Progress 08/15/03 to 08/14/07
Outputs
This study contributed knowledge relevant to the use of organic wastes as soil amendments through chemical characterization, laboratory experiments, and field trials. Laboratory work showed that one proposed method for improving the quality of pulp and paper sludge is not feasible, but it was also shown that mixing of organic wastes can be used to control N availability and losses. Field trials generally showed no productivity gains in either woody biomass crops or Christmas tree due to organic waste application, although N-poor sludge did not depress yields.
Impacts
This work addressed the utilization of pulp and paper sludge and other organic wastes as soil amendments. Sludge samples from five pulp and paper mills in New York State were chemically characterized. Nitrogen (N) and phosphorus (P) concentrations were low in primary sludge (N < 0.2%, P < 0.05% of dry mass). Concentrations of metals were well below US EPA standards for organic waste suitable for land application. The enrichment of sludge via N fixation was studied using batch incubations. Sludge readily supported N fixation by endogenous bacteria, and rates were much higher than for woody detritus in natural ecosystems. However, rates (<3000 nmol acetylene/g-d, <1000 nmol dinitrogen/g-d) were too low for significant N enrichment over an incubation period of weeks or months. A simulation model was developed to explore the potential effects of N fixation on N cycling. Results suggest that even low rates of N fixation may influence the magnitude of N immobilization and
timing of N mineralization. The effect of organic waste application on N cycling in soil was explored using laboratory incubations with applications of sludge, dairy cattle manure, and combinations of both. Results showed that sludge immobilized N for some time before net mineralization began. The magnitude of N immobilization and the timing of N mineralization were influenced by the proportions of sludge and manure added. N immobilization by sludge took place even with surface application of sludge. Results show that it is possible to control both N immobilization and mineralization (and resulting leaching of N) by combining organic wastes that have differing properties. The effect of paper sludge, dairy manure, and urea on the productivity of a short rotation woody crop (willow, Salix dasyclados Wimm.) and Christmas trees was studied over two years. None of the applications (sludge, manure, manure plus sludge, and urea, at a rate of 100 kg N/ha-yr or higher) consistently increased
above ground woody biomass production of willow relative to control plots. However, application of sludge or manure increased foliar calcium for older shrubs (one year old above ground growth on 10 yr old root systems). Foliar N concentrations were lower in the sludge application treatments in younger willow crop (new above ground growth on one year old root systems), but sludge application did not cause a statistically significant decrease for older shrubs. The lack of effects may have been due to low levels of rainfall during the summer in which applications were made (2005). The same soil amendments were applied to Douglas-fir (Pseudotsuga menziesii) and balsam fir (Abies balsamea) Christmas trees planted one and six years previously, respectively. Application rates were 10 N g/tree for Douglas-fir and 30 g N/tree for balsam fir or greater. Urea application to balsam fir caused an increase in diameter growth after one year, but the effect was not apparent after two years. Manure
application led to an increase in diameter growth after two years. Sludge application depressed foliar N in balsam fir after two years, but increased diameter growth in Douglas-fir, potentially due to weed suppression.
Publications
- No publications reported this period
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Progress 09/30/03 to 09/30/04
Outputs
To date, we have made some progress on all components of the study, but do not yet have results from field trials. Additionally, work on nitrogen fixation in pulp and paper sludge is continuing, and we expect to further characterize some important developments in the future. We have demonstrated that pollutant concentrations in primary sludge from five pulp and paper mills in NY State are well below EPA limits for land applied biosolids. Concentrations of metals in primary sludge range from < 1/1000th to 1/25th of EPA's limits for land applied biosolids. In the microbial component, our work shows that nitrogen-fixing cellulolytic microbial consortia are present in pulp and paper waste sludge. We have found that nitrogen fixation readily occurs in primary sludge at a range of moisture contents (60-90%) at rates much greater than natural rates for decomposing detritus in natural ecosystems (up to ca. 1000 nmol dinitrogen/g-d). These results can facilitate the treatment
and use of pulp and paper sludge. Though rates of nitrogen fixation are high relative to natural rates, we have not yet been able to reach rates required for substantial N enrichment of sludge over a reasonable length of time to improve its fertilizer capacity. Mathematical analysis using microbial bioenergetics suggests that, even given sufficient time, final N content may not be high enough to warrant the treatment costs in most cases (< 2% N). However, our results to date suggest several benefits of land application of sludge, including continued nitrogen fixation in the field. We have recognized the importance of producing multiple products from sludge, and our microbial work is focusing on simultaneous biomethanation and nitrogen fixation. Results to date show that it is possible to utilize this method to produce biogas from N-deficient organic wastes. These results could lead to the development of a low-cost process for treating and producing energy from pulp and paper sludge,
which we are currently exploring. This process could be important in many areas other than pulp and paper mill waste treatment and disposal. Current work in this area is focused on defining the kinetics and bioenergetics of this process, and contrasting it with conventional biomethanation. It is possible that kinetics may limit the applicability of this process. Field trials are focusing on willow biomass production and other forestry products. Results from this important component of the study are not yet available. Trials include treatments designed at maximizing field rates of nitrogen fixation, and other treatments that incorporate high N animal wastes for greater N availability. As described in the proposal, we are studying hydrologic and solute fluxes in response to fertility management practices. This component will provide estimates of down-stream impacts of biomass production practices, which are rare in the literature.
Impacts
This study will produce information and processes that are expected to facilitate the use of pulp and paper sludge as a soil amendment. Basic research carried out in this study will address the possible utilization of nitrogen fixation in pulp and paper sludge and other organic wastes.
Publications
- No publications reported this period
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