BIOGAS AND LIQUID BIOFUELS
Introduction
Background
Biomass residues can also be converted into various non-solid fuel forms. These fuels are referred to as biogas and liquid biofuels. The aim of this conversion process is to improve the quality, specific energy content, transportability, etc., of the raw biomass source or to capture gases which are naturally produced as biomass is micro biologically degraded or when biomass is partially combusted. Biogas is a well-established fuel for cooking and lighting in a number of countries, whilst a major motivating factor in the development of liquid biofuels has been the drive to replace petroleum fuels. In this fact sheet we will be looking at some of these fuels, their applications and …ver más…

Small-scale biogas digesters usually provide fuel for domestic lighting and cooking.

Figure 2: Floating Cover Digester

Biogas & Liquid Fuels

Intermediate Technology Development Group

Application

1m3 biogas equivalent

Lighting
Cooking
Fuel replacement
Shaft power
Electricity generation

equal to 60 -100 watt bulb for 6 hours can cook 3 meals for a family of 5 - 6
0.7 kg of petrol can run a one horse power motor for 2 hours can generate 1.25 kilowatt hours of electricity

Table 1: some biogas equivalents
Source: adapted from Kristoferson 1991.
Some countries have initiated large-scale biogas programmes, Tanzania being an example.
The Tanzanian model is based on integrated resource recovery from municipal and industrial waste for grid-based electricity and fertiliser production.
Biomass gasification
The process of biomass gasification is distinctly different form that of biogas production.
Gasification is the process by which solid biomass materials are broken down using heat to produce a combustible gas, commonly known as producer gas. Common feedstocks for combustion include wood, charcoal, rice husks and coconut shells.
The biomass gasification plant consists of a reactor, similar to a simple stove, into which the solid biomass fuel is fed. The supply of air to the fuel is, however, carefully controlled to allow only partial combustion of the fuel to take place. During this process gases are