3.3.3. Example: Energy Analysis in Biodiesel Production from Oilseeds
Different oilseeds can be used for energy production in the form of biodiesel. Energy use efficiency in biobased systems is defined as the ratio of energy output to energy input. Energy use efficiency of oilseeds production varies based on the type of oilseed and location. Some oilseeds such as canola and carinata have relatively low energy use, while the production of sesame requires a higher energy use (Table 3.3). Energy use efficiency of oilseeds production ranges from ~1.5 for sesame to 4.28 for canola.
Experimental studies have been conducted to analyze energy use in biofuels from bio‐based systems. Energy inputs during crop production, transportation, and conversion processes for canola and carinata were estimated based on experimental studies in Spain (Cardone et al. 2003). It was found that energy was mainly used in the oilseed production and transportation steps (Figure 3.3). There are several transportation steps, including transportation of oilseeds from fields to the elevator (local storage), which is mainly done by trucks, transportation from storage facilities to the oil extraction facilities, and delivery of oil to the biorefineries using rail transportation facilities. Energy use for extraction of oil from oilseeds and conversion to biodiesel is low because of the high capacity of industrial facilities at the biorefineries.
3.3.4. Energy Supply from Bio‐Based Systems
Biomass has been identified as the most reliable potential source of energy and feedstock for the industrial sector until 2050 (United Nations Industrial Development Organization, 2019). Currently, biomass supplies 10% of the total energy demand, and 68% of this is in the form of fuelwood (World Energy Council, 2016). One third of energy use in pulp and paper industries is supplied by biomass and waste (United Nations Industrial Development Organization, 2019). Utilization of biomass as a feedstock is being expanded to the fuels and chemicals industries that used to be conventionally supplied by petroleum‐based sources. Based on the estimation by United Nations Industrial Development Organization (2019), by 2050, biomass can supply 37%, 25%, 18% and 10% of the total process heat in chemical and petrochemical, non‐metallic minerals, paper and pulp, and wood and woody products industries, respectively. In 2016, biomass was the only renewable source of liquid fuel in the transportation sector with 103 billion L of ethanol, 31 billion L of biodiesel and 5.9 billion L of hydrotreated vegetable oil produced globally, which contributed to only 0.3% of the total energy demand (REN21, 2018). However, an increase in bio‐based products from $203 billion worth in 2015 to $487 billion worth in 2024 was forecasted (Biotechnology Innovation Organization, 2017). Biofuels and biochemicals offer several advantages such as lower environmental impacts and product security when compared to depleting petroleum‐based fuels and chemicals, which drives the expansion of the bio‐based economy and incentivizes the development of bio‐based systems.
Table 3.3 Total energy use and energy use efficiency of oilseeds production.
Sources: Adapted from Ruiz‐Mercado, G. J., Smith, R. L., and Gonzalez, M. A. (2012). Khan, S., Khan, M. A., Hanjra, M. A., and Mu, J. (2009).
| Oilseed | Total energy use (MJ/t)* | Energy use efficiency (decimal)* | ||
|---|---|---|---|---|
| Average | SD** | Average | SD** | |
| Soybean | 9360 | 3248 | 2.43 | 0.79 |
| Canola | 5565 | 1124 | 4.24 | 1.40 |
| Carinata | 4340 | 1732 | 3.14 | 1.09 |
| Sunflower | 8532 | 2580 | 3.25 | 1.09 |
| Sesame | 1 5930 | 1793 | 1.57 | 0.19 |
* Data were collected from Canakci et al., 2004; Cardone et al., 2003; Hamzei and Seyyedi, 2016; Iriarte et al., 2010; Kallivroussis et al., 2002; Kusek et al., 2016; Mousavi‐Avval et al., 2017; Mousavi Avval et al., 2011; Pahlavan et al., 2012; Ramedani et al., 2011; World Energy Council, 2016.
** SD stands for standard deviation.
Figure 3.3 Energy use in different steps of biodiesel production from canola and carinata as the feedstock.
Source: Cardone, M., Mazzoncini, M., Menini, S. et al. (2003).
Figure 3.4 Interconnection of water‐energy and SDGs.
3.4. THE FRAMEWORK FOR WATER‐ENERGY NEXUS IN BIO‐BASED SYSTEMS
Energy is used in water supply, and the bio‐based systems use water and energy to produce different types of biofuels and bioproducts (Figure 3.4). For developing the bio‐based systems, sustainable use of energy and water in the production of fuels and chemicals is a challenging task. Sustainability of energy and water in bio‐based systems needs to be considered collectively and cannot be effectively resolved in isolation. While addressing the SDGs, to deal with this issue, a nexus approach is needed. The water‐energy nexus is one of the most complex, yet critical, issues that the society faces. Water and energy are interconnected resources that face numerous challenges including a growing global population, economic crises, poverty, hunger, and climatic uncertainties.
Water‐energy nexus refers to the relationship of how energy is used in water supply, and how water is used in energy supply and conversion (Figure 3.5). In bio‐based systems, the main products follow the post‐harvest logistics for delivery to the conversion step, while by‐products are used for other purposes. Then, biomass is converted into biofuels and electrical energy which is used to supply water for cultivation of agricultural crops in the bio‐based systems.
Developing renewable energy sources from bio‐based systems creates additional stress on water resources. For this reason, the lack of water availability in some regions limits the development of bio‐based energy systems. Water demand for biofuels production ranges widely;