Page 53 - CAPE Green Engineering Syllabus 2016.docx_Neat

The ethanol is removed from the fermentation mixture by fractional distillation while the carbon
dioxide is captured and processed.

The distillation process requires large amounts of heat and
produces huge amounts of liquid waste rich in organic
material called stillage or vinasse. The improper disposal
of this vinasse can have significant negative consequences
for the environment especially the waterways. The large
amounts of organic material lead to eutrophication and
unpleasant odours. To address this vinasse disposal issue
DDL has installed a biomethanisation plant which converts
the vinasse into biogas which is rich in methane and other
combustible gases. Since the biomethanisation process
coverts the organic material via bacterial processes the
organic load of the vinasse is reduced significantly and the
liquid waste is now rendered less harmful to the
environment. This waste may now be utilised as an
organic fertiliser.

Figure 2-Unique Wooden Still
(http://www.cocktailsoldfashioned.de/2011/02/demera
ra-distillers-limited-guyana-rum/ (accessed Oct 07, 2014)

Figure 3-The three-stage anaerobic fermentation of biomass (GTZ project Information and Advisory Service on
Appropriate Technology (ISAT)

This biogas, which is a green fuel, is used to fire the boilers to supply the steam required for the
distillation process at the distillery. Currently the biomethanisation plant supplies approximately 70
per cent of the fuel utilised by the boilers on a daily basis.

CXC A36/U2/16 49