De-inking Paper Sludge Research Articles

Examination of environmental quality of raw and composting de-inking paper sludge

Paper sludges were traditionally landfilled or burned. Over the years, the use of paper sludges on soils has increased, as well as the concerns about their environmental effects. Therefore, the chemical characterization of paper sludges and their young (immature) compost needed to be investigated, and over 150 inorganic and organic chemicals were analyzed in de-inking paper sludge (DPS). In general, nitrogen, phosphorus and potassium contents were low but variable in raw DPS and its young compost. The contents of arsenic, boron, cadmium, cobalt, chromium, manganese, mercury, molybdenum, nickel, lead, selenium, and zinc were also low and showed low variability. However, the copper contents were above the Canadian compost regulation for unrestricted use and required a follow-up. The fatty- and resin acids, and polycyclic aromatic hydrocarbons were the organic chemicals measured at the highest concentrations. For resinic acids, care should be taken to avoid that leachates reach aquatic life. For polycyclic aromatic hydrocarbons, naphthalene should be followed until soil content reaches 0.1 μg g −1, the maximum allowed for soil use for agricultural purposes according to Canadian Environmental Quality Guidelines. In young compost, the concentration of these chemical families decreased over time and most compounds were below the detection limits after 24 weeks of composting. In raw DPS, among the phenol, halogenated and monoaromatic hydrocarbons, dioxin and furan, and polychlorinated biphenyl families, most compounds were below the detection limits. The raw DPS and its young compost do not represent a major threat for the environment but can require an environmental follow-up.

Effect of de-inking paper sludge compost application on soil chemical and biological properties

A 2-yr field study evaluated the effect of applying compost of de-inking paper residues and poultry manure (DSPC) on the chemical and biological properties of Tilly silt loam (Gleyed Humo-Ferric Podzol) in Sainte-Croix de Lotbinière, Qué bec, Canada. The experiment began in 1996 with snap bean ( Phaseolus vulgaris L. ‘Centralia’) and continued in 1997 on the same plots with potato ( Solanum tuberosum L. ‘Gold Rush’). In 1996, treatments included three rates of mineral fertilizer (MF) (60, 120 and 180 kg P2O5-K2O ha-1), three rates of DSPC (14, 28 and 42 Mg ha-1 on a dry matter basis) alone or in combination with MF, and an untreated control. In the spring of 1997, main plots were divided into four subplots and P fertilizer was applied at 0, 44, 88 and 132 kg ha-1. The DSPC increased soil pH and water content. Soil inorganic N increased just after DSPC application, but this effect lasted only 1 yr. Soil Mehlich-3 extractable P showed a significant increase due to DSPC application and the increase was much larger when DSPC was applied in combination with P fertilizer. Soil phosphatase and urease activities were also increased by DSPC. Application of DSPC increased soil Mehlich-3 extractable K and Mg contents. Except for Mn and Zn, soil Mehlich-3 extractable heavy metal contents were not influenced by DSPC. This experiment indicates that compost derived from a mixture of de-inking papermill sludges and poultry manure is a potential source of nutrients for crops and can effectively improve chemical and biological properties of low fertility or degraded soils. Key Words: De-inking sludge, paper biosolids, poultry manure, phosphorus, potassium, enzyme activity

Composting of de-inking paper sludge with poultry manure at three nitrogen levels using mechanical turning: behavior of physico-chemical parameters

De-inking paper sludge (DPS) is rich in carbon (C) but poor in nitrogen (N). Thus, it has a high C:N ratio which limits the composting process. Accordingly, the goal of this study was to investigate the effect of three N treatments on DPS composting. Compost piles of 100 m 3 were formed by mixing raw DPS with poultry manure and chicken broiler floor litter, giving on average 0.6%, 0.7% and 0.9% total N. The changes in physico-chemical parameters, total weight and fiber losses, and maturity of composting piles of DPS were monitored during 24 weeks. The compost piles had a neutral to alkaline pH throughout the study. Inorganic N decreased whereas organic N increased over time for all treatments. These changes in magnitude were different among N treatments resulting in a final total N content of 0.9% for the 0.6% N treatment whereas final total N contents of 0.7% and 0.9% N were measured for the 0.7% and 0.9% N treatments. The total weight, cellulose and hemicellulose losses were higher in 0.6% N treatment giving the lowest C:N ratio after 24 weeks of composting. However, none of the 24 week-old composts of DPS were mature based on their final C:N ratio and colorimetric test of maturity. Except for copper, their final total trace element contents meet most known standards or guidelines for organic soil conditioners. Overall, 0.6% N treatment was the best to enhance DPS composting using mechanical turning, but a period of more than 24 weeks was required to reach compost maturity.

Organic Wastes for Improving Soil Physical Properties and Enhancing Plant Growth in Container Substrates

Summary Increasing rates (5, 10, 25 and 40% v/v) of 6 sources of organic wastes were substituted for peat to assess changes in the physical properties of peat-perlite substrates and investigate the relationship between plant response and these properties. Wastes were either fresh or composted bio-filter sludge (FBF and CBF), sewage sludge (FSS and CSS), and de-inked paper sludge (FDP and CDP). Geranium plants (Pelagornium× hortorum ‘Orbit Hot Pink’) were grown in the substrates. Growing substrates' saturated hydraulic conductivity (Ks), air-filled porosity (f a), pore tortuosity (t), and relative gas diffusivity (Ds/Do) all increased linearly (p = 0.0001) as the rate of organic wastes increased. Geranium plant height (PHT), shoot dry mass (SDM) and root dry mass (RDM) were either linearly or quadratically decreased (p = 0.0001) as the amount of waste increased in the substrates. During both growing seasons, Geranium SDM and RDM were either linearly or quadratically correlated with Ds/Do and t. Organic was...

Effect of Deinking Paper Sludge Compost On Nutrient Uptake and Yields of Snap Bean And Potatoes Grown in Rotation

The paper industry in Canada faces a challenge of economically sound and environmentally safe disposal of massive amounts of residues. A field study was conducted in 1996 and 1997 to evaluate the effects of application of a compost derived from a mixture of deinking paper residues and poultry manure (DSPC) on P and K uptake, and yields of snap bean (Phaseolus vulgaris L. cv. Centralia), and potato (Solanum tuberosum L. cv. Gold Rush). The experiment was conducted on a Tilly silt loam (Gleyed Humo-Ferric Podzol) located in Sainte-Croix de Lotbinière, Québec, Canada. The DSPC was applied in the spring 1996 at 0, 14, 28 and 42 Mg ha−1 on a dry matter basis, and supplemented or not with mineral fertilizer (MF) at 0, 60, 120 and 180 kg P2O5-K2O ha−1. In 1997, P fertilizer was applied in subplots at 0, 100, 200 and 300 kg P2O5 ha−1. Snap bean yield increased significantly with DSPC and MF application. Apparent P and K recoveries from MF by snap bean decreased with DSPC or MF rate. In combination with DSPC, P and K recoveries from MF by snap bean were smaller at all rates than those with no DSPC. Based on nutrient uptake, P and K in DSPC were more available than in MF. Potato yield in the following year was not significantly influenced by the previous treatments nor by supplemental P fertilizer added in the second year. This experiment indicates that compost derived from a mixture of deinking papermill sludges and poultry manure is a potential source of P and K for crops and will increase crop yields in the application year.

Decomposition of de-inking paper sludge in agricultural soils as characterized by carbohydrate analysis

Increasing amounts of de-inking paper sludge (DPS) are available from paper mills, and could be used to improve soil fertility because of their high organic matter content. Our aim was to use chemical fractionation and carbohydrate characterization to determine the transformation and decay rates of DPS in different soils when large loading rates are applied. DPS was added to a well-drained silty clay loam (Typic Dystrochrept) and a poorly-drained clay loam (Typic Humaquept) at rates of 0 (control), 50 or 100 Mg dry matter ha −1. Soil samples were obtained periodically during 726 days after sludge incorporation. Soil organic matter was fractionated into hot-water extractable (HWC), mild-acid extractable (MAC) and strong-acid extractable carbohydrates (SAC), and acid-resistant carbon (ARC). The MAC fraction mostly contained hemicellulosic sugars, whereas SAC fraction included most cellulosic glucose. The contribution of microbial saccharides to the different carbohydrate fractions increased during DPS decomposition. The carbohydrate composition indicated that the chemical fractions reflected the net balance between disappearance of sludge carbohydrates and appearance of newly synthesized microbial carbohydrates. The MAC, SAC and ARC fractions in DPS-amended soils, had relative degradabilities of SAC > MAC > ARC. The sludge used, appeared to decompose according to a two-phase pattern, with an initial rapid-decay phase mostly determined by SAC and ARC disappearance (mean residence time 0.1 and 0.3 year, respectively), and a second slow-decay phase: largely characterized by ARC disappearance (mean residence time 8.5 years). DPS decomposed more slowly at the highest application rate, presumably because the capacity of soil microbes to decompose C was temporarily limited by nutrient deficiency. Chemical fractionation and carbohydrate analysis proved useful to study quantitatively and qualitatively the decomposition and transformation of wood-derived residues in agricultural soils.

220 Growth of Evergreen Shrubs in Potting Mixes Made with De-inked Paper Sludge

De-inked paper sludge from a newsprint mill was evaluated as a substitute for sofwood bark in container media. Rooted cuttings of `Youngstown' juniper (Juniperus horizonatlis), Fraser photinia (Photinia × fraseri), and `PJM' rhododendron (Rhododendron) were planted in 3-L plastic pots that contained potting media amended with 0%, 20%, 40%, 60%, 80%, or 90% paper sludge and 80%, 60%, 40%, 20%, or 0%, respectively, bark (by volume). All mixes contained 10% sand and 10% peatmoss except for the 90% mix, which lacked peatmoss. After 19 weeks, plant heights were measured for photinia and rhododendron, but average plant width was measured for juniper. Shoot dry weights were also determined for all species. Juniper and photinia seemed to be the most tolerant of media amended with up to 40% paper sludge, whereas rhododendron was the most intolerant species. Shoot dry weights of juniper or photinia were similar for plants grown in media containing 40% or less paper sludge. Shoot dry weights of rhododendron plants grown in 40% sludge were 23% lower than those grown in 0% or 20% paper sludge, which were similar to each other. Plant heights followed similar trends to those of the shoot dry weights. With the exception of juniper, shoot dry weights and heights were drastically reduced if the potting mixes contained more than 40% paper sludge. These results demonstrated that de-inked paper sludge could be substituted for up to 40% of the bark in a container medium for two of the three species tested.

Active carbon pools and enzyme activities in soils amended with de-inking paper sludge

Application of paper mill wastes generally improves soil organic matter content, biological activity and physical properties. However, the impact of large application rates (>50 Mg ha−1) on soil microflora and their activity has not been assessed. A field study was undertaken on a well-drained clay loam and a poorly drained silty clay loam amended with de-inking paper sludge (DPS) at rates of 0 (control), 50 or 100 Mg ha−1. K2SO4-extractable C (Cext), soil water content (SWC), microbial biomass C (MBC) and different enzyme activity rates were periodically measured in soil during 1075 d following DPS incorporation. Compared with control soils, Cext content increased by 100 to 200%, and soil water content increased by 35% following incorporation of DPS at 100 Mg ha−1. Those differences decreased in time as DPS decomposed. Soil MBC increased proportionally with the rate of DPS amendment and was about twice the amount in soils amended with 100 Mg ha−1 compared with the control. Microbial quotient (ratio of MBC to total soil organic C) was greater in DPS-amended than in control soils until day 370, reflecting the input of labile C from DPS. Compared with the control, fluorescein diacetate hydrolysis and alkaline phosphatase activity rates increased by 40 to 100% when adding 50 Mg DPS ha−1. However, the rates were similar for 50 and 100 Mg DPS ha−1. We concluded that DPS promoted microbial growth and activity in the soil by improving C and water availability. However, levelling off of enzyme activity at a DPS loading rate above 50 Mg ha−1 could reflect changes in soil microbial community, or some kinetic interference or nutrient deficiency induced by excessive C input. Key words: Microbial biomass, active carbon, soil enzyme, paper sludge

Aggregation and Organic Matter Decomposition in Soils Amended with De‐Inking Paper Sludge

De‐inking paper sludge (DPS) has been traditionally disposed of by burning or landfilling, but could be used as an organic amendment in agricultural soils. Our objective was to assess the impact of DPS incorporation on organic matter and aggregation of a clay loam (Typic Dystrochrept) and a silty clay loam (Typic Humaquept). Whole soil C, particulate (>53 μm) and light fraction (density <1.8 Mg m−3) C, and water‐stable aggregation were measured periodically during a 3‐yr period after a single application of DPS at rates of 0 (control), 50, and 100 Mg ha−1 Microscopic observations of water‐stable aggregates were also performed. Adding DPS increased whole soil C content, which remained greater than in the control for the duration of the study. After 2 yr, about 40% of the initial material remained in the soil. The proportion of residual C attributed to DPS and present in the particulate fraction remained constant at 70 to 90% during the first 2 yr of the study, whereas the proportion of residual C present in the light fraction decreased from >95% for fresh DPS to <50% after 2 yr. One year after incorporation of DPS, the proportion of water‐stable aggregates >1 mm was 2 to 6 times larger in amended soils than in the control. This effect was still statistically significant after 3 yr. Microscopic observations revealed that DPS formed into clusters of wood fibers which became encrusted with mineral particles. We hypothesized that this encrustation provided physical protection to the decaying DPS which remained particulate (>53 μm) in size and progressively densified to >1.8 Mg m−3 As a result, water‐stable macroaggregates were formed with DPS as a central core.

Effects of de-inking paper sludges on soil properties and crop yields

The paper mills in Quebec produce approximately 330 000 Mg of raw de-inking paper sludges (RDS) per year. These residues are rich in cellulose and lignin and may be used as soil conditioner. The effects of RDS on soil chemical properties, barley (Hordeum vulgare L. 'Chapais') growth, nutrient uptake and yields, and their residual effect on a subsequent strawberry (Fragaria × ananassa Duch. 'Kent') crop were investigated on a Tilly silt loam (Gleyed Humo-Ferric Podzol) from 1994 to 1996. Four rates of RDS (0, 15, 30 and 45 Mg ha−1) on a wet-weight basis were combined with four rates of supplemental N-mineral fertilizer (0, 45, 90 and 135 kg ha−1) as NH4NO3 The soluble inorganic N content of soil sampled 30 d after treatment application was significantly lower in plots treated with 45 Mg RDS ha−1 at all N rates. However, soluble inorganic N concentrations increased significantly with RDS rate to 20-cm depth in June 1995. The RDS application increased soil water content and Mehlich-3-extractable P, K, and Ca in the first year. Barley yields were reduced by 50% when 45 Mg RDS ha−1 was applied without supplemental N-mineral fertilizer. The amount of N-mineral fertilizer needed to overcome N immobilization resulting from RDS increased with RDS rates. Strawberry yields were not significantly affected by residual RDS or N-mineral fertilizer. Changes in plant tissue metal contents were not significant. The results of this study indicate that RDS application has a positive short-term effect on soil water, P and K availability but reduces plant-available soil N in the growing season after spring application. The RDS may be used effectively as soil amendment if the crop receives adequate supplemental N-mineral fertilizer. Key words: De-inking paper sludge, N immobilization, barley, strawberry

Use of De-inked Paper Sludge in Potting Mixes for Geranium and Zinnia Production

De-inked paper sludge from newsprint recycling was evaluated as an alternative amendment in bedding plant production. `Sweet Dreams' geranium (Pelargonium × hortorum) and `Crystal White' zinnia (Zinnia angustifolia) were grown in square 10-cm pots in one of five media. Media contained 0%, 20%, 40%, 60%, or 80% de-inked paper sludge by volume. All mixes contained 10% perlite, and peatmoss was used to bring the volume to 100%. Initial chemical and physical characteristics of the media were determined. Plants were grown in a greenhouse for 8 weeks, and then plant height, shoot dry weight, and average plant width were determined. Media containing 20% or less paper sludge had an average pH of 4.4, whereas those containing more sludge had an average pH of 7.0. Cation exchange capacity of the media decreased significantly as the volume of sludge increased. Media containing 60% or more paper sludge were better aerated, but held less water than those made with 40% or less de-inked sludge. Geraniums grown in 20% or less paper sludge were at least 18% taller than those grown in medium containing 40% or more de-inked sludge, but average dry weights and plant widths of these plants were unaffected by the media. Zinnia plants grown in 20% or less paper sludge produced four times more shoot dry weight and were at least 34% taller and 20% wider than those grown in 40% or more sludge. Overall, zinnias grown in 40% or more sludge were unacceptable for commercial sale. A volume of 20% de-inked paper sludge could safely be included in potting media used for production of `Sweet Dreams' geranium and `Crystal White' zinnia.

Tree Growth in Potting Media Made with De-inked Paper Sludge

De-inked paper sludge from a newsprint mill was evaluated as a substitute for softwood bark in container media. Whips, 1.2 m tall, of `October Glory' red maple (Acer rubrum L.), European birch (Betula pendula Roth), and `Royalty' crabapple (Malus L.) were planted in 15-L plastic pots that contained potting media amended with 0%, 20%, 40%, 60%, 80%, or 90% paper sludge and 80%, 60%, 40%, 20%, 0%, or 0%, respectively, bark (by volume). All media contained 10% sand. After 22 weeks, plant heights, trunk diameters, and shoot dry weights were determined. Initial pH of media increased as the amount of paper sludge in the media increased, with the 90% sludge mix having pH 7.2. Paper sludge had a low initial CEC. Physical properties of all sludge-amended media were suitable for tree growth, but media containing 80% or more paper sludge shrank in volume by 10% to 12% by the end of the study. All maple and crabapple trees grown in all sludge-amended media grew as well as those in 80% bark (control mix). In fact, maple and crabapples trees in 40% sludge produced at least 10% and 36% more total shoot biomass, respectively, than trees in 80% bark. Although birch trees grown in 40% or 60% paper sludge grew as well as control plants, those grown in 80% or more sludge were at least 11% shorter and produced 24% less total shoot biomass (leaves, stems, and trunk dry weight) than control trees. These results demonstrated that de-inked paper sludge was a worthy substitute for up to 40% of the bark in a container medium for the three species tested.

Aeration Criteria and Plant Response in Peat Substrate Amended with Six Sources of Organic Wastes

Increasing rates (5%, 10%, 25%, and 40%, v/v) of six sources of organic wastes were substituted for peat to assess changes on the physical properties of peat–perlite media and the subsequent plant response. Wastes were both fresh and composted bio-filter, sewage sludge, and de-inked paper sludge. Geranium plants (Pelagornium ×hortum `Orbit Hot Pink') were grown in the media. Saturated hydraulic conductivity (Ksat) and air-filled porosity (AFP) were successively measured with a Cote infiltrometer and by time-domain reflectometry. Pore space tortuosity (PST) and gas relative diffusivity (Dp/Do) were calculated. Both physical and plant growth parameters were significantly affected by the source and rate of application of waste. Ksat (P = 0.0001, r = 0.937), AFP (P = 0.001, r = 0.984), PST (P = 0.0001, r = 0.935), Dp/Do (P = 0.0001, r - 0.872) linearly increased as the rate of waste increased in the media. However, plant height (P = 0.0001, r = 0.856), root dry weight (P = 0.0001, r = 0.994), and shoot dry weight (P = 0.0001, r = 0.963) either linearly or quadratically decreased as the rate of waste increased. Decreases in plant growth parameters were most likely due to high salinity of organic wastes.

Effects of De-inking Sludge on soil Properties and Corn Growth

The large amount of organic carbon content present in de-inking residues makes them attractive for use in agricultural soils as an organic soil amendment. Greenhouse bioessays were undertaken to evaluate the agronomic value of de-inking sludge (DS). It was incorporated in a sandy soil to study the effects of different rates of de-inking residue amendments and N fertilizer combinations on soil properties and growth of corn. Particular attention was given to trace element concentrations. In a split factorial design, three variables were investigated: harvest time (after 20, 40, and 60 days), application rates of DS (0, 35, 70, and 105 t·ha–1), and four N rates (0, 140, 280, and 420 kg·ha–1). Chemical analyses of the fresh residues did not indicate the presence of heavy metals at levels potentially toxic to the environment. Soil chemical properties were clearly improved following the incorporation of DS. For example, adding different amounts of DS had a significant impact on the pH, the cation exchange capacity, and soil moisture. In addition, salinity was not affected with DS application. Seed germination was high in all the treatments and was not significantly influenced by DS application. Moreover, results on vegetative growth indicated a good relationship between the C:N ratio and biomass production. The DS combined with supplemental fertilizer seems to have a positive effect on plant growth. Overall, these results suggest that the limiting factor in de-inking paper sludge valorization is the amount of N available to the plant. Also, no other toxic products were found that could be harmful to the environment.

UTILIZATION OF BIOSOLIDS IN HORTICULTURE

Canadian environmental policies are aimed at reducing by 50%. the quantities of refuses intended for landfill by year 2000. In this perspective, landspreading and composting biosolids have been investigated as solutions. Paper sludges, wood wastes, and municipal solid wastes (MSW) are important components of landfill biosolids, but they are attractive by-products for agricultural use. Research projects were initiated to characterize the paper sludges produced by Daishowa Co. in Quebec City, wood wastes produced by Hydro-Quebec, and MSW composts produced from waste treatment at RITDM (Chertsey) and Conporec (Sorel). De-inked paper sludge and wood wastes have been landspreaded for growing potato and landscaping, whereas composted paper sludges have been evaluated as part of potting media for growing greenhouse plants and landspreaded for turfgrass production. The chemical and biological characteristics of these biosolids were investigated for their fertilization potential and their effect on plant growth.