In the manufacturing of plywood the waste is unavoidable. The waste from wood processing can be divided into two types, namely the waste from primary wood processing and the waste from secondary wood processing. The waste from the primary wood processing is resulted from sawmill industry, plywood industry and pulp and paper industry while the waste from plywood industry can be in the forms of core, spur trim, round up, clipping, trimming, sawdust, sander dust. In general, the waste from plywood industry is approx. 40–50%. Almost all parts of the process of plywood production contribute to the production of waste with the difference in number and characteristics. Types and sources of waste from plywood industry include:
Solid waste
The solid waste generated by plywood industry almost exists on each machine so that its quantity is very large, reaching 40 percent of the volume of incoming logs. The high percentage of solid waste in the production process requires each plywood company to utilize the solid waste optimally. The solid waste generated in the production of plywood includes log salvage, log end, sawdust, wood bark, edging, leftover peel, remaining pieces of log, remaining pieces of veneer, veneer which is not standard, remaining pieces of core, core reject, glue solids, glue spills, remaining pieces of side panel, slab, sander dust, residual sludge of WWTU (Waste Water Treatment Unit), boiler ash, packaging paper, film face, and polyester coating.
The solid waste from plywood production is dominated with wood waste. In addition to the wood waste, there is domestic solid waste, which is the waste from the labor activities, because a plywood industry generally uses a large number of human resources. The domestic solid waste is in the form of paper, tissue and plastic. Factors influencing the generation of solid waste produced by plywood industry are” (a) The number and the condition of log for plywood production, (b) The processing methods and the number of wood waste remanufactured for further production, (c) The production machines dan (d) The number of labors in plywood industry influencing the number of domestic solid waste.
Liquid waste
Liquid waste from plywood production is generally generated only from the washing process of the glue spreader machine and the washing process of other production equipment. This makes the composition of the liquid waste only consist of water and materials used in the manufacturing of adhesives. Based on its original source, namely glue spreader machine, the liquid waste contains materials corresponding to the type of adhesive used. For example, for the adhesive type of urea formaldehyde, its original source is urea formaldehyde resin of industrial flour, kaolin, hardener, filler etc. For the other types of adhesives, the difference is only on the resins used, namely melamine formaldehyde resin and phenol formaldehyde resin. However, in general the biggest composition or content of each adhesive is resin, reaching 70 to 80 percent of the total adhesive mixture, while the rest are additional materials whose composition is different from each other. The characteristics of liquid waste from plywood industry are generally dominated by the value of pH, BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand), TSS, phenol, and total ammonia. Liquid waste treatment system will be determined by the parameters of the liquid waste generated. By knowing the types of the parameters in liquid waste, the treatment methods and the choice of the equipment types required for the treatment can be set. In plywood industry, the factors which influence the generation of liquid waste are as follows (a) Types of materials used in adhesive manufacturing, (b) Amount of water used in the washing process of equipment and production machines, (c) Change frequency of glue/ adhesive used (d) Production systems/processes used (dry/wet) dan (e) Number of employees in the plywood industry that will affect the amount of domestic waste water
Pollution and Environmental Quality Standards
Pollution is the introduction of living things, matter, energy and/or other components into the environment and/or the change of the environment order by human activities or natural processes, so that the quality of the environment decreases to a certain level causing the environment to be less or no longer to be able to function as intended. Basically the activity of an industry is to process input into output. The observation on the industrial pollutant sources can be implemented in the input, the process, and the output by considering the specifications and types of the waste. Pollution caused by the industry is resulted from the waste coming out of the factory and containing hazardous and toxic materials. Pollutants come out together with waste through the medium of air, water and soil which is the component of natural ecosystem. The waste that comes out of the factory and goes into the environment can be identified as a source of pollution, and as the source of pollution it is necessary to identify the types of pollutants released, along with their quantity and its exposure range. The excessive use of water, the disposal systems that do not yet meet the quality standards, and less skilled employees are some of the factors to be considered in identifying the sources of pollution. To prevent any environmental pollution by such various activities of plywood industries, it is necessary to control the environmental pollution by setting the environmental quality standards. Environmental quality standard are size limits or levels of living things, matter, energy, or components that exist or should exist and/ or pollutant elements that are tolerable in a particular resource as the elements of the environment The analysis results of liquid waste that went into the reservoirs in the plywood industries normally shows the quality that was far worse (exceeding the threshold limit value) than it should be for plywood industry, even lower than the quality of water in the River. Therefore, the plywood industries carried out the treatment in WWTP (Waste Water Treatment Plant) so that the waste water discharged into the river environment would meet the threshold limit value. The recirculation of sludge considered hazardous and toxic waste and reusing (recycle) process better to be avoided rather than any use. The waste that comes out of the factory and goes into the environment can be identified as a source of pollution, and as the source of pollution it is necessary to identify the types of pollutants released, along with their quantity and its exposure range A potential risk to human health is by contamination of surface and ground water due to leaching from the hazardous waste dump sites, leakages and spills of effluents carrying culverts, deep well disposal of liquid wastes. In order to prevent such environmental degradation, adequate control should be an integral part of the industrial activity and disposal practices of the waste generated from the industry.
AUTHOR: S. C. Sahoo, Scientist, Indian Plywood Industries Research &Training Institute, (IPIRTI)