The need for sustainable drainage systems, in new construction and existing developments, is driving change within all areas of the industry. With more pressure on companies to evaluate the environmental and social impacts of their businesses, there is an increasing demand in both surface water and foul water drainage sectors to understand how sustainable drainage systems can be implemented.
In this context, sustainable precast concrete drainage channels will include the design, installation and operation of pipelines at the lowest environmental impact in addition to the more common interpretation of the term "SuDS" as the overall management of surface water which aims to mitigate flood risk, improve water quality and create amenity space and encourage biodiversity.
Concrete pipeline manufacturers realised the scale of the challenge at an early stage and have been implementing a range of sustainable drainage systems on an ongoing basis.
A detailed research programme was set up by British Precast Drainage Association to look at the carbon footprint of our products and to establish how they compare to other types of pipeline products and construction methods. The study was audited by independent consultants Carbon Clear. The result is a set of three reports covering (Report 1) the carbon footprint of concrete pipes and manholes (Report 2) how concrete pipes compare to plastic pipes and (Report 3) a comparison between circular precast concrete manhole systems and other solutions.
In order for sustainable precast concrete drainage channel drainage systems to comply with the requirements of PAS 2050, a peer review has been carried out by the Transport Research Laboratory (TRL).
The cradle-to-gate carbon footprint of concrete pipes ranges from 16.36 to 559 kg CO 2e/metre (DN225 up to DN2100). This is 20-60 percent lower than the values for generic precast concrete derived from many industry databases. It has also been found that generally the cradle-to-site greenhouse gas emissions of concrete pipes were found to be generally better than plastic pipes and up to 35 percent lower CO 2e for DN2100 pipes. The reports also show that DN1200 circular precast manhole systems have 30 to 43 percent lower carbon footprint compared to DN1200 traditional manholes, 1250 x 1250mm box based manholes and DN1050 plastic manholes.
In 1999, independent leading Dutch consultancy INTRON was commissioned to carry out a cradle-to-grave comparative environmental Life Cycle Assessment (LCA) study for seven types of sewer designs in the UK. These included concrete, clay, solid wall PVC pipes, twin wall PVC pipes, Ultrarib, twin wall polypropylene, and spirally wound HDPE pipes. Findings of the study can be found here. Initial findings indicate that concrete was overwhelmingly the favourite over other pipeline materials. This study proves why it is essential that all sustainability claims are based on an appropriate recognised methodology with a clear declaration of system boundaries, scope and study conditions.
Unlike other alternatives made up of imported products and materials (such as HDPE and metals), the entire supply chain of concrete products is based in the UK and bound by its Climate Change Act 2007 to reduce carbon emissions by 80% by 2050. This has led to wholesale reduction in greenhouse gas emissions over a wide range of sectors. The cement industry (the main contributor to concrete's carbon footprint) has been successful in reducing its CO2 impacts by 54% per tonne since 1990. All box culvert manufacturers use recycled steel reinforcement which has a considerably lower carbon footprint compared to virgin steel. Between 2008 and 2011, carbon emissions from precast factories dropped by well over 10%.
We believe that the carbon footprint of a tonne of concrete used in box culvert production stood at 105 kg CO2e/ tonne in 2013 and will continue to drop down every year to 2050.
Precast concrete drainage and box culverts are locally manufactured products. The fact that its entire carbon footprint is based in the UK means that it is easier to trace and verify in terms of environmental efficiency and social sustainability. This may not apply to all alternative solutions which can be manufactured from raw materials imported from locations with no sustainability policies, targets or measures in place. The British Precast Drainage Association carbon study reveals that the carbon footprint of plastic pipeline products can increase by a factor of 2 or 3 if made of resin imported from the Middle East or Asia. This is not the case with box culverts which have a more transparent product chain of custody.