Sector Assessments

Waste Stream and Generation Characteristics of Georgia Pulp and Paper Manufacturers

Wastes are generated by the industrial processes used by Georgia pulp and paper manufacturers. Almost all of the wastes generated are derived from unusable portions of the tree such as bark and lignin. Additional wastes are generated from power generation or from the chemicals used in pulping, bleaching, and chemical recovery. Energy is also a waste stream. Water entering the mill is heated for process use. Thermal energy is emitted to the environment from numerous sources.

The usable portion of a tree is cellulose from which paper is made. Other materials such as turpentine are byproducts which have a market value. Most other components are released to the environment as solid waste, liquids, gasses, or energy derived from combustion.

Toxic Wastes

Toxic wastes reported on the 1993 TRI totaled more than 18.8 million pounds of which 16.4 million pounds were released to the air. TRI releases for 1993 are shown in Figure 2. Of the 26 chemicals reported, methanol was released in the largest quantity at approximately 9.3 million pounds. Methanol is generated from pulping at the rate of 12 to 20 pounds per ton of production in the Kraft process. Bleaching can increase that amount up to 25 pounds. Thermo-mechanical pulping also releases methanol, but in much lower quantities at about 0.5 pounds per ton of pulp. Methanol and other organics (MEK, acetone, etc.) are released primarily from process vents, but are also found in wastewater and the recovery furnace stack. Wastewater leaving the mill can contain large amounts of the methanal; biological destruction of methanol is estimated to be in excess of 99% in wastewater treatment plants. Non-contact recovery boilers available since the 1970s reduce methanol stack releases to near zero. Newer and modernized facilities collect and combust process vent gasses in the recovery boiler, lime kiln, or power boiler furnaces reducing methanol and sulfur releases. Older facilities still have uncontrolled process vents releasing significant amounts of methanol.

Noncondensable gasses are usually burned in the lime kiln or recovery boiler. Mills have traditionally avoided burning noncondensable gasses in the recovery boiler due to an increased risk of an explosion. Some mills have lime kilns which cannot meet the capacity required to burn all noncondensable gasses, or have significant downtime due to mechanical failures. The result is increased emissions of sulfur and organics when the kilns are used to combust noncondensable gasses. Burning noncondensable gasses in the kiln also decreases the lime recovery capacity, thus increasing solid waste in the form of disposed lime mud. A few mills have begun to burn noncondensable gasses in recovery furnaces to take advantage of their greater capacity.

Sulfuric and hydrochloric acids are also released by pulp mills. These materials are combustion byproducts from coal-fired boiler operations. Sulfuric acid is also used in paper making and other mill processes to adjust pH. Zinc is another material reported that is nonpulp related. Zinc is contained in ash from burning tires as a boiler fuel. Tire burning for energy recovery is a popular tire recycling or disposal method.

FIGURE 2 - 1993 GEORGIA TRI RELEASES BY PULP AND PAPER MANUFACTURERS IN POUNDS

Chlorinated compounds such as chloroform are emitted from wastewater and bleach plant process vents. Chloroform is primarily associated with the use of sodium hypochlorite and chlorine bleaching. Mills generally have replaced both of these materials to some degree. Hypochlorite use is discontinuing. Chlorine is being replaced either partially or fully by chlorine dioxide. Ozone is also used in place of chlorine on a limited basis in other states. For these reasons, chloroform emissions have decreased. Dioxin is another chlorine related pollutant. Dioxin levels in effluent from mills that have switched to 100% chlorine dioxide are usually below detectable levels. Chlorine dioxide has replaced chlorine completely, 100% substitution, in three Georgia mills. Several other mills have replaced 20% to 30% of the chlorine used for bleaching with chlorine dioxide.

Chromium and dichloromethane are two chemicals reported from Georgia mills on the 1993 TRI. These are nonpulp related and are due to specific situations that occurred at particular mills.

Solid Waste

Solid waste generation by pulp and paper manufacturers varies between 0.01 and 0.26 tons of waste per ton of product (TPT). The wide diversity is due to several factors. Lime mud and wood yard debris can be large solid waste streams. The sources of these wastes are log handling and insufficient capacity lime kilns. Some mills have sufficient lime kiln capacity and thus produce small amounts of waste. Other mills have reduced wood yard waste by purchasing wood chips and eliminating log storage. Other solid wastes typical in pulp mills are wastewater treatment sludge and digester knots. Sludge and knots are reused in some mills and disposed of in others.

Solid waste is usually disposed of in on-site landfills; some mills use municipal or private landfills. Disposal costs are often very high, exceeding $2 million annually in some mills whether on-site or off-site. Some municipal landfills used by pulp mills have closed. As on-site landfills reach capacity, several mills are considering building new landfills. New landfills can cost $10 to $20 million to open and are not an attractive option to most pulp mills.

• Wood Yard Waste

Wood yard waste generation by Georgia pulp and paper manufacturers varies between 0.02 and 0.06 TPT. Oversized logs, wood debris, decayed wood, sand, soil, and bark are typical wastes. Wood waste can be burned in power boilers if soil and sand are removed. Much of this material is landfilled, or used in the landfill as cover material. Wood chips that are burned for energy are still considered waste by most mills if originally intended for pulping. Several mills indicated that wood yard waste was the largest solid waste stream from their facilities.

Chip making also generates some wood waste. Knots and undersized chips are removed from the chip screen. These materials, along with bark, are usually used as fuel. Clean, palm-sized bark chunks have a high market value as a landscaping material. Some mills sell bark for landscaping. Sawmills and other bark sources that traditionally sold this material to pulp mills for fuel have diverted the landscaping suitable bark to other markets. The smaller, dirtier bark is sold to mills for fuel use. Soil and other debris in this bark must be removed prior to burning or after as increased ash volume, thus creating additional waste.

• Sludge

Various mill sludges are also disposed of as solid waste but are derived from wastewater treatment systems. Primary and secondary clarifier sludges consist of dirt, debris, and cellulose. This material is intentionally rejected due to being out of specification or accidentally due to inherent inefficiencies in the pulp washing systems. At each washing or refining stage, some usable pulp is lost even after passing though save-alls. Deinking sludges are generated from recycling plants and consist of inks, clays, soils, and some cellulose fiber. Mills sometimes dry and burn the sludges for energy recovery and volume reduction. Deinking sludge will have approximately 50% of the energy value of bark. Sludges are sometimes applied to forest or farm land partially as a disposal method and partially to recover nutrients. Sludge generation is reported to be 0.02 to 0.06 TPT. Some pulp mills indicated that improvements have been made in reducing the amount of cellulose inadvertently sent to wastewater treatment. As the cellulose content in sludge is reduced, sludge volume decreases. The sludge generated is then less useful for traditional recycling options such as reuse in ceiling tile manufacture or as fuel.

• Ash

Ash is generated due to combustion. Coal, bark, wood, tires, and sludge are burned producing varying amounts of ash due in part to the amount of noncombustibles in the materials. Ash is disposed of in landfills or has some limited reuse. Wood and bark ash are sometimes used agriculturally for their liming potential. Ash generation rates are approximately 0.04 TPT from Georgia pulp mills. Ashes from different fuels will have varying metal content. Ash from burning tires will contain zinc. Some pulp mills in Georgia burn only wood and bark; other mills primarily burn some mixture of coal, wood, fuel oil, or natural gas.

• Lime Mud

Lime mud is also disposed of as a solid waste. Pulp mills have lime kilns for regenerating lime mud from the liquor recovery process. Often lime kiln capacity does not meet mill requirement, thus requiring disposal of lime mud and purchase of fresh lime. Waste lime mud generation is only related to kiln capacity, not production. Waste lime mud generation of up to 200 tons per day is reported. Other lime related wastes are green liquor dregs and slaker grits in relatively low volumes. Burning of noncondensable gasses in lime kilns can also increase the volume of grits and dregs generated.

• Undigested Knots

Knots generated in the digester and are resin-loaded pieces of wood that are not fully digestible due to poor impregnation with cooking liquor and high lignin content. This material is separated from digested pulp in various screening operations. Some mills mechanically break the knots down and reintroduce them to the digester or pulp stream. Other mills dispose of knots as a solid waste or burn for energy recovery. Undigested knots also contain black liquor and are a source of air emissions.

Wastewater

• Process Wastewater

Water is the largest raw material input in the pulp and paper industry. Georgia integrated brownstock mills will use 5,000 to 12,000 gallons per ton of production. Bleached pulp mills in Georgia have water usages ranging from 13,000 to 25,000 gallons per ton; approximately 50% is used in the bleaching process. Specialty pulp mills can approach 40,000 gallons per ton. Recycle mills also use a considerable amount of water. The lowest water usage noted during this study was 810 gallons per ton at Sweetwater Paper Board, a corrugated recycling mill located in Austell, Georgia. The highest usage was over 17,000 gallons per ton in a recycling mill with deinking processes and bleaching.

Wastewater as previously discussed can contain methanol, chlorinated compounds, cellulose, and other materials. Wastewater removes undesirable material from the process and carries them to a treatment system to partially concentrate and remove, stabilize, or destroy those materials that could damage the environment prior to releasing the water. Wastewater is generated in every washing stage, as well as in the woodyard and chemical generation.

• Storm Water

Storm water may be affected by chipping dust that escapes as fugitive releases from the chipper or chip piles. Bark, debarking dust, and other woody debris are lost around the edges of woodyards. This material was obviously present on the ground around some manufacturing plants visited. Storm water contamination with wood dust is not likely to cause long term problems such as ground water contamination, but can prompt complaints from neighbors, block storm drains, and foul standing water. Storm water runoff is often captured and treated. Wood yard areas and areas where pulp or pulping chemicals are spilled do contribute to storm water pollution and increased treatment costs. Mills typically collect and treat storm water from outside production and storage areas. Increased BOD is the primary storm water pollutant.

Hazardous Waste

Hazardous waste is generated by pulp mills but not in large quantities. Maintenance wastes from degreasing and painting are typical waste sources.

Pollution Prevention Barriers

Economic Barriers

The greatest barrier to pollution prevention in the pulp and paper industry is economic. A pulp mill is a large scale, mostly in-line production process composed of large and expensive devices. In-line production means that all of the product passes through each process component. If one piece fails, then the entire mill ceases to function. There are exceptions. Older mills tend to have many batch digesters while newer and upgraded mills use one or two continuous digesters. Process change becomes riskier as mills move more to in-line production.

A large integrated pulp mill producing 2,000 tons per day of product will cost almost $1 billion to construct if built today. Recovery boilers can cost up to $100 million for new installations. In addition to expensive equipment, the product is very expensive. Virgin bleached pulp prices have been in excess of $1,000 per ton. Upgrades to a pulp mill could require many weeks of construction. A single week of downtime could cost $14 million in lost sales. For these reasons, changes in technology are not implemented until the risk of failure is very low and economic payback high.

Newer pulping technologies are definitely more efficient that older technologies. Due to the cost of equipment and upgrades, it is difficult to justify major changes or replacement of entire systems until the working life of existing equipment has been reached.

Technological Barriers

• Kraft Pulping

The Kraft process is the leading pulping technology in Georgia. Mechanical pulping is used at one mill. Kraft pulping in many ways has remained unchanged; wood, water, energy, NaOH, and Na₂S are the traditional process inputs. Wastes generated are methanol and other various organic chemicals, solid waste, wastewater, sulfur compounds, and waste heat. Reduction in pollution has resulted primarily from pollution control measures such as combustion of vented gasses and scrubbing combustion stack gasses. Equipment modification to improve boiler combustion efficiency has also reduced emissions. Pollution prevention techniques have resulted in improved recovery of NaOH and Na₂S, reduced water usage, and reduced energy usage. Even with these improvements, the Kraft pulping process will continue to produce organic waste. Environmental pollution reduction from the Kraft process will continue to be primarily capture and control since there are few if any methods available for eliminating pollution at the source. Use of catalysts and enzymes in pulping represents the first new technology changes in many years. Catalysts are discussed later in the report under Alternatives to Chlorine Bleaching.

• Bleaching and Pulp Washing

On the other hand, pulp washing and bleaching are continuing to change to reduce waste. Economic barriers and some technical barriers still exist in implementing pollution prevention technologies in bleaching and pulp washing, but there appears to be a steady evolution of these processes to reduce waste and cost.

Technological evolution in bleaching is evident by reviewing the existing bleaching technologies in 1995 compared to 1970. Bleaching began almost exclusively using chlorine and sodium hypochlorite. Due initially to dioxin concerns in the 1980s, alternatives to chlorine were researched and implemented. Chlorine dioxide has now either totally or partially replaced elemental chlorine and sodium hypochlorite. Oxygen and peroxide are also now used in bleaching and prebleaching stages. In addition, various methods to improve delignification in the pulping stage have been developed which reduce the dependence upon chlorine in bleaching.

Organizational Barriers

• Lack of Pollution Prevention Programs

The typical pulp or paper mill in Georgia does not have a program in place to evaluate wastes and develop methods of reducing. The primary focus of pulp mill personnel is to keep the mill in production by meeting quality, production, and environmental regulatory mandates. Mill personnel are extremely busy; tasks beyond the normal scope of work are commonly handled by using consultants. Pulp and paper mills use external consultants for environmental and design services. Through organizations such as the Technical Association of the Pulp and Paper Industry (TAPPI), the National Council of the Paper Industry for Air and Stream Improvement (NCASI), the Environmental Protection Agency (EPA), and other pulp and paper trade associations, technologies that improve environmental performance are well known to both mill personnel and consultants. For this reason, new mills are constructed with leading edge technologies; many older mills have also upgraded. Several pulp and paper manufacturers have corporate programs to reduce waste. In general, these programs are designed to identify and evaluate those leading edge technologies.

• Lack of Waste Accounting

Some of the more mundane aspects of waste minimization and pollution prevention are overlooked. Mills have various means of accounting for waste generation, but these methods mostly focus on major waste steams. Ash generation, sludge generation, solid waste generation, and overall water usage are known. Specific sources of waste and water usage are unknown. Georgia pulp mills generally account for waste generation and cost as overhead. Most mills have not attempted to trace waste generation back to individual processes. In some of the mills, water usage was only known as a total volume. Flows to individual processes, and waste materials contributed to the wastewater stream by individual processes are unknown. Approximately 50% of the Georgia pulp mills have formal pollution prevent plans to evaluate waste and implement waste minimization methods. Even the mills with formal pollution prevention programs tend to look toward the technological solutions and not the simpler methods such as materials management. The simpler methods often require a significant investment of time to develop and implement, but can have very large financial returns.

Air emissions by pulp and paper mills are calculated using emission factors or they are measured. Emissions factors provide an estimate of the amount of a chemical emitted per ton of pulp production. Emission factors are based on the type of equipment used to produce pulp. For example, the emissions factor for estimating methanol emissions from a batch digester and blow tank will be greater than the emissions factor for a continuous digester on a per ton basis. NCASI, EPA, and other organizations publish emissions factors. Emissions calculated by using emissions factors may be higher or lower than measured values depending upon a number of factors. The general state of repair of equipment can also affect emissions; additional emissions due to failures may not be calculated when using emissions factors according to some mill personnel. In one facility, the pulp washer appeared to have some seal damage in an access door emitting steam, liquid, and odor. Other mills had darkly colored liquid streams escaping from pulp washers and storage areas. In every case, the liquid was collected in sewers for treatment at the mill's treatment plant. Air emissions from these failures may not be estimated by using emission factors according to some pulp mill personnel. The use of emission factors does not seem to provide an incentive for repair of relatively minor system leaks such as these. Measurement of emissions may not provide an incentive either since emissions from leaks or failures would be only measured if sensors were located in close proximity or were intentionally measured. Leaks from equipment in disrepair do increase operating cost and actual emissions. Preventive maintenance and leak repair should be included in all pulp mill procedures. Mills that have few leaks, few spills, and maintain a high level of housekeeping may release fewer air emissions than mills that do not maintain equipment or housekeeping as well. However, reported emissions for the two situations may be the same based on stack measurements or emissions factors.

Sources of Pollution Prevention Assistance to Pulp and Paper Mills

Most Georgia mills have received assistance in reducing waste. Some of the sources of assistance are listed below.

Trade Organizations and Technical Assistance Organization

Most Georgia pulp mills are involved in various trade and technical assistance organizations. A listing of some of the trade and technical assistance organizations are provided below. For this reason, pulp and paper mills are well informed of major technical and environmental trends.

• TAPPI Technical Association of the Pulp and Paper Industry - (770) 446-1400
• NCASI National Council of the Paper Industry for Air and Stream Improvement - (904) 377-4708
• IPST Institute of Paper Science and Technology - (404) 894-5700
• Herty Foundation - (912) 963-2600
• P²AD Georgia Pollution Prevention Assistance Division - (404) 651-5120
• EDI Georgia Tech Economic Development Institute - (404) 894-5240
• GTRI Georgia Tech Research Institute - (404) 894-3806
• UGA University of Georgia - Driftmier Engineering Center - (706) 542-8382

The Herty Foundation is an authority of the State of Georgia that offers contractual research and development to the pulp, paper, and nonwoven industries. The University of Georgia also offers the use of a 20 ton per day pulp mill for research of ozone, chlorine free, enzyme assisted, and other bleaching and deinking technologies.

Corporate and Facility Pollution Prevention Programs

Several of the Georgia mills use their corporate engineering and technical resources to reduce waste. Other plants have mill personnel who measure and characterize waste streams with the goal of reducing waste. Whether using corporate or plant personnel, some mills actively track waste generation to the source and seek ways to reduce. A case study is attached in Appendix I describing Weyerhaeuser's approach to waste minimization. Tenneco, Weyerhaeuser, Georgia-Pacific, Fort Howard, Southeast, Federal, Gilman, and Rayonier are some of the major pulp and paper manufacturers in Georgia with waste minimization programs. In each case, the specific goals and methods may be very different depending upon the organization.