METHANE PRODUCTION

Methane Production and The Impacts On The Environment

Methane Production and the Impacts on the Environment

Introduction

Methane is a greenhouse gas whose atmospheric concentration has increased dramatically over the last century. Methane released to the atmosphere by domestic ruminant livestock is considered to be one of the three largest sources on a global scale (Cicerone and Orenland, 1988; Obioh, et al., 2004 and Johnson et al., 2005; and). Methane is the largest potential contributor to the global warming phenomenon (Moss et al., 2000, Johnson et al., 2005) Fermentation of feeds in the rumen is the largest source of methane from enteric fermentation. This influences the production of the different volatile fatty acids which has a marked effect on production of methane in the rumen. Acetate and butyrate promote methane production while propionate formations can considered as a competitive pathway for hydrogen use in the rumen.

Many alternative approaches to reducing methane are considered, both in terms of reduction per animal andreduction per unit of animal product. Consequently, it was observed that the most promising areas for future research for reducing methanogenesis are the development of new products/delivery systems for anti-methanogenic compounds and reduction in protozoal numbers in the rumen. . This paper looks more closely at the reasons for, and the consequences of, methane production from ruminant livestock which in turn is dependent on the quantity and quality of the diets.

The Contributions of Methane to the Greenhouse Effect

The fluctuation of average annual temperature of the earth during the last century has generated much interest in the composition of the earth's atmosphere. The observed increase in concentration of many gases in the troposphere has been related to the increase in global temperatures (Moss, 2000). Records show that during the past 100 years, the earth's average annual temperature has increased by 0.5 -0.7 degrees. The decade from 1986 to 1995 has been the warmest in the 135 years that global temperatures have been monitored (MENZ, 2001). Climate change as a result of green house gases poses a serious threat to the environment, economy and well - being of the populace. The past and current concentration of the main green house gases, rates of increase and atmospheric lifetimes are given as summarized in Table 1.

Table 1: The tropospheric concentrations, residence times and atmospheric trend of various green-house gases.

Contribution of methane to the green house effect

Of all the green house gases, carbondioxide receives the most attention as a factor in global warming, but other gasses are also of major importance, these include methane, nitrous oxide (N20) and chlorofluoro-carbons (CFCs). Methane is an important component of green house gases in the atmosphere, and is the one most associated with animal agriculture. Methane has a thermogenic affect some four to six times that of carbondioxide (Leng, 1993; Moss et al., 2000). Preston (1989) reported that though methane contributes 18% of the overall warming it is accumulating at a fast rate and is apparently responsible for some of the depletion of the protective ozone ...