WRAP:  Struvite

Feb 2013 – June 2013


Digestate produced from AD is a source of the valuable and increasingly scarce fertiliser Phosphorus and it’s recovery from waste streams has long been explored.  Whilst the availability of Phosphorus recovery creates opportunity for displacing synthetic fertilisers from the market place, its commonly found chemical form has been a significant problem for any waste-fluid management.  The chemical Struvite, consisting of ammonia and phosphate around a magnesium centre, has long been a burden to the waste industry.  Non-soluble and forming scaling of pipes and valves it typically needs strong acids or mechanical intervention to remove.  Traditional methods of removal of Phosphorus from digestate can be costly considering removal costs against any economic gain.


This study explored an alternative; the use of AD waste streams to convert the Struvite from a solid to a liquid by means of gas infusion acidification.  Our exploration of utilising waste heat to promote this chemical change, and to reduce the liquor volume, may  change the economics of AD plants by reducing the removal costs but also developing a third income stream – alongside gate fees and energy production – of nutrient sales.


Oct 2015 – Mar 2016

Welsh Government :: Gwynedd CC

The prospect of diversion of road-derived leaf sweepings from composting facilities to landfill is causing concern during a time of cost saving and austerity for the authorities responsible for this function. Due to the nature of the road surface, collected leaves are commonly contaminated with potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs).

This study sought to investigate whether there were spatial or environmental factors that could be used to predict where contamination was very likely to be within or without safe limits, so as to suggest a modification to collection methods; or if that were not possible, to look at identify promising post-collection remediation methods.

This study also drew on Cwm Harry Land Trust’s involvement with the European Interreg IVb project COMBINE, and its technology IFBB.  IFBB was designed to provide a variety of storable fuel media (both solid and gaseous) from marginal biomass through the use of anaerobic digestion and pelletisation of biomass into fuel briquettes. European guidelines on emissions from biomass fuels have directed the development of the IFBB system into providing mitigation steps for reduction or removal of potentially contaminating chemicals from the solid fraction that forms the biomass fuel.  The potential for these mitigation steps to improve leaf litter quality was investigated.