BREATHE BRICKS FOR SUSTAINABLE AND ENERGY EFFICIENT HOUSING

Introduction

Nowadays air pollution has become a huge problem at some cities which tends for causes such as global warming, heat island effect. The countries closer to equator have inherited the problem of hotter climates. They receive comparatively lesser rainfall. Many of them are developing countries including Sri Lanka. As a result, buildings that help to reduce this problem are all the range. In past few years though, designers and architects have started to move beyond simply reducing building’s emissions and started to work with techniques that actually remove pollutants from the air. However, in most incidents, these new technologies have been effecting air, chemically or physically by comes into contact with them. 

What if buildings could work a little more like a vacuum cleaner? What if they could take a more effective role in pulling in pollutants from the sky? This was exactly the concept of inspiration behind the developing of Breathing Brick.

Breathe Brick is a masonry system which is designed and constructed to constitute and be a part of ventilation system of buildings. It filters polluted outdoor air so that it becomes healthy enough to bring directly into occupied spaces. It acts as a pollution absorbing brick where the design is very similar to a vacuum. The pollution vacuums in bricks were developed by assistant professor Carmen Treadle at Cal Poly College of Architecture and Environmental design. The brief brick sucks pollutants in the air and releases filtered air. The innovative material is designed to be a part of a building standard violation system. In short, it is a technology that can be easily applied to the current construction process by performing wind tunnel tests.

Product / Material

The Breathing Brick is designed to form a part of a building’s regular ventilation system, with a doubled-layered facade of the specialist bricks on the outside, complemented by a standard internal layer providing insulation. At the center of the Breathing Brick’s function is cyclone filtration, an idea borrowed from modern vacuum cleaners, which separates out the heavy pollutant particles from the air and drops them into a removable hopper at the base of the wall.

The system is composed of two key parts: Concrete bricks and Recycled plastic coupler. 

1. Concrete Bricks

Breathe Brick unit is a structural masonry component within which is embedded with a cyclone filter. The concrete brick is featured with a faceted surface which helps to direct airflow into the system, and a separate cavity for inserting steel structure. The brick is designed in a way that it can be replaced some exterior.

2. Recycled Plastic Coupler

It helps to create a path from outside into the brick’s hollow center and to align bricks.

It has a two layer facade system with the specialist bricks on the outside and standard insulation on the inside in the center is a cyclone filtration system that separates out the heavy air particles from the air and collects them in a removable hopper.

How “Breathe Brick” Wall Operates?

By the help of the faceted surface of the Breathe Brick, the air outside the structure is directed into rectangular inlet ports. The air that comes into the system is spinned by cyclone filter winnowing out particles.

The cyclone filter is cast directly into the concrete form. The filtered air that passes into the cavity of the double-Wythe wall system could then supply an HVAC system or an adjacent interior space directly. (Breathe Bricks – Operation Mechanism, Applications, Advantages (online))

The Breathing Brick can function with both mechanical and passive ventilation systems, as the brick simply delivers filtered air into the wall plenum; this air can be delivered to the building interior through mechanical equipment or through trickle vents driven by passive systems such as stack ventilation.

Importance as a sustainable product

• Cheap.

• Sustainable.

   Breathe Brick is a clever way of taking the heavy particulates out of the air as a byproduct of making a building

• Environmentally friendly.

• Low Embodied Energy.

• Ease of handling and construction.

• Low Carbon construction. (using of natural construction material)

• Lightweight. (Technique for modification of breathe brick)   

 By replacing sand in concrete by EPS, the brick can be formed into a lightweight brick. Discussed further under Physical properties of Breathe Brick.

• Help to improve thermal comfort.

• Energy efficient.  Since it operates without electricity and makes part of ventilation system. It works with pressure and temperature differentials

• Passively filter outdoor air prior to introduction to an indoor environment.

• Can operate through existing HVAC system or passive as independent system.

• The design of breath bricks can be configured in a wall with window and the cooling system as well.

• It was proven that the system can filter 30% fine particle pollutants and 100% course particles such as dust.

In wind tunnel tests, the system was found to filter 30% of fine aggregates such as airborne pollutants and 100% of course aggregates such as dust. As the entire system is relatively expansive, the Trudell posits the Breathing Brick is a way to lower the pollution level in developing countries, where rapid expansion of industry and less stringent environmental regulations often cause problems. (Rory Stott, www.archdaily.com)

Applications

• Breathe Brick is optimal for one or two story structures in areas with poor air quality.

• It can be used to construct exterior walls (plenum or courtyard, sound walls along freeways, school playground enclosures)

• It is specifically designed for regions with elevated outdoor particulate matter.

Physical properties of Breathe Brick

“Breathing Walls” concept is an innovative construction procedure that can help improve thermal comfort in houses utilizing local materials.

Breathe brick is made up of concrete and plastic couplers made from recycled plastic. The concrete part can be made out of user’s choice. As a technique the brick can be constructed to have light weighted characteristic.  By the introduction of expanded Polystyrene (EPS) which is a replacement for sand, the brick is lightweight and contains various properties of strength and water absorption. EPS has been frequently used in construction industry in production of lightweight building materials such as wall panel and lightweight concrete blocks. Replacement of sand by EPS is based on volume. The replacement percentage of EPS was 0%, 20%, 30%, 40% and 50%. 

Based on experimented results, the density and compressive strength of the brick was decreased as the percentage of the replacement increased. Meanwhile for water absorption properties, it was found that water absorption of the brick was decreased as the percentage of EPS increased. However the properties obtained have been satisfied the requirement where the brick density for lightweight should be less than 1680kg/m3. The strength of load bearing and non-load bearing brick is 11.7MPa and 3.45MPa for each individual unit. Meanwhile, for water absorption, the percentage of water absorption of brick should be less than 12%. From researches it was found that replacement of sand by EPS give significant impact towards strength and water absorption performance of concrete. 

Unfortunately the strength is limited to one or two story buildings. The strength limitation is the major weakness in lightweight breathing brick. But it is more suitable for houses in Sri Lanka.

E. Dilmi D.Z. Abeysekera

Department of Civil Engineering

University of Sri Jayewardenepura  

REFERENCES

• Admin, (17 December  2017), Breathe Brick (online) [Accessed on 25/09/2019],Available at : http://transmaterial.net/breathe-brick

• Madeh Izat Hamakareem, Breathe Bricks – Operation Mechanism, Applications, Advantages (online) [Accessed on 24/09/2019], Available at: https://theconstructor.org/building/breathe-bricks/29216/

• Rory Stott, (12 August  2015), This Innovative Brick Sucks Pollution From the Air Like a Vacuum Cleaner (online) [Accessed on 25 September 2019],Available at: https://www.archdaily.com/771767/this-innovative-brick-sucks-pollution-fromthe-air-like-a-vacuum-cleaner

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CIGARETTE BUTT BRICKS AS A SUSTAINABLE CONSTRUCTION MATERIAL FOR SRI LANKA

Cigarette butts

Global warming and the environment pollution are critical issues which occur due to the development activities in the world. Cigarettes also contribute to the environmental pollution mainly not in a direct way, but due to the improper disposal of the remaining part of the cigarette after it is used. Since cigarette butts are made of cellulose acetate (a plastic) [5] they have poor biodegradability and it will take many years to breakdown and also heavy metals such as Arsenic (As), Chromium (Cr), Nickel (Ni), and Cadmium (Cd) which are trapped in the cigarette filters leach into the soil and waterways during that process [4].

Figure 01: prepared cigarette butt for brick production [1]

Companies produce about 6 trillion of cigarettes every year and smokers help to make over 1200 million kilograms of cigarette butts waste. In Sri Lanka tobacco use costs LKR 214 billion per year (according to the statistics of 2018) in economic loss with substantial human development losses [6]. Dr.Abbas Mohajerani who led the research project about the cigarette butt bricks at RMIT University said that these numbers can be increased by more than 50% by 2025 mainly due to an increase in world population .Their research results show that if 2.5% of worlds’ brick production with the addition of 1% of cigarette butt amount can be lead to completely offset the annual worldwide cigarette butt production [4].

Figure 02 : Trend of smoking in Sri Lanka in Last 10 years by age groups (2009-2018) [6]

Figure 03 : Dr. Abbas Mohajerani [4]

Advantages of Cigarette butt bricks

Conventional fired clay bricks are one of the most common construction materials since the initial ages of the building construction due to their durability, compressive strength, flexural strength and thermal conductivity than other construction materials. Most of the research activities have proved that incorporation of cigarette butts has significant advantages on behalf of construction industry and also a solution for the environmental pollution. Nowadays, engineers and architects encounter some problems such as the thermal comfort and the noise insulation of dwelling areas of buildings. Since they have invented some solutions such as cooling bricks, ventilation systems and alternative materials for concrete and bricks. Since the cigarette butts have good insulation capability, addition of them into bricks reduce household cooling and heating demands [1]. Cigarette butts cause to improve the noise insulation because they improve the porosity of the bricks than the conventional bricks. In addition to that bricks with CBs (cigarette butts) are lighter and cost effective rather than using other raw materials for manufacturing bricks and cuts the energy needed to fire bricks by up to 58% and that leads to reduce the embodied energy [1]. Since the density of the filters are less than the other materials which are used in the bricks production the overall density was reduced up to 30% [3], depending on the percentage of cigarette butts [4]. Durability of these bricks can be increased with the addition of filters because their biodegradability is less than other raw materials which are used in production.

Physical properties of cigarette butt bricks

Cigarette butts have the physical properties as follows,

• Bulk density – 1.80 𝐠𝐜𝐦−𝟑

• Apparent porosity – 30 %vol.

• Apparent density – 2.42 𝐠𝐜𝐦−𝟑

• Water absorption – 16.65 %wt.

Some of the above mentioned properties of cigarette butt bricks such as density are less than other raw materials while properties like water absorption are higher because most of times the filters consist of tobacco residue, sawdust and grass. Therefore, the water absorption of the bricks increases linearly with the increase of cigarette butt content [1].

Figure 04 : Test cigarette butt bricks with different replacement of Cigarette butts [1]

Physical and mechanical properties of cigarette butt bricks were tested with different percentages of CBs (2.5%, 5%, 7.5%, and 10% by weight) and with the three different mixing times to distinguish the results compared to the conventional clay bricks. In 10% CB bricks the dry density was decreased up to 30% and the compressive strength decreased by 88% and the compressive strength of bricks with 1% CB was determined as 19.53 MPa [2] and this is a suitable value for a one or two storey buildings. Influence of the mixing time was observed by using three different times (5, 10 and 15 minutes) for the bricks with 7.5% CB and 15 minutes brick shows 114% increment of strength and 12% increment for density compared to 5 minutes mixing time [7]. Although the values of water absorption, initial rate of absorption and tensile strength decreased by 22%, 29% and 5% respectively.

As a sustainable solution

Heavy metals and other pollutants which are trapped and immobilized in the solid block when the bricks are fired and they cannot leach and mix with the soil and waterways anymore. In addition to that this is a cost effective product because the cigarette butts are very common in our surrounding and it can be supplied without any cost. Therefore, this can be a turning point of construction industry of Sri Lanka as a developing country.

E.M.K.G.A.D.B.Ekanayake

Department of Civil Engineering

Faculty of Engineering

University of Sri Jayewardenepura.

References

1)    Guide, B. and Masonry, B., 2020. Cigarette Butt Bricks - Physical Properties And    Advantages. [online] The Constructor. Available at: <https://theconstructor.org/building/cigarette-butt-bricks/29224/> [Accessed 19 May 2020].

2)      2020. [online] Available at: <https://www.researchgate.net/publication/297892222_A_practical_proposal_for_solving_the_world's_cigarette_butt_problem_Recycling_in_fired_clay_bricks> [Accessed 19 May 2020].

3)    2020. [online] Available at: <https://www.researchgate.net/publication/279577246_Recycling_cigarette_butts_in_lightweight_fired_clay_bricks> [Accessed 19 May 2020].

4)    Engineersaustralia.org.au. 2020. Double Advantage To Using Cigarette Butts To Make Bricks | Engineers Australia. [online] Available at: <https://www.engineersaustralia.org.au/News/double-advantage-using-cigarette-butts-make-bricks> [Accessed 19 May 2020].

 5)    Longwood.edu. 2020. Cigarette Litter --Filters. [online] Available at: <http://www.longwood.edu/cleanva/cigbuttfilters.htm> [Accessed 19 May 2020].

6)    Tobaccounmasked.lk. 2020. Tobacco Industry Country Profile – Sri Lanka - Tobaccounmasked. [online] Available at: <http://www.tobaccounmasked.lk/index.php/Tobacco_Industry_Country_Profile_%E2%80%93_Sri_Lanka> [Accessed 19 May 2020].

 7)    2020. [online] Available at: <https://www.researchgate.net/publication/272599892_Properties_Improvement_Of_Fired_Clay_Bricks_Incorporating_With_Cigarette_Butts> [Accessed 19 May 2020].

OZONE LAYER AND INFLUENCE OF COVID-19

Ozone layer, which is also known as ozonosphere can be found in the lower portion of the stratosphere that is 15-35 km above from the Earth. This layer consists of higher concentration of ozone. 90% of ozone in atmosphere presents in the stratosphere and it is referred as the ozone layer [1]. The thickness of the layer varies seasonally and geographically. As an example, ozone layer is thin near the poles. Ozone layer absorbs most of the ultra violet rays (UV rays) including 97-99% [2] of Sun’s medium frequency UV light. In addition, the layer absorbs solar radiations of wave lengths less than 290 nm and some other harmful forms of radiation. Due to the absorption of the solar radiation by the ozone layer, the temperature of the stratosphere is significantly high.   

Figure 01: The position of ozone layer in the atmosphere [3]

The ozone layer was discovered by the French scientists Charles Fabry and Henri Buisson in 1913.

Production of ozone in stratosphere

At the lower portion of stratosphere, chemical bonds of the oxygen molecules (O₂) break due to high energy solar photons. This phenomenon cause to occur single oxygen atoms.

O₂ + UV => O + O

Then these single atoms combine with remaining oxygen molecules and form ozone (O₃).

O+ O₂ => O₃

Most of the ozone in the stratosphere formed where the solar radiation level is high (equatorial belt).

Depletion of ozone layer

Now, the depletion of the ozone layer is becoming a global problem. It is due to the emission of manufactured chemicals mainly CFC gases (Chlorofluorocarbon) and halons. This problem was firstly described in a paper published by a Dutch Chemist Paul Crutzen in 1969. In his researches it was shown that the depletion was done by nitrogen oxides. Later in 1974, American chemists Mario Molina and F. Sherwood Rowland discovered that the ozone layer is mainly depleted by CFC [4]. CFC and halon cause chemical reactions to break the ozone molecules. It causes to reduce the solar radiation absorbing capacity of ozone layer. CFC is mainly released by the applications such as air-conditioning, refrigeration, blowing agents in foams etc. Halons released by the applications such as combustion.

Figure 02: Ozone depletion process [5]

The high emission of those ozone depleting substances by human cause to occur holes in the ozone layer. For the past few decades, the chemical reaction with the involvement of Chlorine and Bromine, cause the ozone layer deplete rapidly. Ozone depletion is greatly happened in South Pole. This depleted area is known as the ozone hole. This ozone hole was occurred in the spring over Antarctica.

Figure 03: ozone hole [6]

This ozone hole was grown for years. Though the maximum size of the ozone hole is decreasing as shown in the figure below.

Figure 04: Maximum ozone hole area [7]

Ozone depletion cause to have cancer risks (i.e.: skin cancer), eye damages (i.e.: permanent blindness, cataracts), sunburn, etc. [8]

How to protect ozone layer?

By avoiding the processes of emission of the manufactured gases such as CFC and halon, the ozone layer depletion can be reduced. As an example, minimizing the usage of motor vehicles reduce the halon percentage of atmosphere. Maintenance of air-conditioners properly or reducing the usage of air-conditioners can reduce the percentage of CFC in atmosphere. The global authorities (i.e.: The Montreal Protocol) also have taken some legal actions to protect ozone layer by banning the damaging chemicals [9]. And also, it was designated “September 16” as the international day for the preservation of the ozone layer.

Due to the lockdowns in most countries, for COVID-19, it has led to a significant reduction of air pollution due to the limited operation of industries as well as the motor vehicles. Nitrogen Dioxide dropped up to 60% in northern China, Western Europe and the U.S. in 2020 compared to 2019 [10]. And also, particulate matter pollution has gone down by 35% over northern China [10].  The reduction of the emission of CFC gases and halon in these days also likely protecting the ozone layer. Though, the reduction of air pollution due to lockdown is not the reason to close the ozone hole [11]. Main reasons are polar vortex, high-altitude currents that are responsible for bringing cold air to polar regions [11].

Polar vortex is a large area of low pressure and cold air surround the Earth poles. This effect is decreasing during summer season. Polar vortex is typically weaker in the Arctic region due to the presence of nearby land and the mountain ranges that disturb the weather. In this season, the ozone layer is healing mainly due to the unusual strong and long-lived polar vortex, and it is not mainly due to the air quality changes [12]

D.M.T.S. Rathnayake,

Faculty of Engineering,

University of Sri Jayewardenepura.

References

[1]	D. Wuebbles, "ozone layer, Atmosheric science," BRITANNICA, 17 April 2020. [Online]. Available: https://www.britannica.com/science/ozone-layer. [Accessed 14 May 2020].
[2]	B. Sparling, "The Ozone Layer," NASA Official, 30 May 2001. [Online]. Available: https://www.nas.nasa.gov/About/Education/Ozone/ozonelayer.html. [Accessed 14 May 2020].
[3]	"Biology Review of the Ozone Hole and Global Warming," School Tutoring Academy, 28 June 2015. [Online]. Available: https://schooltutoring.com/help/biology-review-of-the-ozone-hole-and-global-warming/. [Accessed 14 May 2020].
[4]	D. Wuebbles, "Ozone layer atmospheric science," BRITANNICA, 17 April 2020. [Online]. Available: https://www.britannica.com/science/ozone-layer. [Accessed 15 May 2020].
[5]	"What is Ozone Depletion?," eSchool Today, [Online]. Available: eschooltoday.com/ozone-depletion/what-is-ozone-depletion.html. [Accessed 14 May 2020].
[6]	E. Gray and T. Stein, "2019 Ozone Hole is the Smallest on Record Since Its Discovery," NASA TV, 21 October 2019. [Online]. Available: https://www.nasa.gov/feature/goddard/2019/2019-ozone-hole-is-the-smallest-on-record-since-its-discovery. [Accessed 14 May 2020].
[7]	EU, "Protection of the ozone layer," European Commission, [Online]. Available: https://ec.europa.eu/clima/policies/ozone_en. [Accessed 14 May 2020].

CLIMATE CHANGE AND CARBON FOOTPRINT

        Introduction

This topic is closely related to Environmental Engineering. Global warming is becoming a huge problem all over the  world including Sri Lanka. Global temperature rise, warming oceans, shrinking ice sheets, glacial retreat, decreased snow cover, sea level rise, declining arctic sea ice, extreme events, ocean acidification are the some of the evidence of the global warming. The rising temperature can be felt and it keeps rising compared to past. It’s becoming intolerable.  The world's average surface temperature has risen by about 0.98 degrees Celsius compared to late 19th century(Climate Change: Vital Signs of the Planet, 2020). 

Figure 1:  World's average surface temperature by years (Climate Change: Vital Signs of the Planet, 2020)

Sea level has risen by 96 (± 4) mm compared to late 19^th century, at the moment rate of rising is 3.3 mm per year and every year it’s  keep accelerating (Climate Change: Vital Signs of the Planet, 2020).

 

Figure 2: Sea level by years (Climate Change: Vital Signs of the Planet, 2020)

Greenhouse gas emission is the main reason behind global warming. Water vapour, carbon dioxide, methane, nitrous oxide and ozone are the primary greenhouse gases. Carbon dioxide (CO₂) is one of the most important and abundant greenhouse gases in the atmosphere. On the other hand, CO2 is necessary for the composition of the environment, but having excess amount of CO₂ is problematic. The excess CO₂ is generated by human activities such as factory exhausts, vehicle exhaust, burning materials and industrial revolution and globalization are also to be blamed for the increase of CO₂ in the atmosphere; CO₂ level in 1750 was 280 ppm, it has increased by nearly 47% and now in 2020 it has risen to 412 ppm (Climate Change: Vital Signs of the Planet, 2020). It was estimated that fossil CO₂ emissions were 18,454,691 tons in 2016 and it was stated that CO₂ emissions per capita 0.88 tons per person in 2016, an 8% increase over the previous year record (Sri Lanka CO₂ Emissions - Worldometer, 2020).

Figure 3: Carbon dioxide level by years (Climate Change: Vital Signs of the Planet, 2020)

Figure 4: Sri Lanka fossil CO2 emission by sector (Sri Lanka CO2 Emissions - Worldometer, 2020)

In the city of Kandy, the polluted air has already become an issue due to vehicle exhaust being trapped in between the mountains. This has caused diseases, rise in temperature and is harmful to plants. It’s better to take action now to reduce CO₂ emissions before it causes irreversible damage in the future (Population exposure risk assessment to air pollution in Kandy city area, 2012). Cities like Colombo are also at high risk due to population and rapid rise in personal vehicles; the polluted air has been trapped in between high-rise buildings. Hence air quality drops down and also temperature rises due to heat island effect.

Heat Island Effect

When vegetation is replaced by asphalt roads, concrete buildings and other structures to facilitate the growing populations, heat island effect occurs. These structures absorb solar radiation, causing surface temperature and overall ambient temperatures to rise. Removal of vegetation reduces the evaporation and shading, while evaporation and shading are cooling the environment naturally. High rise buildings and other modern structures trap  hot air in between them and reduce the air flow. Vehicles, air conditioners and factories further increase the heat island effect. Even at night temperature will be high due to the emission of heat that is absorbed in day time. Hence heat island effect can occur throughout the year, day and night.

Figure 5: Illustration of Heat island effect (What Is the Heat Island Effect? - Green Ribbon, 2020)

                                

Current solutions practiced in Sri Lanka

• In Sri Lanka, 82.4 % of electricity is produced using fossil fuel and only 17.6% produced from renewable energy sources like hydro power plant and wind mills (CEB, 2020). Therefore, the government focusesing on renewable energy capacity development (ceylonCeylon electricity board, long term generation expansion plan 2018-2037, 2018).

Figure 6: Renewable energy capacity development

• Solar development program of the government, Ceylon Electricity Board is promoting such as Development of Rooftop Solar PV Installations and Development of 60 x 1MW Solar PV Projects (ceylonCeylon electricity board, long term generation expansion plan 2018-2037, 2018).

• Building and developing the wind mills in mountain and coastal areas to generate electricity such as Development Mannar Wind Farm Project.

• Central Environmental Authority has enforced a new tax system in 2007 for the CFLs and LED bulbs, which are energy efficient. This encourages the customers as well as the industry people to produce and supply more CFL and LED bulbs. It reduces the demand and wastage of electricity (climate Climate change mitigation – sri lanka’s perspective, 2012).

• Burning solid waste is also a cause of excess CO₂ so Waste Management Authority is working on safe disposal of waste while the National Council for Sustainable Development is improving recycling and safe removal of solid waste in every local authority (Climate change mitigation – sri lanka’s perspective, 2012).

• Government promoting agriculture, home gardening and urban agriculture, which can reduce CO₂  emissions.( Climate change mitigation – sri lanka’s perspective, 2012)

• Gasoline vehicles are one of the major CO₂ emitting sources; therefore, the government is promoting electric cars by reducing import taxes on electric cars. Further, to reduce the number of private vehicles government is trying to improve public transport (Climate change mitigation – sri lanka’s perspective, 2012).

Conclusion

Three things should be pure and harmless in the world; the food we eat, the water we drink and the air we breathe. Hence, we are in a critical stage; we are responsible for the surrounding environment and we have to ensure a better future for the coming generations. It’s essential to find a solution for this issue. One person alone can’t change the situation, thus we have to think and act as a community. By taking simple steps we can reduce the carbon footprint such as avoiding private transport and using public transport more, using renewable energy sources like solar energy, hydro power and wind power, reforestation and etc.

Sritharan Seran

Department of Civil Engineering,

University of Sri Jayewardenepura.

References

Ranasinghe, D. (2012). CLIMATE CHANGE MITIGATION – SRI LANKA’S PERSPECTIVE. Proceedings of International Forestry and Environment Symposium, 15(0), pp.290-296.

Climate Change: Vital Signs of the Planet. (2019). Climate Change: Vital Signs of the Planet. [online] Available at: https://climate.nasa.gov [Accessed 28 Apr. 2019].Green Ribbon. 2020. What Is The Heat Island Effect? - Green Ribbon. [online] Available at: <http://www.gardinergreenribbon.com/heat-island-effect/> [Accessed 12 April 2020].

Worldometers.info. 2020. Sri Lanka CO2 Emissions - Worldometer. [online] Available at: <https://www.worldometers.info/co2-emissions/sri-lanka-co2-emissions/> [Accessed 13 April 2020].

 2012. Population Exposure Risk Assessment To Air Pollution In Kandy City Area. Colombo: NBRO, p.6.

 Climate Change: Vital Signs of the Planet. 2020. Climate Change: Vital Signs Of The Planet. [online] Available at: <https://climate.nasa.gov/> [Accessed 10 April 2020].

018. CEYLON ELECTRICITY BOARD, LONG TERM GENERATION EXPANSION PLAN 2018-2037. CEB, pp.page 5-1 to 5-20.

Ceb.lk. 2020. CEB. [online] Available at: <https://www.ceb.lk/electricity-generated/en> [Accessed 13 April 2020]