Impact of water management on methane emission dynamics in Sri Lankan paddy ecosystems

Paddy ecosystems constitute a dominant source of greenhouse gases, particularly of methane (CH₄), due to the continuous flooding (CF) practiced under conventional paddy cultivation. A new management method, namely alternative wetting and draining (AWD) (i.e., flooding whenever surface water levels decline to 15 cm below the soil surface), is an emerging practice developed to mitigate CH₄ emissions while providing an optimal solution for freshwater scarcity. Despite extensive paddy cultivation in Sri Lanka, no systematic research study has been conducted to investigate CH₄ emissions under different water management practices. Thus, field experiments were conducted in Sri Lanka to investigate the feedback of controlled water management on seasonal and diel variation of CH₄ emission, water consumption, and crop productivity. Adopting the same rice variety, two water management methods, continuous flooding (CF) and alternative wetting and draining (AWD), were compared with plants (W/P) and without plants (N/P) present. The emission of CH₄ was measured using the static closed chamber method. The results show a 32% reduction in cumulative CH₄ emission, on average, under AWD when compared to CF. The yield under the AWD was slightly higher than that of CF. Although it was not statistically significant (p > 0.05) there was not any reduction in yield in AWD than in CF. The total water saving under AWD ranged between 27–35% when compared to CF. Thus, the results support (without considering the effect of nitrous oxide) AWD as a promising method for mitigating CH₄ emissions while preserving freshwater and maintaining grain yield in paddy systems

Environmental issues and management in primary coffee processing

The paper examines the broader environmental issues and environmental management aspects of primary coffee processing in general and more specifically how it is addressed in India. Primary processing, the production of green beans from the coffee fruits, is practised to bring out more flavour. Coffee is an important global commodity, yet seen from a systemic view the producers and consumers of such an important commercial commodity are far apart. Primary coffee processing, with all its attendant environment impact, takes place at the producer end. The consumers in general are unaware of these impacts. The various methods of processing, the processing steps and the waste discharge associated with them are reviewed. A review of pollution and associated management methods is presented. An anaerobic bioreactor design developed and tested in a few Indian coffee plantations as a simple solution is also described

Biomass based energy system for a South Indian village

The biomass resources, existing utilization levels and the efficiency of its use have been analyzed for a South Indian village. A biomass based energy efficient strategy has been devised to meet all the energy needs of the village, including substitution of fuels such as electricity and kerosene used in specific activities. Results indicate that the potential as well as the technologies exist for such substitutions. The proposed strategy will lead to an increase in the efficiency of energy use, reduce human drudgery and make villages more self reliant

Nitrogen pool, flows, impact and sustainability issues of human waste management in the city of Bangalore

Cities in the developing countries have multiple modes of human and animal waste treatment and disposal that finally decide the overall impact on the urban ecosystem, and these have been studied for the city of Bangalore. Four modes are found, namely underground sewage systems, decentralized soak pits and septic tanks, open defecation and a miniscule effort at composting. The extent of N released per unit area is high, ranging between 0.44 and 1.4 t $ha^{-1}$ of the urban landscape.In this study the N release and outflow have been estimated. The N entering or flowing in the lithosphere,hydrosphere and in wastewater streams forms the major component. The pool size has first been determined. The size and movement through these pools were estimated with a view to determine the state of the N cycle and if there is a cause for alarm in similar cities in other developing countries. N contribution from human waste (excreta and urine) forms the singlelargest influx and sewage flowing out of the city forms the single largest efflux of N pool. Owing to a seemingly large use of soak pits and open conveyance of sewage in some parts of the city, coliforms and $NO_3$–N have seeped into shallow and deep-ground aquifers and show up in ground- and sub-soil waters in the city.The level of N in these waters at a few places is slightly higher than the permissible limits. This suggests that there is a need to find alternatives to modes like the ubiquitous soak pit, such that pollution of shallow and deep aquifers is avoided in the future. Currently,there is little effort in stripping the waste water off N.Also, there is no significant effort in recovery and reuse of nutrients, and this is required to increase the sustainability levels

Biogas reactors as a resource recovery system in coffee pulp processing

Coffee is an important global product. In fact it ranks only second to oil in traded price volatile commodities of the world - a relatively unknown fact! In most countries where coffee is produced it is for external trade and India is also not an exception. Many developing countries produce coffee and the world's largest consumer is United States, which accounts for nearly 25% of the global consumption. The bulk of coffee produced is exported bringing in foreign exchange to these developing economies. However, environmental aspects of coffee production have by and large being ignored

Environmental Issues and Management in Primary Coffee Processing

The paper examines the broader environmental issues and environmental management aspects of primary coffee processing in general and more specifically how it is addressed in India. Primary processing, the production of green beans from the coffee fruits, is practised to bring out more flavour. Coffee is an important global commodity, yet seen from a systemic view the producers and consumers of such all important commercial commodity are far apart. Primary coffee processing, with all its attendant environment impact, takes place at the producer end. The consumers in general are unaware of these impacts. The various methods of processing, the processing steps and the waste discharge associated with them are reviewed. A review of pollution and associated management methods is presented. An anaerobic bioreactor design developed and tested in a few Indian coffee plantations as a simple solution is also described

Treatment of gray water using anaerobic biofilms created on synthetic and natural fibers

Gray water treatment and reuse is an immediate option to counter the upcoming water shortages in various parts of world, especially urban areas. Anaerobic treatment of gray water in houses is an alternative low cost, low energy and low sludge generating option that can meet this challenge. Typical problems of fluctuating VFA, low pH and sludge washout at low loading rates with gray water feedstock was overcome in two chambered anaerobic biofilm reactors using natural fibers as the biofilm support. The long term performance of using natural fiber based biofilms at moderate and low organic loading rates (OLR) have been examined. Biofilms raised on natural fibers (coir, ridge-gourd) were similar to that of synthetic media (PVC, polyethylene) at lower OLR when operated in pulse fed mode without effluent recirculation and achieved 80-90% COD removal at HRT of 2 d showing a small variability during start-up. Confocal microscopy of the biofilms on natural fibers indicated thinner biofilms, dense cell architecture and low extra cellular polymeric substances (EPS) compared to synthetic supports and this is believed to be key factor in high performance at low OLR and low strength gray water. Natural fibers are thus shown to be an effective biofilm support that withstand fluctuating characteristic of domestic gray water. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved

Evolving biomass-based biogas plants: The ASTRA experience

Anaerobic digestion of animal waste in biogas plants for energy, manure and sanitation has made a significant impact in quality of rural life wherever it has been deployed. Insufficiency of animal dung resources limits the use of this technology to only an eighth of the overall Indian rural population. Yet the convenience of a biogas plant in rural households has led R&D efforts to extend the use of biogas plants to other nonanimal dung biomass feedstock and rural residues.Fermenting typical biomass residues in conventional slurry-based biogas plants has been far from successful. Most attempts to convert rural biomass residues into ‘flowable’ slurries like animal dung have rarely been successful. Alternative concepts were required. Achieving successful quasi-continuous fermentation of biomass residues has come through a break away from the ‘slurry’ fixation and animal dung digester designs of the past. A better understanding of the underlying processes has greatly helped evolve new fermentation concepts. Success has emerged only through use of multi-stage processes, where key fermentation properties of biomass feedstock have been acknowledged and digesters designed accordingly. Here, a 25-year effort in understanding the processes of biogas and biomass fermentation, developing new techniques and technologies to ferment biomass feedstock and efforts at simplifying the technology to enable sustainability carried out at the Centre for Sustainable Technologies, IISc, Bangalore is described. Finally, integration of the two or three fermentation steps into a single reactor configuration has enabled evolving simple-to-use digester designs for biomass feedstock, namely the plugflow and the solid-state stratified bed digesters

Utilization of Biogas Digester Liquid for Higher Mushroom Yeilds

Biomass based biogas plants play important role in the sustainable development of rural India. These biogas plants apart from providing biogas (CH4+CO2) that can be used for cooking and other purposes also provide two other byproducts such as Biogas Digester Liquid (BDL) and Biogas Digester Residue (BDR). These byproducts contain proportion of locked nitrogen in the form of ammonia, and other nutrients such as phosphorus that can be further utilized to produce valve added products like mushroom. In this study biogas digester liquid was used as a nutrient supplement in place of water for cultivation of mushroom specie like P. florida. it was observed that the mushroom bags supplemented with biogas digester liquid gave higher yield (P. florida gave 2.4kg/kg substrate) compared to bags sprayed with water (standard bags, 1.5kg/kg substrate). The time required for pin head formation, fruiting body was also reduced by spraying biogas digester liquid. Also the mushroom samples, leachate and solid substrate were analyzed for TKN, TP and TOC. Higher degradation of the substrate was seen in P. florida by spraying BDL than compared to control bags that were sprayed with water. (C) 2016 Published by Elsevier B.V