Industrial symbioses in cement production
In short: A creative recycling is taking place, as the waste products from the local energy plant are used as a raw material producing cement. The regional energy plant produces electricity. During this process electrostatic filters remove fly ash in the flue gas and a plaster system that removes sulfur. The gypsum is sold to Aalborg Portland (a cement factory) as a raw material in producing cement. The fly ash is also used as an additive to cement. Finally the heating left over from the production of cement is used to heat the city of Aalborg.
Aalborg Portland is one of the largest cement producers in the Northern part of Europe. The company is one of the world leaders in energy efficient production of high quality cement. Furthermore, they are the world leading producer of white cement.
High temperatures and unique process conditions make cement kilns ideal for the use of alternative fuels and raw materials. Fossil fuels, particularly coal and petcoke are increasingly being substituted at Aalborg Portland by CO2 neutral biofuel such as meat and bone meal and wood waste. All constituents in these alternative fuels are fully utilized and no new by products are formed.
Aalborg Portland began using fly ash in cement production more than 30 years ago. Fly ash is a byproduct of electricity production at the power plants. A number of other by products has since been included in the cement production. Under a longstanding partnership, Aalborg Portland supplies chalk slurry to a local power plant, which uses it in the flue gas cleaning process. This process in turn produces desulphurization gypsum which is used by Aalborg Portland as a replacement for natural gypsum.
Furthermore, production of cement takes place at very high temperatures. Aalborg Portland cleans the flue gases from the kilns and uses the high temperature of the flue gases to heat the residents of Aalborg city. The heat supplied corresponds to the annual heat consumption of around 21.000 households. This heating is also used for the company’s own factory and offices.
The products supplied by Aalborg Portland make a useful and key contribution to society’s climate challenge. However the focus on sustainability and environmental responsibility also extends to product development and production. This has required significant investments. Production of cement results in CO2 and other emissions. For many years significant investments have been made in reducing emissions, particular CO2, SO2 and NOx. Since 2010 aprox. 15m EUR have been spent on climate and environmental improvements. These initiatives are set to continue as Aalborg Portland plans to install as many as 10 large wind turbines, which will potentially replace approx. 40% of the company’s existing power consumption with renewable energy. Around 40% of the company’s power consumption is already based on renewable energy.
Aalborg Portland’s energy and environmental conditions are disclosed openly in annual environmental reports. It is also directly visible to the buyers of company products. Environmental product declarations exist on the cements. Finally all the products from Aalborg Portland can be recycled and all the constituents can be fully utilized.
The symbioses between Nordjyllandsvaerket, Aalborg Portland and partly the city of Aalborg by providing heat to the residents is a strong evidence that recycling among industry and society can go hand in hand42.