Sweden’s largest biogas reactor to Nymölla?

Stora Enso’s pulp and paper mill at Nymölla may become home to Sweden’s largest biogas reactor. The wastewater from the mill contains organic material, and this could be collected and digested. A project to build such a plant has been awarded SEK 58 million from Klimatklivet.

The Biogas Tour at Nymölla Mill

Nymölla mill is one of few remaining pulp and paper mills using the sulfite process. The pulp is used to manufacture, among other things, copy paper and forms that have particularly high requirements for quality and brightness. The paper is bleached with hydrogen peroxide in a closed circulation; the raw material comes from monitored and sustainable forestry operations; and the mill has every environmental label and certification you can conceive.
Excess heat from the mill is used for district heating in the municipalities of Bromölla and Sölvesborg.

“We produce 85% of our energy needs ourselves,” says Ola Petersson, environmental manager at Nymölla mill.

58 million from Klimatklivet

Researchers on Biogas Tour summer 2017Researchers on Biogas Tour summer 2017 Photo credit: Monica WestmanWastewater from the sulfite process contains slightly more residue than wastewater from the more commonly used sulfate processes. This means that the mill must use more cleaning steps before the water can be released into the sea at Hanöbukten.

“We have wanted to include an anaerobic step in the cleaning process to produce biogas since 2008, and we were granted environmental permits for this in 2011. We’re expecting a decision whether the project can start this autumn”, he says.

At the start of June 2016, however, Swedish Biogas International, which has recently been acquired by the Finnish company Gasum, received SEK 58 million from Klimatklivet, to build a biogas reactor at the Nymölla mill. A letter of intent has been signed by both parties, and now project manager Henrik Höglund and environmental manager Ola Peterson are champing at the bit.

Largest biogas plant in Sweden

It is planned that Nymölla will lend its wastewater to Gasum, which will convert the organic residual in it to biogas. The potential yield has been calculated to be 90 GWh per year, which means that this biogas plant will be the largest in Sweden.

Nymölla will receive in return significantly cleaner water, which is a further environmental feather in its cap, while at the same time the cost of chemicals will be lower, as will also energy consumption, since fewer aeration ponds will be required.

“But we’re keeping the cleaning plant, since we must be able to obtain the same high degree of cleaning independently of whether the biogas plant is operating or not. We cannot become dependent on an external party,” says Ola Petersson.

Photo credit: Monica WestmanGasum will then take over the gas and decide how it is used or sold.

“It will be 12-18 months after the decision before we produce any gas, and we are now focussing on getting the investment approved”, says Ola Peterson.

Previous research at the Department of Thematic Studies – Environmental Change at Linköping University has shown that the forestry industry has a huge potential for providing biogas material.

“Nymölla is probably one of the most suitable mills for anaerobic digestion and biogas production. If the process can be established here, several other mills in Sweden may follow suit,” says Mats Eklund, professor in environmental technology and management.

 

Klimatklivet

Klimatklivet provides investment for measures that reduce the emission of carbon dioxide at the local level, and is administered by the Swedish Environmental Protection Agency. A total of SEK 2 billion is to be awarded to projects before 2018. The county administrative board in Skåne has commented the investment: “Biogas gives the greatest climate benefit for the money invested. And the effect on Hanöbukten is also expected to be positive, in addition to the benefit for the climate”.

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