ISSN: 1659-2751

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Evaluation of the Production of Methane from Coffee Pulp and Mucilage from three Processing Plants in Costa Rica

Abstract

The objective of the experiment was to quantify the standardized production of CH4 from pulp and mucilage obtained from three coffee processing plants, in two time periods, collected during the 2012/2013 harvest season. The method used was the biogas batch test for fermentation of organic materials. The pulp was characterized through analysis to determine C/N ratio, which presented values between 20 to 30; for ST, with values between 8 % and 25 %; for SV, with between 68 % to 93 % and pH, which ranged from 7.0 4 to 7.34. Mucilage analysis results indicated a C/N ratio of 17 to 31; ST values between 3 % and 9 %; SV values of 74 % to 85 %; and pH from 6.7 to 7.5. All of the analyses indicated that the majority of the parameters were in the optimal ranges for anaerobic digestion. The CH4 production curve from the pulp substrates was an exponential function whereas the mucilage samples modeled a diauxic growth curve. The CH4 production from pulp was between 143 mL/g SV and 251 mL/g and from the mucilage was 303 mL/g SV. There were statistically significant differences between the samples from the processing plants and the harvest season for pulp, but no significant differences for mucilage.

Key words: coffee, CH4, mucilage, pulp, production.

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