We have some exiting updates from our innovative trials in collaboration with CPL Industries (CPL) and University of Nottingham (UoN), which look set to increase recycling rates for local authorities and capture even more carbon through our recycling process.
As part of the anaerobic digestion (AD) of food waste, STGP generates around 10,000 tonnes of AD screenings per annum.
This is any material greater than 0.75mm which is removed from the digestate during screening to enhance our high-quality fertiliser for our farmers. We usually dispose of our screenings via energy from waste facilities. However, in collaboration with CPL and the UoN we have been exploring some highly promising technologies that solve this waste disposal burden and reduce the associated carbon emissions.
Bio-coal
CPL have built a pilot scale hydro-thermal carbonisation plant (HTC), to turn wet wastes into low carbon bio-coal to displace some of their high carbon domestic fuels. The bio-coal is deemed carbon neutral by the UK government and represents an 80% reduction in NOx emissions compared to coal.
Here STGP’s AD screenings are subjected to high pressures (20bar) and temperatures (>500oC), mimicking the long‐term natural process of coal formation. The process takes a matter of hours rather than millennia to produce a bio-coal that can be burnt and mixed with conventional domestic fuel.
The process will reduce our carbon emissions related to AD screenings. Currently it is expected that the process carbon emissions of the HTC are c.50% less than the 21.29kg CO2e/tonne emitted via EfW.
Biochar
The next stage of the trial sees STGP, CPL and UoN undertaking feasibility studies to turn the bio-coal into a biochar fit for sequestration via high temperature torrefaction (HTT).
The study has been awarded funding by BEIS from the direct air capture and greenhouse gas removal programme.
Current data shows it is possible to transform the AD screening-derived bio-coal into a stable biochar that meets the voluntary European Biochar Certificate (EBC) standard, meaning it is fit for sequestration.
This would lock a great proportion of carbon into the biochar which can stay stable in the ground for centuries.
Potential benefits to local authorities include:
- Increased recycling rates
If the bio-coal/biochar products can get End of Waste classification, this will push the screenings residues from our AD process higher up the waste hierarchy, recycling rather than just recovering this waste stream.
- Additional Carbon Capture
Data shows a combination of HTC followed by HTT can sequester approximately 40% of the initial carbon in the AD screening residue.
If you would like to learn more about the treatment of source segregated food waste at our AD facilities, get in contact with us at: commercial@stgreenpower.co.uk.
