Water is a critical and potentially limiting factor for the development of biofuels. The agricultural sector already uses over 70 percent of available freshwater resources. By 2025 an estimated 1.8 billion people will live in areas with absolute water scarcity. Some of the same pressures on land availability also apply to water availability, such as population growth. Climate change may also change rainfall patterns, which could then affect local water supplies.
Water is a critical and potentially limiting factor for the development of biofuels...
Figure 3.3.1 compares the water necessary to produce, transport, and convert a given crop into a fuel in two different regions. This shows important variations, and points to the need for careful matching of energy crops and production and conversion systems with available water supplies. The global trade in biofuel crops has created a ‘virtual water exchange’ where some countries with low water resources ‘export’ their water in the form of biofuels.
It is important to consider not only the efficient use of water in the context of a single activity, but also the cumulative effects of several activities in one region on a watershed. Usually a distinction is made depending on the source of the water, for example whether production is entirely rainfed or irrigation is needed. An illustration of the water requirements of selected biofuel crops shows which biofuels demand the most water.
Figure 3.3.1 - Variation in blue water footprint for selected energy crops
Box 3.3.1 Water footprint
The water footprint of an individual, community or business is defined as the total volume of freshwater used to produce and consume goods and services. It is an indicator of water use that looks at both direct and indirect water-use of a consumer or producer. Water use is measured in water volume consumed (evaporated) and/or polluted per unit of time.
The total water footprint comprises three different types of water – green water, blue water and grey water. Green water refers to water which has evaporated during crop
The water footprint is one of several concepts and tools developed to measure the impact of water flow and consumption in terms of quality or quantity. Applying various tools helps to gain a more comprehensive view of effects, both isolated aspects as well as interrelated effects of biofuel growth; Blue water is the amount of (evaporated) surface and ground water used for irrigation; and Grey water refers to water contaminated during the production process.
The international Standard for Water Footprinting specifies requirements and guidelines to assess and report the water footprint based on LCA. The standard aims for consistency with carbon footprinting and other LCA impact categories.
Source: UNEP (2009) Guidelines for Social Life Cycle Assessment of Products, UNEP (2010) http://lcinitiative.unep.fr
The water footprint is one of several concepts and tools developed to measure the impact of water flow and consumption in terms of quality or quantity. Applying various tools helps to gain a more comprehensive view of effects, both isolated aspects as well as interrelated effects of biofuel production and agriculture. Water availability varies in space and time, so water appropriation should always be considered in its local context. This can be measured by studying the changes in isotopic composition of local water, or standard mean ocean water (SMOW).
Moreover, underlying data sources need to be interpreted in context. For example, rainfed jatropha is produced in Mali as a biofuel, which means that it receives less water than in many comparable contexts, but also with somewhat lower output of biofuel. India in contrast, has been irrigating jatropha to achieve commercially acceptable yields. The two contexts will produce different water footprint measurements. Sugarcane is a good example of how these figures might be confusing, because sugarcane is a water-intensive crop but, depending on local conditions, it can have a lower water footprint relative to fuel output.
Figure 3.3.2 - Average water requirement for biofuels
Figure 3.3.3 - Nitrogen runoff
Figure 3.3.4 - Agrochemical use in US agriculture
Water quality issues are also important. Fertiliser and pesticides used to cultivate feedstocks, as well as contaminated effluents discharged from conversion plants, can cause increasing levels of pollution to waterways. This may constrain the growth of biofuels production in developed and developing countries with already high agricultural production levels.
An example illustrates the level of nitrogen persistent in various regions of the United States and agrochemical use for different feedstocks.
Similarly, agricultural runoff is pervasive in the Mississippi river basin, an area also known as the country’s corn and ethanol belt. Although much of the runoff is linked to corn production for food, feed and fodder, further increases in biofuel crops might cause an overload in runoff into these water bodies to the point where they cannot recover. It is worth noting that a potential collapse of the watershed could occur as a result of the cumulative effects of environmental stress from agricultural production alone, and not just from biofuels production. This example highlights the need to enact policies safeguarding overall water availability and quality over an entire watershed, promote water-efficient biomass production, and implement water-efficient management methods.
Figure 3.3.5 - Agriculture in the Mississippi River Basin
Figure 3.3.6 - Biofuels in China: crop production and water scarcity
Box 3.3.2 Firm strategy for biofuels in China
In 2009 China produced 2 billion litres of biofuels, ranking the country third behind Brazil and the USA. The Chinese government has set ambitious targets seeing biofuels as not only contributing to the country’s rapidly expanding energy needs, but also as a way of providing rural employment. With China having 20 percent of the world’s population but only seven percent of its arable area, biofuels production is clearly constrained by land availability. However, a far more precious resource may be the most limiting factor yet: water.
Southwest China has seen large biofuels development partly sustained by access to large water reserves including two of the world’s great rivers – the Yangtze and the Mekong. Despite access to a more plentiful supply of water from these rivers there are concerns about the impact of mass cultivation of biofuels on water resources and quality. In the north, with only 14 percent of China’s water resources, the challenges related to biofuels production could be far more acute, according to the China Institute of Water Resources and Hydropower Research.
Water management is an increasingly difficult balancing act between electricity generation, food production, industrial use and direct human consumption. An example of a water management strategy in China is the recent South-to-North Water Diversion Project. Started in 2010, it is an example of ambitious geo-engineering to rewire the water map of China. This project seeks to quench the thirst of stressed regions in the north facing, amongst other things, the possibility of expanded biofuels production that would inherently compete for the same water as is needed for growing other crops, including food.
Recognising these interactions, and in response to price increases for food crops around the world in 2007-8, the government has imposed a ban on further construction of biofuels plants using grain as feedstock. Chinese biofuels production - so far mostly based on corn and wheat - is now looking for other feedstocks, including those for advanced biofuels. Effects on overall food production and land use remain to be monitored.
The case of China illustrates the importance of national planning processes, such as creating comprehensive water-management strategies, and addressing the complexity of interactions at the outset. At the same time, biofuels policies should be flexible to allow scope for adjusting them and national strategies as science and research advance.
Source: Global Subsidies Initiative (2008). Biofuels – at what cost? Government support for ethanol and biodiesel production in China. U.S Department of Agriculture (2009). China Biofuels Annual. GAIN Report Number: CH9059 IEA (2010). Sustainable Production of Second Generation Biofuels www.iea.org/papers/2010/second_generation_biofuels. pdf ICRAF: The World Agroforesty Centre (2007). Biofuels in China: An analysis of the opportunities and challenges of jatropha curcas in SW China.