Material description and quantity estimations
Zero fibre is surplus wood from the pulp industry. In Lake Näsijärvi, off the shore of the Hiedanranta area in Tampere, lies approximately 1.5 million cubic metres of zero fibre, which prevents the local recreational use of the lake (Lahtinen 2016). In addition to zero fibre, the pulp industry wastewater also contains lignin, organic binders, kaolinite (clay), potassium carbonate, as well as heavy metals and other contaminants (Kuokkanen ym., 2008). The zero fibre has ended up at the bottom of the lake along with the wastewater discharged into the lake. As a slowly decomposing mass, zero fibre forms a fibre sediment at the bottom of the lake. (Lahtinen 2016.)
According to Ramboll Finland Oy’s study, the fibre sediment in Lake Näsijärvi mainly consists of organic matter and contains a large amount of nutrients and some metals, such as arsenic, cobalt, copper, and mercury. In terms of pH value, zero fibre is acidic (Autiola & Holopainen 2016).
In order for the recreational use of Lake Näsijärvi to be able to be increased, the fibre sediment must be removed from the bottom of the lake. The following challenges and innovation needs are, however, related to dredging (Holopainen & Tolvanen 2017).
- Control of odours created by the presence of organic fatty acids
- Prevention of the muddying of water due to dredging and the emissions into the air, so that the soft sediment can be carried along to other parts of the lake/water body.
- Economic solutions for the dredging and recovery of zero fibre
There is an ongoing project called ‘Zero Waste from Zero Fiber’, funded by the Finnish Ministry of Agriculture and Forestry, whose objective is the treatment of the zero fibre obtained form Lake Näsijärvi in an economical and sustainable way without significant environmental impacts. A new microbiological process, with the aid which valuable chemicals, biogas, and organic fertilisers can be manufactured from zero fibre, is also included in the recovery process. There are a great deal of similar sites around the world, so the solution can be applied to other parts of Finland as well as to other countries. (MMM 2017.)
Business-related challenges and opportunities
The recovery possibilities of zero fibre have been studied to a great extent and the material can, at best, be utilised in a variety of ways. The use of zero fibre as a raw material in the production of biogas has been studied as one potential recovery method (YLE 2017). Ojanen’s (2017) thesis supports the biogas production potential of fibre sediment. The production of biogas in the tests performed in connection with the thesis succeeded in test bottles, and almost all of the organic matter was converted into methane and carbon dioxide. In order to maximise the methane production, other nutrients and trace elements are also required in addition to zero fibre to ensure microbe growth. (Ojanen 2017.) In terms of acidity, the fibre sediment in Lake Näsijärvi is, in its current form, disadvantageous for the production of methane gas. When organic matter decomposes further, the methane production potential increases (Holopainen & Tolvanen 2017).
Studies have been conducted in relation to, e.g., mass stabilisation, due to which zero fibre can be utilised in earth construction by mixing it with ash and poor-quality land mass. A Master of Science Thesis completed for Ramboll Finland Oy and ordered by the City of Tampere analysed the stabilisation of zero fibre (i.e., the transformation of the geotechnical properties for construction use) with varying blend component and binder concentrations. The clay, silt, and cement used as blend components and binders improved the recovery possibilities of zero fibre. Additional studies are, however, required in relation to the environmental acceptability and long-term durability of the stabilised material and the optimisation of the quality and quantity of the binders (Holopainen 2015.) At the moment, also an innovation partnership project is underway in relation to mass stabilisation (HILMA 2017).
Furthermore, the possibility of dredging, drying, and utilising the fibre sediment in energy production is currently being investigated (Holopainen & Tolvanen 2017). In addition, zero fibre can also be used for increasing the amount of organic matter in soil (YLE 2016). The promising innovations include the use of this kind of sludge as a thermal insulation material or a paper or wood laminate. Zero fibre also has the potential to function as a carbon adsorbent in a variety of water treatment processes. (Jaria ym., 2017.)
References (mainly in Finnish)
Autiola, M. Holopainen, M. 2016. 0-kidun pilaantuneisuustutkimus. Tutkimusraportti. Ramboll Finland Oy.
Holopainen, M. Tolvanen, H. 2017. Kantakaupungin yhteiskaava 2040. Hiedanrannan rakentamisen ympäristö- ja terveysvaikutukset.
Holopainen, M. 2015. Stabiloidun 0-kuidun geotekniset ominaisuudet ja pitkäaikaiskestävyys. Rakennustekniikka. Tampereen teknillinen yliopisto. Diplomityö
Jaria G., Silva C.P., Ferreira C.I.A., Otero M. & Calisto V. 2017: Sludge from paper mill effluent treatment as raw material to produce carbon adsorbents: An alternative waste management strategy. Journal of Environmental Management – Volume 188, 1 March 2017, Pages 203-211.
Kuokkanen, T. Nurmesniemi, H. Pöykiö, R. Kujala, K. Kaakinen, J. Kuokkanen, M. 2008. Chemical and leaching properties of paper mill sludge. Kirjassa Chemical Speciation & Bioavailability. Volume 26 No.4. Taylor & Francis
Lahtinen, L. (2016). Selluteollisuuden nollakuitusedimentin hyödyntäminen biokaasuprosessissa. Diplomityö. TTY.
Ojanen, L. 2017. Nollakuitusedimentin nestejakeen metaanintuottopotentiaali. Energia- ja ympäristötekniikka. Tampereen ammattikorkeakoulu. Opinnäytetyö.
Hiedanrannan rakentamisen vaikutusarvio. Tampereen Kaupunki ja Ramboll. Luettu 26.10.2017