Climate change and innovative paths to a more sustainable future

Abstract

The challenges posed by climate change and greenhouse gas net-zero transition are discussed. Several key technology areas which require innovation are briefly reviewed in this article, including renewables, energy storage, distributed energy resources, CO₂ utilization, agriculture, and the synergy between Al and energy transition. The shift in mindset from “re-cycling” to “re-using” and a redefinition of “wealth” for a more sustainable future are also proposed.

Graphical abstract

Keywords

sustainability / energy transition / distributed energy resource / CO₂ utilization / agricultural revolution

1 Challenges of climate change

Climate is the long-term average over decades and seasons of the local weather. Fig.1 shows the Intergovernmental Panel on Climate Change (IPCC) finding on the observed and simulated global temperature rise between 1815 and 2020. The black line is the measured temperature, the green line shows the simulated natural only scenario, and the orange line is the simulated human activities plus natural scenario. It has clearly showed the global temperature rise is caused by human activities such as power generation, transportation and many other things. Over the past decades, increased heat waves, floods, forest fires, droughts, water shortages, rising sea levels are all the evidences of climate change. The other indicator is the water stress level, which is defined as the proportion of water withdrawn for use in agriculture and other human usage in relation to available renewable freshwater resources. Many parts of the world such as the United States, northern China, India, and the Middle East, face very high water stress levels, which indicates that agriculture could be at risk in these regions. Subsequently, there is a possibility of the so-called "climate refugees", which may have a profound impact on the politics both domestically and internationally.

Fig.1 Global annual average surface temperature between 1850 and 2020 (reproduced from IPCC [1]).

Full size|PPT slide

As shown in Fig.2, the global average concentration of atmospheric CO₂ has increased from around 280 ppm in 1 AD to 415 ppm in 2020. The rise in CO₂ quantitatively agrees with the estimate of human-caused CO₂ emissions minus the amount being reabsorbed on land and ocean. The decreased ratio of ¹⁴C/¹²C in the atmosphere also quantitatively agrees with the addition of ¹²C only, which has resulted in the temperature rise. In addition to carbon dioxide, methane and nitrous oxide are two other greenhouse gases (GHGs). As seen from Fig.3, they have the very similar profile going from 1800 to 2020. Their profiles started very flat and then had a very precipitous rise in the last decades. Methane is 84 times worse than carbon dioxide in terms of greenhouse gas effect, but its lifetime only lasts for about 10 years before it’s turned into carbon dioxide. Nitrous dioxide is 300 times worse than carbon dioxide and it lasts for more than 100 years. Roughly 50% of the methane and more than 3/4 of the nitrous oxide come from fertilizer and food production. We must control their emissions as well.

Fig.2 Global average of atmospheric CO2 (ppm) since 1 AD (reproduced from UCSanDiego website [2])

Full size|PPT slide

Fig.3 Historical concentrations of CO2, CH4 and N2O (reproduced from IPCC [3]).

Full size|PPT slide

Fig.4 shows the transitions from the wood-burning era to the beginning of the industrial revolution, which is the beginning of the use of coal, and then later on petroleum and natural gas. This data suggests the transition from wood to coal and then to oil and gas took roughly 60 years or more. It’s actually more alarming than the graph shown in Fig.5. Instead of phasing out fossil fuels such as coal, oil and gas, we just added more energy supplies. This is a real challenge to reduce greenhouse gas emission.

Fig.4 Share of energy consumption in the US (1776–2022) (adapted from US EIA [4]).

Full size|PPT slide

Fig.5 Global primary energy consumption and transitions, 1800–2023 (reproduced from OurWorldinData website [5]).

Full size|PPT slide

By the end of 2023, GHG emissions have reached 52 G tons of CO₂ equivalent in the world. To stop the greenhouse gas emissions, we have to radically change everything. Fig.6 shows several projected pathways for greenhouse gas emission from now to 2100. The orange color shows the pathway based on the current policies and the yellow color shows the pledges and target by United Nations (UN) and IPCC. The purple and green lines are 2.0 and 1.5 °C pathway. To get to 2 °C by the end of the century, we have to be negative carbon emission in all sectors, and for the 1.5 °C pathway, we must take more aggressive actions to achieve even more negative emission. That’s the challenge and we need innovations.

Fig.6 Global greenhouse gas emissions and warming scenarios (reproduced from OurWorldinData website [6]).

Full size|PPT slide

2 Innovation needed for climate change

Fig.7 shows the global CO₂ emission by sectors in 2023. About 38% of emission comes from power industry, followed by 21% from transportation, 16% from industry and about 9% from buildings. To achieve zero GHG emission, we must eliminate all CO₂ and other greenhouse gas emissions from the materials we use, such as steel, concrete, plastics, chemicals, and textiles. We also need to remove greenhouse gas emission from the entire food supply chain. Because of that, we’re going to need a 4th industrial revolution powered by carbon-free energy and the 4th agricultural revolution.

Fig.7 Global CO2 emissions by sectors (2023) (Source: Statista website [7])

Full size|PPT slide

2.1 Progresses on renewable energy

The renewable energy has been made great progress in the past decade. As shown in Fig.8, the world average cost of solar energy was $378/MWhin2010,anditwentdownto$68/MWh in 2019. The cost of onshore wind was also reduced from $86/MWhto$53/MWh from 2010 to 2019. There are recent advances in solar materials called perovskite, which is made from calcium titanium oxide minerals and could be tuned to various band gaps. Its solar cell efficiency is now up in the mid 20% range. A combination of silicon and perovskite which consists of several layers of prostrate, is now becoming a real possibility. The durability of this material has been improved from a few months survival to 5 years survival. There is now an optimism that it maybe get to 20‒30 years. If this could be achieved, perovskite may surpass silicon as the next generation solar material.

Fig.8 Global weighted-average of levelized costs of energy by sources (reproduced from OurWorldinData website [8]).

Full size|PPT slide

Based on the current price, the levelized cost of electricity from wind and solar has become less expensive than that from natural gas. The world has plenty of solar resources, however, the sun doesn’t shine all the time, so it’s not a turn on source. The full cost of renewable energy also has to include the backup generation capacity, the energy storage, and an enhanced transmission and distribution system. So it actually has to be 2 times less expensive than natural gas or coal, but it could be achieved.

2.2 Challenges of high-percentage of renewable energy

Over a hundred of countries in COP28 have pledged to triple renewable power capacity by 2030. When the world is transiting to clean energy, it faces the challenges how to use or manage the high-percentage of renewable energy. California in the United States has about 60% of carbon-free electricity generation now, which is mostly solar. It aims to achieve 90% carbon free electricity by 2035 and 100% clean electricity by 2045, which is ahead of the rest of the world. However, California has already faced the challenges of “duck curve” problem. As shown in Fig.9, the solar power becomes over-supplied during the noon time, which electricity could be free and you have to throw it away, but when the power demands suddenly ramp up in the late afternoon/early evening, there is short of power supply due to the intermittent nature of solar power. This issue will get even more challenging as California transitions from 60% to 90% of clean electricity in the next decade. So we need to find a solution.

Fig.9 California’s “duck curve” (source: Masterresource [9]).

Full size|PPT slide

2.3 Energy storage

The energy storage is one of the important technologies needed for the clean energy transition. The pumped hydro storage (PHS) accounts for 95% of all electrical storage capacities in the world. In 2021, China has about 36,000 MW of pumped storage capacity, followed by the US and Japan, as shown in Fig.10. In the US, the Federal Energy Regulatory Commission (FERC) reported in 2022 that 27 licensed pumped storage projects with a total additional installed capacity of nearly 18.9 GW, which will increase around 1.9 times of the PHS capacity in US. China had 50.94 GW of PHS capacity by the end of 2023, and plans to expand to 270 GW by 2030 which will have more pump storage than the rest of the world combined by far. It is very important to have the pumped hydro capacity because of the increased amount of renewable energy Also, environmental regulations will need to allow the flow of water downstream of dams can be stopped for a few hours each day so that surplus renewable energy can be used to pump water from a small holding pond below to dam to the reservoir.

Fig.10 Capacity of pumped hydropower storage by countries/regions (2022 and 2023) (Source: Statista [10]).

Full size|PPT slide

Beyond that, we also need other forms of storage. Fig.11 shows the types of energy storage in terms of gigawatt or terawatt hours of capacity. The Y axis shows how long that stored energy would last. Chemical batteries have made remarkable progress since 1992. Fig.12 shows the energy density of different types of batteries in terms of volume and mass. In the automobile sector, we hope that both of the battery’s energy density per volume and per mass are as large as possible. The blue circle marked on Fig.12 refers to the energy density of a Li-ion battery. It is predicted that the energy density per unit mass will approximately double by 2030, and the energy density per unit volume will also go up, likely 1.8 times. Regarding the cost of batteries, in 2000, the price of Li-ion batteries was over $2,000/kWh,butitbegantoplungedramaticallysincethen.By2020,thecosthasbeenreducedto$100/kWh. It is possible that cost could go down, at least twofold, to $50/kWh by 2030. However, the learning curve has to stop if we run out of the material resources. It has been known that there is not enough cobalt and nickel, so the electric vehicle (EV) battery manufacturers in China and US are beginning to switch to iron phosphate. There is also a limited amount of lithium mineral ores, but the scientists are exploring the innovative ways to extract lithium from abundant salty underground water and even sea water, which may provide a sustainable solution for lithium supply.

Fig.11 Capacity of stored energy by types of energy storage technologies (adapted from Chandrasekar et al. [11] under the terms of CC BY license).

Full size|PPT slide

Fig.12 Energy density of different types of batteries in terms of volume and mass (adapted from Zhang et al. [12] under the terms of CC BY license).

Full size|PPT slide

Other than batteries, the chemical energy storage has received much attentions recently. It turns the renewable energy or any other energy into a chemical, notably hydrogen, but also methane, ammonia or methanol. The cost of so-called “grey hydrogen”, produced from methane or natural gas, is approximately $1.50/kg, but this process also emits CO₂. If you take the same process but capturing CO₂ and requesting it safely for a long period of time, the cost of this so-called “blue hydrogen” may go up as twice as the price of gray hydrogen. However, the cost of green hydrogen, produced from renewable energy, is now around $6/kg, which must be reduced to get it competitive with gray/blue hydrogen. Researchers are exploring better ways of designing electrolyzers, aiming to eliminate the precious metals to reduce the cost. Meanwhile, we found another issue in the last couple of years. If the hydrogen leaks into the atmosphere in sufficient quantities, it keeps methane in the atmosphere longer. The current available metrology for detecting hydrogen uses mass spectroscopy, so we may not be able to put hydrogen into major pipelines until a remote sensing technology for hydrogen leaking is developed. Undoubtedly, hydrogen will be part of the energy supply system. It could be used to decarbonize steel, plastics, chemicals, fertilizer, and aviation fuel.

2.4 Distributed energy resource technologies

It is expected for a significant increase of Distributed Energy Resources (DERs) penetration over the next decade, which will also play an important role on the pathway to carbon net-zero. A diverse portfolio of DERs may include but are not limited to energy efficiency, distributed solar/wind power generation, demand response, and electric vehicles. The DER technologies will provide several benefits, including enhanced energy resilience, energy cost saving, and improvements in human and environmental health.

Energy efficiency is a foundational and cross-sectors decarbonization strategy and it is also the most cost-effective option for greenhouse gas emission reductions in the near term. At COP28, over a hundred countries committed to doubling the rate of energy efficiency by 2030. It is estimated that improving energy efficiency could deliver around 20%‒25% of the emissions reductions needed by 2050. A wider range of energy efficiency technologies could be adopted, including heat pumps, energy efficient appliances or equipment, waste heat recovery, smart energy devices and energy management system. The human’s behavior change can also play an important role in the adoption of energy efficiency and energy/material conservation measures.

Demand response can be a low-cost and effective way to improve power balance and system reliability, particularly during the evening peak period when solar production is rapidly declining and it is critical to bring resources online or shift demand for short periods of time. Microgrids will be increasingly important for integration and aggregation of high penetration distributed energy resources. The US Department of Energy envision microgrids will become essential building blocks of the future electricity delivery system by 2035 to support resilience, decarbonization, and affordability.

The virtual power plant (VPP) is a valuable, flexible and viable solution as it may be able to shift demand away from peak periods and also to support integration of distributed energy resources such as rooftop solar panels, electric vehicles, smart water heaters and heating, ventilation, and air conditioning systems (HVACs). The VPP could coordinate hundreds of thousands of devices to work together to balance energy supply and demand on a large scale. It could enable high percentage of clean electricity to be integrated with lower costs and less new capacity. The US Department of Energy currently aims to expand national VPP capacity to 80 to 160 GW by 2030. That’s roughly equivalent to 80 to 160 fossil fuel plants that need not be built. Given the increasingly widespread adoption of electric vehicles, charging stations, and smart home devices, connecting these resources to VPP systems improves the grid’s ability to balance electricity demand and supply in real time. The emerging artificial intelligence technology will also help VPPs become more adept at coordinating diverse assets.

2.5 Renewable energy based on CO₂ recycling

The goal is to achieve 100% renewable energy based on the recycling combustion products, primarily CO₂. As the diagram shown in Fig.13, the concept is to take CO₂ and water, use any clean method of converting them into feedstock. We need to take CO₂ everywhere from points of sources, but ultimately from the atmosphere, because the CO₂ concentration in air is certainly going to go over 450 ppm within one or two decades, and it may go over 500 or 600 ppm in the long run. The syngas, i.e. H₂ and CO, could be the first feedstock and then you can begin to make linear hydrocarbon chains from that. This is the ultimate goal in many respects, because linear hydrocarbon chains have very high energy density to make jet fuel, diesel and gasoline fuel. Once you have these green fuels in the form of a liquid, ideally at room temperature, you can put them into a supertanker and deliver it around the world. The oil shipping tankers could serve as intercontinental energy “transmission lines”, making it possible to take advantage of regions abundant in renewable energy.

Fig.13 Renewable Energy based on CO2 recycling.

Full size|PPT slide

2.6 Agricultural revolution

We will need a 4th agricultural revolution since we must eliminate GHG emissions from the entire food supply chain which contributes ~20% of GHG world-wide emissions. The 3rd agricultural revolution started with development of nitrogen-based fertilizers, which boosted crop production yield and helped feeding the increasing population in the world. However, the nitrogen-contented fertilizer has caused severe impacts to climate change because it releases nitrous oxide (N₂O) out of the soil to the atmosphere. The N₂O is the third most important long-lived GHG. A possible solution is to plant artificial microbes that has been altered with the crop to be raised. The microbes in the soil could feed the plant and it enters into a symbiotic relationship with the plant. This way could reduce the amount of fertilizer significantly; virtually no fertilizer may be needed. Therefore, the goal is to design microbes that enter into the same symbiotic relationship with all the major grains, but it depends on the specific soil conditions. So we need to find a rapid way of developing synthetic biology microbes for different soil. Current synthetic biology technology allows for the insertion of only one gene at a time. If dozens of genes could be inserted with reasonable cell survivability, the optimization speed would be increased exponentially. Researchers in Prof. Steven Chu’s laboratory at Stanford University have developed a way to insert ten genes at a time with high probability. Also, they are beginning to understand how the soil microbes are not just single microbes, but it is a microbial community. And this understanding may help us get away from the nitrogen-based fertilizers potentially.

The crops may also play an important role in capturing CO₂ directly from the atmosphere. About 52 Gt of CO₂ equivalent are emitted annually, and at least 10–20 Gt of CO₂ capture from air will be necessary. It turns out that photosynthesis is an effective natural carbon capture method through crops. Supposedly we only eat a small fraction of crops we plant, and we can take the rest of corps as carbon residue and sequester it by compacting and drying it. It may be a way of getting at least to the few gears on range.

2.7 The synergy between AI and clean energy transition

The booming of artificial intelligence (AI) technologies has tremendous potential to support and accelerate clean energy transition. In contrast to the conventional power system, the new power system with carbon free electricity are becoming vastly more complex as it needs to support multi-directional flows of electricity between distributed generators, the grid and end-users. Al provides a low-cost and reliable tool to optimize and efficiently integrate variable renewable energy resources into the power grid, to support an electrification system across all the sectors, and to manage adeptly demand-side flexibility. It can become an essential enabler and accelerator for the energy transition. In addition, the processes of discovering, developing and deploying advanced materials for the next generation of clean energy and storage technologies, or the new genes of microbes for green agriculture, are highly capital intensive and often take many years to complete. AI could also significantly advance progresses in these applications.

Meanwhile, it is noteworthy to know that Al computing will also require a huge amount of electricity. For example, in 2022, Google reported that machine learning accounted for about 15% of its total energy use over the prior three years. While we leverage all of advantages of Al for energy transition and decarbonization, we also have to building energy-efficient models and green and sustainable computing for Al technology itself, including but not limit to utilizing Al hardware powered by green electricity, recycling waste heat, optimizing computing resources and using best practice for energy efficiency. We must develop an innovate synergy between Al computing and power system.

3 Changing mindset

We have a war against climate change, and we urge people to take immediate actions. The action could be as simply as some behavior changes in our routines. For example, we need to change the “use once and throw away” mentality that’s been established in the last several decades. When we drink a plastic bottle of water, then we throw it away. Instead of doing that, we should use a reusable cup/bottle to drink the water and reuse it again. So the goal is to “re-using,” rather than just recycling. This mindset is also very important when we build buildings. The shell of buildings could be made to last several hundreds of years. As a good example, the Forbidden City is about 600 years old and is made of wood. That’s carbon sequestration for 600 years. We could grow forest to make wood for buildings, and then we could grow more forest that could capture CO₂ from the atmosphere and make more things. And to the extent that you can replace steel and concrete with wood, it’s an effective way for carbon sequestration. We should develop a policy that would encourage wood building instead of steel and concrete. The people have also begun to use wood as structural materials for 10‒20 stories high rise buildings, so that’s a fundamental change.

We also need a different measure of “wealth.” In all cultures and societies, people are usually going to have fewer kids when they get wealthy. This has led to declining population in many countries, most notably Republic of Korea, Japan, and China. Is it possible to have rising prosperity with the declining population? The increased economic prosperity of virtually all countries is based on having more young workers to support a smaller aging population. This is so-called a Ponzi scheme in the US. It is a form of fraud that lures investors pays profits to earlier investors with funds from more recent investors. A Ponzi scheme can maintain the illusion of a sustainable business as long as more new investors contribute new funds. There may be a solution by re-defining wealth and robot-assisted jobs including assisted living, which may allow us to have increasingly better lives, provide quality care to an aging population, and know how to break the global Ponzi-scheme. It is very important to ask what kind of production we should be looking for. If we measure production of GDP based on cars, it’s one or more cars per adult driver in the US that drives up GDP. You built a building and tear it down in 50 years, then you build another building that drives up GDP. It is not always good for the things that drive up GDP. There should be quite a few things that could drive up GDP while tackling the climate crisis. We need a new model of how to improve our standard of living that does not rely on population growth, increased production and consumption of “stuff.” We want to feel our family and neighborhoods are safe, and our country is safe from hostile takeover. We want health and vitality in old age, remain emotionally connected in our old age.

4 Summary

Climate change presents a serious challenge and urgent crisis which the world must confront. To achieve GHG net zero transition, we must eliminate all GHG emissions from the materials we use, such as steel, concrete, plastics, chemicals, textiles, and the entire food supply chain. Therefore, we need to have the 4th industrial revolution powered by 100% renewable energy and the 4th agricultural revolution.

Innovation is required across different technology areas on the path to achieve GHG net zero. The full cost of renewable energy needs to be further reduced. To accommodate the high percentage of renewable energy, energy storage is one of the important technology solutions. While the pumped hydro storage is the primary energy storage option in the world, the battery technologies has made great progresses with increased energy density and reduced cost, but the limited material resources for the batteries needs to be solved. The other chemical storage options such as hydrogen and ammonia have also received more attention. In addition, the distributed energy resources including energy efficiency, distributed solar/wind power generation, demand response, and electric vehicles could make essential contributions to accelerating clean energy transition. VPPs could also be a valuable solution to improve power balance and system reliability. We also need to develop technologies to recycle CO₂ into green fuels to promote a circular economy. Innovation is also needed in agriculture to replace nitrogen-based fertilizer for removing GHG emission from the food supply chain. Lastly, the booming of AI technologies have tremendous potentials to support and accelerate clean energy transition, but we also need to develop an innovate synergy between Al computing and power system.

Beyond the technology innovation, there must be a shift in public mindset from “re-cycling” to “re-using.” We should develop a policy that would encourage wood building instead of steel and concrete. We also need a different measure of “wealth,” and develop a new model to improve our standard of living while addressing climate crisis. With all of these concerted efforts, we can create a more sustainable future.

References

[1] IPCC. Climate change 2021: The physical science basis. Summary for Policymakers, 2021

[2] UCSanDiego . The keeling curve. 2006, available at the UCSanDiego website

[3] IPCC . Climate change 2021: The physical science basis. Technical Summary, 2021

[4] U.S. Energy Information Administration. Nonfossil fuel energy sources accounted for 21% of U.S. energy consumption in 2022. 2023-6-29, available at website of eia.gov

[5] Hannah Ritchie, Max Roser. CO₂ and greenhouse gas emissions. 2023, available at website of OurWorldinData

[6] Hannah Ritchie, Max Roser. Global greenhouse gas emissions and warming scenarios. 2022, available at website of OurWorldinData

[7] Ian Tiseo. Global distribution of CO₂ emissions 2023, by sector. 2023-9-5, available at website of Statista

[8] Roser M. Why did renewables become so cheap so fast ? 2022-12-1, available at website of OurWorldinData.org

[9] Robert Bradley Jr. California’s duck curve hits record lows. 2023-5-23, available at website of Masterresource

[10] Statista Research Department. Capacity of pumped storage hydropower worldwide in 2023, by leading country. 2023-4-23, available at website Statista

[11] Chandrasekar A, Flynn D, Syron E. Operational challenges for low and high temperature electrolyzers exploiting curtailed wind energy for hydrogen production. International Journal of Hydrogen Energy, 2021, 46(57): 28900–28911

[12] Zhang L L, Wang Z L, Xu D. . The development and challenges of rechargeable non-aqueous lithium–air batteries. International Journal of Smart and Nano Materials, 2013, 4(1): 27–46

RIGHTS & PERMISSIONS

2024 Higher Education Press 2024