There is, by now, a general consensus that transitioning to a low-carbon economy is critical for mitigating the effects of climate change. Supporting carbon-cutting efforts entails a move away from fossil fuel-fired power generation and concurrently a shift towards low-carbon electricity sources. How much of a country’s energy should come from renewable sources is debatable and generally needs to be determined with awareness to countries’ peculiar needs and their respective stages of economic development.
A new study examines the environmental impacts and resource requirements of large-scale global implementation of a variety of low-carbon power generation technologies as backbone of a new low-carbon power supply infrastructure. Basically, this research goes one step further than previous life-cycle assessments (LCAs), now tracing the interaction between different technologies and therefore picking up where those static LCAs of individual technologies left off. Namely, “that, per unit generation, low-carbon power plants tend to require more materials than fossil-fueled plants and might thereby lead to the increase of some other environmental impacts.” In this respect, the primary focus is on two interesting questions:
1. Would a shift to low-carbon electricity systems increase or decrease other types of pollution?
2. Would the material and construction requirements of such an infrastructure be large relative to current production capacities?
The authors of this research study are Edgar G. Hertwich and Thomas Gibon of the Norwegian University of Science and Technology in Trondheim and their colleagues. The study entitled “Integrated life-cycle assessment of electricity-supply scenarios confirms global environmental benefit of low-carbon technologies” is published in the renowned science journal ‘Proceedings of the National Academy of Sciences’ (PNAS). The authors explain their new research design as follows:
“Energy-scenario models normally do not represent the manufacturing or material life cycle of energy technologies and are therefore not capable of answering [the above] question[s]. (…) To assess the trade offs of increased up-front emissions and reduced operational emissions, we present, to our knowledge, the first global, integrated life-cycle assessment (LCA) of long-term, wide-scale implementation of electricity generation from renewable sources (i.e., photovoltaic and solar thermal, wind, and hydropower) and of carbon dioxide capture and storage for fossil power generation. We compare emissions (…) for the climate-change-mitigation (…) and business-as-usual (…) scenarios of the International Energy Agency up to 2050 [thereby examining] impacts in terms of greenhouse gas (GHG) emissions, eutrophication, particulate-matter formation, and aquatic ecotoxicity resulting from pollutants emitted to air and water throughout the life cycle of each technology. We also compare the life-cycle use of key materials (namely aluminum, iron, copper, and cement), non-renewable energy, and land for all investigated technologies per unit of electricity produced.”
So, why is this study significant and unique?
The authors stress that this LCA addresses “the feedback of the electricity system onto itself and [uses] scenario-consistent assumptions of technical improvements in key energy and material production technologies.”While renewable technologies can require much higher initial investments in infrastructure than fossil fuel-fired power systems, the authors’ main finding in the study at hand is that “only two years of current global copper and one year of iron production will suffice to build a low-carbon energy system capable of supplying the world’s electricity needs in 2050,” with the potential to reduce pollution-related environmental impacts of power generation. And this conclusion remains valid in the face of a connected finding that “11–40 times more copper for photovoltaic systems and 6–14 times more iron for wind power plants [are required per unit of generation vis-à-vis comparable conventional power plants].”
In detail, the comparative LCA of technologies yields the following research results:
1. Renewable energy sources have significantly lower pollution-related environmental impacts per unit of generation than, for example, state-of-the-art coal-fired power plants and even modern natural gas combined cycle power plants (NGCC) in all of the impact categories considered. Note, while the latter tend to lie between renewable technologies and coal power in terms of climate change and ecotoxicity (for that, see EPA here) – i.e. the study of toxic effects caused by natural or synthetic pollutants on the entire ecosystem such as “nonhuman organisms, populations, or communities” – NGCC plants, most importantly, show much higher contributions of particulate matter exposure (see graphic B). Perhaps surprisingly, this holds true for both examined scenarios – with or without CCS (Carbon Capture and Storage). This indicates that natural gas is not as ‘clean’ as the current US government often reports.
2. Wind and solar power plants tend to require more bulk materials (iron, copper, aluminum, and cement) than coal- and gas-fired electricity per unit of generation (see graphics G–J). In this respect, the report notes: “For renewables (…) materials contribute 20–50% of the total impacts [- in contrast to fossil fuel-fired power plants’ relatively small contribution to total environmental impact -] with CSP tower and offshore wind technologies showing the highest shares. [Overall,] the environmental impact of the bulk material requirements of renewable technologies (…) is still small in absolute terms compared with the impact of fuel production and combustion of fossil-based power plants.”
3. While CCS reduces carbon dioxide emissions of conventional power plants it increases other life-cycle indicators especially for particulate matter or ecotoxicity (see graphics B–C). By the same token, CCS obviously requires more bulk materials for initial construction. The authors also stress that the “carbon capture process itself requires energy and therefore reduces efficiency,” which mostly explains the surge in air pollution and concomitant material requirements per unit of generation.
Environmental Impacts and Bulk Material Requirements of Power Generation Technologies
Source: Hertwich/Gibon et alia in PNAS
4. As for the material requirements, the construction and operation of the envisioned ‘2050 electricity system’ would “require less than 20% of the cement, 90% of the iron, 150% of the aluminum, and 200% of the copper” vis-à-vis 2011 material production levels, according to the study. Here, the authors draw the conclusion that “meeting copper demand could be problematic due to declining ore grades, [which, conversely,] would result in potential increases in the environmental costs of copper production.”
GHG Emissions Associated with Production of Bulk Materials for Each Technology
Source: Hertwich/Gibon et alia in PNAS; Supporting Information (SI) Appendix;
Abbreviations: PV–photovoltaics, CSP–concentrating solar power, H–hydropower, W–wind power, C–coal, NG–natural gas, Poly-Si–polycrystalline silicon, CIGS–copper indium gallium selenide, Reservoir 1–type of hydropower reservoir used as a lower estimate, Reservoir 2–type of hydropower reservoir used as a higher estimate, Offshore steel–offshore wind power with steel-based foundation, offshore gravity–offshore wind power with gravity-based foundation, CCS–CO2 capture and storage, IGCC–integrated gasification combined cycle coal-fired power plant, SCPC–supercritical pulverized coal-fired power plant, NGCC–natural gas combined cycle power plant.
While the authors of the study only seem to be concerned with the copper supply going forward, other bulk material requirements cannot be deemed completely insignificant. Rather, if the growth of renewable energy sources around the globe continues and follows along an upward trajectory, other crucial bulk materials such as met coal and iron ore may command much higher prices in the medium to long term. Additionally, this will necessitate significant cuts to current production rates for those materials first, before potentially resulting in a new commodity super-cycle when the growth of renewables eventually merges with an uptick in global economic growth. Demand for these commodities at the regional level will likely be driven by increased demand for cheap power generation in developing countries and a general construction boom in Africa, South Asia and South America.
