Tracking carbon in construction product manufacturing05 October 2021

The cutting operation

At the Energy Management Exhibition (24-25 November), SOE is presenting a panel discussion on reducing energy consumption. It features members working across industry. Also speaking is Matthew Jenkinson, Tarmac Alfreton senior site manager, who will discuss his work to document and reduce the site’s CO2 usage. He spoke to Will Dalrymple

Now that the UK has left the EU, it is replacing the European emissions trading scheme (ETS) originally set up in 2005 with a UK version. Large-scale users are legally-required to meet consumption limits, which are set on a permanently-reducing scale, or pay a carbon charge. It’s a process that Tarmac is currently developing to ensure it complies with all the statutory requirements.

Matthew Jenkinson: “At our sites, that’s anything that burns fuel – cement kilns, for example. I’m responsible for a plant that makes Toplite aerated blocks, breeze blocks, as they may be commonly referred to. In my factory, the main energy usage is steam used to pressurise the autoclaves. This is generated by a natural gas boiler.

“The manufacture of Aircrete blocks is significantly different to other block products and is essentially a chemical process, where powdered aluminium is used in the product mix to create hydrogen that aerates the blocks. Once this process is complete, the blocks are cooked in autoclaves for up to ten hours at pressures ranging between seven and 12 bar and a temperature of around 200°C. There is a significant amount of energy required to complete this process, and this is something we are constantly trying to reduce.”

OE: How are you doing this; are you performing a site survey?

MJ: “We measure all the systems on the plant that can create CO2, this includes natural gas, electricity and diesel for the mobile plant. We have 27 electricity meters, four gas meters and three water meters (although they don’t all directly contribute to CO2, but they are still included in the overall energy usage at Tarmac).

“We have been recording this information for many years and this will be used as a baseline to develop the future reduction targets. In October-December 2021, there will be verification visits from an external body to check these details, which in England is the Environment Agency. By February, we are expecting a report to verify the emissions levels which will give me detailed information on the CO2 outputs. We hope to submit that in March, and it will be the baseline in the coming years.

MJ: “The UK has signed up to legal commitments to reduce its CO2 emissions. Emissions trading schemes are in place to limit these and drive improvements to reduce them. A cap is set on emissions that any site can produce and is reduced annually, they are part of our license to operate and are a legal requirement so we must comply. Failure to comply can result in significant penalties. Qualifying sites have the legal responsibility to measure and report their emissions.

“We are required to measure our carbon emissions on an annual basis and report them to the regulator in line with the process set out in the permit. Greenhouse gas emissions permit (GHGE) sites are required to purchase and surrender allowances at a rate of one allowance per tonne of CO2. There are two types of GHGE permit: one for sites that have a combined thermal capacity of over 35MW. The other type of site is a hospital or small emitter permit (HSE). These have a combined thermal capacity between 20MW and 35MW. HSE sites are given an emissions target that decreases annually. Where targets are exceeded, a penalty per tonne of CO2 is required to be paid.

“As the site manager, I am required to measure and report all site CO2 emissions from fuels used in combustions processes. Although purchased electricity creates CO2, it is not covered by UK ETS at this time. Also, the UK ETS is only concerned with equipment that is static in use. Examples of this are kilns, boilers, heaters, generators, pumps, welders, mobile crushers, mobile screeners, mobile heaters and drill rigs. Truly mobile kit is not covered; for example, quarry vehicles, loading shovels, excavators and forklifts. However, I do still measure these and look for initiatives to reduce the amount of energy used in these processes.

“I must ensure that I have accurate onsite measurement records for fuels used that are traceable to source and to be available for an external verifier to visit site and check of what equipment is on site, that we are following our permit and that data is being recorded accurately.

“The company is also now currently migrating to an SAP system that will improve the way we monitor our finances, energy usage and materials. The SAP change will make the system more automated, and provide better visibility across the company, to make it easier for people to access and see what’s happening. There are also better links with energy suppliers through smart metering and other technology such as energy portals which make our usage more visible.”

OE: You are also responsible for reducing output. How are you accomplishing that?

MJ: “I have reduced our overall gas consumption by 3% since 2018 due to a new boiler we installed at the beginning of 2019. The previous one was 30 years old. As part of that, we use some heat recovery and a hot well to preheat the boiler water by using the latent heat in the waste steam from the process, and so reduce the amount of energy used.

“We are also using the steam contained in a fully-pressurised autoclave to transfer into the next one after the process has finished; this can recover up to 2bar of pressure. Over a year this can make significant savings in costs and hence emissions. We have only just started this process so we will measure the effects over the full year of 2021.

“Other energy-reduction initiatives that I have undertaken in the past two years include the change to full LED lighting across the factory. That has had a significant benefit, and the outlay has been recovered in reduced electricity costs in 14 months.

“We are also investigating the potential to recover heat from the condensate that comes out of the autoclaves during the cooking process, and the possibility of combined heat and power systems, as well as using biomass instead of natural gas. I am also in discussions with my neighbours on the industrial estate where we are based, to investigate the potential of shared energy sources and systems. Tarmac is committed to driving down energy use as part of its commitment to be a responsible and sustainable supplier of building products, and this is something we take very seriously and work hard to improve.”

William Dalrymple

Related Companies
Tarmac Topmix Ltd

This material is protected by MA Business copyright
See Terms and Conditions.
One-off usage is permitted but bulk copying is not.
For multiple copies contact the sales team.