Grass from public green spaces an alternative source of renewable energy in tropical countries

Abstract

Grass from public green spaces of the tropical city of Palmira (Colombia) was analyzed to determine its potential to produce renewable energy trough anaerobic digestion. After pruning labor, grass samples were taken fresh in a representative way to form a big final sample. This sample was characterized and the grass species contained therein were identified. In a first experiment, a standard biochemical methane potential test was carried out at 37°C during 60 days. In a subsequent batch experiment, methane yield was optimized in terms of total solid concentration. Nine representative grass species were identified along with their nutritional content. It was found that the ultimate methane yield of the grass examined is 0.327 m3CH4/kgVSadded, which is comparable with that reported for grass silage. A volatile solids removal of 44 % was observed, and a removal of 45% cellulose, 12% hemicellulose, 4% lignin was found at the end of the experiment. Maximum methane yield was obtained at 4% of total solids, which may be recommended in a conventional anaerobic digestion process. Although more research is needed, this research showed that an economical and simpler operation can be suggested for the digestion of fresh grass in a tropical country like Colombia.