Production of biogas from coffee husk waste with rumen fluid and mixture of rumen fluid and cow dung

Abstract

Coffee is the second largest traded commodity in the world and also produces by-products and residues. Coffee husk waste is an abundant lignocellulosic material and has the potential to be used as raw material for biogas production. This study compared the production of biogas from coffee husk using rumen fluid with a mixture of rumen fluid and cow dung. In the pretreatment process using ethanol, the waste consisted of 65.90% cellulose, 24.95% hemicellulose, 0.21% lignin, 2.16% pectin, 1.08% protein, 3.11% tannins, 0.91% caffeine, and 3.78% polyphenols. The decrease in TS (total solid) and VS (volatile solid) values for C-RC (coffee-rumen fluid-cow dung) was greater than for C-R (coffee-rumen fluid) as 32.20% and 42.47% were obtained for C-RC, while the values for C-R were 19.32% and 38.37 The VFA (volatile fatty acids) values for C-R and C-RC were 1.09% and 2.24%. The biogas produced for C-R was CH4 of 14.4%, CO2 of 13.75%, and H2 of 0.59%, while that for C-RC consisted of CH4 of 22.3%, CO2 of 4.11%, and H2 of 0.36%. The yield of biogas for C-R was 0.48 Nm3/(kg COD removal) and for C-RC was 1.95 Nm3 /(kg COD removal).