"You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete."

Buckminster Fuller, philosopher, futurist and global thinker (1895 - 1983)
"Then I say the Earth belongs to each generation during its course, fully and in its right no generation can contract debts greater than may be paid during the course of its existence"

Thomas Jefferson, September 6, 1789
"History teaches us that men and nations behave wisely once they have exhausted all other alternatives"

Abba Eban
Under the patronage:

Panel: Perspectives on 100% Renewable Energy Systems around the World


Moderator: Prof. Henrik Lund

Climate action is urgent and the ambitions is to reduce the emissions from fossil fuels by deploying large-scale renewable supply in energy systems. The ambiguous aim is to reach for the 100% Renewable energy solution. Such energy supply would support the implementation of several of the UN's Sustainable Development Goals.

The SDEWES conferences has been among the frontrunners in introducing and leading the scientific discussion on how to design and implement 100% Renewable Energy solutions. In recent years, the research in this field has gained increasing attention. Since 2004, at least 180 scientific articles has been published on the field and the numbers are increasing. Most studies analyse energy systems for the final 100% renewable state, while a small, though increasing, number also investigate energy transition pathways; how to reach the target. Europe, and thereafter the US and Australia, are well researched, while other parts of the world lack behind.

This panel present a status on these efforts in essential parts of the world and discuss the perspectives on 100% Renewable Energy Systems around the world.

Prof. Christian Breyer
LUT University, Lappeenranta, Finland
Gaps in 100% renewable energy research
show abstract

The latest update on 100% RE articles lists about 290 articles, dominated by studies for Europe. Several major regions in the world are not yet studied well, for instance Africa, Middle East, South Asia and Southeast Asia. The power sector is studied best, whereas the industry sector and the transport sector beyond the road mode are not yet studied sufficiently. Studies on the transport sector deviate for the share of synthetic fuels, mainly due to a wide range on assumptions of biofuels. First insights on a global scope indicate that the cost in the power sector decline the more low-cost renewables are used, whereas the cost transition in the entire energy system may be stable throughout the transition. Several international institutions do not find 100% renewables pathways, which is in most cases linked to fully outdated cost assumptions for solar photovoltaics, which are partly assumed to be higher in the year 2050 compared to the 2019 market level, even in present publications. It is of utmost importance to get fully outdated solar PV cost assumptions fixed in energy scenarios of all kinds, asap, in particular outside the 100% renewables community, since strongly distorted policy recommendations are the consequence, which is not acceptable in the age of climate urgency.

Prof. Neven Duić
University of Zagreb, Zagreb, Croatia
100% RES energy systems – electrification, hydrogen or e-fuels?
show abstract

It is now clear that transition to decarbonised energy systems will include mainly huge investment in new wind and solar capacities, while other renewables use will be limited by their limited and already used potential. That creates issues with integration of variable renewables, that can be solved either by electrification, hydrogen or e-fuels.  The limit of cheap and easy integration for wind is around 20% of yearly electricity generation, while a combined wind and solar may reach 30% (before duck curve hits 0), pending on necessary improving of transmission capacities and flexibilization of conventional power plants. Going any further asks for implementation of free energy markets, demand response, coupling of wholesale and retail energy prices, and integration of electricity, heating/cooling, water and transportation systems. The cheapest and simplest way is integrating power and heating/cooling systems through the use of district heating and cooling (which may be centrally controlled and may have significant heat storage capacity), since power to heat technologies are excellent for demand response. This may not be socially feasible everywhere, in which case electrification of residential heating would require smart grid implementation. Electrification of low energy density transportation (personal cars, local delivery and local buses) allows not only for significant increase of energy efficiency, but also, the electric cars, due to low daily use, may be excellent for demand response and even for storage. This will necessarily bring smart grids development and digitalisation of power systems, allowing also for demand response from buildings, appliances etc. Heating/cooling and transportation smart electrification can allow reaching renewable share of 80% in energy system, but the remaining 20% - the part of transportation and industrial processes that cannot be electrified, as well as the backup of power system in times when neither wind nor solar are available, may be more of an uphill battle without technology breakthrough. Biomass can probably cover half of that demand, while carbon dioxide from biomass combustion may be hydrogenised using hydrogen produced from excess renewables, resulting in electric fuels (i.e. e-hydrogen, e-ammonia, e-methane, e-methanol, e-DME). Alternative pathways to partial electrification of heating and transport, using electric fuels, result in much higher costs, much higher needs for primary energy, and the system that retains current inefficiencies. Therefore, hydrogen and other e-fuels should be used only where electricity is not feasible, but there will still be huge need for those fuels, probably around 50% of primary energy will be used to produce such fuels.

Prof. Mark Z. Jacobson
Stanford University, Stanford, United States
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Prof. Natasha Markovska
Research Center for Energy and Sustainable Development - Macedonian Academy of Sciences and Arts, Skopje, North Macedonia
The views from the IPCC SR1.5
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On invitation of the UNFCCC, in October 2018, the Intergovernmental Panel on Climate Change (IPCC) provided a Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emissions pathways (known as SR1.5). Citing over 6,000 scientific references and using contributions of 91 authors (32% women), the Report does not only assess what a 1.5°C warmer world would look like, but also the different pathways by which global temperature rise could be limited to 1.5°C. Although reflecting different futures in terms of global politics and societal preferences, and thus different trade-offs and co-benefits for sustainable development and other priorities, all 1.5°C pathways share certain features – by mid-century, CO2 emissions falling to net-zero with renewables supplying 70 percent to 85 percent of electricity and unabated coal use being largely phased out. Also, all 1.5°C pathways with limited or no overshoot project the use of carbon dioxide removal (CDR) on the order of 100–1000 GtCO2 over the 21st century. CDR is necessary for both moving to net-zero emissions and for producing net-negative emissions to compensate for any overshoot of 1.5˚C. Still, it must be noted that CDR deployed at such a scale is unproven, and is a major risk to our ability to limit warming to 1.5˚C

As to the 100%-renewable energy scenarios, the IPCC SR1.5 acknowledges the growing body of relevant scientific literature which goes beyond the wide range of Integrated Assessment Models (IAM) projections of renewable energy shares in 1.5°C and 2°C pathways. However, it points out that although the representation of renewable energy resource potentials, technology costs and system integration in IAMs has been updated since the Fifth Assessment Report, leading to higher renewable energy deployments in many cases, none of the IAM projections identify 100% renewable energy solutions for the global energy system as part of cost-effective mitigation pathways.

At this panel, the SDEWES science might shed a different light on the role of 100% renewable energy systems in 1.5°C pathways…

Prof. Xiliang Zhang
Tsinghua University, Beijing, China
show abstract

Panel: The sustainability of plastic and its alternatives


Moderators: Prof. Jiří Jaromír Klemeš, Ms. Yee Van Fan

Plastic waste has received high research attention in the recent year due to its impact on the ecosystem. The plastics frequently have a short retention time (user phase) and improper disposal, not complying with the circular economy. Recycling is a promoted practice. However, the implementation is costly and requires advanced technologies due to the sensitiveness to composition (type), colour and contaminants. Some amount of plastic waste is claimed to be recycled by exporting into the developing countries; however, it has not always happened and created even political tensions.

Plastic material has similar or even better characteristics such as corrosion resistant, water resistant, versatility, durable, cheap, lightweight compared to metal, paper or wood. Bio-based plastic and degradable plastics also have its own footprint. Complete displacement of plastic may not be more sustainable, and it has to be assessed with the support of a comprehensive quantitative accounting method.

The panel presents the plastic waste issues (including the utilisation) and aims to discuss the perspective on the following topics:

  • Plastic Leakage (debris to micro)
  • Disposal Solution and the Implementation of Plastics Ban
  • Footprints (Plastic, Energy, GHG) and Accounting Methodology
  • Replacement and Sustainability of its Alternatives
  • Roles of Academia and Policy Makers

Prof. Mário Costa
Instituto Superior Técnico, Lisboa, Portugal
Pyrolysis of Non-Recycled Plastics
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Non-recycled plastics are causing a huge environmental problem. A possible solution is its valorization through pyrolysis. Plastic pyrolysis technology is, however, poorly developed, being the needed economic investment quite high so that competition with current oil production prices is very difficult. To bring it to an industrial scale, pyrolysis needs to reach a compromise between economic viability, regulatory compliance, and environmental impact. It should be stressed that pyrolysis of non-recycled plastics result in a higher reduction of CO2 emissions as compared to incineration processes with energy recovery. For this technology to become profitable it needs to have enough supply of appropriate feedstock and be further developed to maximize the quantity and quality of the end products at competitive prices.

Prof. Slaven Dobrovic
University of Zagreb FAMENA, Zagreb, Croatia
Plastics in environment - do we look for a solution?
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Today’s understanding of all the implications of accumulation of various types and forms of plastics in environment is limited, but still, this issue is already recognized as one of the biggest environmental challenges of this lifetime. This emerging global problem is not only a result of improper management of municipal or industrial waste, but also a release of plastic particles due to wear and tear during the lifecycle of a product and finally the intentionally added microplastics within a product, designed to be emitted during their lifecycle.

Finding and implementing solutions is going to be long lasting, complex, demanding and expensive with results depending on how effectively will involve all the relevant players.

Recent news that industry started funding global alliance to find and implement 1 billion US$ worth solutions to eliminate plastic waste in the environment may be a sign that an era of greater industry responsibility has begun.

Legislative solutions as a ban of single use plastics could be an important part of solution since it is hard to expect that collecting rate od very light and cheap plastic products will sufficiently increase. Reducing consumption and Extended Producer Responsibility schemes covering the cost to clean-up, applied to products frequently found as marine litter are also among effective measures to tackle this immense global problem. Working on environmental awareness might stimulate change in behavior around waste and environment. After all, raising the sense of responsibility for environment among all groups, from citizen, employee, employer, academician to the president of the state is crucial.

Prof. Aoife Mary Foley
The University of Manchester, Manchester, United Kingdom
Flitting and Frogleaping a Human Solution to Managing the Planet
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Humans have a terrible habit if flitting from one technology or product to another when they believe that one is cheaper and more efficient and faster or more recently greener to produce and or use. History tells us that we can discover quite the opposite is the case after the fact. At the time we move to a new technology or product all seems great and the naysayers are judged to be troglodytes and anti-progress. We moved swiftly from trains to highways, glass to plastic and now we are planning to abandon the internal combustion engine to move to electric vehicles. We can already see that moving unchecked away from glass to plastic has led to serious environmental concerns. But moving unchecked away from plastic to paper and other materials needs careful consideration to foresee and weigh-up the pitfalls. This short panel talk will examine this societal push to constantly leapfrog from one technology to the next.

Prof. Ting Ma
Xi'an Jiaotong University, Xi'an, China
Technologies and Challenges of converting waste plastics to fuel
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In the past 30 years, little waste plastics has been recycled and caused severe environmental pollution in China. However, the garbage classification has been received considerable attention in recent years, which bring great opportunity for the recycling of waste plastics. Therefore, there are huge demands for the high-efficiency and environmentally friendly waste plastics to fuel conversion technologies. In this talk, three critical problems are discussed. Firstly, the waste plastics categories, characteristics and treatment methods in China are presented. Secondly, the conversion technologies of waste plastics to fuel including thermal cracking technology and catalytic cracking technology are summarized. Finally, the effects of heat transfer on the technologies of converting waste plastics to fuel are discussed, and some suggestions are provided to enhance the conversion efficiency. 

Prof. Daniel Rolph Schneider
Faculty of Mechanical Engineering and Naval Architecture University of Zagreb, Zagreb, Croatia
A small contribution to the debate on the sustainability of plastic waste management
show abstract

The plastic production in the world is growing at a rate of approximately 4% per year. Plastic production in Europe reached almost 65 million tonnes in 2017. The biggest producer of plastic products today is the packaging industry which makes up for almost 40% of European plastic converter demand. In one year roughly 80% of produced plastic packaging in Europe turns into waste. In 2016, for the first time, a larger share of overall collected post-consumer plastic waste in EU was recycled (31%) than landfilled (27%), while the rest was energy recovered (42%) mostly by incineration. The new EU target for packaging waste prescribes 70% recycling by 2030 (in which 55% for plastic), which will be difficult to achieve without efficient separate collection and material recovery of packaging waste.

Recyclable waste sorted out of separately collected waste in MRF is only 20-35%. The rest is energy recovered as a fuel (SRF, RDF) for waste-to-energy and cement plants (if we want to avoid landfilling entirely). Material recovery facilities face today problems with contamination of (plastic) waste, but also complexity of waste (more different and new materials, and pollutants), which puts limits to today’s mechanical (but also chemical) technologies for waste sorting, processing, recycling and recovery. Data shows that the overall efficiency of performance of MRF for non-hazardous mixed waste materials in practise is only about 30-40% of the theoretical efficiency, which is not enough to reach (economically) the required rates set by new EU targets.

Different EPR schemes can help in collection of lightweight packaging waste (of which around half is a plastic waste). Especially successful are Deposit Refund Systems (DRS) for beverage containers. DRSs in Europe achieve collection rates of 80-90%. Modern DRSs are proved themselves with large amounts of collected and recovered waste packaging with a small amount of impurities within the collected material, which is a prerequisite for high-efficiency recycling in a closed loop system (e.g. bottle-to-bottle).

There are other more advanced ways of energy recovery of plastic waste than incineration. Pyrolysis and gasification convert plastic waste into valuable products: fuels, chemicals and energy. Also, chemical depolymerization, catalytic cracking and reforming, and hydrogenation, are considered as chemical recycling in which plastic waste is converted into feedstock material that can be used to produce new polymers.


Benchmarking the performance of cities across energy, water and environment systems
related metrics presents an opportunity to trigger policy learning, action, and cooperation to bring cities closer to sustainable development.