Uncovering the Green, Blue, and Grey Water Footprint and Virtual Water of Biofuel Production in Brazil: A Nexus Perspective

Raul Munoz Castillo,Fernando Miralles-Wilhelm,Joaquim Guilhoto,Kuishuang Feng,Klaus Hubacek,Laixiang Sun

doi:10.3390/su9112049

Abstract

Brazil plays a major role in the global biofuel economy as the world’s second largest producer and consumer and the largest exporter of ethanol. Its demand is expected to significantly increase in coming years, largely driven by national and international carbon mitigation targets. However, biofuel crops require significant amounts of water and land resources that could otherwise be used for the production of food, urban water supply, or energy generation. Given Brazil’s uneven spatial distribution of water resources among regions, a potential expansion of ethanol production will need to take into account regional or local water availability, as an increased water demand for irrigation would put further pressure on already water-scarce regions and compete with other users. By applying an environmentally extended multiregional input-output (MRIO) approach, we uncover the scarce water footprint and the interregional virtual water flows associated with sugarcane-derived biofuel production driven by domestic final consumption and international exports in 27 states in Brazil. Our results show that bio-ethanol is responsible for about one third of the total sugarcane water footprint besides sugar and other processed food production. We found that richer states such as São Paulo benefit by accruing a higher share of economic value added from exporting ethanol as part of global value chains while increasing water stress in poorer states through interregional trade. We also found that, in comparison with other crops, sugarcane has a comparative advantage when rainfed while showing a comparative disadvantage as an irrigated crop; a tradeoff to be considered when planning irrigation infrastructure and bioethanol production expansion.

Highlights

The interdependency between land, energy, and water systems has gained increasing interest as demand for these vital resources is growing around the world, leading to resource scarcity and adverse environmental impacts [1]
To calculate virtual water flows (VW), we extended the multiregional input-output (MRIO) system based on Leontief’s demand-drive model, Equation (1), with the water coefficient matrix, as follows: x = (I − A)−1(y + e) where x is a vector of the gross output of the 3969 industry sectors; I is an identify matrix; A = Z/x, is a technical coefficient matrix describing inputs into the production of industry sectors to produce one unit output of these sectors and the hat symbol denotes the diagonalization of gross output vector x; (I − A)−1 is the Leontief inverse matrix which captures the total input requirement to produce one unit of final consumption product; and y is the summation of rows for final consumption matrix Y
It is worth noting that the grey water footprint triggered by sugarcane production is 64% higher than its blue water footprint, a significant amount that has to be taken into account when comprehensively assessing total water appropriation due to water pollution by sugarcane and ethanol production

Summary

Introduction

The interdependency between land, energy, and water systems has gained increasing interest as demand for these vital resources is growing around the world, leading to resource scarcity and adverse environmental impacts [1]. There is increasing competition for these resources from other economic sectors, domestically and from abroad. The stress on these resources is further enhanced through their vulnerability to climate change. Several world regions are already experiencing security challenges in food, energy, and water systems (FEWS), adversely affecting sustainable development [1]. In this context, the bioenergy sector is at the core of the energy-water nexus. The impacts may be even higher, especially given climate change [6]

Methods

Results

Conclusion