Ecological Sustainability

202 Ecological Sustainability

of bacteria on the organic substrate to produce CO

2

and H

2

. The dissolved

CO

2

forms bicarbonates, which are combined by methanogenic bacteria with

hydrogen ions to form methane and water (MacDonald 1990). Thus, under

natural conditions, methane is generated along with CO

2

. This decomposi-

tion gas moves to the surface (air) by mechanisms of molecular diffusion and

convection. Diffusion is the result of a concentration difference between two

different locations. Diffusive ow is in the direction of decreasing concentra-

tion. Convective ow occurs when a pressure or temperature gradient exists

between two locations (Hariri and Chou 2008).

The biogenic methane from methanogenic bacteria–derived energy from

garbage ...