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Circle Economy and ICLEI have partnered up to initiate the go to knowledge hub of case studies about the circular economy in cities. The Cities Collection is a repository of case studies that demonstrate the role of cities in the circular transition, and includes policies, business cases and research articles. Cases in the Collection flow into an ecosystem of digital products which support users in transitioning cities to circularity, for example [Ganbatte](https://ganbatte.world/cities/) and <a href="https://circulars.iclei.org/" target="_blank">ICLEI Circulars</a>, both part of the <a href="https://circulars.iclei.org/circle-lab-for-cities/" target = _blank">Circle Lab for Cities Programme.</a>




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Circular Cities

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Starter Kit collection

Policy case

Impact on the availability of resources as well as their effect on living organisms, ecosystems, and components of the environment.

Ecological Impact

Impacts on the financial condition of a company, as well as the the economicconditions of its stakeholders and on economic systems at local, national, andglobal levels.

Economic Impact

Direct and indirect reduction in economic costs

Cost Savings

Reduced green house gas emissions released into the biosphere

Reduce Emissions (SDG13)

Minimise waste through diversion: Instead of sending waste to landfill, it is redirected into other industrial processes for handling, treatment, recycling, recovery, or reuse in various forms. 

Minimise waste through design: At the outset of a process of project, plan and design such that there is zero waste or minimal waste during production, use, and at end of life. 

Minimise Waste (SDG12)

Reduced use of fossil fuel energy sources and/or increased use of renewable energy

Reduce Energy Consumption

Societal Services

Providing water and sewage services, including water collection and distribution, water treatment systems and sewage treatment facilities

Water and Sewage

Utilise waste streams as a source of secondary resources and recover waste for reuse and recycling

Use waste as a resource

Recover waste energy or generate fuels and energy from waste streams

Energy recovery from waste

Recovering and reusing waste heat, gas, etc. for energy

Recovery and reuse of waste energy

Biogas produced by the anaerobic digestion of organic solid waste can be used as an energy source for cooking, lighting and generate electricity, replacing thus other fuels. Moreover, the treatment of organic waste alleviates the solid waste crisis in urban and peri-urban area if the developing world.


Use biogas

Wastewater (blackwater and water from industrial processes) can be treated and reclaimed for agricultural and industrial purposes. Moreover, depending on economic factors, wastewater treatments can be adopted for supplying domestic freshwater. 

Use wastewater

Other

'Manage' influences the use and function of physical and material elements within the urban environment. 

Manage

Infrastructure

Develop infrastructure to support resource cycling

Eliminate waste by maximizing the recovery of resources at the end of the use phase so that they can be reintroduced into production processes


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Recover

Process waste into valuable industrial inputs or consumer products; distribute processed waste to users.

Process waste and ensure its re-entry into industry at its highest value

Residual organic and food wastes can offer a quasi-renewable and low-carbon source of energy. By processing organic wastes, often under high temperatures, pressures and in the absence of oxygen, organic wastes can be transformed into fuels, which can be used for heating, electricity generation, as well as transportation. A variety of technologies have been developed to generate biogas from organic materials, for example, anaerobic digestion. Such facilities can vary in scale from single units that can process the waste of a single building or neighbourhood, to large-scale facilities that can process the majority of the organic wastes generated from the entire city. 

Cities have a key role to support the utilisation of organic materials as biofuels due to their close oversight and influence on the urban waste management system. In particular, cities can support the financing of large-scale facilities to help to overcome the investment costs, as well as develop relationships with businesses to operate such facilities. 


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🍏  💧  Biogas from organic materials

Cities consume about 75% of global energy and emit between 50% and 60% of global greenhouse gases (UN-Habitat). To reduce the negative impact of their energy consumption, cities need to shift away from fossil fuels and move towards renewable energy sources. Such a shift will help cities work towards their climate change mitigation and adaptation action plans. Renewable energy technologies such as wind, water, solar, and geothermal can also help improve access to energy in vulnerable and marginalised neighbourhoods through, for example, decentralised, off-grid solutions.

Renewable energy technologies can harvest the energy in nature’s processes, such as wind, and solar radiation and geothermal heat, that can be replenished within a human lifespan. In contrast, fossil fuels are materials that are not replenished within a human lifespan and are combusted for energy, losing the fuel material and resulting in emissions.

Local governments can develop sustainable energy plans, considering different energy resources and requirements, to develop a robust strategy for the development of renewable energy technologies and infrastructure throughout the city. They can also institute specific legislation and tax systems to regulate energy production and consumption, incentivise research and development of cleaner, more efficient technologies. Via Power Purchase Agreements cities can buy renewable energy from green energy providers and fix the price in order to provide security to financial institutions to finance renewable energy infrastructure. Furthermore, increasing awareness and facilitating capacity-building on planning urban sustainable energy projects can help the uptake of clean energy across the city by different stakeholders—from citizens to businesses and institutions. Facilitating collaboration, then, will be crucial, since private companies operate most of the world’s energy systems.


⚡ Energy Systems

Governments

Impacts

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Industries

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A framework of policy instruments that enabled and encourage the transition to the circular economy

Policies

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A framework of policy instruments that enable and stimulate the transition to the circular economy

The principles of a circular economy concern designing out waste, regenerating ecosystems and keeping items in use. Decoupling the economy from material flows—improving the rate of resource productivity faster than the economic growth rate—is also a consistent guide. By evolving with the growing number of applications of circular economy principles, and consolidating these strategies across thematic areas, Circle Economy’s Key Elements Framework (KE) renders the elements of the circular economy salient and serves as a basis to derive contextual strategies and interventions. 


The Framework consists of:
- Core Elements: Activities directly handling product or material flows; and uniquely,
- Enabling Elements: those that remove obstacles for core actors.


Key elements of the circular economy

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Circle Economy's framework of strategies and activities that define the circular economy

Urban Opportunities

The Circular City Actions Framework provides urban changemakers with five complementary strategies they can use to start working towards a more circular system. 

The framework is action-based to provide users with concrete strategic directions and showcase the desired outcomes of each strategy. 
The framework consists of five complementary **strategies**, under which **sub-strategies** provide further detail. Finally, each sub-strategy consists of a diversity of tangible **solutions** which are framed in relation to key thematic areas. 

Note: solutions are currently focused on:
- 🍏 **Food systems**
- 🏢  **Built environment**
- 👕📱  **Consumer goods**
- ⚡ **Energy Systems**
- 🚌 **Mobility Systems**
- 💧 **Water Systems**

More thematic areas are coming soon...

'Click through each of the five strategy cards below to explore the framework and circular economy case studies in more depth!'



This framework was developed in collaboration with ICLEI, Metabolic and Ellen MacArthur Foundation with support from the MAVA Foundation. Read more about it [here]( https://circulars.iclei.org/action-framework/). 



Circular City Actions Framework

An action-based framework for local governments working towards circular cities

Thematic Areas

City Stakeholders

SummaryThe City Council of Almada provides wastewater treatment service that accounts 
for almost 100 percent of wastewater within the city. This is a result of a municipal 

strategy which aims to achieve full coverage of the drainage networks and treatment 

systems within Almada™s territory; a goal towards which the City Council has allocated 


The Portinho da Costa Wastewater Treatment Plant (WWTP), the subject of this case 
study, demonstrates the City Council of Almada™s commitment to ensuring that water 
circulates within closed loops in the municipality. A closed loop water cycle not only 
allows for repeated use of water resources, it also contributes to the preservation of 

biodiversity in the Tagus estuary, which provides numerous ecological functions and 



WWTP is connected to one of the three municipal wastewater drainage systems, and 

serves approximately 80,000 inhabitants across the territories of Costa de Caparica, 

Trafaria and part of Caparica. 
This case study documents the recovery of the biogas generated in the wastewater 
treatment process and highlights its importance within the framework of the Local 

Strategy for Climate Change of the Municipality of Almada.
Introduction: the importance of biogas recovery Anaerobic digestion is being increasingly used in wastewater treatment systems. The 

main goal of this process is the stabilisation of the primary and secondary sludge 

resulting from the treatment, rather than the production and use of biogas. Typically, 



considered a useful energy by-product that can be harnessed. 

that if all the worlds organic waste which is processed through anaerobic digestion 

the result would be the savings of approximately 5 percent of global fossil energy.
The potential energy recovery with this technique is considerable and can be utilized 
in any WWTP equipped with anaerobic digesters for the treatment of sludge. However, 

considering biogas conservation during the project planning phase provides greater  







which recovers energy from biogas, represents integrated local action which progresses 


Almada, PortugalRecovering energy from biogas produced  in wastewater treatment plantsPopulation / Land area
174 030 (2011) / 72 km²  
Municipal budget 
77,5 M• (2015)Greenhouse gas inventory Yes, since 2003
ICLEI Case Studies189March 2016Facts & FiguresAlmada has been a member of 

ICLEI since 20012Biogas is suitable for use within energy conversion equipment such as power units 
(motor + generator), cogeneration units for heat (thermal energy) and electricity 

output, and even boilers for hot water and/or steam production. The possibility of 

producing and internally using biogas in the WWTP as a "free" fuel, which also serves 

to reduce GHG emissions, proved to be enough evidence to justify the technical, 

(SMAS) have invested in the design and construction of the Portinho da Costa WWTP.
Almada: between land and seaLocated on the south bank of the Tagus River across from Lisbon, Almada is one of the 
18 municipalities within the Lisbon Metropolitan Area. The municipality has 175,000 

full-time residents and an estimated 8,000,000 visitors per year. It occupies a surface 

of 72 km2, 40 percent of which is built up urban area and 24.2 percent is a lush forested 


to the east and north lay the Tagus River, while to the west lays the Atlantic Ocean. 
Almada™s Atlantic Ocean beachfront, Costa de Caparica, extends for approximately 13 km and is a popular summertime destination for Lisbon residents as well as foreign 
visitors.The Almada City Council has long been developing policies and strategies towards a 
more sustainable city. The Local Strategy for Climate Change of the Municipality of 
Almada contains a number of actions targeted at reducing the energy consumption 




been technically supported by the Local Energy Management Agency of Almada, 





sustainble investemnts within the municipality.
Along these lines, the City Council of Almada has been a signatory of the Covenant 
Photo: Ajuntament de Barcelona
Photo 1: A cogeneration engine at 
Portinho da Costa WWTP3of Mayors since its inception, and has embraced the challenge of reducing its energy 
consumption and GHG emissions by 20 percent as a contribution to the EU common 

3x20 objectives.
Most recently, Almada subscribed to the Paris City Hall Declaration during the COP 
21 and embraced the ambitious commitment of reducing its emissions 80 percent by 

2050.Planning in Ten Year Intervals
Every 10 years, the Municipality of Almada approves an updated local development 

strategy, and water and wastewater management have factored heavily in many of 


 1960™s - First Plans made for the wastewater drainage network and water supply 
network. 1980™s Œ Plan & construction of the wastewater drainage network; construction 
and renovation of the water supply network 
 1990™s Œ Plan & construction of wastewater treatment plants
 2000™s Œ 100% urban water cycle coveraage
 2010™s

water and wastewater systems to climate change.
Almada™s Strategic Plan also includes guidelines and actions for its wastewater 


 Pollution prevention and assets management, with the use of technology for 
intensive measuring and monitoring Œ in parallel with sewer rehabilitation Œ to 


 Pollution reduction, through adaptation of older WWTP™s to current EU regulations Sludge valorization, through biogas energy recovery and re-application to 

agricultural lands  
 

treatment System within the municipality, as indicated in Table 1. The plan also 

includes targets for the development of sustainable urban drainage solutions, 

including harvest and retention of rainwater.
Measures towards the 2033 targets have already been implemented to address the 





ballasts) to minimize energy consumption. Biogas recovery through cogeneration has 

been implemented to maximize energy production and minimize external energy 

dependence. Physical-chemical treatment plus biological treatments ensure process 


Table 1:  Almada™s Strategic Plan 
targets for 2017/2033Performance indicators and targets2011
20172033
3/km)660060002000Sewer rehabilitation (% of total)
0.1%0.5%2%Energy optimization in pumping stations (kWh/m
3 100m)0.650.450.35Reclaimed wastewater (%)
2.36%3.5%10%Regulation compliance (%)
89%100%100%4Further additional measures are already being explored, including maximizing use of 
renewable resources through installation of solar panels and photovoltaic panels, as 

well as WWTP 8-year energy auditing programs to reduce electric energy consumption. 


lighting, energy management tools and professional training.
Explaining the Initiative:Energy in Portinho da Costa WWTP 
Portinho da Costa WWTP produces energy which corresponds to that which is used in 
the treatment of the sludge and electricity consumed it the various processes. Since 

its inception, the project foresaw the potential of supplying these energy needs by 
installing a cogeneration system powered by the biogas produced within the same 
WWTP.Biogas stems from the digestion of the sludge originated in the primary and secondary 
treatment of wastewater. Sludge, which is mainly formed by the organic matter of the 
initial sewage, is the ideal substrate for the application of a treatment process known 
as anaerobic digestion (biological degradation in the absence of oxygen). This process 

results in the production of biogas, a form of renewable energy, essentially consisting 
of methane (CH4) and carbon dioxide (CO
2), which may be used as fuel.
Graph 1: Annual community energy 
use in Almada as of 2012 by sector 

(MJ/year)Graph 2: Annual community 

emissions in Almada as of 2012 by 

sector (tonnes CO2eq)5Biogas from Portinho da Costa WWTP: a noble renew-able energy
the methods that allow for recovering 

waste should be considered in all cases, as 
they combine energy generation with an 


used for energy production, biogas which 


to this group.The importance of biogas as an energy 
resource is due to its main constituent, 

methane. This compound has a high heating 
value, which makes it a very valuable utility 

for the cogeneration of thermal energy and 

electricity. However, its direct release to the 
atmosphere is harmful, since methane has a 
global warming potential approximately 21 
times higher than that of carbon dioxide.
Biogas composition varies according to 
the waste characteristics and operating 
conditions of the digestion process. On 

average, it is 60 percent methane (CH4) 

and 40 percent carbon dioxide (CO2). Other gases such as nitrogen (N2) and hydrogen 

sulphide (H2S) are also present in the 

composition, but only in trace amounts. The 

laboratory analysis of the biogas produced 
at the Portinho da Costa WWTP displays a 
percentage of over 65 percent methane.
While, in absolute terms, biogas energy is a lower grade of energy than most of 

into other forms), the fact that it is both a by-product and renewable makes its use 



used, it is always possible to produce at least one form of energy, be it electrical, 

thermal or mechanical.The cogeneration system of Portinho da Costa WWTPThe cogeneration system of Portinho da Costa WWTP consists of two power units 

(motors and alternators) that feed on the biogas stored in two double membrane 


The power units (2 x 250 kW) allow for converting approximately 33 percent of the 
energy contained in the biogas into electricity. About 60 percent of its energy is 


from the thermal energy present in the exhaust gases and engine cooling circuits. The 

loss of energy in the co-generation process amounts to just 7 percent.
Figure 1: Energy equivalence of 
biogas with 70% methaneFigure 2: Diagram of the Portinho da 

Costa WWTP cogeneration system
6Portinho da Costa WWTP: an ecological WWTP that turns waste into 
energyThe co-generation system of Portinho da Costa covers about 40 percent of the energy 
needs of the facility, equivalent to about 550 MWh per year. In environmental terms, 

these energy savings translate into a decrease of 40 percent of GHG emissions, which in 

absolute terms represents a reduction of 180 tons of CO
2. In addition to the reduction 
of emissions due to the displacement of 

the use of natural gas and electricity, this 

measure also decreases the amount of 
carbon dioxide equivalent that would 
otherwise be released from the disposal 


This is, therefore, a significant 
contribution from the Almada SMAS to 



reduce GHG emissions which originate 
within the municipality. 
The construction of the Portinho da Costa 
WWTP ensures the additional treatment of 24 percent of the wastewater in 
the Municipality of Almada without 
increasing emissions from the waste 
sector. This performance is due to the fact that the design of this facility provided for 

a cogeneration system to convert biogas into thermal and electric energy. 
The wastewater treatment process of Portinho da Costa WWTP 
Portinho da Costa WWTP receives a daily average rate of around 9 500 m
3 (3 467 500 m3/year). The treatment encompasses a solid phase process and a liquid phase 

followed by an advanced physical-chemical treatment (the primary treatment). This 





25m deep and 150m from the bank of the Tagus River. 
In the solid phase, the sludge resulting from the primary and secondary treatment 
of the wastewater is thickened by gravity. In the next step, this thickened sludge 

undergoes a digestion in a mesophilic regime (35°C temperature), using the heat 
generated by the cogeneration engines to maintain an operating temperature that 
maximizes the generation of methane.
The digested sludge is then dehydrated by centrifugation, stored in silos and used 




higher than 96%), produces biogas, repurposes the sludge as agricultural fertilizer, 
and reuses the treated wastewater for washing and watering green spaces.
Photo 2: Primary treatment of sludge 
at Portinho da Costa WWTPPortinho da Costa WWTP design parameters
Project lifetime [3]2020Population served [3]140.000 inhabitants equivalent
Tratment capacity [3]
22.400 m
3/day
Biochemical Oxygen Demand 5-days 
(BOD5): 96%Chemical Oxygen Demand (COD): 97%

Total Suspended Solids (TSS): 97%
Anaerobic digestion design parameters
Biogas storage capacity
2 x 200 m3Cogeneration design parametersElectricity production capacity
2 x 250 kWClimate change mitigation
Potential greenhouse gas emissions 
reduction687 t CO2/yearTable 3: Technical characteristics of 

the Portinho da Costa WWTPFigure 3: Energy balance of the 

Portino da Costa cogeneration plant7Lessons Learned Municipalities should consider energy recapture and cogeneration at the draft 
stage of constructing new facilities in order to ease their physical integration in the 

wastewater treatment plant and its operation.
 




community associated with this measure.
 
the possibility of harnessing the biogas energy generated in the anaerobic digestion 

process, and included this as a requirement in the public procurement procedure 

to select the design of the treatment plant.
 Process control, close monitoring, and planned maintenance can help to ensure 

continued good performance of the system and delivery of expected savings and 



essential.Replication The technology used in the Portinho da Costa WWTP is all commercially available and 

poses no obstacles to use. Existing WWTP™s that already have anaerobic digestion in 
place to treat sludge, but which are not yet harnessing the energy potential of biogas, 
can potentially replicate elements of the Almada model. 
The key issue to bear in mind in the implementation of such a project is that the 

of in-house expert knowledge and expertise allows for identifying the needs and 
opportunities for energy recovery of waste, or a by-product of the wastewater 
treatment process.Energy carrierConsumption prior to cogeneration              

(MWh/year)Consumption with 
co-generation 
(projections for 2020) 
(MWh/year)Energy savings 
(MWh/year)Energy savings (%)Electricity1,778967811
46Natural gas1,282511,23196Total
3,0601,0182,04267Policy  Long-term municipal strategy and action plan for water and wastewater, and a long-standing committment to 


Finance 
 Funding was provided through grants
Organizational arrangements and 

capacity  Technical support was provided by Local Energy 
Management Agency of Almada, AGENEAL, and Almada™s 

Water and Sanitation Municipal Services, (SMAS Almada)
Stakeholder engagement  Harnessing of energy from the biogas was included as 
a requirement in the public procurement procedure to 

award the design of the treatment plant
Technology
 Anaerobic digestion for biogas production coupled with 

electricity and heat cogeneration
Table 4: Projected potential energy 
savings enabled by the cogeneration 

plant when fully operational (2020)
Table 5: Key features of Almada's 
approach to the Portinho da Costa 

WWTPHarnessing biogas reduces operating costs with the acquisition of energy while it also 
avoids GHG emissions. The major costs towards such a WWTP are those associated 
with the acquisition and installation of equipment, which are recoverable within its life 




Costs and FundingThe investment in Portinho da Costa WWTP was approximately 10 million Euros. 

Funding was secured through grants from the European Investment Bank (EIB) and 

EEA Grants. The use of biogas for cogeneration enables operational cost savings through the 
displacement of natural gas and grid electricity consumption, which in 2011 amounted 


(changed from 6% to 23%), the savings associated with energy amount to at least 

60.000•/year.References[1] Estratégia Local para as Alteracoes Climáticas, Sector Resíduos, Medida ME8 Œ 
Energias Renováveis: aproveitamento de recursos endógenos Œ Cogeracao a biogás em 

ETARs Municipais
[2] Almada Wastewater Drainage and Treatment System - WWTP Portinho da Costa, 
Alexandra Sousa, Waste Water Treatment Department, Water and Sanitation Municipal 


[3] http://www.smasalmada.pt/web/portal/etar-do-portinho-da-costa 
Key ContactsCâmara Municipal de Almada
City Council of Almada

Department for Energy, 

Climate, Environment and 
MobilityRua Bernardo Francisco da Costa, 42, 2800-029 Almada, 

Portugal
Tel. +351 21 272 25 10
Email: almada21@cma.m-almada.ptAcknowledgements Authors: Catarina Freitas 
 Câmara Municipal de Almada, 
Departamento de Energia, 

Clima, Ambiente e Mobilidade 

| City Council of Almada, 

Department for Energy, 

Climate, Environment and 

MobilityAlexandra Sousa
 Serviços Municipalizados 
de Água e Saneamento 
de Almada, Departamento 

de Tratamento de Águas 

Residuais | Municipal Water 

and Wastewater Services 

of Almada, Department of 

Wastewater Treatment
Carlos Sousa 
 Agência Municipal de Energia 

de Almada, AGENEAL | Local 
Energy Management Agency 
of Almada, AGENEALEditors: Ana Marques, Senior 




Research, ICLEI World 

SecretariatTranslator: Diana Mota
This series of local case studies is produced within the Urban-LEDS project funded 
by the European Union, and implemented by UN-Habitat and ICLEI, which has the objective of enhancing and the transition to low emission urban development in 
emerging economy countries.They represent solely the views of the authors and cannot in any circumstances be 

Almada

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Municipality of Almada

<p>Almada, Portugal, is paving the way towards a carbon-efficient urban water cycle. As a coastal city, progressive water and wastewater management is a priority for the City Council of Almada. The construction of the Portinho da Costa Wastewater Treatment Plant (WWTP) represents a circular model of wastewater treatment that includes a closed-loop water cycle and a system of biogas energy recovery.&nbsp;</p>