Investment in the Chemical and Industry Park Zeitz: Sewage sludge ash from the region made into fertiliser pellets for the region
Increasing sustainability: Sewage sludge is an undervalued raw material
Wiese Umwelt Service GmbH, a certified waste disposal company based in Berga/Elster in Germany, plans to build a state-of-the-art thermal sewage sludge recycling plant at the Chemical and Industry Park Zeitz that will come into operation in 2024. It will use the resulting ash, which contains low levels of pollutants, to manufacture phosphorus fertiliser for use on arable and organic farms in the region. The sustainable recycling process reduces resource use and makes a positive contribution to the regional circular economy.
“The process of disposing of sewage sludge is undergoing major changes,” said Michael Wiese and explained: “There are increasing legal restrictions on using sewage sludge as an agricultural fertiliser and a requirement to recover the phosphate will soon be introduced.” Since Wiese Umwelt Service GmbH was founded in 1994, it has constantly had to adapt to changing circumstances. The family-owned company’s core business is composting municipal sewage sludge for agricultural use. It currently runs twelve composting plants in Saxony, Saxony-Anhalt and Thuringia which process a total of 300,000 tonnes of sewage sludge per year. The composted sludge is used on agricultural land, which means that it is returned directly to the regional nutrient cycle. However, amendments to the Fertiliser Act and the Sewage Sludge Ordinance will make the soil-related use of sewage sludge increasingly difficult in future. “But sewage sludge has considerable recycling potential. It contains the essential raw material phosphorus in particular,” explained Michael Wiese. On the site of the Chemical and Industry Park Zeitz in the far south of Saxony-Anhalt, his company aims to put its latest innovative idea into practice. “By using a high-quality process to recycle the ash with a phosphorus content,” he said, “we can achieve a very high phosphorus recovery rate from the sewage sludge.”
Once again, he is working to improve the environmental sustainability of his concept, which offers a long-term, reliable disposal option for sewage sludge producers at a predictable cost. The recycling plant in Zeitz will provide a solution that meets the needs of producers and the requirements of the legislation. Wiese brought on board a specialist sewage sludge recycling company with extensive experience to help him realise his vision of an environmentally friendly combustion plant with phosphate recovery. Emter GmbH from Bavaria built its own mono-combustion facility for sewage sludge in Altenstadt in 2008. The existing technology is being developed further for use in Wiese’s plant in Zeitz. The sewage sludge will undergo thermal treatment in an ultra-modern system and the nutrient-rich ash will be recycled into a high-quality, slow-release phosphorus fertiliser. Wiese explained that the combustion process completely destroys all the organic pollutants in the sewage sludge.
Limited resources from countries in crisis
As a result, the process represents one solution to an imminent problem. The recovery of phosphorus from sewage sludge will be required by law from 2029 at sewage treatment plants designed for more than 100,000 residents and at plants designed for more than 50,000 residents from 2030. As Wiese explained: “Phosphorus is an essential nutrient for all organisms, because growth is not possible without it. But it is a limited resource and is often polluted with cadmium and uranium. Germany has to import its supplies of phosphates, but the limited deposits are found in only a few countries, some of which are politically unstable.”
Wiese has had the support of the sewage treatment plant operators in the region for some time. They have to demonstrate by the end of 2023 which phosphorus recovery measures they plan to introduce. “The farmers in the area also have a significant interest in the high-quality fertiliser we will be producing,” said Michael Wiese, referring to the businesses that are his long-term customers. The cost of artificial fertilisers has been rising for several years. The ban on exports of ammonium nitrate and phosphates from Russia and the resulting increase in fertiliser prices on global markets has led to growing demand for a locally produced phosphate fertiliser.
From the perspective of Michael Wiese, as the owner of a medium-sized business, the new sewage sludge drying and combustion plant with phosphate recycling is an important investment in sustainability and in safeguarding resources for the next generation. He has received support from the Investment and Marketing Corporation Saxony-Anhalt and from the Chemical and Industry Park Zeitz. “The self-contained site is the ideal location for this project,” said Arvid Friebe, managing director of Infra-Zeitz Servicegesellschaft mbH, the company that runs the park. “A total of 100,000 tonnes of dewatered sewage sludge from the three German regions of Saxony, Saxony-Anhalt and Thuringia can be transported to the plant every year using routes inside the park without the local residents even being aware of it,” explained Friebe. He was also able to allay concerns about smells: “The sewage sludge will be delivered to an enclosed bunker where the air is continuously extracted and fed into the combustion process. This results in a slight reduction in pressure within the bunker that prevents smells from escaping.” Arvid Friebe is already enthusiastic about the state-of-the-art plant.
Thomas Böhm, head of business development for the Burgenland district, also believes that the Chemical and Industry Park is the ideal location for the plant, because it is home to several companies that have already committed to introducing green concepts to combat structural change.
“A total of 21 new jobs will be created in the municipality of Elsteraue near Zeitz and around 19,650 tonnes of phosphate fertiliser can be produced here every year and supplied to local farmers,” said Michael Wiese and gave a brief description of the manufacturing process: “When it arrives, the sewage sludge consists of 75 percent water. It must be dried to increase its calorific value before it undergoes the mono-combustion process in the two highly efficient belt dryers. In the next stage of the process, the fully dried sewage sludge is burnt at a temperature of 850 degrees without the need for additional fuel in a grate firing system that is in continuous operation. Grate firing is a form of combustion specially designed for sewage sludge. The resulting flue gases are cleaned in a state-of-the-art unit equipped with biofilters. The design of the flue gas cleaning system allows all the statutory emission thresholds to be met. During the next stage, the ash, which is low in pollutants, is treated to convert the phosphorus it contains into a bioavailable form. The end product – fertiliser pellets – is manufactured using an energy-saving thermal pulping process specially developed for the plant.”
Turning the ash into a saleable fertiliser on the site in Zeitz avoids the need for the ash to be transported from one region to another. As Michael Wiese explained, this reduces both costs and CO2 emissions.