Our priorities for making the most of our resources
For many years we have been a leader in converting sewage to energy and fertiliser using anaerobic digestion, and we are now applying this expertise to food waste too. We know that emerging technologies will allow us to extract even more value from waste, and this will continue to be a core focus for our innovation and investment. In the rest of our business, our comprehensive waste audit data provides the starting point for pinpointing areas of focus for our zero landfill aspiration, and we now need to maintain our efforts to meet the government’s ambition of zero avoidable waste by 2050.
But we know that landfill diversion is only part of the picture. As much as we can, we need to use less and utilise our existing resources better. Understanding in more depth the relative impacts of different waste categories will allow us to prioritise our actions as we look to reduce overall waste generation in addition to optimising end of life. We will increasingly look upstream to our supply chain to identify opportunities to reduce material use and source more sustainably.
Our priorities are:
Turning waste into resources and energy
As a water company, one of our biggest waste streams is sewage from homes and businesses. The sludge produced as part of our wastewater treatment process makes up 55% of our total audited dry waste.
Our two biggest opportunities for valorising’ sewage are:
- Using waste to generate energy
- Extracting valuable products from waste
Our AD operations produce around 145,000 dry tonnes of treated biosolids
Extracting valuable products from waste
Sewage sludge contains far more potential than just the energy that can be generated. Our AD operations produce around 145,000 dry tonnes of treated biosolids which we send to agricultural land as fertiliser, reducing the need for production of conventional fertiliser, a significant source of greenhouse gas emissions.
Our food waste plants, too, produce a digestate rich in nitrogen, potassium, phosphate and other trace elements that is highly valued within the agricultural community. Our composting facilities produce a soil improver that is PAS 100 and Compost Quality Protocol certified.
In addition, we are creating opportunities to recover other resources from sludge, such as nitrogen, ammonia, phosphorus, nutrients and cellulose. We already have a full scale plant that recovers nitrogen and phosphorus in the form of struvite at Nottingham wastewater treatment works and we have delivered a range of demonstration scale trials of other sustainable solutions for nutrient removal such as ion exchange and algal bioreactors.
Recycling grit and screenings is another area of focus where we know there is potential for improvement through composting or use in construction.
The more efficiently we can extract valuable products from waste, the more we are supporting the delivery of a circular economy that protects the earth’s resources and environment.
Scaling innovation requires investment
We are now in a position to tap into additional sources of debt funding to support our sustainability ambitions, through our Severn Trent Sustainable Finance Framework. In March 2020 we completed our first debt issue under the framework, which was used to assist in the development of our Severn Trent Green Power business. In June 2020 we issued our first sustainable bond, with a value of £300m, used to finance green and social projects across the business.
While waste from office and facilities is associated with some of our highest value and impact waste - such as cabling, and rare earth metals components in electronics, our capital works - construction and maintenance activities - use the largest volumes of material. Of this, excavated highway waste is one of our most significant categories of waste by weight - around 87,000 tonnes a year - and we currently divert two thirds of this away from landfill, a figure we are working to increase.
However, waste tonnage is only a crude measure of the impact of material use on the environment. We use data to actively target the highest impact areas of our material use. So for example, we will specifically target the GHG emissions associated with concrete and steel through: (1) developing opportunities to source low-emissions product sources, (2) reducing material use through re-thinking asset design and management, and (3) finding ways to extend the life of our infrastructure through technology and good stewardship.
Working in this way requires evidence and analysis. So we will build on our Scope 3 emissions assessment to gather other relevant data to allow us to assess the most impactful areas for action.
Putting the circular economy into practice across our business will also mean working extensively with our contractors and suppliers to influence their operations. This is a big challenge, and one where we are early on in the journey. Our ambition is to create an approach that can be embedded across working practices, policies and procedures. This will include supplier selection processes and contractual criteria, as well as engaging in joint initiatives and partnerships to push innovation in key areas.
Making the most of our resources: our to do list
- Zero avoidable waste to landfill
- Build on our waste audit by identifying the most impactful waste reduction opportunities
- Create and embed a circular economy approach across the business
- Assess supply chain material use and identify key opportunities for improvement
- Identify opportunities and approaches for working with suppliers and contractors
- Continue to invest in innovation to drive extraction of resources from sewage sludge