouse gases (GHGs) and the role of groundwater as an indirect pathway of GHG emissions into surface waters in a gaining stretch of the Triffoy River agricultural catchment (Belgium). To this end, nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂) concentrations, the stable isotopes of nitrate, and major ions were monitored in river and groundwater over 8 months. Results indicated that groundwater was strongly oversaturated in N₂O and CO₂ with respect to atmospheric equilibrium (50.1 vs. 0.55 μg L⁻¹ for N₂O and 14,569 vs. 400 ppm for CO₂), but only marginally for CH₄ (0.45 vs. 0.056 μg L⁻¹), suggesting that groundwater can be a source of these GHGs to the atmosphere. Nitrification seemed to be the main process for the accumulation of N₂O in groundwater. Oxic conditions prevailing in the aquifer were not prone for the accumulation of CH₄. In fact, the emissions of CH₄ from the river were one to two orders of magnitude higher than the inputs from groundwater, meaning that CH₄ emissions from the river were due to CH₄ in-situ production in riverbed or riparian zone sediments. For CO₂ and N₂O, average emissions from groundwater were 1.5 × 10⁵ kg CO₂ ha⁻¹ year⁻¹ and 207 kg N₂O ha⁻¹ year⁻¹, respectively. Groundwater is probably an important source of N₂O and CO₂ in gaining streams but when the measures are scaled at catchment scale, these fluxes are probably relatively modest. Nevertheless, their quantification would better constrain nitrogen and carbon budgets in natural systems.

Dissolved methane concentrations in shallow groundwater are known to vary both spatially and temporally. The extent of these variations is poorly documented although this knowledge is critical for distinguishing natural fluctuations from anthropogenic impacts stemming from oil and gas activities. This issue was addressed as part of a groundwater research project aiming to assess the risk of shale gas development for groundwater quality over a 500-km² area in the St. Lawrence Lowlands (Quebec, Canada). A specific study was carried out to define the natural variability of methane concentrations and carbon and hydrogen isotope ratios in groundwater, as dissolved methane is naturally ubiquitous in aquifers of this area. Monitoring was carried out over a period of up to 2.5 years in seven monitoring wells. Results showed that for a given well, using the same sampling depth and technique, methane concentrations can vary over time from 2.5 to 6 times relative to the lowest recorded value. Methane isotopic composition, which is a useful tool to distinguish gas origin, was found to be stable for most wells, but varied significantly over time in the two wells where methane concentrations are the lowest. The use of concentration ratios, as well as isotopic composition of methane and dissolved inorganic carbon (DIC), helped unravel the processes responsible for these variations. This study indicates that both methane concentrations and isotopic composition, as well as DIC isotopes, should be regularly monitored over at least 1 year to establish their potential natural variations prior to hydrocarbon development.

Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site in Raymond, New Hampshire, USA, showed evidence of locally enhanced As mobilization in relatively reducing (mixed oxic-anoxic to anoxic) conditions as determined by redox classification and other lines of evidence. Redox classification was determined from geochemical indicators based on threshold concentrations of dissolved oxygen (DO), nitrate (NO 3 – ), iron (Fe2+), manganese (Mn2+), and sulfate (SO 4 2– ). Redox conditions were evaluated also based on methane (CH4), excess nitrogen gas (N2) from denitrification, the oxidation state of dissolved As speciation (As(III) and As(V)), and several stable isotope ratios. Samples from the residential-supply wells primarily exhibit mixed redox conditions, as most have long open boreholes (typically 50–100 m) that receive water from multiple discrete fractures with contrasting groundwater chemistry and redox conditions. The methods employed in this study can be used at other sites to gauge redox conditions and the potential for As mobilization in complex fractured crystalline-rock aquifers where multiple lines of evidence are likely needed to understand As occurrence, mobility, and transport.