When evaluating the economics of implementing an alternative adhesive technology, a full range of applicable factors must be taken into account. Conventional tools used to analyze and compare costs and benefits of alternatives leave out a number of important cost factors, such as environmental compliance and future liability. Costs that must be considered for a complete analysis include raw adhesive purchase and transportation; capital equipment; energy consumption; production rates; operator efficiency; and regulatory compliance.
Raw Adhesive Purchasing Costs/Transportation Costs
The purchase price of waterbased adhesives is generally 15%-20% less than solvent-based adhesives. Since waterbased adhesives generally have the same amount of solids present as solvent-based adhesives, a comparison based entirely on the price of each type of adhesive is valid. Consequently, waterbased adhesives are more economical to purchase.
Once the adhesives are purchased, there is a cost in actually getting them to the user. Premixed waterbased adhesives are essentially the same volume as solvent-based adhesives, so there would be little difference in transportation costs between the two adhesives. However, dry waterbased adhesives require less volume than the equivalent amount of solvent-based adhesives, thus reducing the freight costs for the amount of adhesive needed for the same coating area.
Capital Equipment Costs
The National Risk Management Research Laboratory published an analysis comparing capital costs of solvent-based and waterbased adhesive systems. This analysis showed, in 1993 dollars, that capital costs for waterbased adhesive systems are 8% less than conventional solvent-based adhesive systems, even when costs of air emissions controls are excluded. (Ref. 6) The additional requirement of emission control systems makes solvent-based adhesive systems much more expensive, as does the need for explosion-proof equipment in solvent-based adhesives processes.
Manufacturers considering a switch to waterbased adhesives must take into account not only the costs of capital, but also operational costs. These operational costs include production costs, energy costs, and regulatory costs, and although they are discussed separately below, these costs often overlap with one another. In addition, overhead operational costs for waterbased adhesives may be lower than costs for solvent-based adhesives due to a reduction in insurance costs, since the risks associated with the solvents are essentially eliminated. (Ref. 6)
Many of the production costs for waterbased adhesives are the same as for solvent-based adhesives. However, if the waterbased adhesives are formulated on-site, additional costs can occur. Large, water resistant mixing tanks with non-corrosive piping, fittings, stainless steel mixers and pumps must be installed. Such costs can range from $7,000 to $60,000 per tank (assuming a fiberglass tank), 50 cents per linear foot for PVC piping, $1,000 to $2,000 per stainless steel mixer assembly, and $1,500 to $2,500 per stainless steel transfer pump. As noted earlier, most of these costs can be avoided by receiving premixed waterbased adhesives delivered in bulk containers from the adhesive supplier. There will still be a need to keep the adhesive agitated, to avoid settling of the adhesive, but much of the piping and tank storage will be avoided. There may also be an initial, one-time production cost resulting from downtime for new maintenance procedures and training. Table 4 compares solvent-based with waterbased technologies with regard to productivity, floor space requirements, and operator efficiency.
Table 4(Ref. 6)
Approximate Productivity/Efficiency/Floor Space Comparisons of
Solvent-based Systems and Waterbased Adhesives
Solvent-Based Waterbased Speed (ft/min) 750 750 Length of production line (ft) 150 150 Operators 3 to 4 3 to 4
Both waterbased and solvent-based adhesives require the use of large drying and curing ovens in which the carrier fluid is evaporated. These ovens can be costly to operate due to high energy consumption. However, systems that are entirely waterbased will not need pollution control devices, which may decrease energy usage for the facility.
By greatly reducing or eliminating emissions of HAPs and other VOCs, the waterbased adhesive technologies offer significant savings in avoided emission control equipment costs, permitting fees, and hazardous waste disposal charges. There are also reductions in monitoring costs, since the waterbased systems do not require the stringent monitoring of the exposure of employees to solvents, or the explosive limits of those solvents. Avoided regulatory costs are a significant factor to consider when comparing alternative adhesive systems.
Waterbased systems generate wastewater and solid sludge wastes during cleaning processes. These amounts are largely dependent upon site-specific cleaning practices. The 1996 National Risk Management Research Laboratory report estimated that wastewater disposal costs were $350 per week (volume and shipping costs), compared to minimal costs for solvent-based adhesive systems. (Ref. 6) It is also possible, depending on the discharge requirements of the local sewage treatment agency, that untreated wastewater may not meet local standards; thus a facility may have to operate an onsite wastewater treatment plant. (Ref. 6)
Waterbased adhesive systems generate more solid waste than solvent-based systems. One estimate assumed that costs increased in proportion to the increased amount of start-up substrate required for the waterbased adhesive system, and this start-up was five times that of solvent-based systems. (Ref. 6)
The National Risk Management Research Laboratory determined that the operating costs for waterbased adhesives (in 1993 dollars) is approximately 33% lower than for solvent-based adhesive operations. This analysis included wastewater disposal costs. (Ref. 6)
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