WATER FOOTPRINT ANALYSIS OF BIOETHANOL FROM MAIZE ...

WATER FOOTPRINT ANALYSIS OF BIOETHANOL FROM MAIZE AND
SUGARCANE IN SOUTH AFRICA
Executive Summary of Maria Iodice’s M.Sc. thesis
CENTRE FOR ENVIRONMENTAL POLICY
IMPERIAL COLLEGE LONDON
Academic Year 2008-2009
Supervisor: DR AUSILIO BAUEN
Objectives:
Three main objectives were identified:
1. Calculation of the water footprint (WF) of ethanol from maize and sugarcane in South
Africa.
2. Comparison of the two crops’ refining processes; investigation of the most water
consumptive phases and potential solutions.
3. Investigation of the likely consequences of biofuel expansion in South Africa for the
country’s water resources and economy.
Introduction
Currently biofuel feedstocks account for only about 1 percent of the global cropped area, with
a similar percent of crop water use. However there has been an exponential growth in biofuel
production since 2000, and nations worldwide have put in place ambitious expansion
programmes for the future.
Growing biofuel production rises several socioeconomic and environmental concerns, among
which the implications on water resources; although the effects of growing biofuels on global
water requirements are apparently minor, they have an impact that was not present before
and thus is not fully predictable.
Water use efficiency varies greatly among biofuel crops, and is also dependent upon other
factors such as climate, growing period and agronomic practice. Developing countries such
as South Africa, Poland, Turkey, India and China, which are already facing a scarce water
situation, are likely to suffer from exacerbating water shortage problems even without putting
in place large-scale bioenergy production.
Methodology
The analysis carried out in this study draws from the concept of water footprint (WF)
introduced in the last decade and successively refined by professor Arjen Hoekstra at
UNESCO-IHE and further developed at the University of Twente, in the Netherlands. The
methodology was substantially drawn from Chapagain at al. (2004), although the virtual
water content of ethanol is finally estimated not only on the basis of the ethanol market value
as Chapagain et al. (2004) suggest, but also the ethanol energy content; the ethanol yields;
and the by-products only.

According to Hoekstra and Chapagain’s method (2004), the virtual water content of a
processed product – i.e. its water footprint - depends on the virtual water content of the
primary product from which it is derived – the raw material – and also from the water needed
for the refining process. A summary of the data and steps for the calculation of water
footprint of ethanol is illustrated in figure 1.
Figure 1: Steps in the calculation of the water footprint of biofuels. The dotted panels and arrows indicate
the additional methods used in this study .
Adapted from Chapagain et al (2004)
Given the importance of the localization of productivities in WF analysis, this study focuses
on South Africa for a number of reasons: its discussed position as a prominent biofuel
producer in the future with an high national demand for fuel projected to increase even
further; its long debated problem of water scarcity that is likely to be further exacerbated in
the future due to Climate Change; the ease of finding data compared to other developing
countries in Africa; and the relatively scarce water consumption quantification of the
bioenergy sector as compared to China and India. The choice of the country has also
determined the selection of the crops (maize and sugarcane) as well as the type of biofuel
(ethanol) analysed in this study.
Technical data on crop water requirements was drawn directly from Chapagain et al. (2004),
whereas data relative to processing water requirements, by-products, energy content and
market price of the two crops analysed was gathered from varied literature and web sources.
When necessary, experts’ opinion 1 has been gathered to confirm data assumptions and
methodologies. The calculation of the processing water requirement (PWR) of the two
ethanol feedstocks is based on best water practices currently adopted in ethanol plants in
Brazil and US, assuming that South Africa has the potential to put in place the same
practices. Thus the analysis attributes major responsibility for water consumption to the
agricultural process, which reflects current agricultural practices adopted in the country.
1 Dr Ausilio Bauen and Professor Colin Thirtle, Imperial College.

Results
The analysis shows that, overall, maize has a water footprint significantly higher than
sugarcane, with 22 m 3 /L of ethanol versus sugarcane’s 19 m 3 /L of ethanol despite the higher
water requirements of sugarcane for growing and for being processed. The WF is also
estimated according to the ethanol energy content and the by-products mass and energy
values, always with sugarcane performing better than maize. However, results are sensitive
to data relative to crops’ yields and production in the country examined, as well as the market
price of ethanol, which tend to favour sugarcane over maize in this study.
Additionally, the major consumptive phases of the refining processes of maize and
sugarcane have been investigated (figure 2 and 3). These resulted to be: slurry cooking and
distillation for maize processing; and sugarcane washing, fermentation, and alcohol
condenser cooling for sugarcane processing.
Figure 2 and 3: Schematization of the refining process of maize and sugarcane.
Adapted from: Sielhorst et al, 2008

Moreover, this study investigated the actual and potential water footprint of the biofuel
industry in South Africa and its likely consequences on the country’s water resources. The
analysis showed that South Africa is approaching water scarcity for almost the totality of its
territory, however its current total water footprint, as reported by Chapagain et al (2004) is
low, with almost 40 Gm 3 /yr (931 m 3 /yr per capita). However, the situation could radically
change due to a growing biofuel industry, which at current level of production has a total
water footprint of 9.1 Gm 3 , assuming all ethanol derives from maize, and 7.7 Gm 3 if all
ethanol comes from sugarcane. This water footprint, already significant for the local water
resources, becomes alarming with the biofuel projections of 2030: the water footprint of a
national bioethanol industry would amount to 33 Gm 3 when totally supplied by sugarcane,
and 39 Gm 3 when supplied by maize 2 . Thus, the total water footprint of South Africa will
inevitably increase if predicted biofuel expansion plans will materialise, with potential impacts
on the local water resources.
Discussion, Conclusions and Implications
The results showed, overall, a smaller water footprint of sugarcane as compared to maize;
although many uncertainties persist as to the actual impact of sugarcane feedstock on local
water sources. In fact, although ethanol from sugarcane has a lower water footprint per
energy unit in South Africa than in other countries, its cultivation is done by means of
irrigation. This is likely to result in a higher impact on the water resources, especially in a
water-constrained territory.
Despite some methodological shortcomings related to the nature of the analysis and data
sources, this study succeeded to provide an understanding of the major causes for water
consumption in biofuel feedstock growth and refining. It also indicated consequential threats
to the South African environment and economy, paving the way for further analysis into this
subject.
This study demonstrates in fact that the promotion of first generation biofuels in South Africa
poses notable threats to the country’s scarce water resources. Second generation biofuels
that are drought resistant, such as jatropha, could potentially avoid this risk, however there is
no sufficient data to carry out a water footprint analysis of these biofuels, as their production
started only recently.
Finally, weather sugarcane is a better ethanol feedstock than maize and bioethanol should
be promoted in South Africa will only be determined through further, in depth economic and
environmental analysis. The WF analysis, in fact, is an useful tool to calculate the embodied
water of a product and estimate its potential impact on the water resources of the producing
country, however it does not provide enough information on the state of water resource
management and techniques used, nor on the economic value of the embodied water of the
product. It is therefore necessary to complement it with further research to assess the
sustainable use of water of biofuels in a specific country.
References:
Chapagain, A., K.; Hoekstra, A., Y. 2004, Water Footprint of Nations, Research Report
Series No. 16, Unesco IHE, The Netherlands.
Sielhorst, S.; Molenaar, W., J.; Offermans, J. 2008, Biofuels in Africa: an assessment of risks
and benefits for African wetlands, AIDE environment edn, Wetlands International,
Amsterdam, The Netherlands.
2 Assuming the state of technology remains unaltered.