Never an opportunity wasted

One of the problems with industrial waste is how to dispose of it in an environmentally-conscious way. A new project in Norway makes it possible to turn some of that trash into treasure – in the form of biogas – and to make it accessible for use as clean fuel for large vehicles.

Can decomposed paper mill slurry and fishery waste take on a new life as biogas? A project started in Moss, Norway in 2012, looked into the process of cleaning and liquefying such biogas for use as fuel. “The demonstration project was an immediate success,” says Arne Jakobsen, Business Development Manager for Wärtsilä Norway. “So we were contacted by the municipality of Oslo to scale this up and build a plant in Vormsund, outside Oslo, and we now have another contract to build an even larger plant.”

The new plant will be located at the paper mill in Skogn, a small village approximately 75 km north of Trondheim along the shore of the Trondheim fjord, and it will be the largest of its kind in Northern Europe — and quite possibly the world. Currently, paper mill waste slurry at the Skogn plant is treated with electrolysis before being released into the Trondheim fjord. The new biogas plant will replace this energy-intensive process while repurposing the waste into a clean, fossil fuel alternative.

After the waste is collected, digested and converted into clean biogas, it is liquefied and cooled to -160°C, then stored in insulated tanks for use as transport fuel. Much of the biogas produced will most likely fuel Norwegian public transit vehicles – a sector that is currently a large consumer of fossil fuels.

Innovative use for traditional components

The components used in the liquefaction process are not new innovations—in fact, they are readily available and proven to be effective. The novelty is in the highly advanced process design and control system that has been expressly built to liquefy small, methane-based gas streams. According to Jakobsen, “What makes this special is that we use traditional components and a unique mix of refrigerants that circulates in the system. This enables a short delivery time and high efficiency. The innovation is coming up with the idea of the concept, making it a commercial product, and putting it into operation.”

The cryogenic liquid biogas has two primary advantages over compressed gas biofuels: the distribution of the fuel to the customer and the usage of the fuel. Jakobsen explains that, “With compressed gas, the customers need to be within a 100-150 kilometre radius. But the liquid  biogas can be transported 1,000 kilometres and still be competitive, which is what makes this commercially viable.”

This fuel has a variety of potential uses, strengthening its position as an advantageous fossil fuel alternative. One of the big advantages of liquid biogas is that it can easily be converted to compressed gas for gas buses, and the liquid biogas can be used directly as fuel, when a heavy vehicle or vessel would require too large a volume of compressed gas to store it onboard.

The fact that Wärtsilä is able to scale up this process significantly – to a capacity of 25 tons of liquid biogas per day – is also impressive. “It is a game-changer in the biogas fuel market,” says Øystein Ihler, Development Director of Climate and Energy Programme for the City of Oslo.

New means to combat climate change

Scaling up the production and use of liquid biogas will provide several environmental benefits. Perhaps the most important advantage is the replacement of fossil fuels with no net production of carbon dioxide (CO2). Additionally, waste becomes an input rather than an output, thereby reducing overall waste treatment and storage. And finally, sulphur oxide (SOx) emissions, a primary cause of acid rain, as well as emissions of nitrogen oxide (NOx) and small particulate matter, which causes poor air quality, are virtually eliminated.

As new and tougher environmental targets continue to be set, especially after the landmark agreement resulting from COP21 in December 2015, the future of fossil fuel-reducing alternatives like liquefied biogas is bright. Now that the biofuel can be produced economically and sustainably, plants like this one can pave the way for reductions in fossil fuel use and greenhouse gas emissions. The next step is to expand its use. As Jakobsen explains, “To meet the targets in time, we need to reach the largest users of fossil fuels and provide them with biofuel instead.”

© 2018 Wärtsilä