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The construction sector uses a significant share of global energy — and a large part of this goes to the production of building materials. However, the Metsä Wood mill in Lohja, Finland, produces laminated veneer lumber (sold under the name Kerto LVL) in a way that generates more bioenergy than is used in the process. The rest of the bioenergy is used by the surrounding town.

When it comes to energy efficiency in construction, the focus has so far been on the energy used to operate a building. “We have to evaluate the net energy balance of buildings over their whole life cycle and turn our attention to the production of the materials, which is the most energy intensive phase,” said Matti Kuittinen, architect and researcher from Aalto University.

The Metsä Wood mill in Lohja is a great example of the joint production of construction products and bioenergy. First, as much of the wood as possible is used for Kerto LVL. Part of the sawdust and wood chips generated in processing the engineered wood are used for pulp, and the rest for bioenergy production. A bio heating plant has been built next to the mill to capture the full potential of the production. The heat energy produced at the plant covers the needs of the mill, and the excess is provided to help meet the needs of the surrounding town, which makes the Lohja mill 100 percent energy self-sufficient. The heat produced for district heating compensates for the purchase of electricity needed for the mill’s operation. The plant covers 80 percent of Lohja’s heating.

“The local bio heating plant is a significant support for reaching our ambitious low carbon energy goals,” said the mayor of Lohja, Mika Sivula. Lohja is part of Finland’s national scheme to reduce greenhouse gas emissions by 80 percent by 2030. “Due to the bio heating plant, we have reached our first milestone: 15 percent reduction of greenhouse gas emissions by 2016,” Sivula said.

The focus of improving efficiency has to shift from the energy used to operate a building to the production of the construction materials — the most energy-intensive phase in a building’s life cycle. The European “Energy Performance of Buildings Directive” requires all new buildings to reach nearly zero energy class by 2020. However, zero energy buildings are not enough.

“The energy used to produce the materials for a building is 50 times more than the energy used to operate it for a year,” Kuittinen said.

Information provided by Metsä Wood (metsawood.com).

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