Assessing the life cycle environmental impacts of hydroelectric generation in Ethiopia

Highlights

• Eleven operational hydropower plants in Ethiopia were environmentally assessed using LCA.

• Medium-scale hydropower plants have higher impacts than large plants, which confirm the belief that large hydropower is cleaner than smaller one.

• Construction and installation phase causes significant environmental impacts.

• Contribution of transportation is less than 2%.

• End-of-life recycling of metal scraps effectively leads to reduced metal depletion.

Introduction

Renewable energy sources are considered as promising options for mitigating energy security and ensuring environmental sustainability. Hydropower is one of the renewable power generation technologies with considerable potential to reduce net fossil-based greenhouse gas emissions next to solar and biomass [1]. Hence, hydropower plays an important role in renewable power generation worldwide. According to the 2019 reports of the International Renewable Energy Agency [2] and International Hydropower Association [3], the global total installed hydropower capacity in 2018 was 1292.4 GW, which was 55% of the total renewable power. According to these reports, the new hydropower capacity put into operation in 2018 was around 21.8 GW where China added the largest capacity (8.5 GW), followed by Brazil (3.9 GW) and Pakistan (2.5 GW. In the same year, total hydropower installed capacity in Africa was 36.7 GW, which was 8.4% higher compared to the year 2017. Ethiopia, South Africa, Angola, Egypt and Congo Democratic Republic have the highest developed hydroelectric power with an aggregated installed capacity of 16.1 GW that represents 43.9% of the installed capacity of the region.

The existence of many large rivers that flow from highlands to lowlands endowed Ethiopia a huge hydropower potential. Ethiopia is often described as the water tower of northeastern Africa. The gross, technical and feasible hydropower potentials of the country are about 74, 45 and 18 GW respectively, which are equivalent to about 954, 286 and 143 TWh electricity per year [4], [5]. The current hydropower installed capacity has reached 3822 MW [3], which is only 8.5% of the technically feasible hydropower potential. Ethiopia is developing hydropower plants, as it is relatively cost effective, not only to fulfill the domestic needs but also to export surplus electricity to the neighboring countries. There are big hydropower projects that are under construction, including the halfway finished Grand Ethiopian Renaissance Dam (GERD), probably the largest hydroelectric power plant in Africa with capacity of 6350 MW [3]. With the objective to meet domestic energy demand and climate change control initiatives, the government has set its climate resilient green economy (CRGE) strategy implementation plans to develop hydropower up to 22,000 MW by 2030 [6].

Hydropower plants convert the potential or kinetic energy of water into electricity. They don’t burn fuel to generate energy and hence they have low environmental impacts compared to conventional fuel-based energy technologies. However, studies revealed that hydropower development has considerable direct and indirect ecological and social impacts [7]. The direct impacts include disruption of river ecosystems and habitants due to damming of rivers, siltation, and displacement of people and risk of failure. These direct and local impacts can be identified and evaluated using relevant environmental impact assessment methods and proper mitigation measures could be incorporated during planning phase. On other hand, the indirect impacts arise due to natural resource consumptions and emissions during their life cycle stages. These indirect and global impacts should be examined from system perspective.

Life cycle assessment (LCA) is a well-established and standardized method for identifying and evaluating potential environmental impacts of product systems throughout their life cycle stages in holistic manner [8]. LCA has been applied to assess overall impacts associated with energy technologies and systems on holistic perspective covering raw material extraction and production, component manufacturing, construction, operation and end-of-life waste management [9], [10], [11], [12], [13]. In addition to primary actual impacts, LCA also considers induced potential impacts related to supply chains of inputs and processes. Because potential impacts may be more important than the primary ones, Pang et al. [14] recommends they should be considered if the purpose of the LCA study is to compare energy technologies or to support policy decisions. In the last two decades, LCA has been widely used to assess the environmental impacts of energy systems [10], [15], [16], [17], [18], [19]. Regarding hydropower generation systems, there are many LCA studies focusing on either to evaluate single impact indicator such as GHG emission (e.g. [20], [21], [22], [23]), water footprint [24], [25], [26] or group of these impacts like GHG emission and energy intensities [27], or several of these factors [14], [28]. Other LCA studies presented the effect of size, type and location on impacts of hydropower systems. For instance, Zhang et al. [27], Bakken et al. [24] and Atilgan and Azapagic [29] claimed that impacts of large hydropower systems are lower than smaller ones for the same energy output because larger projects usually have a longer lifespan as well as greater output. Moreover, Zhang et al. [30] evaluated two hydropower systems: one with earth-core rockfill dam (ECRD) and the other with concert gravity dam (CGD) and found that the former is more environmentally friendly than the later one.

Most of the LCA studies on hydropower have been done in Asia (mainly in China), North America and Europe. Although the environmental performance of hydropower plants depend on their types, sizes and locations [31], [32], [33] and electricity data is vital to perform LCA studies for other product systems [34], there are only few studies for Africa [31], [35] based on LCI data from secondary sources and databases. There is no reported LCA study on hydroelectric generation technologies from Ethiopia. The main objectives of this study are, thus, to estimate the average LCA data for operating hydropower plants; to identify the highest contributing process to the overall impact and to compare the environmental performance of these plants with other hydropower plants studies in the world. This study would provide a significant basis for conducting LCA studies on other products and generate performance metrics such as environmental product declaration (EPD) for economically significant export products of Ethiopia. The study has also regional significance as the Ethiopian electric system has been already supplying electricity to Sudan and Djibouti and envisioned to supply to other countries in the region.