Rapid and deep decarbonization of power supply worldwide is required to limit global warming

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A rapid and deep decarbonization of power supply worldwide is required to limit global warming to well below 2 °C. Beyond greenhouse gas (GHG) emissions, the power sector is also responsible for numerous other environmental impacts. An international team of scientists in their study has found this.

Producing electricity in a climate-friendly brings huge benefits for our health – mainly due to a reduction of air pollution from combusting fuels.

The scientists’ study report said in the “Introduction” section:

“The international community has agreed to limit global warming to well below 2 °C, and to reach net greenhouse gas (GHG) emissions neutrality in the second half of the twenty-first century. Electricity supply is the single most important emissions source sector, accounting for around 40% of global energy-related CO2 emissions. It also offers the largest low-cost potential for emissions reductions, and thus cost-optimal strategies for keeping global warming to below 2 °C typically feature near-zero electricity sector emissions by mid-century, and rely increasingly on electrification to minimize fossil fuel use in the transport, industry and buildings sectors.”

The scientists – Gunnar Luderer, Michaja Pehl, Anders Arvesen, Thomas Gibon, Benjamin L. Bodirsky, Harmen Sytze de Boer, Oliver Fricko, Mohamad Hejazi, Florian Humpenöder, Gokul Iyer, Silvana Mima, Ioanna Mouratiadou, Robert C. Pietzcker, Alexander Popp, Maarten van den Berg, Detlef van Vuuren and Edgar G. Hertwich – write in the study report, “Environmental co-benefits and adverse side-effects of alternative power sector decarbonization strategies”, published in Nature Communications (volume 10, issue 1, 2019 article number: 5229):

“Beyond economic costs and GHG emissions, sound climate policies also have to take into account other sustainability dimensions, such as those laid out in the UN’s Sustainable Development Goals (SDGs) adopted by the United Nations in 2015. The energy sector is the origin of a wide variety of environmental impacts. While much of the public debate focuses on its contribution to global warming via greenhouse gas emissions, energy supply systems also account for substantial shares of other environmental impacts, such as air and water pollution, land occupation, water use, ionizing radiation and nuclear waste, as well as fossil and mineral resource depletion. Energy system futures therefore are particularly relevant for SDGs 3 (health), 6 (clean water), 12 (responsible consumption and production), 14 (life below water) and 15 (life on land).

“Thus far, there is only very limited system-level research on the benefits and adverse side-effects of future decarbonized power supply in terms of nonclimate environmental impacts. Process-detailed integrated assessment models (IAMs) of the energy-economy-climate system are frequently used to analyze alternative climate change mitigation strategies and their implications, with a focus on greenhouse gas emission reductions. Only recently other specific environmental impacts such as air pollution, land-use for bioenergy or water demand have been included in IAMs, but so far, none of these studies considers the breadth of impacts studied here. Accordingly, a consistent and holistic evaluation of co-benefits of different mitigation pathways is still missing.”

The report said:

“Power supply also accounts for a substantial share of mineral resource depletion, mostly for the construction of power generators. In 2010, around 5% of global copper, 2.5% of aluminum, and 3% of iron went into the electricity supply sector. Mineral resource depletion accounts for the aggregate demands from these bulk metal demands along with some 20 other important mineral resources. It should be noted that concerns about mineral resource depletion involve a large number of minerals, not all of which are covered by life-cycle impact assessment methods. For example, the indicator used here does not include neodymium or dysprosium (used in certain wind turbines), or indium or tellurium (used in certain photovoltaic cells). In all scenarios, nonfuel mineral depletion increases relative to current levels. In contrast to all other indicators, we find that all climate policy scenarios feature higher mineral resource requirements, and that in the NewRE scenarios 2050 mineral resource depletion is around twice as high as in FullTech, and around four times higher than in the baseline. This is explained, first, by the higher per-unit metal requirements for renewable technologies, particularly solar PV; second, the fact that wind and solar technologies require substantial material upfront investments before operation (which here are attributed to the year of construction); and finally, to a lesser extent, the additional metal resources required for the build-up of additional grid and storage infrastructure to accommodate the variability of wind and solar power supply. We further find that different decarbonization strategies result in distinctly different profiles of risks and co-benefits. Wind and solar-based decarbonization (NewRE scenario) consistently achieves highest reductions in health-related environmental impacts. Fossil technologies — especially coal — dominate aggregate health impacts by far; thus, their faster and deeper phase-out in the NewRE scenarios yields greatest benefits, with around 60% lower aggregate mortality compared to Conv, and an around 50% decrease relative to FullTech in 2050. The most prominent contributors to health impacts are air pollution and human toxicity.”

It said:

“NewRE decarbonization also minimizes pollution-related ecosystem impacts compared to Conv and FullTech scenarios. Aggregate ecosystem damage, as derived from the corresponding ReCiPe endpoint characterization factors, are dominated by land occupation and natural land transformation. These land-use related impacts are highly uncertain and of comparable magnitude across the different decarbonization scenarios: While NewRE scenarios are characterized by greater land-requirements for wind and solar power as well as grid expansion, the higher bioenergy deployment in the Conv scenarios induces greater natural land transformation.”

The scientists found:

“Decarbonization will fundamentally change the resource requirements of the power sector, away from fossil fuel inputs and towards mineral resources (FullTech and NewRE) and geological storage space for CO2 (FullTech and Conv). For the NewRE scenarios in 2050, fossil depletion decreases by 90%, while bulk material requirements increase four-fold compared to baseline levels. In addition, certain wind power and photovoltaics technologies also rely on specialty minerals, such as dysprosium or indium, which are not addressed in the resource depletion assessment method employed here, but are subject to geopolitical supply risks. The low-carbon transformation, especially if it relies heavily on wind and solar technologies, can be expected to have profound implications for the geopolitical landscape, pointing to the need for flanking the global clean energy effort with an integrated critical materials strategy.”

The report said:

“Fossil fuels by far dominate resource surplus costs, the aggregate ReCiPe endpoint indicator for resource depletion. This result suggests that the benefit to society stemming from reduced fossil requirements in NewRE outweigh the burden due to additional mineral resource depletion. In addition, it should be kept in mind that much of the 2050 resource requirements for wind and solar installations can be attributed to upfront investment for electricity produced later, and that mineral resources are amenable to recycling, while fossil resources are not.

“In terms of technologies, fossil fuels are the major drivers of health impacts and also dominate resource surplus costs; thus, their reduction in the context of climate policies yields substantial benefits. Bioenergy emerges as the greatest driver of ecosystem damage, chiefly due to land occupation and induced loss of natural lands. On the other hand, numerous studies have demonstrated the importance of bioenergy for the 1.5 and 2 °C targets, both due to its versatility in substituting fossil fuels and the possibility of generating negative emissions. This underlines the need for an integrated global land management to navigate the tradeoff between climate change mitigation and conservation.”

In the “Discussion” section of the report, it was said:

“The world is currently witnessing a dynamic and robust growth of wind and solar power, which is also expected to become the most important contributor towards near-term CO2 reduction efforts worldwide. Our results suggest that further relying predominantly on these new renewables in the transition towards a near-zero emissions power system also reduces most nonclimate environmental impacts on the system level compared to strategies that limit the contribution of wind and solar power largely in favor of greater CCS deployment.

“It is important to bear in mind that our forward-looking global analysis with wide system boundaries, despite the methodological advancements brought by integrating integrated assessment models and prospective life-cycle assessments, is subject to significant limitations and uncertainties. For example, the linearized approach of life-cycle impact assessment cannot account for scale-dependent variations in per-unit impacts, e.g., due to threshold or saturation effects, or interaction among different environmental impacts. Human toxicity and ecosystem impacts are subject to spatial variability. Changes in population and age structure matter for health damages, ecosystem damage will depend on future land-use patterns, and the economic consequences of resource depletion on competing resource uses. Our study accounts for dynamic changes in technical systems (e.g., increased material efficiency of PV cells, or reduction of air pollution due to end-of-pipe measures), but lacks a dynamic description of crucial nonclimate environmental mechanisms, mostly due to a lack of knowledge or demonstrated importance of relevant developments. While our analysis accounts for uncertainties in energy technology deployment as well as innovation in individual technologies, we were not able to account for uncertainties in the characterization factors translating stressor flows to environmental impacts.”

“When looking at the big picture – from the direct emissions of power installations, to the mining of minerals and fuels for their construction and operation, to the lands necessary for the energy supply infrastructure – we found that the best bet for both people and environment is to rely mainly on wind and solar power,” Gunnar Luderer explains. He is lead author and deputy chair of PIK’s research domain on transformation pathways.

He said: “A main winner of decarbonisation is human health: switching to renewables-based electricity production could cut negative health impacts by up to 80 per cent. This is mainly due to a reduction of air pollution from combusting fuels. What is more, the supply chains for wind and solar energy are much cleaner than the extraction of fossil fuels or bioenergy production.”

The scientists compared three scenarios of decarbonising the power sector by 2050: One focused mainly on solar and wind power, a second relying mainly on carbon capture and storage in combination with biomass and fossils, and a third route with a mixed technology portfolio. In all scenarios, land use requirements for power production will increase in the future. By far the most land-devouring method to generate electricity is bioenergy.

The researchers used complex simulations sketching out the possible paths of decarbonising the electricity supply (Integrated Assessment Modelling) and combined their calculations with life cycle analyses.

“Per kilowatt hour of electricity from bioenergy, you need one hundred times more land than to harvest the same amount from solar panels,” said Alexander Popp, head of the land use management group at the Potsdam Institute.

Alexander Popp said: “Land is a finite resource on our planet. Given the growing world population with a hunger for both electricity and for food, pressures on the land and food systems will increase, too. Our analysis helps to get the magnitudes right when speaking of the at times much-hailed technology of bioenergy.”

Anders Arvesen from the Norwegian University of Science and Technology (NTNU) said: “In combining two pairs of analytical spectacles, we were able to look at a wide range of environmental problems, from air pollution to toxicants, from finite mineral resources needed to manufacture wind turbines to the extent of lands transformed into bioenergy plantations if relying on negative emissions. This is a promising approach also to tackle other sectors, like buildings or the transport sector.”

“Our study delivers even more very good arguments for a rapid transition towards a renewable energy production. However, we need to be aware that this essentially means shifting from a fossil resource base to a power industry that requires more land and mineral resources,” adds Luderer.

Luderer said: “Smart choices are key to limiting the impact of these new demands on other societal objectives, such as nature conservancy, food security, or even geopolitics.”




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