PROJECT DESCRIPTION
BACKGROUND
Wastewater treatment sludge (WWTS), both urban and industrial, contains a substantial amount of organic matter from a range of sources, such as pathogenic microorganisms. Along with metals and toxic compounds, this matter must be managed properly to avoid environmental impacts and risks to public health.
The annual amount of industrial sludge produced is affected by economic trends and therefore difficult to predict. It is nevertheless estimated to amount to 0.4 million tonnes in Italy and 4 million tonnes in Europe as a whole.
In Europe, a significant number of industrial companies are located industrial districts, parks or zones. Such arrangements generate mixed industrial wastewater, comprising a range of contaminants in varying concentrations. The treatment and recovery of industrial sludge is therefore more challenging than municipal sludge since it may contain high concentrations of hazardous or toxic compounds such as heavy metals and toxic organic chemicals.
After stabilisation and dewatering processes, WWTS is sent to landfills, directly re-used in agriculture or composted, or incinerated. However, the re-use of WWTS in agriculture could lead to nutrient leaching, impacts on soil biodiversity and greenhouse gas emissions (e.g. CH4 and NOx), despite re-use having a lower environmental impact than other options.
OBJECTIVES
The CROSS-LIFE project aims to develop an integrated sludge management technology that reduces the amount of WWTS treated at end-of-life (EoL). The technology combines thermal, chemical and biological processes to convert the carbon content of sludge into bio-based crotonic acid, which can be used as a new feedstock in the bio-based chemical/polymer market. The coupling of hydro-thermal carbonisation technology (HTC) with high-pressure solid-liquid separation with filter press will reduce the volume of WWTS for disposal by 50-80%.
Specifically, the project aims to:
- Reduce the amount of sludge to be disposed of by about 80% in comparison to the current EoL approach;
- Reduce the carbon footprint of EoL approaches for WWTS management; and
- Demonstrate the replication of sludge reduction and crotonic acid production using sludge from urban wastewater treatment provided by AqA (replication partner).
RESULTS
Expected results:
- Produce around 1.5 tonnes/year of bio-based crotonic acid from sludge without the use of solvents or hazardous chemicals;
- Reduce the volume of WWTS to be treated at EoL by around 260 tonnes/year by the two companies involved in the CROSS-LIFE project as WWTS suppliers; and
- Reduce GHG emissions by around 13 tonnes/year by producing bio-based crotonic acid which has a lower carbon footprint than fossil-based crotonic acid (the carbon footprint of conventional crotonic acid is 13.5 kg of CO2 per kg of crotonic acid while for the bio-based acid it is 4.8 kg of CO2).
