Since 2017, partners in Kalundborg Symbiosis have been investing in green transformation of the energy supply.
Biogas: Together with Ørsted, Bigadan has established a full-scale biogas plant in Kalundborg. Construction started in early spring 2017 and the biogas plant was commissioned during spring 2018. The biogas plant first converts sludge/residues from insulin and enzyme production at Novo Nordisk and Novozymes into biogas, which is subsequently upgraded to bionatur gas. After degassing, the biomass is used as fertilizer on fields. It's a double-up on residue recycling.
Heat pump: Similarly, Kalundborg Utility has invested in a new heat pump to utilise residual heat in wastewater. The heat from industrial wastewater is part of the city's district heating solution. The heat in the wastewater is actually used three times. First, at the companies themselves, where the organic content is used to produce biogas; second, at the treatment plant, where the hot water makes the biological processes "run faster", allowing more than twice as much wastewater to be treated as otherwise; and third, at the heat pump, where the residual heat is used before the treated wastewater is discharged. Heat pumps are the new technology because they can work with renewable energy sources such as solar and wind. Kalundborg wastewater treatment plant receives about 6 millionm3 of wastewater per year. The treated wastewater has an average temperature of 24-25 degrees. The wastewater is led to a heat exchanger where a heat pump, using electricity, extracts the energy and boosts it up to 72-87 degrees district heating. This takes place during periods when district heating is most needed in the city. By cooling the wastewater by 10 degrees, the heat pump can annually produce about 80,000 MWh of district heating, which can cover over 30% of Kalundborg Utility's annual purchase of district heating. The heat pump makes it possible to use even more of the heat from the waste water from the various industries in Kalundborg.
Conversion of Asnæsværket from coal to wood chips: the conversion of Asnæsværket means that customers in Kalundborg and the surrounding area will receive green energy from the plant instead of energy based on coal. Today, Asnæsværket's new wood chip-fired power plant block, Asnæs 6, supplies green district heating and process steam to Symbiosen, as well as electricity to the Zealand electricity grid. The new wood-fired unit works in conjunction with Asnæsværket's electric boiler and Kalundborg Utility's large heat pump. This ensures that green power is used when available at competitive prices, while wood chips from sustainably managed forests ensure that Kalundborg's needs for process steam for industry, district heating for homes and electricity are met entirely without the use of coal and with high security of supply and flexibility. With the conversion of Asnæsværket from coal to biomass, a new residual stream has been created, namely the water released when wood chips are fired in ASV6. Asnæsværket cannot use the approximately 65 million litres of flue gas condensate itself, but they can at the neighbouring Kalundborg Refinery. Once the condensate has been treated, including in the planned osmosis and ion exchange plant, the clean water will be piped to the refinery. Here, the purified water can be used as boiler water, covering about 1/3 of the Refinery's needs. Without the agreement, the refinery would have to use surface water from Tissø and process it itself to the required quality.
