Three ways to re-purpose waste from the pulp and paper-making process

At Mondi, we prevent waste wherever possible. But as with all major manufacturing processes, some by-products are unavoidable. When this happens, we look at waste as a resource out of place. And rather than disposing these materials, we find new uses for them across our business and in entirely different industries.

This is central to our efforts to achieve zero waste to landfill, which is good for the environment, good for our business, and helps our customers to meet their own sustainability requirements with a more circular supply chain.

Since 2020, we have achieved a 44% reduction in specific waste to landfill. Let’s look at three of the innovations that make this possible:

1. Soil improvement from fibre residues

Water is a critical resource for our pulp and paper mills, from debarking logs to cooking pulp and beyond. As part of these processes, it picks up residues from wood fibres, chemicals and other substances, which we remove and treat so the water can be safely returned after use.  

Fibre residues, sometimes called sludge, is what’s left behind after this treatment. It’s a mix of organic and inorganic components and chemicals from the treatment process that would otherwise be disposed of without further use.  

But at our containerboard mill in Kuopio, Finland, we have collaborated with Soilfood to unlock the rich organic matter and nutrients in this by-product and re-use it as a valuable soil improvement resource.  

This is utilised in agricultural fields to improve soil structure, enhance water retention and increase microbial activity, all supporting healthier crop growth. As well as re-purposing waste, this helps to reduce chemical fertilizer use and the risk of runoff into local waterways.  

2. Tall oil as a bio-based fuel

In the kraft pulping process, wood chips are cooked using chemicals to break down the organic substance which binds their fibres together, known as lignin. A by-product of this process is tall oil.

We refine this tall oil for use as a valuable bio-based fuel, both for our own energy requirements and for other industries as a substitute for fossil fuels, supporting our focus on increasing the use of renewable energy. It can also be extracted, purified and re-purposed as a secondary raw material to the chemical industry, going into products like adhesives, rubbers and inks.

3. Cement from lime mud

After the lignin in wood chips is removed in the kraft pulping process, we send the remains to a recovery boiler in order to turn the mix back into usable cooking liquor which can be used to produce pulp once again. But as a by-product of this recovery process, a substance known as lime mud is produced. This is primarily made up of calcium carbonate.

At our Ružomberok containerboard mill, we adjusted our process to avoid landfilling this lime mud and instead enable it to be utilised as a secondary raw material in the cement industry, where its high calcium carbonate content makes it a valuable substitute for quarried limestone.

What can circular thinking do for you?

Mondi’s commitment to circularity is not just about process efficiency – it’s about collaborating with our customers to create fit-for-purpose packaging that’s sustainable at each stage of the value chain.

We would love to hear from you and discuss how we can help you with your own sustainability journey.