Sustainable Cities™

Kalundborg: Industrial Symbiosis - Waste makes resource

Industrial Symbiosis is a collaborative enterprise in which the by-products of one industry become valuable resources for one or several other industries. The overall result is of direct economic benefit to the companies involved and widespread environmental benefit to the surrounding region. By 1998, Kalundborg could already boast that internal collaboration between industries had amounted to savings of 160 million dollars since the project’s outset.


Kalundborg is a medium-sized town on the north-west coast of Zealand, 105km from Copenhagen, home to 16,500 residents and host to the world's most well known example of industrial ecology; Industrial Symbiosis. The motivation for exchange arose in the early 1970s from a mutual effort to reduce costs by seeking income-producing uses for "waste" products. Gradually, those involved realized that a carefully managed exchange of energy and materials could enable mutual economic benefit whilst reducing the environmental impact of large industrial operations.

Today, Kalundborg's Industrial Symbiosis comprises eight core companies; DONG Energy Asnæs Power Station, Statoil-Hydro Refinery, Gyproc A/S, Novo Nordisk, Novozymes, recycling company RGS 90 A/S, waste company Kara Noveren I/S and Kalundborg Municipality. Each company is bound to each other via an intricate network of flows; flows of steam, gas, water, gypsum, fly ash and sludge.

Ideas on the industrial symbiosis, November 20, 2008 by Timothy Terway, Flickr Creative Commons

Excess steam from Asnæs Power Station is exported to Kalundborg's combined district heat and power supply and to both Statoil and Novo Nordisk who use it as an incoming heat source before exporting it back to Asnæs as condensed steam for cooling the plant. Gyproc A/S receives excess gas as an input energy source from Statoil- Hydro Refinery and industrial plaster as an input material source from Asnæs power station. Calcium and recycled treated waste water are added to the sulphur extracted from the flue gas at Asnæs to form industrial plaster: SO2 CaCO3 ½O2 2H2O=CO2 CaSO4•2H2O (Sulphur Calcium Oxygen Water = Gypsum).

Insulin production at Novo Nordisk A/S releases material which is exported to surrounding farms as pig fodder. A by-product of the yeast fermentation process is converted into yeast slurry. This replaces approximately 70% of the soy proteins in traditional feed mixes. Novo Nordisk A/S adds sugar, water and lactic acid bacteria to the yeast in order to make it more attractive to the pigs.

Cradle-to-cradle principles encourage us to make waste into food and fuel just as nature does. Kalundborg's Industrial Symbiosis shows the benefit to both economy and environment which can occur when such principles become reality.


Kalundborg moves into the future

Kalundborg is now setting its focus on renewable energy and resources. Asnaes power station has recently pledged a 50% switch to renewables by 2020, with 'block 5' (generation from coal) due to close, and biomass replacing its current quota of raw material.

A pioneering enterprise lead by Inbicon and supported by the network facilitating EU project, Cluster Biofuels Denmark (CBD), is pursuing how the symbiotic model can enable a significant increase in effectiveness when generating energy from biomass. For example, surplus steam from the Asnaes plant can be used to better prepare the straw for the energy generation process. With straw as the input material, the outputs are bioethanol for fuel (for transport etc.), C5-molasses as animal feed and solid biofuel for application in both domestic and district heat and power generation. Inbicon's plant can also be adapted in order to receive other forms of biomass material; corn stover, grasses, bagasse, household waste etc.

Flow diagram of the Industrial Symbiosis in Kalundborg, 1995, courtesy of the Kalundborg Centre for Industrial Symbiosis

Last updated Tuesday, January 21, 2014