Find Out How we Saved 4021.48 tonnes of CO2 Emissions
If you’re wondering? That’s the equivalent of:
The site in the Wirral was left by the previous landowners with circa 30,000 tonnes of mixed waste comprising of soils, hardcore, general waste etc.
Phase 1 of the site clearance was to remove circa 9000 tonnes of mixed waste from the ‘shed and surrounding areas’.
The waste had been deposited approx. 4 years ago and was of major concern to the Environment Agency and emergency services, mainly due to the potential fire risk and pollution i.e., Dust, Odour, Scavengers and leaching into nearby water courses.
The new owners obtained various quotes from contractors to remove the waste directly to landfill. One of those contractors, Knotweed Services (UK) Ltd came up with a different solution. Their aim was to minimise the current environmental impact, remove waste safely and compliantly and reduce the overall environmental impact I.e. Not send it all to landfill and consequently reduce the carbon footprint.
Knotweed Services (UK) Ltd & the landowners worked to obtain a LEP (Local Enforcement Position) with support of Maderne Ltd & Jon Hillyard Consulting Ltd.
These materials would then be re-used on site for the future development of the site, this would also reduce the amount of materials that would need to be imported to the site in the future as the ground level needs to be significantly increased. The LEP was granted in summer 2022 and works commenced on the clearance of phase 1 in August 2022 and was completed early Jan 2023.
Out of the estimated 9000 tonnes of material in ‘phase 1’ weighbridge records confirm that 3200 tonnes were sent to a waste recovery site and the surplus volume has been separated into two forms, hardcore and soils. The estimated tonnages of these are 1500 ton hardcore & 4300 tonnes of soil. No waste was sent directly to landfill during these works. This approach differed from other contractor’s proposals and considered the BPEO – Best Practicable Environmental Option, and was ‘Knotweed Services (UK) Ltd’ aim to reduce the carbon footprint.
The above pic from google earth does not show the extent of the waste in phase 1 but attempts to show the areas and phasing and potential risks of pollution to neighbouring receptors.
The remaining areas onsite are namely phase 2 and phase 3. Which are estimated at 5000 tonnes and 16000 tonnes respectively. Phase 2 works commenced in Jan 23 and phase 3 will commence in the summer of 2023. These clearance works will adopt the same treatment approach as phase 1. The below calculations do not include phase 2 & phase 3.
Phase 1 – Early clearance works (sept 2022)
Approximately 9000 tonnes of mixed wastes were removed/treated for site use in summer/autumn 2022.
Phase 1 completed early Jan 2023 (Some of the hardcore stockpiled to the right of the building)
If we had assumed that 9000 tonnes of waste had been sent of site (based on a 20-ton load) this would equate to 450 vehicles leaving site. By leaving 5800 tonnes on site this has reduced the number of vehicle movements by 290.
The nearest landfill site to the subject site is Gowy Landfill operated by FCC. This is approximately 12 miles. Assuming that this landfill could accept this waste and tonnage. This is not guaranteed.
A HGV with a Euro VI engine travelling at 40mph (64kph) with a weight capacity of 20-26 tonnes omits 660 grams of CO2 per Kilometre. Find out more by clicking here.
With the nearest landfill being 12 miles away = 19.31 Kilometre
660-gram x 19.31 = 12744.6 grams
If this was a return journey = 25.48 kg
25.48kg x 290 = 7389.20kg = 7.38 tonnes of CO2
Had 450 loads gone directly to landfill this would have been 25.48kg x 450 = 11,466 kg = 11.46 tonnes of CO2.
A landfill produces (with methane extraction) approx. 541 kg per ton of CO2. However, I have taken an average of ‘Household residual waste’ & ‘Commercial and Industrial waste’ as low quantities of waste types listed below were present meaning I am using a mean average of 446.204+467.008/2 to give a value of 456.60kg of CO2 per ton.
Energy recovery produces approx. 21kg per ton of CO2. (tabled below – click to view full screen).
(Table from Defra Carbon Conversion factors 2022)
CO2e means the number of metric tonnes of CO2 emissions with the same global warming potential as one metric ton of greenhouse gas.
If 9000 tonnes had gone directly to landfill this could equate to 4109.40 tonnes of CO2 emissions.
4109.40 tonnes + 11.46 (haulage) = 4120.86 tonnes of CO2.
By using Knotweed Services (UK) Ltd approach 5800 tonnes of material have remained on site. 5800 tonnes x 456.60 = 2648.28 tonnes of CO2 saved.
The remaining 3200 tonnes of material was sent to energy recovery meaning 67.2 tonnes of CO2 would be omitted whereas if it had been sent to landfill this would be 1461.12 tonnes of CO2, meaning 1393.92.16 tonnes of CO2 were saved.
In order to process the material 2 x 360 excavators were used, 1 x front tipping dumper & 1 x trommel screener. Regardless of the destination the 2 excavators and dumpers would have been required, the only difference is the trommel screener. Materials were separate at approx. 15 tonnes per hour and this was to get the optimum recovery rate at source, thus avoiding more potential tonnage leaving site. All plant is modern equipment with ad blue systems and economical diesel engines.
The recovery site selected by Knotweed Services (UK) Ltd was Fletchers Waste Management Ltd that are 61 miles away (98.1km)
Using the same figures above the 160 vehicle movements moving the 3200 tonnes (based on 20 ton loads)
660 grams per km x 91.1km (x2) = 196.2 km and 129,492 grams = 129.5kg
129.5kg x 160 = 20720 kg / 1000 = 20.72 tonnes of CO2
If the site had not been cleared?
We now know that there were 3200 tonnes of mixed combustible type waste amongst the 9000 tonnes in ‘Phase 1’. It is difficult to quantify the exact CO2 emissions that would have arised had the pile caught fire however according to ‘Zero waste Europe.eu’ each tonne of waste that is ‘openly’ burnt the CO2 emissions are 0.7-1.7 tonnes of CO2. If we average that at 1.2 tonnes of CO2 per tonne, based on 3200 tonnes of waste =
3200×1.2 = 3840 tonnes of CO2 released.
*This does not also include any type of pollutants of emissions that would have arisen had the pile caught fire and also does not include disposal of any residues i.e. contaminated fire water, also the 5800 of salvageable material (hardcore/soils) may have become contaminated and therefore disposed of in landfill.
Soils and hardcore
Soils absorbs CO2. Calculations have not been made for the 4300 tonnes of soil and 1500 tonnes of hardcore on site and are therefore classed as neutral.
9000 tonnes direct to landfill + transport = 4109.40 + 11.46 = 4120.86
3200 to recovery + transport = 67.2 + 20.72 = 87.92
Saving 4021.48 tonnes of CO2 Emissions
1 tonne of CO2 = 31 to 46 trees
1 tonne = driving 23000 miles in an average car
1 tonne =18 dairy cows
1 tonne = 25 million plastic straws
1 tonne =500 x CO2 fire extinguishers
1 tonne = 121643 smartphones charged
1 tonne = 1 x passenger (average emissions) on a return flight from Paris to New York
4021.48 x 31 to 46 trees = (Average) of 38 = 152,816.24 trees
4021.48 x 23000 miles = 92,494,040 miles in an average car
4021.48 x 18 dairy cows = 72386.64 dairy cows
4021.48 x 500 fire extinguishers = 2,010,740 CO2 fire extinguishers
4021.48 x 121643 Smartphones charged = 489,184,892 smart phones charged
4021.48 x 1 passenger on return flight from Paris to New York = 4021.48 trips
As previously mentioned, this only includes Phase 1, More significant savings will be made on Phase 2 & Phase 3 using the same approach as Knotweed Services (UK) Ltd did on Phase 1.