Page 282 - Low Temperature Energy Systems with Applications of Renewable Energy

268 Low-Temperature Energy Systems with Applications of Renewable Energy

Table 7.1 Biogas output and methane content from various kinds of waste.

Biogas output,
3
Raw material dm /kg dry matter Methane content, %
Cattle humus a 200e300 50
Pig humus a 340e480 60e75
a
Horse humus with straw 250 56e60
Potato tops 420 60
Corn stalks 420 53
Wheat straw 342 58
Sunflower husk 300 60
Silage 250 84
Fresh grass 360 52
Beet 430 84
Carrot Waste 250 60
Wood sawdust 220 51
Solid sewage sludge 570 70
Fecal sediment 250e310 60
Household waste and garbage 600 50
a
Black, broken-down, stable organic matter in soil.
The hierarchy of ways to intensify the process of anaerobic fermentation of a sub-
strate in bioreactors is shown in Fig. 7.9. Mixing with a rotational speed of 50e80 rpm
provides the optimum mode [16,17].
To produce biogas, bioreactors with various design features are used. Indicators of
the effective operation of such an installation are the productivity (the biogas output
per unit volume of biomass), the duration of the working cycle, and energy consump-
tion to ensure the intensification and thermostabilization of bioconversion. These in-
dicators mainly determine the cost of biogas production.
The process of bioconversion of organic waste requires significant energy con-
sumption, which can render the bioreactor uneconomic. Thermostabilization and
intensification of anaerobic fermentation in bioreactors is an effective solution to the

Fig. 7.9 Classification of factors for improving the energy efficiency of biogas production
processes.