Using low carbon emitting synthetic materials and recycling waste will be a welcome move towards decarbonization of the construction industry.
GR Infraprojects - Atasi Das, Assistant Vice President
The major components that produce the oxides of carbon in the construction industry are cement and bitumen. For infrastructure development, usage of cement is inevitable, be it buildings, metro rails, tunnels, airports, highways, or any under or above ground structure. The manufacturing of cement itself produces a large amount of carbon dioxide. For flexible and semi-rigid pavement construction, bitumen is required for the wearing, base, and intermediate courses of pavement layers. The heating of bitumen in the plant during construction releases carbon monoxide.
Extracting, Recycling, Reusing Bitumen
As a contractor in the roads and highways industry, our focus is on the best utilization of existing bituminous materials that have been excavated from hundreds of kilometers of sections of the project corridors, where RE walls are constructed on the existing 2-lane or 4-lane highways at the time of upgradation, and during widening (4 or 6-laning). Instead of burying the “black gold” or the “bitumen” underneath, the bitumen is extracted and recycled into the new bituminous courses, and the granular materials are recycled in the new granular layers. This helps reduce the carbon emission during mining of aggregates.
We have successfully completed a few projects; one of them is in the Bihar State in which we utilized 60% Reclaimed Asphalt Pavement (RAP) material, leading to 50% reduction of fresh bitumen and 60% reduction of fresh aggregates in the bituminous layers.
- Using synthetic materials like geogrids, geocells, geotextiles, etc. for multi-faceted usage in slope stabilization, ground improvement, stabilization, pavement reinforcement, etc. in order to reduce consumption of natural resources like stones, aggregates, bitumen, cement, and steel, which lead to carbon emissions one way or the other.
- The highway industry is now looking for alternatives to bitumen & steel, as the manufacturing process of bitumen & steel also emits carbon monoxides. Options include using a bamboo crash barrier instead of a metal crash barriers, GFRP Bars (Glass Fiber Reinforced Polymer) replacing steel in non-critical structures and Bio-Bitumen for partial replacement of bitumen.
- Since waste management is important for decarbonization, contractors can use rejected materials from RE wall blocks and paver blocks for embankment protection. We are using rejected RE blocks for slope protection purpose to promote zero waste management as shown in the image below.
- We are using Municipal Solid Waste (MSW) materials in the construction of embankments, granular layers, etc. Waste from the tyre industry is being utilized as Crumb Rubber in the modification of bitumen for improved properties. Waste plastic utilization in bituminous wearing course has started after it was made mandatory by NHAI.
Carbon reduction schemes: pros & cons
Awarding carbon credits has proved to be very effective in European countries for promoting emission reduction. In India, there is no policy yet, but a government body is working towards preparing some schemes in which all the stakeholders will be accountable and responsible for regularly monitoring the exact amount of materials being put into a project and the amount of carbon that each material emits directly or indirectly and compare that with other materials of similar cost. Finally, the incentive shall be based on the overall reduction compared to the initial proposal.
Since there is no policy for carbon credits in India, the Environment Ministry will be responsible for mandating such schemes and for monitoring projects. It will work in conjunction with related ministries for smooth workflow. Monetary benefits provided for reducing carbon emission will promote the scheme within the construction industry, which will then be quick to adopt the schemes.
The main issue while adopting decarbonization schemes is that the new design or construction strategy may have a longer time requirement as compared to the initial proposal. Since there is no relaxation or extension of the time clause, the stakeholders or the implementation agencies will take a backfoot in the fast-paced construction world. Approval from an authority or consultant will become a tedious job and the project may be unnecessarily penalized.