Bioenergy Implementation Plan - South-East Regional Authority

of the cereal and the latter can be done in either a wet or a dry process. In the wet milling process the conversion of
starch is done after separation and in the dry milling process the sugar conversion is done during the separation. In
either method the conversion is typically achieved by hydrolysis.
Figure 7.4: Flow Diagram of Bioethanol Production
Molasses Animal Feed Process Heat
Sugar Beet
Sugar Extraction
Fermentation and
Distillation
Bioethanol
Cereal
Starch Separation
and Sugar Conversion
Fibrous Part
of Plant
Dried Grains
Animal Feed
Fermentation and Distillation
During the fermentation process the sugar is fermented into alcohol using yeast and other microbes. When the
fermentation is complete the liquid is distilled to obtain the desired concentration of ethanol as water and solids are
separated from the alcohol.
Co-Products
Animal feed is one co-product of ethanol production from both sugar beet and cereal. The starchy part which is utilised
in ethanol production only represents a small part of the crop, while the residue contains a considerable amount of fibres.
7.4. Anaerobic Digestion
Anaerobic digestion (AD) is a method used to treat agricultural and other organic wastes. Anaerobic bacteria convert part
of the biomass into biogas which can be used to generate energy.
Figure 7.5 shows the process of biomass conversion to biogas. The biomass is fed into the reactor tank where it is heated
and kept for 2-3 weeks. The biogas production is dependant on different parameters such as the moisture content of the
waste and the temperature and retention time in the digestion tank.
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south-east regional authority
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