Construction and Demolition Waste
Constructionand Demolition Waste
Constructionand Demolition Wastes constitute a big contribution to the waste ofdifferent countries. C&D wastes can be classified as major andminor wastes. We can practice reusing, reducing and recycling inorder to minimize these C&D wastes. The production of thesewastes contributes to the emission of greenhouse gases like carbondioxide that promotes global warming. We can minimize the carbondioxide emission if we will learn on how to conserve energy andfuels. C&D wastes also have embodied carbon dioxide and theirquantity should always be observed. Calculations are presented herein order to achieve the values of embodied carbon dioxide content ofvarious materials. Calculations are also provided here that show thatrecycling emits less carbon dioxide than landfilling.
Wasteshave been a major problem of our society today. Every person in theworld produces wastes. The crisis here is where we are going to putthe waste that we produce? It has been a major project of our localand national government to make sure that these wastes are treatedproperly so that it will not harm our health and our environment.Practicing the three R’s of waste management can be a big help tominimize our waste to reduce, to reuse and to recycle. Wastes havemany classifications and if you know how to classify them, you wouldknow how to treat them. Greenhouse gases should also be minimized inorder to lessen the effects of global warming that greatly affectsour environment today.
Professionals,scientists and engineers now work hand in hand in order to beinvolved on the scientific and technical aspects on proper wastemanagement in order to create innovative ways in handling them.Proper waste dissemination to people is an important factor in theimplementation of these innovations. Implementing sustainable andproper waste management also needs a deep understanding of therelevant social, legal, regulatory and economic issues involved.
Statisticshave shown that the almost one-third of the waste products in theUnited Kingdom is largely generated by the industry of constructionand demolition. This gives rise to a problem because the saidindustry contributes the largest waste contributor in U.K. sinceapproximately 120 million tons of wastes are generated by this kindof industry. Though the country’s waste from construction anddemolition was minimized by 1.6%, most of their wastes are still sentto the landfill where 80% of them cannot be recycled, that imposes athreat to the environment (1).
Carbondioxide or CO2isan example of greenhouse gas that is primarily emitted throughvarious human activities. The most common activity of humans thatreleases carbon dioxide is the burning of fossil fuels like dieseland coal for energy consumption. Energy consumption is used for somehuman necessities like for transportation, electricity and forindustrial processes. Though carbon dioxide is present naturally inthe Earth’s atmosphere, humans are altering that balance by addingmore quantities of it to the environment. We should take actions nowin reducing the emission of carbon dioxide in order for us to have asustainable environment which is capable to cater living things.
Constructionand Demolition (C&D)wastes are wastes in which the primary cause of their generation isthrough activities like constructions, renovations and demolitions ofstructures like roads, buildings, bridges. Wastes from excavationswhich can either be segregated or mixed are also considered as C&Dwastes (2).
Wastescan be in forms of different qualities, quantities and nature. Sincewastes are represented in various forms, it is difficult for them tobe separated or classified into categories under similar componentsand structures. Instead, they have just been classified into the morecommon or major C&D and the less common or minor C&D.Classified under major C&Ds are concrete, steel, bricks, timber,gypsum, asphalt roofing, rubble and stones like granite, marble andsandstone. Wastes classified under minor C&Ds are the wooden orlaminated panels, iron and plastic pipes and conduits and electricalfixtures.
Afterthese C&D wastes are classified and categorized, they willundergo to a waste management process which is composed of four keyphases. C&D wastes need to go to at least one of these key phasesbefore these wastes are put to landfills.
III.Minimizing C&D Wastes
Reductionfrom the name itself is the process of reducing wastes fromconstruction and demolition. It may be difficult to achieve but itcan be done through careful planning and estimating the quantity ofthe raw materials that are needed in construction and making surethat the amount and type of materials that are delivered to the siteare just enough for construction (3).
Bestexample of reduction is the constructions of “Green Buildings”.This type of buildings are constructed following the standards of theBuilding Research Establishment Environmental Assessment Methodology(BREEAM) and the Civil Engineering Environmental Quality Assessmentand Award Scheme (CEEQUAL) which are the leading organizations in theworld that asses, rate and give qualification standards in creatingand developing civil engineering works. Every Green Building isconstructed with the probable wastes limited. Precise and accuratecalculations are made so that the raw materials that are availablewill be maximized for the reduction of wastes and costs when thestructural design is to be implemented (3).
Reusingis the recovering process of the raw materials of wastes from the C&Dand then utilizing them again for another use. Lots of materials fromdemolitions and constructions can be used again making reusing as aneasy task. Most materials from C&D than can be reused areplumbing fixtures, cabinets, doors, bricks, windows, lightingfixtures etc. It is more advisable to reduce and reuse than torecycle since recycling might require additional expenses and efforts(4).
Recyclingof C&D waste can be done in three ways. One way is when thedemolition wastes that can still be recycled are moved to a processorsituated in a different place from the site where they get separated,sorted, and recycled. Another way is that the C&D wastes that canstill be recycled are sorted and categorized in the C&D sitebefore moving them to the offsite processor where they will berecycled. The last way of recycling is when all of the demolitionwastes are sorted, separated and then recycled in the same site ofdemolition (4).
Onthe other hand,if the wastes are not reusable and recyclable anymore, they will bedumpedinto thelandfill that will serve as their “final resting place.” Wastesthat will be transported to the landfill should be approved first bythe receiving facility. Agreement on both sides regarding the typesand the quantities of the materials to be dumped should also be made.If a waste material is considered as a toxic material, toxicity testsshould be administered first before putting them in the landfill.Special wastes like paint and asbestos are not accepted in alllandfills because they need special measures when being dumped.Putting of wastes in illegal sites is considered as a crime and ispunishable by the law.
IV.Effects of C&D Wastes
A.Dust and Pollution
Impropermanagement of C&D wastes can have negative environmental impactslike dust, odour emissions, toxic leaching and noiseand vibration. Dust is made when the vehicles on the site move whenthe sand is dry. When the vehicles move, the dust is dispersed on thesite and in the air which can bring health problems when inhaled. Thequantity of the dust that is dispersed in the air can depend on somefactors that include the land area of the site, the period of timeperforming the work, the type of work done in the site, weatherconditions and the measures taken to minimize the dust like keepingthem wet or so.
Theprocess of constructing structures and most demolitions usuallyrelease large amounts of concrete dust into the surroundings. Hugequantities of dust cause pollution from the amounts of GHG which arereleased in the process. Some other causes of GHG emission andpollution are vehicles that use petroleum and diesel to run and alsothe process of waste disposal. (5)
Toxicleaching happens when materials or chemicals are dissolving from thelandfills into some natural resources like rivers, soil andgroundwater (24). It poses a great threat because it can induce highamounts of organic contaminants and ammonia that can lead toeutrophication of the natural resources that can reduce the waterquality. It can also cause solid acidification that decreases cropproduction and promote weed plants to grow that steal nutrition fromnative plants and wild flowers (6).
Noiseis a type of an occupational hazard where if exposed to 85 dB andabove can cause hearing impairment, stress and can increase one’ssystolic blood pressure (4). The level of dB that is tolerable andacceptable to the human ears is up to only 85 dB or also known as the“Exposure Action Value.” Exposure to values higher than that canbe harmful to the environment because it impedes the growth of plantsand can be a great inconvenience for birds which primarily rely ontheir sense of hearing in finding their preys. C&D equipment thatinduce noise are usually drillers, forklift, trucks, sortingequipment and mechanical garbs.
D.Embodied Carbon Content
C&DWastes have other unpleasant environmental effects because of mostmaterials in this type of waste has a quantity of “Embodied Carbon”Content. This is the quantity of Carbon dioxide released from thematerial throughout the processes on its life cycle that includesmanufacturing, transportation and the actual construction of thematerial (6).
Concreteis one example of a material that has embodied carbon content. Itreleases CO2emissionsstarting from the raw material’s extraction to the processing of itin the factory, up to its transportation to the site. Embodied carboncontent is an area that is starting to achieve importance becauseadequate knowledge about it can help in the estimations of the CO2 emissionsand the computation process of it will be demonstrated in thecomputation section of this project.
AlthoughGreenhousegases can still have their negativeeffect,it can be used to make the planet viable to living things for keepingit non-frozen. These gases trap infrared rays and reflect it back tothe surface of the Earth that results to the heating of the Earth’ssurface. Though it is a natural process, human activities thatrevolutionized industries led to the increased emission of thegreenhouse gases that outweighed the natural speed of the process.
Globalwarming is another negative effect of increased greenhouse gasemission. The rise in temperature of the Earth led to the melting ofthe ice caps in the peak of the mountains that may decrease snowingin most places which is detrimental to our ecosystem because the snowmakes up our rivers that give life to our world. Another effect ofglobal warming is the increase in sea levels due to the melting ofthe ice in the Antarctic region. When sea level rises, severe stormscan wipe out small islands where big waves are most likely to engulfthem. Heat waves brought by global warming may result to droughtsthat might affect our crops due to weather anomalies and lack ofwater supply from irrigations. Extreme heat can also be an outlet forharmful insects to reproduce that might spread diseases like malariaand dengue this might also be the cause for the extinction of someanimals due to the inability of these animals to adapt to suddenweather changes.
b.The Kyoto Treaty
UnitedNations wanted to raise the world’s awareness initiativeregarding global warming and greenhouse gases through their effortsin 20 years. The Kyoto Treaty in 1997 was signed by 160 countries topledge the slowing down of global warming by decreasing the emissionof greenhouse gases like CO2. This is an indication to the importance of spending energy well toreduce green house gases emission due to the negative effects ofglobal warming not only to our environment but also to our health aswell. (7).
V.Calculations of the Embodied Carbon Dioxide Content of C&DMaterials
Calculationsprocedures will be provided in this section to get the embodiedamount of CO2inwastes from C&D materials. Computations were made through theassumption of a theoretical building that will be developed and builtgiven the weight of the estimated materials. Next calculations willfollow in a step by step manner and then they will be represented ina table. The calculations and computations are from the Inventory ofCarbon and Energy (ICE) which is formed by the Bath University.
Figure1. Components of the Building Material
Weight in Tons
Figure2. Weights of the Materials
Thefirst step is to use Figure 2 to convert the weight of the buildingmaterials from Tons to Kilograms. This should be done to follow thestandards of the ICE document that presents various significant Carbon factors and their units are in Kg.
Takingbricks as an example,
Thenext step is to multiply the converted weight of the materials to thecorresponding carbon factor given by the ICE document which is 0.24for bricks.
Dividethe value from the previous step by 1000 to get the embedded CO2inTons.
B.Interpretation of Data
Wecan see from the table given that though concrete is almost twice thevalue of timber, the emitted CO2oftimber is comparatively higher. This discrepancy is due to thevariations of their Emission Factor Values. It is vital to note thatvarious carbon calculations are available for the use of the generalpublic so that we can observe the track of carbon activities. Variouscalculations have their own purposes where some are used in houses,energy usage, for fuel and diesel, and some are for C&D wastes.
C.WRAP’s C&D Calculator
WRAPproduced a carbon emission calculator which is designed particularlyfor C&D industry. By comparing their respective CO2emission,the calculator can show the importance of recycling waste productsinstead of using landfills for dumping these wastes.
Thecalculator is user-friendly. Instructions are provided in Figure 4 todemonstrate on how can we use this calculator to provide comparisonbetween the release of CO2viathe use of landfills or recycling.
Figure4. Recycling and Landfilling CO2Emissions
Wecan clearly see from Figure 4 that the amount of carbon emitted isreduced when we use recycling rather than the dumping of wastes inlandfills in a significant manner.
VI.Minimizing Energy Consumption and Carbon Dioxide Emission
Itis true that many C&D recycling processes consume energy burnsfuel therefore emit Carbon dioxide. Recycling is an important processto reduce the environmental effects that can be brought by C&Dwastes. In fact, the effects to the environment of the recyclingprocesses are taken into account in the assessment of the positiveenvironmental effects of these processes (8).
Ina construction and demolition waste treatment power plant, there is adirect relationship between the CO2emissionsto the energy consumption. CO2emissionsin this type of plant happen because of the usage of electricity andfuel to drive and power up this plant (9). Diesel is the most commonused fuel to energize the plant. Onsite and offsite processes usethis type of fuel for different uses (10). A large amount of dieselis consumed to run various onsite machines and equipment like loadersand other earth moving equipment for the purpose of heating. Thediesel’s use for offsite processes is for transportation of thesewastes to the offsite power plants (10,11).
Themajor energy consumption as well as carbon dioxide emissions in C&Dwaste treatment recycling plants are operational related, transportrelated and there is an incorporation of the energy consumption tothe emission of CO2ofthe plant.
Operational Energy Consumption and CO2 Emission
TheCO2emissionand the operational energy consumption in a recycling power plant forC&D wastes are primarily made up of the electricity used by theplant if the grid is connected to the power plant. Requirements inthe operational energy include electricity for the operation ofcertain machines and equipment and for lighting and heating. Fossilfuels like diesel are also used in some operational processes (12).
b.Transport Energy Consumption and CO2Emission
TheCO2emissionand transport energy consumption in a recycling power plant are theresult of various activities. One activity that constitutes this isthe transportation of the waste materials from the site of demolitionto the site of the recycling plant. Another activity is the energyconsumed from loading the machineries and equipment. Diesel is alsoused in these activities which is the major reason behind theemission of CO2inthe recycling plant (12).
c.Incorporated Energy Consumption and CO2emission
CO2emissionsand incorporated energy consumptions in a C&D waste treatmentrecycling plant is the result of the machinery’s operations duringconstruction. In general, these are the summation of all the emittedCO2duringthe construction process of the recycling power and the demolition(12). Diesel is still used as the most common source of fossil fuelin these processes.
B.Minimizing the Energy Consumption and CO2Emissionof a Recycling Plant
a.Proper Use of Construction Plant
Theefficient use of construction plants would be a big help to reducethe quantity of fossil fuels burned that will result to CO2emissionto be reduced (13). Factors like these could be considered whenselecting construction plants: selecting the correct equipment ormachine for an exact task, ensuring that all construction plants arefunctioning well and their conditions are all good, low carbon fuelusage and the right operation of these plants like reducing theiridling time to improve their plant life, minimize fuel costs, fossilfuel consumption as well as CO2emission(14).
b.Appropriate Use of the Energy on site.
Energyshould be consumed properly while still doing the processes that areneeded in the entire demolition and recycling processes. Right energyusage for example is through avoiding lightings that are not reallyneeded, turning off of the machines when not in use, andtroubleshooting generators to supply the required and right amount ofcurrent and voltage values to the plant. We can save fuel costs andconsumptions and therefore will reduce CO2emissionstoo (16).
c.Resorting to Renewable Resources as an Alternative Source of Energy
Ifapplicable, renewable energies must be used as an alternative to theuse of fossil fuels like diesel because these renewable energysources emit less CO2andgreenhouse gases emission. We must also adapt to more fuel efficienttransportation modes. The use of motor vehicles that have highefficiencies, reduction of the distance travelled of the vehicles andthat they are driven by competent and skilled drivers and they shouldalso use fuels that minimize CO2emission(13).
GreenBuildings’ designs and concepts come from the structures ofenvironment friendly buildings and structures that are fullydependent on renewable resources. Environment is taken intoconsideration from the beginning of the construction to therenovation up to the deconstruction. The design of such buildingsconsiders the functionality, longevity, economy and comfort of thestructure. Green buildings are also called sustainable or highperformance buildings (15). The idea of green buildings is made toaid in affecting the human and environment on a positive sense. Thisis done by using water, energy and other resources effectively andefficiently. Reduction of waste and pollution to maintain the healthof the occupants and the employees that works in the structure (15).
Thegreen buildings serve as a model to show the importance of limitingenergy consumption, whether it be the processing and extractionprocesses of raw materials of the building, transportation and energyinstallation of energy for heating, lighting and cooling andoperating equipment. The reduction and limiting of energy consumptionwill imply the reduction of greenhouse gases emission like carbondioxide (16).
Lightingis one of the most significant mean of energy consumption in abuilding 40% of the total usage of electricity is dedicated tolighting (17). Improving and developing the lighting system is neededto reduce energy consumption. Using fluorescent compact lights thatemit less heat and has higher efficiency than incandescent bulbs ishelpful in saving electricity. Installation of dimmers and motionsensors to monitor the right lighting in a place should also be usedas well as the use of solar lights that utilize the energy of the sunand not electricity should always be used if possible (18).
b.Efficient Boilers for Heating
Sixtypercent of the energy bills are spent on boilers. The choice forefficient boilers is important if we want to save expenses in ourelectric bills. A-rated boilers yield higher efficiency than the oldgas boilers. Using high-efficient boilers will improve the controlsystem of the heaters and it will also reduce the CO2emission(18). Biomass in this matter offers a sustainable neutral carbonfilter. Biomass boilers offer an alternative environment friendlyheating that equates the emission of carbon dioxide to what itabsorbs without disrupting the carbon dioxide balance in ouratmosphere (18).
c.Usage of Environment-Friendly Products
Asustainable building uses eco-friendly appliances and equipment.Recyclable materials like concrete, glass, granite can cut costs.Other environment-friendly products that we should use are timber,corks and bamboo. They can be used in floor building and insulationand also have positive implications to the health of the occupants(19).
d.Well Planned Roofing
Theroof is a very important part for green buildings not just because itprimarily shelters the occupant but it also serves as a mountingplace for solar panels and for collecting rain water system. A greenroof is a type of roof where plants covered it in the purpose ofreducing the run-off of storm water (19).
D.Construction of In-situ and Prefab.
In-situis a classic way of construction involving the construction of arigid and strong concrete for the primary use of building thefoundation of the structure’s base. This can be done by pouring theliquid concrete into forms that are still removable that rapidlycools down and hardens after that form is removed that will lead astrong wall behind. Prefabrication on the other hand is the term usedby the construction industry to define assemblies that are producedunder factory conditions and then put to the sites of constructionsto incorporate into structures and other civil engineering works(20).
Properunderstanding regarding the positive and negative points of in-situand prefab can be of help to give one an insight to the effects ofthose processes economically, environmentally and socially. Prefab isviewed as a more sustainable design in terms of the raw materials,usage of labours and as well as the quantity of emissions (21).
a.Advantages of Using In-Situ
Theon-site pouring of in-situ yields less room for error. That sectionis unmovable and stable that will result to a crack free, very rigidand solid insulated section. The section’s strength can be improvedby adding steel reinforcements which is a very popular method ofconstruction. The sections of in-situ can also be innovative. It canbe designed in such a way that it can suit various purposesregardless of the project’s site. Through computer modelling, wecan make precise and interesting new designs if we learn to utilizeour modern technology. This type of on-site activity can also opennew jobs to labours (22).
b.Disadvantages of Using In-Situ
Thistype of set-up can be very time consuming because it will take a lotof time and effort to constantly check the condition of the in-situ.The concrete would also need days in order to dry up and if no propersteps are made, this might impede the progress of the building’sconstruction. The process can also be tedious to labourers becausethere is a long time for waiting to pour and remove the forms of theconcrete. It will also require higher compensations to these workersin order to pay them properly. The quality of in-situ can also beuncertain because factory standards are not applied. Quality may alsosuffer if unforeseen circumstances like weather are not taken intoconsideration. Skills and proper management, stability and rigidnessof the materials to be used also play key factors in achieving thequality of the structure (23).
c.Advantages of Using Prefabrication
Significantreduction to the construction time as well as to the operations costcan be achieved by using prefab. It will not be necessary totransport building materials like cement, bricks, and steel thereforecutting the transportation cost. This process is also a sustainablechoice since the manufacturing is done off the site, enough materialswill be used and less wastes will be produced. Noise and dust arealso reduced during prefabrication. This process does not depend tothe climate changes that can save energy used for other processeslike cooling, heating and as a result, less carbon dioxide is emitted(24).
d.Disadvantages of Using Prefabrication
Expensivetransportation fees might happen because prefab sections usually havehigher volumes and therefore will entail a higher cost fortransportation. Special measures should also be done because prefabsections require cranes to install and move them to their desiredplaces. Installation of prefab sections requires precision thatrequires skills, time and effort. Prefab sections are veryrecognizable that gives it a dull design appearance. Jobopportunities will also be cut off since the production of sectionsdoes not require on-site workers (25).
People,engineers and construction workers should be aware of the effects ofConstruction and Demolition wastes to our environment and to ourhealth. We should all know how to minimize the production of thesewastes or if we know how to prevent them, the better. Energyconservation should also be made because the burning of fossil fuelslike diesel has been contributing to the emission of greenhousegases. We should recycle these wastes and the recycling plant that wewill use should also comply to the environmental standards set toprotect our environment.
Ifwe will reduce the usage of energy, we can lessen the quantity ofcarbon dioxide that is emitted to the atmosphere. Another result ofthis is that we can minimize the energy dependence of our nation sothat there would be no scarcity in power and we can also save money.We should fully utilize power plants that use renewable energy assources since they emit much lesser amounts of greenhouse gases andtheir fuel supply is abundant. Efficiency of equipment and plantsshould also be increased through improving and developing operationand maintenance practices.
Analysesare now conducted to assess the potential impacts of wastes, energyconsumption and carbon dioxide emission. The factors that affect themmust be taken into consideration and should be included early in theplanning stage of projects and proposals. Continuous monitoring isalso significant when implementing actions in order to check ifactivities and projects follow our goal to minimize waste andgreenhouse gases in our environment.
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