Enhancing biogas quality of indigofera plant waste through co-digestion with cow dung

^a Chemistry Department, Institut Pertanian Bogor, Jl. Raya Dramaga, Bogor, Indonesia
^b Mechanical Engineering Department, Universitas Sebelas Maret, Jl. Ir. Sutami 36 A, Surakarta, Indonesia
^c Chemisty Department, Universitas Sebelas Maret, Jl. Ir. Sutami 36 A, Surakarta, Indonesia
^d Economic and Business Faculty, Universitas Sebelas Maret, Jl. Ir. Sutami 36 A, Surakarta, Indonesia

Abstract

The production process of indigofera plants yields 10% of blue natural dyes and wastes are 90%. The biomass wastes from the extraction of indigofera plants are classified as difficult to process in an Anaerobic Digester (AD) because of the large content of hemicellulose in the Indigofera stems. Therefore, the study reports the anaerobic digestion of Indigofera plant wastes co-digested with cow dung for enhancing the biogas quality. The digestion process was conducted in a vessel of 160 L with various weight ratios between Indigofera biomass and cow dung by 0%, 25%, 50%, 75%, and 100%. The results show that the AD reactor temperature kept above 29.5°C with a pH between 6-7 were the key factors for enhancing the biogas quality. The co-digestion between 50% indigofera wastes with 50% cow dung yielded biogas with a CH4 content of about 42% and H2S concentration below 40 ppm showing that the biogas has the potential to be further improved in quality and can be used to fuel the stove and power generation.