Waste sludge finds new life as biofuel

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Waste sludge finds new life as biofuel

August 31, 2018 - 05:08
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BRUSSELS, Aug. 21, 2018 (Press Release) -Treating wastewater from industrial plants is an expensive business, requiring a lot of energy and generating high carbon emissions. EffiSludge for LIFE has a solution to this – converting waste sludge from the process into biogas.

Project beneficiaries Scandinavian Biogas Fuels and Biokraft have built a biogas plant for processing waste material generated by the Norske Skog pulp and paper mill in Skogn, Norway. The mill can produce around 500 000 tonnes per year of newsprint, the paper on which newspapers are printed. “On average, 20 000 m3 of wastewater are processed there every day, equal to the water volume of eight swimming pools, generating sludge that is incinerated on site,” says project manager Dr Francesco Ometto.

However, EffiSludge for LIFE is demonstrating a more sustainable method of wastewater treatment, thanks to the integration of the mill’s existing wastewater treatment plant with the new biogas facility, which has just starting producing biomethane. “It consumes less energy and chemical nutrients, and uses the residues for biogas production, reducing the overall carbon footprint of wastewater treatment,” Dr Ometto explains.

Wastewater is treated by active microbes in the water which multiply and consume the pollutants within it, producing a material called activated sludge. Instead of drying and incinerating this waste, the project processes it with additional organic biomass, such as fish waste, to make biomethane (through anaerobic co-digestion). This is cooled to obtain liquid biogas, a fuel particularly suitable for heavy transport.

Creating value from waste

In this way, EffiSludge for LIFE is turning a costly waste product into a valuable resource. Once the project has achieved stable production of biogas in the next few months, the focus will shift to the next stage. “By upgrading the Norske Skog mill’s wastewater treatment plant to support EffiSludge conditions of operation, we expect to see a saving of up to 500 g of carbon dioxide per cubic metre of treated wastewater,” says Dr Ometto. The upgrade will involve improving the activated sludge’s quality to enhance its biomethane potential and the efficiency of its conversion into biogas.

The solid residues from the biogas production process are a valuable fertiliser expected to be used by local farms in Norway. The leftover water, which has a high nutrient content, will be recirculated back into the wastewater treatment system, replacing most of the chemicals required today.

Overall, the project should cut the wastewater treatment plant’s electricity consumption by 50% and, with less need for energy and chemicals, its annual carbon emissions are expected to fall by 3 500 tonnes. “This is equivalent to the amount of CO2 emissions required to produce 1 000 reams of paper!” Dr Ometto adds.

Potential for more

EffiSludge for LIFE has huge potential for replication elsewhere in the paper sector and in other industrial processes that generate wastewater requiring treatment (e.g. food processing and chemicals production). Around 180 million tonnes of pulp and paper products are manufactured worldwide every year, a quarter of which is made in Europe. If the EffiSludge concept was applied to many of the mills in Europe today, the project manager estimates that carbon emissions could be reduced by hundreds of thousands of tonnes.

“We have a great opportunity to demonstrate at commercial scale the project’s value in terms of industrial symbiosis and the circular economy,” concludes Dr Ometto. “Biogas production is no longer merely a way to process organic waste into energy. Integrating biogas solutions into existing industrial processes opens the way to significant energy, chemicals and carbon savings that aren’t otherwise achievable.”