Efficient recycling and disposal of sewage sludge .. (LOTECOTEC)
Efficient recycling and disposal of sewage sludge with innovative thermo-catalytic low temperature conversion technique
(LOTECOTEC)
Start date: Nov 1, 2006,
End date: Apr 30, 2010
PROJECT
FINISHED
Background
The long term disposal of sewage sludge is a major environmental problem. Conventional sludge treatment methods (e.g. incineration) are not ideal solutions to the complex problem of disposal. It is therefore important to introduce more comprehensive alternatives for sludge handling and disposal when planning sewage management strategies. In response to this problem, 15 municipalities in the region Pfattertal in Bavaria, have decided to invest in a joint self-sufficient sewage sludge treatment facility.
Objectives
The overall objective of the LOTECOTEC project was to demonstrate an efficient alternative for the environmentally sound disposal and recycling of sewage sludge. Specifically, the project aimed to set-up and operate a pilot plant using LoTeCoTec technology for the thermo-catalytic low temperature conversion (LTC) of sludge. Another key goal of the project was to present a viable concept for commercial use of the waste products of the LTC process.
Results
The LOTECOTEC project successfully demonstrated that decentralised wastewater sludge management is technically feasible with the technology.
The process can be adapted either to produce LTC coal, oil and gas (the project's primary focus) or to skip the oil fraction and produce only LTC coal and gas.
Results from the pilot plant indicated that emissions from the process were significantly lower than using conventional sludge digestion with subsequent biogas combustion.
LTC coal resulting form the conversion of sewage sludge has a heating value (Hi) of about 10 MJ/kg, LTC oil 30 MJ/kg and LTC gas 10 MJ/kg. In total the calorific yield is higher than the energy demand for the conversion process within the LTC plant (about 550 kWh per tonne of sludge with 90% dry matter).
So the LTC-coal can be used as a good fertiliser as it contains minerals and phosphorus. Plus it is free of hazardous organic substances and dioxins which make sewage sludge problematic.
The beneficiary also calculated that a plant of the size as in the project would save 40 000 transport kilometres (sludge) by truck per year.
The LIFE team also successfully demonstrated that there are uses for the LTC products: LTC coal in the brick industry and as a fertiliser; LTC gas for process heating. However, the project encountered a setback when LTC oil was legally classified as waste, making its reuse impossible.
Another setback to the project was the fact that the energy content of the Pfaffertal sludge - and consequently the oil and gas yields of the process - was considerably lower during the project phase than it was at the time of the proposal.
Furthermore, because of a dramatic decline in the cost of conventional sludge disposal (from â¬170/tonne in 2006 to â¬40-70/tonne by 2010), the beneficiary calculated that the LTC plant would not be economically viable and so decided to discontinue its operation at the end of the LIFE project and not to engage in further dissemination activities.
However, the project partners ZWT and AWT are continuing to develop the LoTeCoTec technology, which they presented at the Biochar Symposium in Bayreuth, Germany in July 2010. With reported interest in the technology from the Czech Republic, China and Brazil, the partners see opportunities for its use in larger plants and with industrial sludge inputs of a higher calorific value than at Pfaffertal. During the LIFE project, the technology was tested with media other than sewage sludge, including residues from bioethanol production and slaughterhouses, as well as grease separator waste.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).
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