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ENVIRONMENTAL ANALYSIS OF A DEMOLITION WASTE RECYCLING PLANT ON ENERGY CONSUMPTION AND CO2 EMISSION

Environmental Analysis 9

ENVIRONMENTALANALYSIS OF A DEMOLITION WASTE RECYCLING PLANT ON ENERGY CONSUMPTIONAND CO2 EMISSION

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Summary

Allthe stakeholders in the construction, demolition and recyclingindustry have an immense interest to cut down on the amount of carbonemission and consumption of energy. In most industries, carbonresults from construction materials. Buildings are demolished andwhat results are large piles of demolished wastes. The demolitionitself expends a lot of energy in moving machinery especially movingthe wastes to a new location. Due to wastes piled up, they emit a lotof carbon dioxide. To avert this, the demolished wastes need to berecycled immediately despite the fact that a lot of energy from thisrecycling will be incurred. Thus the wastes from such demolishedstructures which emit carbon have been more focused.

Itis worth noting that any process of demolition is divided based onmaterial, onsite, factory and transport (10). In addition, carbon andenergy consumption can be reduced achieved through construction ofprefab structures and not in situ structures as suggested by theQuick scan tool. The demolished wastes are recycled and there are anumber of ways of recycling it. The wastes are of mainly smallstones, blocks, gravel and bricks. They need to be used for differentpurposes and some can be reshaped and used for building other houses. The smaller particles can be used on the floor before aggregate isadded. However, there is a lot of energy emitted during this exerciseand a lot of dust is emitted.

Thereare a number of ways which can be used to reduce carbon and energyconsumption. This is through reduction of construction weight andmaterials used and minimizing the demolition since it emits a lot ofcarbon from the demolished structures and leads to loss of energy asa result of energy used during those demolitions. Energy consumptioncan be reduced by use of green electricity and reduction of transportroutes (11).

Inaddition, the use of carpooling and green energy will do great. Thewastes generated should be recycled to minimize transportation of newmaterials. However, government should come up with the maximum carbonrequired for companies to produce and close those companies whichdon’t adhere.

Inthe past, there has been a lot of awareness on climate change and itsimpact on the man. This awareness has really affected demolition andrecycling industry since they are the key emitters of carbon and lackknow how on reduction of CO2 and energy consumed and due to carelessdemolitions without recycling of materials (5).The research tries to find out how demolition companies attempts ominimize CO2 emission and energy consumption and tries to find outwhich materials are preferred for construction between in situ andprefab structures which emit less CO2 and consume less energy. Thisresearch is divided into two sections the first section deals withproblem qualitative analysis and the second deals with explanation ofthe construction structures and the recycling of wastes.

1.0Problem Analysis

Theurge to protect the environment is mainly focused on carbon dioxidereduction and reducing energy consumption (1). The demolitioncompanies have also made measures to reduce these effects. Thecompany that takes measures to reduce carbon emission should get highchances of acquiring tenders from the government (26). The industryis focused on the building sector since CO2 production is in userphase.It is also focusing on civil engineering sector since it is in chargeof nearly 80% of energy consumption (4).The phase’s civil engineering includes studies on energyconsumption and CO2 emission of the industry and recycling tominimize equipment transportation (11).

Thereis a challenge during the CO2 calculation after completion of thedesign due to no measures for carbon reduction. The only solutionsare the recycling of materials, use of green energy and carpooling.The research focus on recycling of in situ and prefab types ofconcrete constructions wastes by uses of concrete as majorly byproduct of demolition.

Theproblem shows that the clarity of energy consumption and CO2 emissionof various demolitions from the civil engineering industry is not yetestablished (27). In addition, the main objective of this study is toanalyze the effect of recycling the wastes from demolition (5).

2.0Research Methodology

Theresearch questions are as follows: Does recycling minimize on energyconsumption and carbon emission? What are the factors influencing theresults? In addition other sub-questions which will be on:

  • What is an in situ concrete structure?

  • What is a prefab structure?

  • What are the contrast and comparison of energy consumption and CO 2 emission?

  • What are the benefits of recycling after demolition

  • What are the costs incurred in recycling

  • What are the challenges experienced in recycling(5)

Theresearch scope focuses on demolition and recycling of prefaband in situ wastes. The effect ofconcrete will be researched, andhow these affect the emissions from demolished watses transport,onsite and in factory and its recycling (5). Assumptions will be madeon CO2 emissions and energy consumption in its production processes(13). Thisresearch will look at the generation of uncompleted products,transportation of equipments and materials while the emission factorswill be assumed. At the site number of employees will be checkedwhile outside the work, the transportation will be checked (7).Thus,the research methodology will involve four stages namelyLiterature study and interviews, creating the quick scan tool,results and sensitivity analysis and conclusions and recommendations.

3.0Literature Study

Theliterature study gives the information on CO2 emission fromdemolition wastes. It also provides the recycling concepts which aidin carbon reduction and energy consumption reduction. In addition,it demonstrates the use of GHG protocol which is used tomeasurethe green house gas emission as it provides a method for calculation.These gases include CO2, SF6. CH4, N2O, HFCS and PFCs5.

Inaddition, Energy and CO2 are well focused since energy consumptionand CO2 emission are linked together from demolition wastes (14). TheCO2 emissions results from diesel and electricity. In thecalculation, research on consumption and CO2 emission at variousprocesses are done (5). The following table gives the generaloverview of green houses gases and CO2 emission.

Greenhouse gas

CO2-e

CO2

1

CH4

21

N2O

310

SF6

23900

HFEs

100-500

HFCs

150 – 11700

Afterdemolition, the wastes are recycled. This is through using thematerials directly or indirectly. Sometimes, the wastes are shapedinto usable forms that are then used again in construction. Inaddition, they can be used within the firm and avoidingtransportation to other areas. This will minimize energy consumption.Transportation leads to use of diesel which emits a lot of CO2 to theenvironment. The demolition itself should reduce carbon emission byreducing the unrequired energy, using green energy and use ofefficient fossil fuels (7). Other types of energy include windmillson the construction and demolition recycling site (2). In additionthe wastes need to be recycled in the site again to reducetransportation energy consumption and carbon associated with it.

Cement,concrete and reinforcement are focused elements in the civilengineering sector.

Sand,aggregates and water are mixed to form Concrete (15). Cement is thegreatest emitter of CO2 (5).Incomparison, the concrete in wastes is the second available materialafter wood and steel in energy consumption and CO2 emission. Wood is,CO2 neutral while steel is stronger than concrete but concreteisenergy efficient (8). Onsite, concrete is more energy consumingmaterial. During recycling, the high strength concrete can beproduced by reducing water in it

Nevertheless,the cement, concrete and enforcements should be well taken care of tominimize carbon reduction and energy consumption.

Thedefinitive compositions of concrete mixtures are:

5

4.0Insitu and Prefab

Insituisthe oldest way of construction and is nowadays improved. It is aconcrete element or structure which is poured onsite and is not movedaway afterwards (5).

Alot of energy is consumed during the recycling of in situ structuresdue to

  • Placing reinforcement

  • Pouring the concrete

  • Compacting the concrete

Transportationis the main factor here in CO2emmission and is contributed bytransport of equipment and people (5).However, the recycling of the materials at the site can aid inminimizing the energy consumption and carbon release.Lastly, the equipments used include concrete pumps, cranes,pre-stressing equipment, compacting equipment and foundation ramgenerator16.

Prefabsarestructureswith elements produced in another place than the site of constructionsite.

Prefabmaterials are mainly used in because of the following reasons

  • There is limited space

  • Construction time is long

  • To make sure quality of elements

  • Expensive labour

Interms of labor the wastes made of prefab concrete needs a lot oflabor during its recycling than the in situ structure. Equipment usedinvolves use of cranes in demolition and this uses a lot of energy.If maximum energy is used permission need to be gotten (18).

Inthe calculation values, large CO2 and energy consumption can bereduced by use of materials or recycling are possible by use ofprefabs up to 45% concrete and 45% reinforcement19. In summary,prefabs mode of demolition wastes need more labor and equipment,calculation is difficult due to each feature of a structure andreduction of materials leads to reduction of CO2and energyconsumption(5).

5.0The Quick Scan Tool

QSTassist to

  • Determine the difference on CO2 emmission and energy consumption between in situ and prefabs wastes

  • Designing of viaduct

  • Answers the research question

Itis applied to assist establish friendly demolition methods andestablish differences in CO2emmission and energy consumption from thedemolitions (5).

QSTassist in viaduct construction and demolition and recycling of wastesdue to:

  • Improve quality of results

  • Accurate output

  • More conclusions

Aviaduct has many elements such as columns, beams and foundations.

Worst-casescenario is a set of other processes of demolition and recycling andcontains in situ with minimal energy supplies on site (20).Thecalculation of required material is done and transportation figuresare same (5). Worst case scenario is used to compare other methods ofconstruction and demolition and recycling of wastes and no conclusioncan be made. QST is set by adjusting methods and variables of theproject to get optimum solutions and investigate varied emissions(21). The output is then used in designs and QST outcome givesdifference of CO2 emission and energy from the wastes.

Resultof the QST is the estimation of emission.QST is used to establish thedifference of emissions and energyconsumption between prefab and insitu construction demolition andrecycling methods andthere are parameters required to be filled in the QST to makecomparisons. In addition assumptions are used in setting it(22).

Discussionon Emission Factors and Calculation Values

Researchon emission is at initial phases and is calculated using GST. Thedubocalc is used to measure environmental impact of a demolitionstructure (23).Fromthe assumptions there isneed for scope and assumptions in emission calculation. The relevantdata can beprovidedby various institutions and every activity should be measured by QSTin order to reduce the energy consumption and CO2 emission (24).The work hours in factories affects the CO2 emission.

Theemission factors are the electricity, waste material,Transportationand equipment(24). There are varied differences in emission factors andcalculation values because of

  • Used scopes

  • Different source

  • Influence of uncertainty

Conclusionsand Recommendations

Conclusion

Thereis an interest of reduction of CO2 and this paper is on analyzing theCO2 and energy consumption from wastes being recycled and the effectof recycling these wastes. The quick scan tool is used in thefollowing elements

  • Material

  • Transport

  • Factory

  • Onsite

Resultsfrom the tool vary due to

  • Prefab, use less energy and emit less CO2 than insitu because of a number of reasons.

  • Difference between construction methods

  • Sensitivity analysis

  • Emission factors used in the tool

Recommendations

Itis recommended that the demolished waste material should be reducedand ideas on how to reduce emissions should be sought. In additionthe materials resulting from demolition should be recycled and thedemolitions should be minimized to reduce wasteful energy and carbonemission from the wasted materials. Recycling aids in transportationreduction hence reduced energy consumption and carbon release. Thegovernment should give incentives to companies that have propermeasures of emission reduction during tendering.

Thefossils should be replaced with neutral CO2 fuels and the Demolitionand Recycling companies should consider the following

  • Cost of prefab element

  • Insitu construction

  • Shadow price

  • Informing employees

Concerningthe demolition waste and recycling, the renewable energy fortransport should be used to fulfill the obligation of travelling.After the construction, the structures can be refurbished orrenovated in terms of small scale to reduce demolitions which emitscarbon and leads to high energy consumption.This action can lead to carbon saving minimizing emission.

Toaid the waste recycling and reduced CO2 emmission, exchangein excess construction material, aggregate construction wastelandfill and landscape soils should be encouraged. The otherconsiderations to be considered includes the:

Challenges

  • These are in promotion of exchange networks

  • Storing and transfer of site materials logistics

  • Quality of the materials to be exchanged

  • Having a central point for storage when there is no demand

Benefits

Thebenefits which results from recycling leads to savingcost in:

  • waste treatment

  • landfill

  • materials to be purchased

  • fuel for transport

  • natural resource conservation

  • reduction of environmental and congestion effects in road transport

Costs

  • the cost of exchange networks is meted by the services provider and can gotten back by charging fee for use

Thewaste, reduction and recovery can be done through encouragementand support of reduction transportation materials in waste managementfacility through prevention waste, recycling and recovery andpromotion of efficient logistics return schemes, exchange ofmaterials and use of locally produced materials.In addition, havingwasteto landfill andimplementation of a action plan for construction waste of anorganization.

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