PROJECT DESCRIPTION
BACKGROUND
The total sewage sludge production in Europe is about 9-10 Million tons per year (Eurostat 2015). At EU level, sludge disposal is regulated by the Waste Framework Directive, the Urban Wastewater Treatment Directive and the Sewage Sludge Directive. Some EU Member States still rely primarily on agricultural use because sludge contains high concentrations of organic substances, which promotes humus formation and is a low-cost source of essential nutrients. However, Germany is increasingly focusing on combustion and passed a bill in 2017 which regulates and restricts the use of sewage sludge as fertilizer after 2029. This leaves large waste water treatment plants with the need to find other ways to deal with the large amount of sewage sludge created. Particularly, there is a need to develop marketable ways for retrieving phosphate from sewage sludge that is incinerated, to meet the phosphate demands of agriculture and other industries, as well as to provide sustainable and safe solutions for the waste management of sewage sludge. In addition, phosphate rock is listed as a critical raw material on the EU Critical Raw Material list (79% of the resources are in Morocco). A drawback from obtaining phosphorus from phosphate rock deposits is that they are often contaminated with uranium and heavy metals.
OBJECTIVES
The LIFE Sludge2resource project will reduce phosphate mining and will set new European standards for sewage sludge recycling. The project is focusing on resource recovery and conservation, on energy efficiency, on climate protection and, in particular, on soil and groundwater protection. The project aims to integrate a sewage sludge incineration plant and a phosphorous recovery plant into an existing waste incineration plant.
The projects specific objectives are to:
Improve sewage sludge recycling using existing infrastructures for waste recycling. The planned mono-incineration plant for sewage sludge (SSIP) as well as the Phosphorus Recovery Plant (PRP) will be attached to an existing waste incineration plant (WIP), so that the new plant takes up almost no extra land; Generate site synergies, since the power requirement of the SSIP is covered by the generation of electrical energy from the waste incineration plant (which operates 53% CO2 neutral). Moreover, the findings will be used to increase the efficiency of the overall process of existing plants; Carry out technological evaluation studies for planned replication and transfer cases;Incineratehalf of the amount of sewage sludge generated in Schleswig-Holstein (northernmost state of Germany, approx. 3 million residents), which corresponds to about 30 000 tons (dry matter) per year; Validate a process to recover more than 85% of phosphorus from sewage sludge ash; Implement and validate a process that replaces the freshwater supply required for the operation of waste incineration and phosphorus recovery (approximately 35 000 cubic metres per year) with water from the sewage sludge, therefore saving important water resources; Raise awareness concerning resource efficiency aspects and non-controlled phosphorus emissions into the environment; and Reduce the need for phosphate rock extraction. The project contributes to the implementation of the EU Waste Framework Directive, the Urban Wastewater Treatment Directive and the Sewage Sludge Directive. It also implements the EUs Circular Economy Action Plan, in particular the topics Turning waste into resource and Closing Loops of Recovered Materials; the latter in accordance with the revised waste legislative framework and the new Fertilising Products Regulation (COM(2019) 1009).
RESULTS
Expected results:
The SSIP will produce about 2 450 tons of phosphoric acid, 3 383 tons of gypsum and 362 tons of iron and aluminium salts, which will be sold at current market prices; The water obtained during sludge drying will be recycled and used in the WIP and PRP, with the use of recovered water resulting in freshwater savings of 20 417 m;The energy from SSIP will be used for district heating and hot water: Around 4 000 households will be supplied with CO2 -neutral energy (40 000 MWh/a);CO2 savings of 45 376 t. This is the result of 28 226 t CO2 savings through district heat generation by the SSIP (compared to a hard coal-fired cogeneration plant), and 17 150 t CO2 savings at the PRP (CO2 emissions related to mining of phosphate rocks will be avoided); Improved water quality: If sewage sludge is not usedfor fertilizing, there is less nitrate, nitrite, medicines, microplastics and nitrogen input into groundwater. According to the German Environment Agency (UBA) the concentration of nitrogen is of 44 000 mg/kg sewage sludge. Here 70 000 t of sewage sludge will be processed, thus 3 080 t of nitrogen will not be released into the groundwater; Waste reduction: 992 t of sewage sludge ash. After applying the TetraPhos method, the resulting ash will be reduced from 12 000 t to 10 300 t; More than 85% of the phosphorus in sewage sludge ash will be recovered. Assuming an average of 96 g/kg phosphorus content in sewage sludge ash this corresponds to about 572 t phosphorus recovery for the SSIP; This plant avoids the extraction and release of cadmium (Cd) and uranium (U) in the environment, compared to the mining of phosphate rock.
