https://aseaniwrm.water.gov.my/about‐us/2 2 https://sustainabledevelopment.un.org/memberstates
3 Water‐Energy Nexus in Bio‐Based Systems
Seyed Hashem Mousavi‐Avval1, Asmita Khanal1, Juliana Vasco‐Correa1, Luis Huezo1, and Ajay Shah1*
1Department of Food, Agricultural and Biological Engineering, The Ohio State University, Wooster, OH, USA
*Corresponding author
ABSTRACT
Bio‐based systems, namely those producing fuels and non‐food products from biomass, could affect the path towards achieving the United Nations’ Sustainable Development Goals (SDGs). A nexus approach is needed to evaluate the sustainability of bio‐based systems in terms of supply and use of energy and water. Evaluation of water and energy interconnections in the bio‐based systems by a nexus approach helps improve water and energy security by integrated management of the resources use, while transitioning to a greener economy. This chapter focuses on water and energy supply and use in bio‐based systems and discusses the interconnection between water and energy, exhibited in the water‐energy nexus. Then, the metrics and decision‐making tools to evaluate the sustainability of water and energy in bio‐based systems are explained. Finally, the challenges and opportunities in the sustainable development of energy and water supply and use in bio‐based systems are discussed.
3.1. INTRODUCTION
Bio‐based products and fuels are produced from renewable biomass sources such as conventional food crops and dedicated energy crops, forestry products, and organic residues (Langeveld et al., 2010). Bio‐based systems refer to those producing non‐food bio‐products and biofuels, and they consist of the biomass production and conversion processes. Bio‐products include a wide variety of products from those with low value and high volume, such as glycerin and lactic acid, to those with high value and low volume, such as those used in food or pharmaceuticals industries (Langeveld et al., 2010). Biofuels include gas, liquid, or solid fuel types produced directly or indirectly from biomass. The bio‐based systems in this book chapter refer to those which are used to produce agricultural crop‐based biofuels.
3.1.1. Bio‐Based Systems for Achieving the Sustainable Development Goals
One of the challenges of the twenty‐first century and beyond is the development of secure and sustainable sources of energy, and supply of clean water and food for the exponentially growing world population (Waskom et al., 2014). World primary energy consumption in 2015 was estimated as ~13.7 Billion Tons of Oil Equivalent (IEA, 2018). In addition, the world water use in the same year was estimated as ~ 4 trillion m3 (IGBP, 2015). Population growth creates shortage in energy, water and food supply. By 2050, compared to 2015, 80% more energy and 55% more water will be required to meet the increasing population demand (Waskom et al., 2014). The countries are responsible to facilitate the effective implementation of the Sustainable Development Goals (SDGs), set by the United Nations General Assembly (UNCTAD, 2014). Among the SDGs, those related to the conservation of the natural resources and environment are of high importance for reducing the risks of natural disasters and ensuring the resource security for future generations. Bio‐based systems play an important role in achieving the SDGs by: (i) sustainable management of water resources (SDG 6), (ii) sustainable development of energy resources (SDG 7), (iii) adopting the sustainable production and consumption concept (SDG 12), and (iv) developing the renewable energy sources for tackling climate change (SDG 13).
Figure 3.1 Carbon cycle of biofuels.
Substituting petroleum‐based fuels with biofuels allows the conservation of natural resources and mitigates greenhouse gas (GHG) emissions by reducing the environmental burdens associated with petroleum‐based fuels, thus contributing to the attainment of the SDGs. The supply of biofuels mitigates the environmental impacts due to the use of fossil fuels, because of carbon dioxide uptake by plants during the growing phase (Figure 3.1).
3.1.2. Interconnection of Water and Energy in Bio‐Based Systems
Water and energy are two necessary resources for human life. Energy production from bio‐based systems can reduce the environmental impacts and increase the energy security of the nations by reducing the reliance on fossil fuels. Water being a scarce source is important in biobased systems. Thus, bio‐based systems can contribute help achieve the global climate change mitigation goals, but this needs valuable resources such as water and energy in the process. Some of the other key concerns associated with the development of bio‐based systems include food security because of the use of food crops for energy supply, risks of increased emissions during biomass production and processing, and reduction in biodiversity due to land use change by expansion of bioenergy crops. External factors such as lack of economic competitiveness of biofuels with petroleum‐based fuels is also restricting the expansion of bio‐based systems for energy purposes. Development of bio‐based systems that advance the SDGs requires policies and measures to ensure sustainability of the systems (IRENA, 2019), including a rational use of energy and water throughout the entire cycle.
3.1.3. Overview of the Chapter
The goal of this chapter is to exhibit the interactions of water and energy in the development of bio‐based systems as a mean for achieving the SDGs. Accordingly, energy use and supply in bio‐based systems are explained, and water supply for bio‐based energy production as well as the role of bio‐based energy in water supply are discussed. Then, the water‐energy nexus in bio‐based systems is presented, and finally the tools and metrics for quantifying the sustainability of water‐energy nexus are explained.
3.2. WATER SUPPLY AND USE IN BIO‐BASED SYSTEMS
3.2.1. Water Availability
More than two thirds of the earth’s surface is covered with water (USGS, 2016). However, ~97.5% of that is saltwater which cannot be used for industrial, agricultural, or residential purposes. Of the remaining freshwater, ~1.75% is frozen in glaciers, and the rest is available as ground water (~0.68%) and freshwater in lakes and rivers (0.07%) (USGS, 2016). Freshwater is used for residential purposes (11%), industries (19%), and agriculture (70%) (FAO, 2016). Water is essential in all sectors, and bio‐based systems utilize large quantities of water, increasing the pressure on this already scarce resource. Water in bio‐based systems is not the most expensive input; however, unlike other resources, it has no substitutes. Water is required at different stages in bio‐based systems, from irrigation during biomass production up to recovery of the final products after biomass processing. However, water consumed during biomass production and processing have different intensities of water use. Water used for irrigation during biomass production is consumed in the process, which means no wastewater is generated. However, some of the water used during the processing may be reused by wastewater treatment and purification processes. Steam used in the process can also be reused after being condensed to water.
3.2.2.
