The Water-Energy-Food Nexus (WEF Nexus) addresses the interrelated nature of our global natural resource systems. This reflection aims to better understand the interactions between the natural environment and human activities, and to suggest a more coordinated management and use of natural resources. A set of solutions are proposed and some best practices at the international level on the coordinated use of water and energy are presented.
Keywords: WEF Nexus, Integrated Resource Management, Water and Energy Security
JEL classification: Q24, Q25, Q28, Q40, Q42, Q 48
Suggested citation: Alloisio, Isabella, The Water-Energy-Food Nexus (July 31, 2015). Review of Environment, Energy and Economics (Re3), http://dx.doi.org/10.7711/feemre3.2015.07.003
The Water-Energy-Food nexus (WEF nexus) addresses the interrelated nature of our global natural resource systems. It presents a conceptual approach to better understand and systematically analyze the interactions between the natural environment and human activities, and to work towards a more coordinated management and use of natural resources across sectors and scales. The WEF nexus is a key topic in the post-2015 sustainable development agenda, and it aims to tackle simultaneously different issues, such as food and water security, the connection between global warming and water scarcity, and between climate change and food production, as well as energy security, and the connection between energy production and water and land use. (Fig.1).
Figure 1 - The Water-Energy Food Nexus
Global projections indicate that demand for freshwater, energy and food will increase significantly over the next decades under the pressure of population growth and mobility, economic development, international trade, urbanization, diversifying diets, cultural and technological changes, and climate change (Hoff H., 2011) Climate change will exacerbate the pressures and risks associated with variations in the availability and distribution of water resources, and consequently of food and energy supply. By 2050, global water demand is projected to increase by 55 percent, driven mainly by growing urbanization in developing countries, whereas total global water withdrawals for irrigation are projected to increase by 10 percent. By the same year, 60 percent more food will need to be produced in order to feed the world population, which is predicted to reach 9.1 billion (UNDESA, 2013). Global energy consumption is projected to grow by one third, with the demand for electricity having the lion’s share with a 70 percent increase by 2035 (IEA 2013).
The WEF nexus approach, alike the integrated water resources management (IWRM), considers the different dimensions of water, energy and food on the same level playing field and recognizes the interdependencies of different resource uses. Because of its complexity, the WEF nexus is not characterized by a single all-fitting solution, but instead by the need for an integrated approach in order to find solutions on how to provide food, energy, and water for a population of 9 billion by mid-century, without overwhelming our environment.
The Water-Energy Nexus
Water and energy are closely interdependent, as they are major consumers of one another, and choices made in one domain have direct or indirect consequences on the other. Energy is required for the extraction, treatment and distribution of water, and electricity accounts for an estimated 5-30 percent of the total operating cost of water and wastewater utilities. On the other hand, water is required to produce, transport and use nearly all forms of energy. Freshwater withdrawals for energy production accounted in 2010 for 15 percent of the world’s total water use, and are expected to increase by 20 percent through 2035 (IEA 2013).
The power sector’s dependence on water creates vulnerabilities and risks that are exacerbated by extreme weather events induced by climate change. Severe droughts or elevated temperatures may lead to diminishing the performance of thermal power plants - which are high water intensive – or can even hinder the capacity of the power sector to achieve sufficient cooling, thus leading to power outages. Therefore, water constraints are among the most important factors for deciding where to build power plants and what specific cooling system to opt for. Cooling systems without the use of water exist, such as air cooling, but at present these are prohibitively expensive. Conversely, climate change can also benefit electricity production in certain areas exposed to an increase in precipitations.
Unlike in the water sector, the energy sector can switch to other resources. Water resources required in power generation can be substituted, e.g. by solar and wind energy. The latter not only have a very low carbon footprint, but also consume little water. Nevertheless, wind and solar energy have the important disadvantage of being intermittent and thus needing base load systems such as thermal power or hydropower. Conversely, although other Renewable Energy Sources (RES) such as hydropower, concentrated solar power and biofuels reduce the carbon footprint, they have a very high water footprint. Among RES a special focus is reserved for geothermal energy power plants, which have the dual advantage of producing base load and clean energy and of having a low water footprint. In particular, geothermal binary cycle power plants utilize a closed loop system allowing for the re-injection of water back into the geothermal reservoir.
As for fossil fuel-based energy, thermal power plants use large quantities of water because of cooling systems that are responsible for around 50 percent of total freshwater withdrawal . In the upstream sector, extraction and production of unconventional energy sources are much more water intensive than conventional oil and gas. Both the hydraulic fracturing technique (better known as fracking) for shale gas extraction, and open-pit mining or in situ drilling techniques for tar sand extraction require a barrel of water for each barrel of gas and oil produced.
In the field of climate change mitigation, Carbon Capture and Sequestration (CCS) systems are very important in any national decarbonization pathway. Nevertheless, implementing CCS in an existing power station will have some effect on its water consumption, requiring additional water for cooling. Estimates show that with the addition of a CCS system, the increase in water consumption per megawatt of electrical output can be as high as 90 percent.
Having treated water consumption issues in energy production, we will now illustrate one example of energy need for water production. Desalination of salt water and pumping of freshwater supplies over long distances may contribute to reducing water scarcity, but in the process it will increase energy use. Desalinated seawater is very high energy intensive compared to clean water from locally produced surface water and from reclaimed wastewater. Moreover, the two most common techniques for desalination have both an important although different water footprint. Indeed, if reverse osmosis plants consume 4-6 kWh to desalinate one cubic metre of treated water, the multistage flash technique consumes much more, up to 21-58 kWh per cubic metre.
The Food-Energy Nexus
Agriculture is linked to energy markets through both indirect and direct costs, and also through the competition of resources, such as water and land for production of food or energy crops.
Energy is not only required to extract, treat and distribute water, but also to produce, transport and distribute food. According to FAO (FAO 2011), the food production and supply chain consumes about 30 percent of the total energy consumed globally. At the same time, the energy sector can negatively impact food production by reducing available land, for instance, through deforestation for biofuels. Not only do biofuels have an impact on land use change but they are also substantially more water intensive than fossil fuels. They require about 10,000 - 100,000 litres of water per GJ of energy, whereas oil and gas production require about 1 - 10 litres per GJ of energy, and oil sands about 100 - 1000 litres (WEF 2011). It is worth noting that water use in biofuel production depends greatly upon feedstock and location. If India relies mostly on blue water (rivers) for irrigation, Brazil is mostly green-water (rainfall) dependent.
Biofuels can compete with food production for water and land and can potentially lower the resilience of food production systems. As for the water footprint, it takes about the same amount of water to produce one litre of liquid biofuel as it takes to produce food for one person for one day. A shift to ligno-cellulosic (second generation) biofuels would decrease competition for land and water. However, this would primarily result in a shift to resources with other opportunity costs, if for example biofuels were grown on marginal lands, rather than a reduction of total resource use. Large potentials for reducing freshwater and land use may lie in the use of algae (third generation biofuels), although this technology is not yet available (Hoff H. 2011).
Biofuel development has also other important drawbacks, as it is generally assumed to be the largest factor in the price increases of cereals on world markets. Evidence exists for the influence of growth in crop-based biofuel production and the supply of grains available on international markets for food and feed production. For example, between 2002 and 2007 the production of ethanol from maize in the United States was responsible for a 30 percent increase in global wheat and feed grain use, and by 2007, nearly a quarter of all maize produced in the US was diverted to ethanol production. Some countries have tried to modify their biofuel production, such as China (the third-largest bio-ethanol producer after the US and Brazil), which has recently moved away from maize to other feedstocks, such as jatropha, because of national food security concerns.
Another aspect that is worth mentioning is net-negative emission technologies, i.e. when CCS is applied to bioenergy. Prospects for the development of this technology seem very uncertain and competing with other sustainable development objectives, such as food security or the protection of biodiversity. Similarly, fuelling future mobility needs with biofuels is deemed to be highly questionable in the longer run.
There are no blueprint solutions, nevertheless a number of areas of opportunity for sustainably improving water, energy and food security exist. These include opportunities for improving water use efficiency in the energy sector, such as:
And opportunities for increasing energy use efficiency in water production and delivery, such as:
The increasing pressure of climate change can provide new opportunities for overcoming lock-in and facilitating integrated resource planning and Sustainable Development Goals (SDGs). The latter, unlike Millenium Development Goals (MDGs), focus on issues of equitable access to natural resources, and as global challenges require global solutions.
If natural resources were managed in a competitive way and through separate approaches such as IWRM, in view of achieving global solutions they should be managed instead in a collaborative way by taking into due consideration the WEF nexus. Fully comprehensive integrated resource planning would help in managing trade-offs and could maximize co-benefits among multiple sectors, and contribute to diminishing costs and guaranteeing a sustainable use of all natural resources.
Technological innovation is needed for increasing resource productivity, and investments that lock development into non-sustainable pathways must be strictly avoided. If investments that increase water or land productivity were designed with the WEF nexus in mind, they would not have a negative effect on energy productivity and the environment, but could instead increase overall resource use efficiency (Hoff H, 2011).
Furthermore, a proper integration of climate change consciousness in the planning and design of infrastructure investments could reduce considerably the risk posed by future climate projections to the physical and economic performance of weather-dependent technologies, such as hydropower plants.
A coherent mitigation policy based on national resource endowments, and an adaptation strategy that balances the risk of inaction with the risk of adapting to climate change in the wrong way (Cervigni G., et al.)., together with careful consideration of all interrelated aspects of the WEF nexus, are pivotal for any suitable energy and climate policy.
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Hoff H. 2011. Understanding the Nexus. Background Paper for the Bonn 2011 Conference: The Water, Energy and Food Security Nexus. Stockholm, Sweden: Stockholm Environment Institute (SEI).
IEA. 2013. World Energy Outlook 2013. Paris. OECD/IEA
UNDESA. 2013. World Population Prospects, the 2012 Revision. New York, Population Division, United Nations (UN), 2013
UNESCO. 2014. The United Nations World Water Development Report 2014. Facing the Challenges, WWDR 2014, Vol. 2
World Economic Forum. 2011. Water Security: Water-Food-Energy-Climate Nexus. The World Economic Forum Water Initiative. Edited by Dominic Waughray. Washington D.C., USA. Island Press.