[IB Biology Ecology Notes]

Biological Fuels



In this context, if is the living and recently dead biological material which can be used as fuel. It is commonly plant material wastes not useful for food, wood products and other industrial uses. It can also include animal wastes, such as manure. Biomass is usually measured in dry weight. Currently, biomass is commonly converted into ethanol (later added to gasoline) or into methane gas (CH4).

Methane Production:

Any biomass can be used to produced methane, although sewage and manure are most commonly used. The biomass is added to a bioreacter, a large container that maintains anaerobic conditions. These conditions encourage the growth of methanogens, bacteria that naturally release methane. Methanococcus and Methanobacterium are 2 examples of methanogenic bacteria.

Some of these bacteria convert the biomass into organic acids and alcohol.

A second group of methanogenic bacteria convert the biomass into acetate, hydrogen and carbon dioxide.

A third group recombine the actate, hydrogen and carbon dioxide produced above into methane gas. Typically, the gas produced by this group is 40-70% methane.

Any methane that is produced can be used directly as a fuel for cooking, heating or lighting. The gas can be compressed into cylinders and used as a fuel for vehicles.

Advantages of Using Biomass to Produce Methane:

a) Helps dispose of polluting wastes.

b) Methane is a renewable and non-polluting fuel.

c) The remaining biomass at the end of methane producing process can be used as an organic fertilizer.