The Paulownia Tree: Waste Stream & Effluent Remediation Capabilities

Tags: : Paulownia tree, Waste Stream & Effluent Remediation Capabilities, Dairy Effluents, coppicing, nitrogen fixing plants, commercial timber, environmental benefits paulownia, biomass of paulownia, odor reducing, transpiration, disinfectant function of paulowniaThe following research was compiled to illustrate the ability of the Paulownia tree to phytoremediate extremely high strength waste from dairy and animal feeding operations. As a result, other effluent waste streams such as municipal and residential wastewater can be remediated much easier and more efficiently than conventional animal waste. Paulownia trees possibly provide an alternate method of absorbing treated effluents derived from municipalities and septic tank systems.

Paulownia Nutrient Utilization for Dairy Effluents

Research authored by:

Dr. Ben A. Bergmann, Department of Forestry, North Carolina State University

Dr. Carl F. Jordon, Senior Ecologist, University of Georgia

Overview 1

Paulownia species grow rapidly, utilize large amounts of nitrogen (including other nutrients), coppice (stump sprout) and regrow rapidly, and have a variety of end uses. Large quantities of nutrients can be removed from animal waste applied to Paulownia trees because of their high biomass production and high foliar nutrient concentrations. The coppicing ability of Paulownia eliminates the need to replant for several rotations; a considerable cost advantage over tree species that do not exhibit this trait. The ability to stump sprout prolifically is an asset in systems aimed at removal of nitrogen, phosphorus, and other nutrients via high biomass production because plants may be cut down more than once during the growing season.

A Paulownia tree farm designed for commercial timber production at 1093 trees per acre will absorb 445 lbs. of nitrogen the first year, 668 lbs. the second year (thinned to 546 trees per acre), 735 lbs. the third year (thinned to 273 trees per acre), 804 lbs. the fourth year, 1166 lbs. the five year, 15,291 lbs, the sixth year, 1,964 lbs. the seventh year and 3,052 lbs. the tenth year. In addition the crop of selection to be intercropped with the Paulownia will increase the amount of nitrogen uptake per acre. {i.e. grass (215 lbs. per acre) corn (265 lbs. per acre)}.

All calculations are based on a conservative value of 2% nitrogen in leaves and 0.2% nitrogen in wood. Actual nitrogen removal rates will likely exceed these estimates given in that is has been shown; that Paulownia elongata foliar nitrogen content can be much higher than 2%. (Bergmann et al. 1998, Kasy and Gouin 1996) and that denser plantings can be used. As with any land application system, protection of surface and groundwater quality is dependent on matching wastewater application volume and concentration with the tree species planted, soil type and weather conditions.

The objective is to increase the environmental benefits of the Paulownia uptake application by bio stimulating the lagoons causing them to become aerobic and eliminate the odor emissions. It is further intended to sub terrain irrigate with the lagoon water reducing the amount of evaporation and the possibility of any odor emissions while providing the most beneficial usage of the nutrient water.

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1. Section A, pages 18-19: Bergmann, Department of Forestry, North Carolina State University

Paulownia Qualities

Biomass Production of Paulownia

Biomass of Paulownia is the main component in a PCI (Paulownia-crop intercropping) system. The quantity of Paulownia biomass reflects the productivity and the flow of materials and energy of the PCI system. Biomass production (fresh weight and oven-dry weight) of Paulownia was investigated yearly from one to eight years after out planting, and the total biomass was divided into the following components - trunk (under crown), branches (big branches, medium branches and small branches), leaves leaf blades and stalks), bark, flower buds, flowers, fruits, roots (stock, thick roots, medium roots and small roots, and litter. The result of the biomass investigation is as follows:

Component of Paulownia Biomass

The biomasses of each part in and for the whole plant of a 3-year old Paulownia were ranked as roots, trunk and leaves. After three years, the listing changed to branches and trunk, leaves, roots, flowers and fruits. The root growth of Paulownia is more dominant than of other organs before it is 3-year old. The growth of above-ground portion (trunk, leaves and branches) became faster with age of the tree. The proportion of biomass of each organ to total biomass was 31.9%, 25.31%, 21.32%, 17.19%, 4.27% and 1.4% for trunks, leaves, branches, roots, flowers and fruits respectively. Among which, the total amount of 30.98% of leaves, flowers and fruits fall off as litter. The cumulative biomass of one Paulownia tree at eighth year was 607 lbs. dry weight. Correspondingly, the total biomass poundage per acre for different spacings of 8-year old Paulownia were estimated at 47,806, 23,890, 16,131, 11,950 and 9,561 lbs./acre of 5 x 10, 5 x 20, 5 x 30, 5 x 40 and 5 x 50 respectively.

Utilization of Paulownia biomass

As mentioned above, the biomass of trunk and branch was 53.22% of the total biomass. About 63.5% of the Paulownia biomass can be easily used as timber and firewood. The root biomass was 7% and of foliage 30%. Full use of the foliage will increase the economic value of Paulownia trees. The leaves drop off due to the effects of early frost not allowing enough time for the trees to transfer the nutrient matters from leaves to root for storage. The nutrient status of the fallen leaves is close to that of the fresh leaves. Paulownia foliage can be used and the dropping off causes no harm to the growth of trees. The nutrient analysis of Paulownia foliage shows the presence of eight amino acids and trace elements such as Fe, Cu, Mn and Zn that are important to animal growth.

Paulownia is also a good nectariferous species. There is about 0.0236 g of pollen in a flower, from which 0.0473 g honey can be produced. A standard group of bees can collect 22-33 lbs. of nectar during a flowering season. To sum up, Paulownia has many suitable characteristics, such as fast growth, deep root distribution, sparse crown structure, multipurpose (timber, fodder, manure and nectar sources), use when grown in agro-forestry systems.

Ecological Effects on the Farming Fields

Soil Moisture and its Physical Features

Soil moisture was one of the main factors affecting soil fertility. The parameters related to the physical characteristics of soil moisture were observed because the physical property of soil moisture was closely related to the soil-ventilating feature. The result indicated that the volume weight of upper soil layers (0-8 inches) decreased with increase of distance from the trees.

The maximum moisture holding capacity also increased with the distance from the trees. The volume weight of upper soil layer at 4 ft. to the tree rows was higher than the control (control means without Paulownia-crop intercropping).

Total Nutrients 2

Extensive aerobic treatment will reduce odor from the liquid waste from a confined animal operation. In the process, however, much of the nutrient value will be lost. For example, much of the organic content of manure will be lost as carbon dioxide; nitrogen will be converted to nitrate and subsequently may be reduced to nitrogen gas.

Water Status in PCI System

The soil moisture content of upper layer (0-24 inches) was 24.2% in PCI field and 24.2% in the control field. The content of lower layer (below 60 cm) was 28.7% in PCI field and 29.5% in the control field. The observations match with the features of root system of Paulownia. When the Paulownia trees are planted in farmland, there is no negative interaction between trees and crops in water intake.

Energy Balance and Evapotranspiration of PCI System

Through the systematic observations of total solar radiation, reflect radiation. wind velocity, temperatures (with wet and dry bulb thermometers), soil temperature and moisture contents of different layers in different PCI models, a description of energy balance of the PCI system was worked out. The net radiation and its components in a PCI system decreased when compared with control plots. However, the proportion of heat flux to net radiation was reduced, while that of latent heat flux and soil heat flux increased The ratio of actual over potential evapotranspiration and soil moisture increased, resulting in less water deficit compared to control plots. Paulownia's effects on these parameters depended on the tree density and growth stage, and their relative distance from one another. The modified energy balance was favorable to wheat growth during its heading and flowering stages under any Paulownia spacings, but the effect on wheat growth during grain filling in denser Paulownia spacing was due to the greater reduction in net radiation, perhaps brought about by the protective effects of the fully developed leaves on trees.

Soil Nutrition Status

Organic matter and nitrogen contents at 0-8 inches below soil surface decreased toward the trees. There was not much difference detected in available P, Ca and Mg. But available K was apparently higher within 5 m from the trees than further distance from the trees. Continuous measurements for three years at the age of 9-11 years old showed that there was not much difference in N contents at 0-23 inches below soil surface in the PCI field, but N contents at 31-40 inches below soil surface at a distance of 20 feet from the trees significantly decreased while compared with the control.

This could explain that Paulownia trees utilized nutrients mostly from lower soil layer (31-40 inches). It was also found that seasonal variation of available Ca and Mg was similar with that of the control. At 2 inches from the trees, however, it increased at 0-8 inches below soil surface perhaps due to the decomposition of Paulownia litter.

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2. Control of Odor Emissions from Animal Operations: Board of Governors of the University of North Carolina, page 22

ODOR REDUCTION DURING LAND APPLICATION 3

Land application of manure typically brings about the most complaints. Fortunately, odors from land application can virtually be eliminated by injection or immediate incorporation of the manure into the soil. These techniques also increase the amount of nitrogen and other nutrients available for crop uptake. Unfortunately, injection and incorporation are techniques most easily adapted to liquid manure application. Incorporation of solid manure typically requires another pass with some tillage implement. This is both time consuming and costly but is necessary to achieve effective odor control.

Another aspect of manure application that generates odors is the agitation of liquid manure storage facilities prior to manure removal. Agitation is necessary to reduce the solids buildup in storage, break up any surface crust, and evenly distribute the nutrients throughout the manure. Reports from many livestock producers suggest that some manure pit additives reduce solids buildup in the storage units. Although there is little university research to support this claim, this technique should be viewed as a possible odor control method. Chemical additives also have the potential to reduce specific gas formation such as hydrogen sulfide during agitation. These additives will have an immediate, short-term effect on gas emissions.

More research is needed to determine dosage rates and costs for this technology. The issue of reduction of odors and/or certain gases like hydrogen sulfide (especially in Minnesota due to the state regulatory agency's H2S emission standard) during manure storage agitation is very critical. Weather conditions, primarily wind speed/direction and humidity should be evaluated before manure is land applied to insure minimal impacts on neighbors and the public. The weather least suitable for spreading manure is high humidity and very light winds or clear, calm evenings. This condition prevents odors from dispersing and thus increases the chance of creating a nuisance or receiving a complaint

Chemical Activities of Soil

Enzyme, the biological catalyst extracted by microorganisms in their living activities, can accelerate the reactions of all biochemical activities of the soil. Results showed that at 0-8 inches below soil surface near the tree) showed more activity of invertase, hydrogen peroxidase, etc. which led to the increase of decomposition of organic matter, composition of humus and oxidation of other components to increase soil fertility.

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3. Odor Control for Animal Agriculture, page 2

Paulownia Foliage as Manure 4

The above analysis shows that PCI caused crop-favored changes in soil properties and nutrient status. It should be noted that all the above changes occurred when Paulownia foliage (80%) was not collected from the field. Local farmers usually collect Paulownia leaves for fodder. If all the Paulownia leaves are left in the field as litter, this will lead to greater changes in soil property and nutrition status in PCI system. The experiment of fertilization was conducted using 2.94 tons of dry Paulownia leaves applied to 2.5-acres open field. The result indicated 30.6% increase of wheat yield and 19.8% increase of cotton yield.

Paulownia foliage is a very good resource for manure and fodder. According to a survey made, there were 24 million Paulownia trees in Luyi County of Shandong Province. The Paulownia trees produced 354,000 tons of leaves which contained about 9,310.2 tons of nitrogen, equal to 20,239.56 tons of urea, crude protein 57,723 tons and crude fat 36,679 tons, 23.244 tons of dry flowers were produced which contained about 1.036 tons of nitrogen, equal to 2,253.7 tons of urea and 6,427 tons of crude protein. The total from both leaves and flowers in the county led to 22,493 tons of urea.

Disinfectant Role of Leaf Secretion 4

The aim was to study the disinfectant role of Paulownia leaf and the possibility to use Paulownia trees in purifying air. This study needed high-level test conditions and so it was conducted in laboratory. The experimental results indicated that:

1. The compounds volatilized from Paulownia leaves can kill Tubercle bacillus (with a rate of 100%). Among the 36 tree species tested, Paulownia, Sorbaria kirilowii and Hibiscus syriacus showed highest antibacterial effect.

2. Paulownia had no effect on Staphylococcus aureus, but it was lethal to Psudomanas aeruginosa (38.8%).

3. Paulownia leaf paste had strongest effect to kill flies among the 20 tree species tested.

Portions of the Complete Study were Condensed & Edited for Republication Purposes

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4. Evaluation and Model Optimization of Paulownia Inter-Cropping System-A Project Summary Report,

International Development Research Centre, Page 9

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