Tallinn: Utilitas' planned seawater heat pump spells algae and odor problems
The Tallinn Urban Environment and Public Works Department finds the preliminary environmental impact assessment for Utilitas' planned seawater heat pump plant near Tallinn Bay insufficient and calls for a thorough revision involving specialists.
The Tallinn Urban Environment and Public Works Department has raised concerns that, under the current proposal for Utilitas' seawater heat pump plant near Tallinn Bay, five tons of phosphorus could enter the shallow sea annually and the problem of coastal odor might become a year-round issue. The Consumer Protection and Technical Regulatory Authority (TTJA) has stated it will consider whether to initiate a full environmental impact assessment.
The plan for Utilitas' seawater intake involves drawing water from about 70 meters deep, approximately nine kilometers from the pump station. According to the preliminary environmental impact assessment, the water would be released back into the sea 200 to 700 meters from the coast, where the depth ranges between 11 and 19 meters. Meelis Uustal, head of the environmental protection division of the department, said that a thorough review of the materials provided had revealed that key parts of the assessment were insufficiently detailed. This raises concerns that the decision not to initiate an environmental impact assessment may have been based on faulty conclusions.
"For example, our biggest concern is that the preliminary assessment fails to address the potential release of hydrogen sulfide and nutrients from the deep layers of Tallinn Bay into the surface layers during this process. This could lead to more extensive algae blooms in the bay and intensify the odor issues, which are already noticeable along Pirita tee every summer," Uustal told ERR.
He added that the chemistry and biology of Tallinn's coastal waters are well-studied, allowing estimates of phosphorus levels at 70 meters depth and calculations of the potential annual phosphorus flow through the system. "The calculations suggest that if this project were realized as proposed, more than five tons of phosphorus would be discharged into Tallinn Bay annually. To put that into perspective, this additional amount would account for about a quarter of the phosphorus currently released into the bay from the city's wastewater treatment plant."
The department also noted that worsening algae blooms and the spread of unpleasant odors near the port, cruise terminal and Old Town could have negative socioeconomic effects, including impacts on tourism, real estate development and coastal property values.
The department expressed confusion over why the TTJA concluded that a full environmental impact assessment was unnecessary, given that the preliminary evaluation did not account for all potential impacts. Both the Environmental Board and the Ministry of the Environment have previously indicated that a full assessment should be conducted.
Uustal reiterated that the main conclusion of the city's environmental department is that the preliminary assessment must be refined. "Experts in the relevant fields should be involved to provide advice on the ecological bioprocesses that will occur when the water is moved, as well as to offer recommendations on feasible technical alternatives," he said.
He confirmed that while the city supports the extraction of heating and cooling energy from seawater, it is essential to consider the local conditions of Tallinn Bay and apply the best available knowledge. "Both the Environmental Board and the Ministry of the Environment agree that an environmental impact assessment is needed. We concur, but the assessment is not a magic bullet. What matters is that the initial data and studies are thorough enough to enable informed decision-making."
Liina Roosimägi, head of the construction activity licensing department at the TTJA, said that the processing of Utilitas' application to modify the building permit for the seawater pipes is currently underway. The submitted feedback has been forwarded to Utilitas and a response is expected by mid-November. After that, the agency will decide whether to initiate a full environmental impact assessment.
"Yes, that aspect will definitely be reviewed. Relevant authorities have also raised this issue and we are evaluating it as well. Depending on the findings, if the preliminary assessment needs to be revised, we will review whether a full environmental impact assessment is necessary," Roosimägi said.
Utilitas submitted its application to install pipes for the heat pump in Tallinn Bay at the end of 2022. Janek Trumsi, a member of Utilitas Tallinn's board, stated that the project is still in the early stages, so it is too soon to provide details, including the planned capacity of the plant. "It depends heavily on how deep the water intake will be and the diameter of the pipes. This phase of the project involves numerous studies – engineering, economic, environmental – and we are not yet ready to say what the capacity will be," Trumsi explained.
However, the Paljassaare heat pump plant, which will use both wastewater and seawater, is already in the design and soon-to-be construction phases. Its total capacity will be 110 MW.
"The Paljassaare heat pump plant is a concrete project and by fall 2026, we expect to see how much heat it will generate. Based on that, we will be able to determine the optimal capacity for the downtown plant," Trumsi added. The proposed location for the downtown heat pump plant is next to the cruise quay.
Trumsi mentioned that the downtown heat pump plant is not yet at a stage where technical solutions for capturing odors have been addressed.
He also clarified that while the Paljassaare plant will use seawater, its primary energy source will be wastewater. "Seawater is used to stabilize the flow of wastewater. This means that if the amount of wastewater fluctuates due to daily cycles or weather conditions, seawater is added to ensure a stable flow. In this sense, the role of seawater at Paljassaare is different from downtown, where seawater would be the sole energy source for the heat pump. At Paljassaare, seawater plays a stabilizing role," the Utilitas representative explained.
"There will be no odor issues from the Paljassaare plant. We will be drawing water from the upper layers and near the shore, so there is no issue with sediment buildup," he added.
The Paljassaare plant is currently in the design phase, with major equipment already ordered and construction set to begin in the first half of 2025. The first output is expected by the start of the heating season in fall 2026. The plant's construction will cost €100 million, according to Trumsi.
As for the downtown plant, the timeline is less certain. The project is still in the analysis and research phase, with specific results expected in the coming years. After that, it will take another two to three years before the plant could be realized. The downtown plant is planned to provide both heating and cooling energy.
Trumsi noted that the potential odor issue has not yet been thoroughly analyzed. "This is one of the factors we are looking into. As mentioned, environmental concerns are a key focus and we will involve specialists in this area. At the moment, we cannot say what the solution or impact will be because we have not yet reached the stage where we are addressing the technical issues related to odor capture," he said.
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Editor: Mirjam Mäekivi