Biomethanation of Carpet Grass (Axonopus fissifolius)

Chima Ngumah, Jude Ogbulie, Justina Orji, Ekperechi Amadi


Axonopus fissifolius commonly called “carpet grass” was subjected to anaerobic digestion for 30 days. Anaerobic digestion was carried out in a batch-fed process at the ambient temperature of 27-290C. Biomethane measurements were obtained by measuring the volume displacement of a saturated filtered calcium hydroxide solution in a transparent calibrated vessel.  42.7g of fresh carpet grass clippings yielded 1.955 L of biomethane. Biomethane potential (BMP) of carpet grass for a 30 day anaerobic digestion was 0.05 m3 CH4 kg-1 TS. The rates of biomethane potentials for the first, second, third, fourth and fifth six-day intervals were 1.5mL g-1 TS (2.81%), 6.4mL g-1 TS (14.58%), 16.1mL g-1 TS (30.18%), 17.74mL g-1 TS (33.25%), and 10.23mL g-1 TS (19.81%) respectively. The total solids, volatile solids and pH of feedstock and digestate were 85.80% and 85.56%, 90.91% and 87.58%, 6.6 (27oC) and 6.9 (27oC) respectively.  The relatively high biomethane potential of carpet grass at the ambient temperature presented in this paper depicts anaerobic digestion as a viable means of profitably treating grass waste for both sanitation and generating biomethane especially in the tropics where the ambient temperatures are usually favourable for optimum biomethanation for most part of the year, thus making the process affordable and less cumbersome.



Renewable energy; anaerobic digestion; grass waste; biogas

Full Text: Ngumah 4 (66) 2013

Print ISSN: 1392-1649
Online ISSN: 2029-2139