“Green energy” is the energy that can be produced while sustaining ecosystem services. Maintenance of the services provided by the ecosystem requires energy, termed the ecosystem maintenance energy (ESME). Including ESME costs in energy accounting enables assessment of an energy plant's ability to produce energy over and above inputs and EMSE costs over the lifetime of the plant. In this work, an assessment of the potential of two renewable energy plants wind and solar photovoltaic to produce “green energy” is undertaken, those were chosen due to their likely dominance of the future energy market. The assessment is done using a methodology that unifies environmental impact assessment, ESME and energy accounting into a single metric termed the green energy return on investment (EROIg). The paper also extends ESME calculation by incorporating ecosystem impacts that were previously unaccounted-for such as: biodiversity loss; delayed ecosystem maintenance; carbon capture by photosynthesis; ozone depletion and formation and ionizing radiation. The solar and wind energy plants considered were sized to produce an equivalent amount of annual energy and were placed at a theoretical location where the capacity factor (CF) is equivalent to the average global utility scale CF for each resource. The study found that onshore wind energy has a greater potential in generating green energy with an EROIg of 17.19. Removal of impacts related to biodiversity loss, which is included here for the first time, is found to play a critical role in plant assessment from both biodiversity and CO2 capture by photosynthesis perspective. Plants needing and providing biodiversity offsets are shown to provide an overall 18%–25% improvement in EROIg. This improvement is triggered by the corresponding CO2 capture by photosynthesis. Some design options were evaluated to determine the sensitivity of the resulting EROIg to the plant design and to the temporal element of the investigation. Those include the addition of battery storage and the delay in action on ecosystem maintenance from a 20-year to a 100-year time horizon which were found to reduce the resultant EROIg by >40% and >87% respectively.

The Intergovernmental Panel on Climate Change’s sixth assessment report (AR6) allocates 15% to 43% of global primary energy to biomass in 2050 across multiple mitigation scenarios. The report also emphasizes the importance of electrification. For increased reliance on electricity and on biomass, bioelectricity is expected to play a major role. It is therefore vital to know whether the energy generation potential of biomass electricity can support the removal of its environmental impact, particularly as generation at large scale is expected to rely almost solely on energy crops. This paper evaluates the potential of short-rotation woody crops in generating green electricity. This is performed using the “Green Energy Return on Investment (EROIg)” methodology, which indicates the net energy generated after investing in ecosystem maintenance energy (ESME). This study found that the EROIg of bioelectricity is marginally larger than unity when converted to its primary equivalent form (EROIg-PE). Three design options were proposed to improve bioenergy’s EROIg. Among these options, pelletizing wood chips has the largest advantage with an EROIg of 1.11 and an EROIg-PE of 3.17. We conclude with a discussion of the indirect advantages of growing energy crops, and discuss how this technique can be used alongside others to help generate cleaner energy.

Conventional methods of climate change (CC) mitigation have not ‘bent the curve’ of steadily rising annual anthropic CO2 emissions or atmospheric concentrations of greenhouse gases. This study reviews the present position and likely future of such methods, using the recently published literature with a global context. It particularly looks at how fast they could be implemented, given the limited time available for avoiding catastrophic CC (CCC). This study then critically examines solar geoengineering, an approach often viewed as complementary to conventional mitigation. Next, this review introduces equity considerations and shows how these even further shorten the available time for effective action for CC mitigation. The main findings are as follows. Conventional mitigation approaches would be implemented too slowly to be of much help in avoiding CCC, partly because some suggested technologies are infeasible, while others are either of limited technical potential or, like wind and solar energy, cannot be introduced fast enough. Due to these problems, solar geoengineering is increasingly advocated for as a quick-acting and effective solution. However, it could have serious side effects, and, given that there would be winners and losers at the international level as well as at the more regional level, political opposition may make it very difficult to implement. The conclusion is that global energy consumption itself must be rapidly reduced to avoid catastrophic climate change, which requires strong policy support.

A vast literature now exists on how modern communication and computational technologies (CCTs)—such as artificial intelligence and big data, and their use in smart grids, smart cities, smart health, and energy demand management—can help overcome both the environmental and socio-economic challenges cities (especially large ones) presently face. Smart grids, for example, promise to allow greater percentages of intermittent renewable energy in the grid, particularly the rapidly increasing supplies of wind and solar energy, and to help match electricity production to demand. There are many potential advantages possible with advanced CCT, but they need careful implementation because many potential problems can also occur. This review first examines what is needed to produce ecologically sustainable and more equitable cities. A critical aspect of this is the need for a global Earth Systems Science approach to include the environmental damages caused elsewhere by a given city. It then examines how the new CCT can potentially help achieve these aims. An important conclusion is that, in most cases, advanced technology availability is insufficient; strong policies are also needed. The shortcomings of actually implemented or proposed approaches are also examined. Finally, it discusses what future decades might bring and the implications for the new CCTs.

The IPCC’s sixth assessment report projects 15% to 43% (44 EJ/y – 310 EJ/y) of global primary energy to be generated by biomass in 2050 across multiple GHG mitigation scenarios. That report also emphasises the importance of electrification to meet GHG reduction targets. With increased reliance on electric power, and increased appeal to biomass, bioenergy for electricity is expected to play a major role in future energy markets. What makes the bioenergy solution more attractive is its reported reasonable Energy Return on Investment (EROI). However, generation at large scale is projected to be greatly dependent on crops and plantations. This shifts the GHG emissions concern to be concerns over land use and other emissions integrated in the bioenergy lifecycle. It is therefore vital to know whether the potential of electricity generation from biomass outweighs environmental impact of bioenergy. This paper evaluates the potential of biomass electricity mainly generated from short rotation woody crops combustion in generating green energy. This is done using the “Green EROI (EROIg)” quantification methodology, which indicates the net energy generated to society after investing in ecosystem maintenance energy (ESME). ESME is a non-monetary weighting mechanism of an entity’s different lifecycle environmental impacts. This study found that the EROIg of bioelectricity is marginally larger than unity when converted to its primary equivalent form (EROIg-PE) which indicates that the technology is somewhat energetically viable if its production was to be green. Three design options were proposed to improve bioenergy’s EROIg performance, these include adding 20% waste wood in the combustion mix, staggered harvesting and plantation to achieve annual harvest and pelletizing wood. This approach appeared to improve the EROIg especially for pelletizing, due to its simultaneous reduction in storage and transport costs, making the production energetically and environmentally viable even at a 1 : 1 secondary : primary ratio with an EROIg of 1.11 and an EROIg-PE of 3.17. We conclude with the discussion of the multiple indirect advantages of growing crops that can be used for energy generation, and a discussion on how this technique can be used alongside others to help them generate cleaner energy while facing the current global climate, biodiversity and waste issues.

In 2022, the record of extreme weather events already includes deep droughts in Sichuan province, China, and California, US; floods inundating a third of Pakistan and serious and repeated flooding in Eastern Australia; heat waves and drought in Europe; and wildfires in Europe and the western US [...]

A number of technical solutions have been proposed for tackling global climate change. However, global climate change is not the only serious global environmental challenge we face demanding an urgent response, even though atmospheric CO2 ppm have risen from 354 in 1990 to 416 in 2020. The rise of multiple global environmental challenges makes the search for solutions more difficult, because all technological solutions give rise to some unwanted environmental effects. Further, not only must these various problems be solved in the same short time frame, but they will need to be tackled in a time of rising international tensions, and steady global population increase. This review looks particularly at how all these environmental problems impact the future prospects for renewable energy (RE), given that RE growth must not exacerbate the other equally urgent problems, and must make a major difference in a decade or so. The key finding is that, while the world must shift to RE in the longer run, in the short term what is more important is to improve Earth’s ecological sustainability by the most effective means possible. It is shown that reducing both the global transport task and agricultural production (while still providing an adequate diet for all) can be far more effective than converting the energy used in these sectors to RE.

Energy efficiency is, in principle, a simple idea: an output of human value, for example, vehicle-km traveled, divided by the needed input energy. Efficiency improvements are regarded as an important means of mitigating not only climate change, but also other environmental problems. Despite the vast number of articles published on energy efficiency, a few people question whether it is a useful or accurate measure in its present form; nearly all papers are either engineering studies, or address barriers to efficiency improvements. This review addresses this issue via a critical review of the literature, including not only papers on energy efficiency, but those on adjacent areas of research that can help broaden the scope, both geographically and conceptually. These shortcomings are illustrated in case studies of buildings/cities and road passenger transport. The main findings of this review are that (1) energy efficiency inevitably has an ethical dimension, as well as a technical one, in that feedbacks are more widespread than they have generally considered to be, and (2) that conventional efficiency measures omit important energy input items, particularly those concerned with the mining the materials needed for renewable energy plants. The key conclusions are that present efficiency measures are not adequate, and future research is needed to overcome these shortcomings.

Humans have always wanted to know what the future holds in store for them. In earlier centuries, people often sought clues to the future from sacred texts. Today, more secular approaches are increasingly used, although the older approaches to the future persist. Modern methods for prediction include trend extrapolation, the Delphi method, mathematical modeling, and scenario analysis, including backcasting. Extrapolation was only possible when reliable past data became available. The Delphi method relies on the judgement of experts in the subject matter. Mathematical modeling has been very successful in the physical sciences, and, in the form of integrated assessment models (IAMs), has been applied to problems such as assessing future energy use. Scenario analysis looks at a number of possible futures and develops internally consistent story lines around each. It is often used in conjunction with IAMs. Each of the four methods, including both their strengths and weaknesses, are discussed in turn. Finally, this entry looks at the future of prediction, and concludes that despite progress in each of the four approaches treated, predicting the future, never easy, is now harder than ever.

Our planet faces several serious and urgent challenges to sustainability including, but not limited to, climate change; however, most researchers argue that technological solutions can solve these problems. This review first examines the prospects for decoupling environmental damages in general from economic growth, considered at the global level; then, it looks at whether the recent advances in information and communication technology (ICT) can help. It is argued that although absolute decoupling may have occurred in some countries—even after accounting for energy-intensive imports—it has not occurred at the global level, which is the relevant level for global sustainability problems. This conclusion is strengthened by the very high correlation over the past three decades found between global gross domestic product (GDP) and several parameters relevant for sustainability, particularly for atmospheric CO2 concentrations and ecological footprint as a function of GDP. ICT innovations relevant to energy use include smart grids and smart cities, especially smart urban transport. A review of recently published papers shows no definite findings of energy or carbon reduction, although some innovations show energy/carbon reduction potential if given strong policy support. Overall, it was concluded that the Earth’s sustainability challenges will probably need deep energy reductions, which in turn require profound sociopolitical changes.

Technical fixes are highly favoured by most decision-makers because they involve the least disruption to existing social and economic order. However, in today’s ‘full world’ they often meet with unintended consequences. In this chapter, we examine a number of these in the context of mitigating climate change: nuclear power; energy-efficient improvement; various technologies for carbon dioxide removal (CDR); and geoengineering in the form of solar radiation management (SRM). Nuclear energy is losing market share, and even the nuclear industry does not predict share recovery. Reductions in energy intensity have not prevented global energy growth, because of unmet demand in presently low-energy countries. CDR in the form of forestation has been implemented in some places, but net loss in global forest biomass is still occurring. Other forms of CDR are still unproven at the very large scales needed. SRM is likewise unproven, and like CDR technologies, would eventually face FF depletion.

In this chapter, we begin with a summary of the key themes of this book: the serious ecological sustainability problems our planet faces; that in the Anthropocene, these problems are increasingly of our own making; that technological solutions are less effective because solutions to one problem can aggravate the other problems; that global inequality is high and still rising. The chapter then discusses some possible changes that could both improve ecological sustainability and global equity. The first of these changes would address the unpaid external costs of FF combustion and use, possibly through carbon taxes. Then the possible changes to transport and agriculture, both important energy-consuming sectors, are used as examples. We then assess the feasibility of these changes, arguing that the lessons from the current epidemic, together with the rise of extreme weather events experienced by an ever-increasing share of the global population, open up space for more rapid social and economic changes. Nevertheless, while the changes are possible to achieve, success is not guaranteed, especially in the near term.

Many cities around the world are aiming to be zero emission or environmentally sustainable, particularly cities in the Economic Cooperation and Development (OECD) countries. This paper contributes to the literature by using a systems approach to argue for a wider view, not only for the full range of deleterious effects of urban transport in a given city itself, but also for its impact on possibly distant locations that supply transport inputs and receive its waste products. The paper uses the published literature to first examine the various adverse effects of urban travel, and then to critically evaluate the proposed technology-based solutions. The main finding is that all these solutions are found wanting to some extent, especially given the limited time frame available; hence, for urban sustainability, large travel reductions are thus needed. It then looks at a very different approach: reductions in urban vehicular travel, particularly by car. Four approaches considered (changing urban land-use, reducing private vehicle travel convenience, introducing carbon taxes, using information technology as a travel substitute), This paper concludes that various measures for decreasing the convenience of car travel, such as by cutting speed limits and parking spaces, as being the most equitable in OECD cities, and potentially capable of rapid implementation.