Field: Paper mill sludge disposal and recovering
Global Technical function: Burning, Recovering, Separating, Substituting, Vitrifying
Technical Function Unit: Chemical separating, Incinerating, Physical separation
Techniques: Sustainable absorbent
Geographic Area: Slovenia


The technology that has been developed within the CAPS project (funded under CIP programme, a grant funding programme) should allow the paper industry to value its waste, particularly in the field of paper mill sludge disposal and recovering. The increasing demand for a more sustainable absorbent and for an appropriate treatment of papermill sludge within papermills, has led the project’s partners to develop an innovative physical separating process in order to convert the paper mill sludge into an efficient absorbent material.  

The latter can be then applied both on water and hard surfaces. In that way, hydrophobic substances (i.e. vegetable, synthetic and mineral oils, animal fats, fuels, organic substances) floating on water surfaces can be absorbed directly. In a second step, the material (i.e. absorbent + oil) can then be used as a secondary fuel through an incinerating process, depending on its calorific value. A last, the inorganic resulting material (from combustion) can be used in the form of absorbing granules dedicated to accidental spills on solid surfaces.

In the oceans, oil spills can damage shorelines and destroy marine life, as the latest ‘Deep Water Horizon’ spectacular accident has shown. It is more and more obvious that oil spills and other environmentally damaging accidents can cost huge sums of money. Moreover, in workplaces, spills can cause hazardous conditions resulting in significant work-related injuries. In order to address these issues, the proposed recovering technology enables to produce an absorbing material from paper mill sludge. The sludge is collected after the de-inking step that performs a flotation process (chemical separating): the so-delivered material is likely to absorb more than 99% of the initial quantity of an hydrophobic substance on the surface of water. This eco-innovative material is called HAWSC  which stands for Hydrophobic Absorbent for Water Surface Cleaning

There are several ways to achieve the separating process when using this eco-innovative material: the absorbent can in fact be used either in a dispersed or a packaged form. In the dispersed form, the absorbent can be directly scattered over the hydrophobic substance that floats on the water surface or over the hard surface area around the spilled substance. Another possibility consists in packaging the absorbent material or even in encircling the spills with a specific designed thick rope filled with the absorbent. The spilled substance can therefore be absorbed by slowly reducing the size of the circle in the middle of the rope.  Furthermore, in order to collect hydrophobic dust (e.g. coal dust) at the water surface, an option may consists in spraying a non-toxic and fully biodegradable hydrophobic liquid (e.g. biodiesel) over the affected area to capture the dust and then to spray the absorbent.

Once the paper mill sludge has been charged with an oily substance, it can be used as a valuable calorific material. The average calorific value for the absorbent before it is applied is 3.8 MJ/kg (megajoules per kilogramme) and depending on the calorific value of the absorbed substance, it can increase up to 33.5 MJ/kg. Thus, the resulting material can be used as a secondary fuel by burning it within power lines or cement factories for instance. Moreover, vitrifying the charged material by using a controlled incineration process may also lead to an absorbent that can at last be used in cases of shore spills of hazardous substances (hard surfaces).

A first production line has been tested at the beginning of 2012 in Slovenia.  The second production line is envisaged in early 2013. Hence the technology Readiness Level is 9 on the TRL scale.

The various outputs of the project will allow the paper industry to value its waste. The ports and marinas as well as the tourism industry will be able to reduce their costs (e.g. lower costs for ports and marinas for water surface cleaning, both in cases of accidental and/or operational release as well as lower costs for petrol stations and restaurants).

The project, which was funded under CIP Eco-innovation, puts forward a sustainable methodology beyond the existing synthetic absorbents by substituting the production of synthetic absorbents produced from fossil fuels with a natural material. After incineration, an additional inorganic absorbent is produced and can be used on hard surfaces. As a result, the life cycle of the initial material is significantly improved.