Abstract
This research investigated the influence of chemical composition on the CH4 production capability, or Biochemical Methane Potential (BMP), of eleven different field grass samples that have the capability to produce methane (CH4)-rich biogas. These grasses were fast growing, has high yield and high digestible organic content (atratum, creeping signal, hamata stylo, mombasa guinea, pangola, para-, purple guinea, rhodes, ruzi, and napier grasses, plus napier grass silage). Anaerobic sludge from a cassava starch wastewater treatment plant was used as an inoculum seed. The BMP was significant statistical differences due to variations in the chemical composition, which was related to the C:N ratio and lignin content in the field grasses. The experimental results showed that the Carbon:Nitrogen (C:N) ratios were in the range of 17.2:1 to 89.6:1 and the BMPs were in the range between 121.5–251.9 Nm3/t VSadded with the maximum CH4 production rate of 3.60–11.46 mL/day. Outstanding BMP levels were found in the para grass, ruzi grass, and pangola grass, with suitable C:N ratio (20:1 to 30:1) and low lignin content. Para grass provided the highest BMP of 251.9 Nm3/t VSadded (4,799 Nm3 CH4/ha). The CH4 yield per hectare of the grasses depends on both its dry matter yield per hectare and its specific methane yield. Therefore, pangola grass had the highest potential as an energy crop with 7,915 Nm3 CH4/ha due to its high CH4 yield (230.9 Nm3/t VSadded) and high harvesting yield (37.5 t/ha).
