Anaerobic co-digestion of coffee waste and sewage sludge

Centro de Engenharia Biológica, Universidade do Minho, 4710-057 Braga, Portugal.
Waste Management (Impact Factor: 3.22). 02/2006; 26(2):176-81. DOI: 10.1016/j.wasman.2004.12.022
Source: PubMed


The feasibility of the anaerobic co-digestion of coffee solid waste and sewage sludge was assessed. Five different solid wastes with different chemical properties were studied in mesophilic batch assays, providing basic data on the methane production, reduction of total and volatile solids and hydrolysis rate constant. Most of the wastes had a methane yield of 0.24-0.28 m3 CH4(STP)/kg VS(initial) and 76-89% of the theoretical methane yield was achieved. Reduction of 50-73% in total solids and 75-80% in volatile solids were obtained and the hydrolysis rate constants were in the range of 0.035-0.063 d(-1). One of the solid wastes, composed of 100% barley, achieved a methane yield of 0.02 m3 CH4(STP)/kg VS(initial), reductions of 31% in total solids, 40% in volatile solids and achieved only 11% of the theoretical methane yield. However, this waste presented the highest hydrolysis rate constant. Considering all the wastes, an inverse linear correlation was obtained between methane yield and the hydrolysis rate constant, suggesting that hydrolysis was not the limiting factor in the anaerobic biodegradability of this type of waste.

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Available from: Madalena S Alves, Dec 21, 2014
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    • "The treatment of coffee extraction effluent is not only important to the primary producers but also to the other countries which import bulks of semi-processed coffee for further processing. Melanoidin has been reported as the main pollutant in the coffee industry effluents [5] [6]. In addition to causing dark color and high remnant COD, melanoidin in coffee has been reported to cause microbial inhibition [7] and may be responsible for the low biodegradability of the effluent. "
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    ABSTRACT: Melanoidin-rich industrial effluents, e.g. from coffee extraction plants and molasses distilleries, can cause potential environmental problems due to the high content of remnant dissolved organic carbon and dark color. It mainly consists of melanoidins and other organic colorants, which are recalcitrant to biological treatment. The current study was aimed to develop a polishing step after anaerobic digestion for the colorant elimination from melanoidin-rich wastewater (molasses distillery wastewater, MDW) using natural manganese oxides. Anaerobically digested MDW was used to test the removal of organic contents and color at different pH values. It was observed that the kinetics of colorant elimination was best described by the second order equation, with a significant dependence on pH. Furthermore, the liquid chromatography with organic carbon detection was applied to analyze the changes in molecular composition during the reaction. There was a preferential removal of low weight melanoidin molecules over higher weight molecules.
    Separation and Purification Technology 08/2015; 150:286-291. DOI:10.1016/j.seppur.2015.07.013 · 3.09 Impact Factor
    • ". Cumulative biogas volume (Nl/kgTS) as a function of the incubation time: comparison between measured data (dots) and modelling results obtained with the first-order kinetic model (lines). the k-values range (0.028–0.054 d À1 ) observed at 37 °C appears close to the one reported by Neves et al. (2006), which refer to a co-digestion of organic waste and sewage sludge (0.035– 0.063 d À1 ). On the contrary, significant differences can be observed referring to the results presented by De Gioannis et al. (2009) and Mou et al. (2015). "
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    ABSTRACT: In this work, the influence of different operating conditions on the biogas production from mechanically-biologically treated (MBT) wastes is investigated. Specifically, different lab-scale anaerobic tests varying the water content (26-43% w/w up to 75% w/w), the temperature (from 20 to 25°C up to 55°C) and the amount of inoculum have been performed on waste samples collected from a full-scale Italian MBT plant. For each test, the gas generation yield and, where applicable, the first-order gas generation rates were determined. Nearly all tests were characterised by a quite long lag-phase. This result was mainly ascribed to the inhibition effects resulting from the high concentrations of volatile fatty acids (VFAs) and ammonia detected in the different stages of the experiments. Furthermore, water content was found as one of the key factor limiting the anaerobic biological process. Indeed, the experimental results showed that when the moisture was lower than 32% w/w, the methanogenic microbial activity was completely inhibited. For the higher water content tested (75% w/w), high values of accumulated gas volume (up to 150Nl/kgTS) and a relatively short time period to deplete the MBT waste gas generation capacity were observed. At these test conditions, the effect of temperature became evident, leading to gas generation rates of 0.007d(-1) at room temperature that increased to 0.03-0.05d(-1) at 37°C and to 0.04-0.11d(-1) at 55°C. Overall, the obtained results highlighted that the operative conditions can drastically affect the gas production from MBT wastes. This suggests that particular caution should be paid when using the results of lab-scale tests for the evaluation of long-term behaviour expected in the field where the boundary conditions change continuously and vary significantly depending on the climate, the landfill operative management strategies in place (e.g. leachate recirculation, waste disposal methods), the hydraulic characteristics of disposed waste, the presence and type of temporary and final cover systems. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Waste Management 07/2015; 43. DOI:10.1016/j.wasman.2015.06.019 · 3.22 Impact Factor
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    • "because even the countries that are not primary producers buy semi-produced coffee from which they process instant coffee. The major source of pollutant in the coffee industry effluent has been reported to be melanoidin, which causes dark colour and high remnant chemical oxygen demand (COD).[6] [7] Melanoidin from coffee has been reported to cause microbial inhibition [8] and may be responsible for low biodegradability of the effluent. "
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    ABSTRACT: Melanoidins are dark colored recalcitrant pollutants found in many industrial wastewaters including coffee manufacturing effluent, molasses distillery wastewater (MDWW), and other wastewater with molasses as raw material. The wastewaters are mostly treated with anaerobic digestion after some dilution to minimize the inhibition effect. However the dark color and recalcitrant dissolved organic carbon (DOC) mainly caused by melanoidin are not effectively removed. The aim of this study was to investigate the removal of color and remnant DOC by different coagulants from anaerobically digested MDWW. From the six coagulants tested, ferric chloride had the highest melanoidin (48%), color (92.7%) and DOC (63.3%) removal at pH 5 and a dosage of 1.6 g/l. Both polymer and inorganic salts coagulants tested had optimal color, melanoidin and DOC removal at acidic pH. The molecular size distribution of synthetic melanoidins by LC-OCD indicated a preferential removal of high-molecular-weight melanoidins over low weight melanoidins by the coagulation. Further studies should focus on how to improve biodegradability of the treated effluent for it to be reused as dilution water for anaerobic digestion.
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