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(2021) 8:35
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and burnt for energy recovery (Bahar et al. 2011; Naqvi et al. 2010a). Other wastes like sawdust and woody mat- ters are also discarded in the landfill. The destination of liquor dregs, grits, lime mud, and mill ash is the landfill after dewatering and drying. The wastewater sludge is disposed of through a burn- ing approach. The conventional sludge treatment pro- cess includes the thickening of the sludge waste which is dehydrated by mechanical means. The prepared sludge is incinerated at optimal conditions. In the pretreatment process blending of sludges is done with the addition of polymer and dewatering is carried out to obtain a dry solid content of 25–40%. Incineration which is the widely practiced internal route for biofuel production in pulp and paper mills is carried out. The deinking sludge from recycled paper production can be incinerated or reused in other mills (Faubert et al. 2016). Current uses of pulp and paper mill waste The pulp and paper mill waste have different chemical constituents and physicochemical characteristics. Based on their chemical and physical properties the wastes are widely used in conventional and industrial applications. As most of these wastes are mainly based on woody fea- tures comprising lignocellulosic behavior they are used as fuel or energy sources for pulp and paper mill or other industries (Simão et al. 2018; Sarkar et al. 2017). Many are used for construction and building as potential and economic substitutes. The major schemes and sectorial applications followed in the current utilization of wastes from pulp and paper mill are summarized (Table 6).
reduced by avoiding disposal of waste from industries. In certain cases, an obligation is placed for selected wastes to terminate as a waste resource. The wastes from pulp and paper mills have a tremendous negative and adverse impact on the environment. Inherently high consump- tion of water is the major cause, and the problems are wider in terms of generation of effluent and other wastes of solid and liquid type. These solid and liquid wastes along with air emissions require effective disposal and treatment approach (Bajpai 2015d). Three different approaches can be used in pulp and paper mill waste management. The first choice is to mini- mize waste in ensuring product efficiency, higher yield of materials, and lower waste management (Mladenov and Pelovski 2010). The second choice is to find a suitable way for reuse to maintain cost improvement and lower environmental approach. This could be done by mate- rial or energy valorization of the generated wastes. The final option is landfilling which shall only be done when a choice is not an option. In minimizing waste generation, it is necessary to cope up with established concrete environmental legis- lations. In line with this concerns related to cost of dis- posal, treatment technologies, and opt for new utilization schemes need to be taken into consideration. Different techniques are adopted for the reuse of the mill wastes which include burning or incineration, biofuel produc- tion, gasification, pyrolysis, and anaerobic digestion (Baj- pai 2015d; Mladenov and Pelovski 2010). As far as the application is concerned; for solid wastes incineration techniques is widely used, whereas anaerobic digestion is widely practiced for wastewater. Landfilling is still the most widely adopted disposal technique. Current trends in the disposal of pulp and paper mill wastes In the current world pulp and paper mill practice, both landfill and incineration techniques are applied for the disposal of waste. The opt for incineration and other reuse options differ from country to country and are based on technology availability and economic growth hierarchy (Ince et al. 2011; Bahar et al. 2011). Most of the solid wastes generated from pulp and paper mills are disposed of as landfills. Landfilling with its critical limi- tations regarding increasing volumes and the possibility of hazardous substances is still the most widely used dis- posal technique by pulp and paper mills. The hazardous matters in the watercourse impose environmental dan- gers as well. As far as the context in most of the devel- oping countries is concerned most of the waste is still landfilled and some are incinerated. The black liquor is incinerated or gassed as a source of fuel energy and where the technology is not available it as well is discarded as a landfill. Rejects are dewatered
Table 6 Current uses of pulp and paper major wastes S. N. Type of waste Utilization scheme Industry
1 2 3
Black liquor
Energy
Pulp and paper
Sawdust
Furniture and building Construction
Sludge
Compost
Agriculture
Energy
Pulp and paper Construction Construction
Cement base
4
Fly ash
Binder Components Soil Amendments Cementitious Material
Agriculture/Forestry
Construction
5
Dregs
Fertilizer Agriculture Wastewater treatment Environmental tech- nology
6 7
Grits
Building Fertilizer Building
Construction Agriculture Construction
Lime mud
Stabilization
Environmental tech- nology
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