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Wed June 16 2021

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Concrete's carbon calculator

19 Apr 12 A new tool from Cemex enables contractors to work out the embedded carbon at the outset of a project " and how to reduce it. Alex Smith explains.

Embodied carbon has become a very big issue for construction. Levies and legislation have turned the spotlight from CO2 emissions of buildings in use, to carbon produced in the manufacture and transportation of construction materials.

One of the biggest drivers for large material firms is the Carbon Reduction Commitment introduced in 2010. It is effectively a tax on CO2 and has incentivised energy-intensive users to assess their carbon footprints and, where possible, cut levels of embodied carbon.

Cemex is one firm covered by the Carbon Reduction Commitment and in recent years it has targeted big reductions in its CO2 emissions after calculating its carbon footprint for manufacturing and distributing concrete.

It has now gone a step further by providing data for embodied carbon on a project-by-project basis. The online carbon calculator means Cemex can show clients exactly how much carbon is being used in the manufacture and delivery of concrete specifications. More importantly, the tool can consider alternative mixes and transportation methods that could potentially reduce carbon emissions by up to 25%.

Tool for contractors

This is just the sort of tool needed by contractors concerned about the carbon agenda, says Cemex UK sustainability director Andy Spencer.

“We're trying to move them from traditional to advanced materials,” he says. “The carbon calculator is a simulator. It allows us to show alternative scenarios that could cut thousands of tonnes of embodied CO2 from projects.

“The calculator includes data on the embodied energy of raw materials as well as the energy use of the plant. In the example of a ready-mix plant, the carbon calculator includes data on the energy used in the plant, including gas, water, electricity and waste, and information on the raw materials used in production such as cement, aggregates, ash and additives.

“It also has details of the CO2 used transporting the raw materials and any energy used in quarrying.”

Cemex gets some of the data from suppliers which, Spencer says, are beginning to realise the importance of “talking the energy language”.

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The final heading in the CO2 report is Delivery and Transport and this records the embodied energy of moving the ready mix concrete by road, rail or river.

CO2 footprint

The CO2 footprint shows the breakdown of emissions by CO2 tonnes for every stage from raw material to final delivery. A pie chart illustrates what each component contributes in percentage terms.

With this information Cemex technical staff can suggest a change in the concrete mix or delivery method to reduce overall CO2. This might mean moving delivery from road to rail or substituting Portland cement with fly ash.

“The whole thing is about collaboration and working with suppliers,” says Spencer. “This tool allows us to be part of the client conversation.”

The carbon calculator works to PAS 2050, a recognised method of measuring embodied carbon. Spense predicts that the currently fragmented measurement industry will move towards a common standard for as the market becomes more competitive.

Spencer says Cemex was reacting to the increasing interest in embodied carbon from the big contractors. “With carbon agenda still uppermost in the minds of clients and legislators it's no surprise construction firms are keen to take measures to cut carbon especially when doing could actually save money,” he says.

The carbon calculator has been used on 40 projects so far from single loads to large complex jobs requiring numerous concrete specifications. Some of the reductions in CO2 as a result of using the tool are impressive.

On one power station project the number of tonnes of CO2 was cut from 25,000 to 18,470 tonnes - a fall of over 26%. Spencer says that on some occasions the tool has influenced the tender outcome. No wonder

Drivers for CO2 measurement:

  • Considerate Constructors Scheme Registered Site Checklist includes carbon footprint as issue for assessment
  • Code for Sustainable Homes requires transport to and from site to be assessed.
  • Strategy for Sustainable Construction calls for 15% reduction in carbon emissions from construction processes and associated transport by 2012 compared to 2008 levels
  • Carbon Reduction Commitment forces large energy users to buy permits if they exceed a cap on CO2.

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