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EVALUATION OF COMPOST FACILITY
RUNOFF FOR BENEFICIAL REUSE PHASE 2
TABLE OF CONTENTS Introduction........................................................................................................................... 1 Section 1 - Investigation of Market Potential................................................................... 3 1.1 Nutrient Value Assessment....................................................................................... 3 1.2 Comparison to Other Commercially Available Organic Products............................... 4 1.3 Results of Commercial Outlet Survey........................................................................ 6 1.4 Investigation of Horticultural and Agricultural Use...................................................... 8 1.5 Investigation of Potential Commercial Value............................................................ 10 1.6 Preliminary Investigation of Transportation Costs.................................................... 12 Section 2 - Dewatering Demonstration........................................................................... 14 2.1 Dewatering Description.......................................................................................... 14 2.2 Thermodynamics Discussion................................................................................... 17 2.3 Product Testing Results.......................................................................................... 18 Section 3 - Bench Scale Growth Trial.............................................................................. 20 3.1 Growth Trial Description........................................................................................ 20 3.2 Growth Trial Details............................................................................................... 21 3.3 Runoff Strengths/Dilutions....................................................................................... 22 3.4 Nutrients Applied................................................................................................... 23 3.5 Growth Trial Results............................................................................................... 24 3.6 Love Israel Field Trial Results................................................................................. 26 3.7 Data Interpretation................................................................................................ 26 3.8 Growth Trial Conclusions....................................................................................... 28 3.9 Strawberry Growth Trial........................................................................................ 28 Section 4 - Economic Analysis Summary and Worksheet.............................................. 29 Summary and Conclusions................................................................................................... 32 Acknowledgments/Information Dissemination Efforts............................................................ 34 Tables Table 1 - Runoff from Four Facilities (Range of Data) 2 Table 2 - Commercial Value of Nutrients in Runoff 3 Table 3 - Runoff Value Assessment 4 Table 4 - Product Descriptions 5 Table 5 - Retail Outlet Survey Participants 7 Table 6 - Agronomic Needs of Crops 8 Table 7 - Calculation of Maximum Agronomic Loading of Tea on Corn Crop 9 Table 8 - Market Value of Commercially Available Organic Fertilizer Products 10 Table 9 - Value Estimate for Cedar Grove Tea 11 Table 10 - Transportation Cost Estimate 13 Table 11 - Time and Temperature Relationships for Pathogen Destruction 17 Table 12 - Test Results for Runoff Sources 18 Table 13 - Results of Concentration Test 19 Table 14 - Growth Study Summary 20 Table 15 - Runoff and Fertilizer Nutrient Comparison 22 Table 16 - Determination of Runoff Dilution Rates 23 Table 17 - Nutrient and Water Loading Rates 23 Table 18 - Total N, P, and K applied (mg/plant) 23 Table 19 - Growth and Potassium Application Differences 27 Table 20 - Results of Strawberry Growth Trial 29 Table 21 - Department of Agriculture Cumulative Nutrient Loading Limits 33 Table 22 - Washington State Standards for Metals 33 Figures Figure 1 - Pilot Dewatering System Description 15 Figure 2 - Runoff Treatments vs. Control Plants for Radish Plant Group 25 Figure 3 - Dry Weight, Flowers, and Buds - Treatments vs. Control Plants 25 INTRODUCTIONThe Clean Washington Center (CWC) funded a two phase project to examine compost facility runoff. The runoff is a pollutant for many of the same qualities that would make it a plant nutrient. Nutrients in the runoff can have a detrimental effect on surrounding surface waters because of the increased plant growth caused by the presence of nitrogen, phosphorus, and potassium. These nutrients are all considered beneficial when added at correct rates to agriculture, gardens, and house plants. Runoff is a major problem for compost facilities. For these reasons, the CWC is interested in developing a marketable product from the runoff. This report contains the findings of the second phase of the compost tea project. Phase 2 looked at implementing concentration techniques and market potential for a tea product. Phase 1 of the project consisted of characterizing the runoff by visiting four facilities, collecting samples during three storm events, and analyzing them for several constituents (BOD, TSS, pH, nutrients, salinity, fecal coliform, color, and a few metals). This report contains some data from Phase 1. The complete report for Phase 1 is available through CWC (Report #CM-97-4, Evaluation of Compost Facility Runoff for Beneficial Reuse). With the lab data from Phase 1, it was possible to determine if the material had nutrients in quantities that would be desirable in a commercial product. Comparisons were made to several commercial organic fertilizer products currently available on the market, and the runoff compared quite favorably. In addition, estimates of the nutrient content of a concentrated product and estimates for commercial value (based on the N:P:K of the products and the concentrated runoff) were made. Growth trials were conducted to determine if the runoff had positive or detrimental effects on plants. Plants were grown and measured for bud/flower production and green mass (marigolds) and root and green mass (radishes). A summary of the results, as compared to MiracleGro and water, are shown in Section 3.5. Table 1 - Runoff from Four Facilities (Range of Data)
* except where noted Phase 2 of the project examined concentrating techniques to produce a thick and commercially viable product. These were conducted at a local large-scale yard debris compost facility. Techniques examined included using residual heat from the composting process and blending pond solids with blower condensate. 1.0 INVESTIGATION OF MARKET POTENTIAL 1.1 Nutrient Value AssessmentAn assessment of the value for the runoff nutrient content is presented in this section. The nutrients in the runoff are considered a pollutant for the same reason that they can be considered a valuable asset. The nutrients are considered a pollutant in surface waters because they cause unnaturally high plant growth rates. Just as these nutrients promote the growth of plant life in surface water bodies, they can be used to promote the growth of agricultural crops, with proper attention to treatment and agronomic loading. In order to assess the value of the nutrients in the compost tea, a comparison was made to the commercial value of nitrogen, phosphorus, and potassium. The pounds of each of these common fertilizers was calculated per 10,000 gallons of runoff based on the average analysis. Table 2 shows the cost of inorganic fertilizers based on the purchase of 50 lb. bags. These quotes were obtained from the Farm Supply Co-Op (Everett, WA). Table 2 - Commercial Value of Nutrients in Runoff
This project examined the quantity of these elements available (on average) in the runoff from each of the four facilities. Table 3 shows the average values for the four facilities and the value of the nutrients available in the runoff. Dry pounds per 10,000 gallons of runoff was calculated for those elements present in the runoff. Dry pounds of each element was calculated as follows: 10,000 gallons x 8.34 lbs/gallon x % solids x ppm or mg/kg of element / 1,000,000 Based on the value presented in Table 3, a value in $/10,000 gallons of runoff was calculated. Using an average of runoff from four facilities, a value of $37 per 10,000 gallons was calculated. This was a hypothetical value and based solely on the nutrient value. Although difficult to quantify, the runoff also contained valuable organic material. The product will have no value unless consumers are educated about its value. Depending on the compost feedstocks, the product may need to be treated first to ensure safety (destruction of pathogens) and into a form consumers would want to purchase. Table 3 - Runoff Value Assessment
1.2 Comparison to Other Commercially Available Organic Products Many organic nutrient supplements are available on the market. Several of these products were examined and compared to the compost tea product from Cedar Grove. Cedar Grove is a large-scale composting facility which has large quantities of runoff to contend with. Currently, the material is collected in ponds and either reused on site or discharged into the King County sewer system for a fee. The comparison to Cedar Grove tea was made because the site produced large amounts of runoff, the organization was enthusiastic about the opportunity to develop a new product, and the facility handled primarily yard debris (and a small amount of other organics). Commercially available products are either in a liquid form or in an emulsion (semi-liquid) state. Each product requires reconstitution in water to dilute it to an appropriate nutrient content, with doses ranging from 1 tablespoon per gallon to 1/2 cup per gallon. Foxfarm™ consists of worm castings, bat guano, mined potash, and kelp. Alaska Fish Fertilizer™ is an emulsion of fish industry by-products; Maxicrop™, SeaSpray™, and Concern ™ are all liquefied seaweed (kelp). Table 4 represents a wide range of N:P:K ratios for these products, as well as the liquid from two sources at Cedar Grove. Most of the products also show analysis data for organic, water soluble nitrogen and ammonia nitrogen. Local retailers stated that the kelp products were “like magic” and often recommended them because of their high trace mineral and growth hormone content. None of the three kelp products included in this study had any printed information about these constituents on their labels. Since the sellers recognize that these are healthy for plant growth, it may be advantageous to analyze and label the compost tea product. The ponds collect material from the entire site. Aerators in the ponds help to keep the liquid aerobic and help limit odors. Thick, settled material was taken off the pond bottom and analyzed. In addition, the liquid coming off the compost blowers (which draw ambient air through the piles) as condensate was sampled and analyzed. An extrapolation was made to show what the nutrient content would be if the liquid was concentrated.
Table 4 - Product Descriptions
The analysis for the solids drawn off of the bottom of the pond showed that the material was approximately 20% solids (a semi-solid state) with a N:P:K ratio of 2 : 0.3 : 0.7. This material may be suitable for sale as is, depending upon the pathogen content. The blower condensate, which was generally stronger than the runoff from the rest of the facility, also eventually ended up in the detention basin pond. This material added much of the BOD5 content to the pond. This, in turn, increased the strength of the discharge to the sewer system. If the blower condensate could be diverted from reaching the pond, the strength of the discharge would go down. An analysis of the blower liquid showed that if it was concentrated to 16% solids, it had a N:P:K ratio of 3.2 : 0.1 : 1. 1.3 Results of Commercial Outlet SurveyA phone/fax survey was completed to investigate the potential for bringing a compost tea product to market. The participants were told that the CWC had a mission to expand markets for recycled goods, and organic residuals were a target waste. Participants were also informed that the tea product was a concentrated derivative of the rainfall runoff from compost facilities, which contained organics and nutrients from contact with the compost. Eight retail outlets were contacted for feedback (listed in Table 5), ranging from nurseries, garden stores, groceries, and home improvement stores. The participants were told that the tea product would be marketed as a companion product to Cedar Grove Compost. The questions on the survey included the following: · Would a liquid organic nutrient supplement as a companion product to Cedar Grove Compost be of interest to your retail market? · Preliminary testing indicates that the product will have nutrient content (N:P:K) in the range of 2 : 0.5 : 1 in the bottle at approximately 20% solids (about the consistency of Alaska Fish Emulsion™). Is this a desirable nutrient content, or would a sweetened product be better? (Products are sweetened by adding bone meal or blood meal in order to raise nutrient percentages). · What type of packaging would you like to see? · What would be the optimum container size? · Would several container sizes be desirable? · Do you have a preference for container type (bucket vs. bottle)? · If a compost tea product is developed and priced competitively or lower than similar organic supplements, would you make shelf space available? · Any additional comments?
Table 5 - Retail Outlet Survey Participants
The majority of the participants had a great deal of interest in a product for sale in a bottle. All expressed more interest in a product which was tied to a proven product (the product that sells well has a proven track record and the companion product will likely have less to prove). The preferred container type was a half gallon or one gallon plastic jug with a handle, similar to a bleach bottle. Several retailers expressed interest in having the bottle recyclable or even made of recycled plastic. Other concerns included the contaminant content in the tea, particularly pesticide content. The budget for this project did not allow for extensive contaminant testing, but any product produced should be tested for pesticides, coliforms, metals, etc. One retailer expressed concern about possible pesticide content in the Cedar Grove Tea. The nutrient content did not seem to be a primary concern to the retailers, although one participant thought it should be sweetened to raise nitrogen levels. In addition, there are several seaweed extracts that work extremely well that contain growth hormones and trace minerals but little N:P:K. Most retailers expressed that if the product works, N:P:K is fairly irrelevant. All participants stated interest in carrying the product. 1.4 Investigation of Horticultural and Agricultural UseThe use of this tea material in an agricultural setting is another possibility and would require loading the tea on the land at a rate which would not exceed the nutrient needs of the crop being grown. Loading to the nutrient needs of the plant is known as the agronomic loading rate. Agronomic loading for several crops is shown in Table 6. Agronomic loading is based on a limiting factor, or maximum pounds per acre of N, P, or K allowed per acre. This limiting factor allows for a calculation of maximum application rate in order to avoid surpassing the N, P, or K loading for the crop. These are general numbers and users should check with a local agricultural extension agent to account for site and soil specific conditions. Table 6 - Agronomic Needs of Crops in lb/acre
EPA, 1987 Table 7 shows the calculations made to determine the maximum loading rate of Cedar Grove compost tea to a hypothetical corn crop. These numbers are general loading assumptions, and any application rates should be checked with a local agricultural extension office. The pounds of N, P, and K per 10,000 gallons of tea, as calculated in Table 3, are shown in the second column of Table 7. The agronomic nutrient needs for corn are shown in column three. The maximum allowable gallons per acre without exceeding the nutrient needs are shown in column four. The lowest of these is the maximum allowable application rate. In this case, the limiting factor is the potassium content of the tea, and 17,900 gallons can be applied per acre. This is equal to an even distribution of 0.7 inches over the entire acre. The following is a sample of these calculations (using the available nitrogen from Table 3): 1211 ppm N dry wt. ------------------------- x 8.34 lb/gal x 10,000 gallons = 101 lb N/10,000 gallons 1,000,000 10,000 gal 180 lb N -------------- x ---------- = 17,900 gallons/acre 101 lb N acre 17,900 gallons ft3 acre 12 in ----------------- x --------- x ------ x ------ = 0.7 inches acre 7.48 gal 43,560 ft2 ft Table 7 - Calculation of Maximum Agronomic Loading of Tea on Corn Crop
For example, if a crop of corn is grown, an agronomic load of 200 lb/acre of nitrogen, 35 lb/acre of phosphorus, and 180 lb/acre potassium is needed. The runoff contains 48.7 lb N per 10,000 gallons, and therefore to achieve 200 lb N per acre, 200/48.7 x 10,000 gallons of runoff would be applied. To achieve the maximum potassium loading rate, 180/100.7 x 10,000 gallons of runoff, or 17,900 gallons would be applied. For this example, a farmer could apply 17,900 gallons of runoff per acre without exceeding agronomic loading rates. This 17,900 gallons per acre equals 0.65 inches of runoff per acre per year (17,900 gallons / 7.48 gallons/cubic feet / 43,560 sq. ft. / acre x 12 inches/ft = 0.65 inches/acre/year). Again, this loading rate can only be applied with DOE approval of pretreatment practices and with Washington State University (WSU) agricultural extension approval. The approval process should begin by contacting the local DOE office to discuss plans for runoff generated at a site. If treatment and discharge to surface water is planned, the DOE would require an NPDES stormwater permit, which regulates quantity and quality of discharge. Applications to contain all of the runoff and reuse it for agricultural use must comply with the Washington Administrative Code (WAC 16-200-7063), four-year cumulative total nutrient loading limits, or with agronomic loading for the chosen crop. Limits for metals loading per acre per year are contained in WAC 16-200-7-64. 1.5 Investigation of Potential Commercial ValueThe following section describes the retail value of commercially available products and derives a conceptual retail value for the Cedar Grove tea. This conceptual market value for the tea product was compared to the cost of concentrating, handling, and bottling to determine the feasibility of such a product. Table 8 shows the market value of the five products, as well as nutrient and value comparisons. One product was specifically chosen for comparison (half-gallon size, Alaska Fish Emulsion™). The emulsion was sold in a concentrated form and had instructions for dilution in order to properly apply nutrients. Side panel information stated that the product contained an N:P:K ratio of 5:l:l, with a solids content of approximately 18%. The half-gallon plastic jugs sold at the retail level for $7.99. Table 8 - Market Value of Commercially Available Organic Fertilizer Products
A tea product can be sold in many container sizes and types. The example shown in Table 9 assumes that it will be sold in gallon jugs. The closest comparison to this was the Alaska Fish Emulsion™ product, which sold at $7.99 per half-gallon plastic bottle. This was equal to a retail price of $15.98. This example assumes a wholesale value of $5 per gallon for the Cedar Grove tea. The N:P:K ratio of the materials drawn off the pond bottom was 2:0.3:0.7, with a total solids of 20%. With proper disinfection (to eliminate fecal coliform and other pathogens), this material may be adequate for sale. It had a comparable N:P:K and had a similar consistency to the Alaska Fish Emulsion™. The blower condensate material was, as mentioned earlier, stronger than the runoff from the rest of the site. Table 9 shows how many gallons of blower condensate were needed to produce 2000 gallons of concentrated tea at 16% solids. The calculation shows that 64,000 gallons would be required to produce the 2000 gallons of tea from the blower condensate. The site had a storage capacity of approximately 8.5 million gallons of runoff, with the blowers generating between 0 and 5000 gallons of condensate per day. Table 9 - Value Estimate for Cedar Grove Tea
Table 9 shows that the nitrogen content of the runoff was very close to that of the emulsion product. The phosphorus average was slightly less, and the potassium was much higher. As mentioned in the previous section, potassium encourages root growth and improves plant resistance to disease. Potassium also increases the size and quality of fruit and increases winter hardiness. Potassium should not be applied at greater than the agronomic rates for the same reasons that it is not wise to over apply nitrogen (potential runoff to surface water). Phosphorus is also present in the runoff. The role of phosphorus in plant growth is important to several processes, including photosynthesis, respiration, and fatty acid synthesis. Heavy concentrations of phosphorus are found in regions of the plant involved in the synthesis of nucleoproteins. Plants lacking in phosphorus may develop dead areas on the leaves or fruit, have a general stunted appearance, and may have leaves with a dark blue-green coloration. Addition of other nutrients can sweeten the tea as well. Nitrogen can be sweetened with the addition of bloodmeal (N:P:K of 14:0:0), and phosphorus can be raised using bonemeal (N:P:K of 2:11:0). A 100 lb bag of bonemeal will add 14 lbs of nitrogen to the mix, and a 100 lb bag of bonemeal will add 11 lbs of phosphorus. This is an inexpensive and easy way to change the N:P:K ratio of the runoff to suit the needs of retailers or farmers. 1.6 Preliminary Investigation of Transportation CostsCosts associated with the transport of the liquid can be estimated by comparison to the transport of biosolids to agricultural sites. Biosolids are transported at approximately 20% solids, and their density is similar to that of water (since they are 80% liquid). These costs can be compared to the cost for disposal to the sewer and to the value of the product to determine if the economics favor transportation to a site. A major metropolitan area in the United States estimates that a 100 mile round trip costs approximately $3.50/wet ton, or approximately 1.3 cents per gallon, or 0.013 cents per gallon/mile. This cost accounts for labor, fuel, operations, and maintenance. This is an approximation for the costs associated with the transport of the runoff from a compost facility in a tanker truck. King County charges a fee for discharge to the sewer of high strength runoff. The 1998 fees are $0.124125/lb of Biochemical Oxygen Demand (BOD) and $0.181032/lb of total suspended solids (TSS). Assuming that a facility discharges a runoff with 2500 ppm of BOD and 2500 ppm TSS (0.25% solids), the fee for discharge is 0.114 cents per gallon. Using this estimate of 0.114 cents per gallon discharge fee and the estimate of 0.013 cents per gallon/mile for transport, an estimate for a break-even distance for transport of the liquid can be calculated. The distance to which the liquid can be hauled without incurring costs above what it would cost to discharge to the sewer in King County is 10 miles (0.114 cents per gallon divided by 0.013 cents per gallon/mile). These estimates are examples only, and all calculations should be based on a sites operating and actual discharge costs. The discharge costs for a facility depends upon the strength of the runoff. This example uses an average runoff strength. Other facilities may have much stronger or much weaker liquid, which could dramatically change these calculations. The sample calculations are summarized in Table 10. Table 10 - Transportation Cost Estimate
These estimates did not include any fee gathered from the farmer. Value of the liquid has been estimated and based solely on nutritional content in an earlier section. This value was approximately $37/10,000 gallons or $0.37 cents per gallon. If this fee could be obtained from a farmer, the break even distance would increase to approximately 40 miles round trip. This distance would include delivery to the site only, not application to the field.
2.0 DEWARTING DEMONSTRATON2.1 Dewatering DescriptionThe dewatering demonstration portion of this project employed a concentration technology using the residual heat from the compost process. Cedar Grove used an aerated static pile composting system, which drew ambient air through the hot pile to provide oxygen to the microbes and strip heat out of the process. The hot, saturated exhaust air was sent through a condensate trap chamber and then through a biofilter for odor control. In order for the biofilter to operate correctly, the exhaust air (approximately 140-150o F) had to be cooled to below 130o F. At Cedar Grove, two methods were employed to cool the exhaust. First, a chamber with a greatly increased diameter existed between the fans and the biofilter, allowing for the flow to slow and heat to dissipate through the walls of the chamber. This chamber was approximately 100 feet long and was surrounded by a greenhouse, which used the residual heat. This method has not always been adequate to sufficiently cool the exhaust, and a tower has been installed to divert a portion of the hottest air to the atmosphere. This hot air stream was used to heat the pondwater to improve the thermodynamics of the concentration apparatus. Figure 1 - Pilot Dewatering System Description
source discharge compost process heat stack Steps for concentrating pond liquid: 1. Fill evaporation tower to fill line from blower condensate drain. 2. Start circulation pump to heat liquid and spray into tower. 3. Continue to circulate until desired consistency is achieved. 4. Air flow is heated to 200 oF with heater (this did not occur at our site test - equipment was not available - this would have improved the transpiration of the water to the atmosphere). 5. Fill bottles with Compost Tea. 6. Heat can disinfect tea - would have to monitor temperatures and retention times (see time and temperature relationship equations below). The time and temperature relationships for destruction of pathogens in sewage sludge are shown below. Equation 1 is for sludge with a solids content greater than 7% solids, and Equation 2 is for sewage sludge with a solids content less than 7% solids. This material had a solids content less than 7% solids and Equation 2 was used in estimating pathogen destruction in the pond liquid. Detention time (D) is in days, and temperature (t) is in oC. Temperatures had to be at least 50o C and a minimum time of 20 minutes to ensure proper mixing. Using Equation 2, the required detention times for several temperatures were calculated and are shown in Table 11. As can be seen, there is a wide range of detention times required over a relatively small increase in temperature. Equation 1 - Sewage sludge at least 7% solids: D = 131,700,000/100.1400t t >= 50o C (122o F) Equation 2 - Sewage sludge less than 7% solids: D = 131,700,000/100.1400t t >= 50o C (122o F) Table 11 - Time and Temperature Relationships for Pathogen Destruction
The design and operation of this setup did not generate enough heat to concentrate the liquid. Supplemental heat needed to be added in order to accomplish the goals originally set. The four loops inside of the exhaust tower did not allow for enough residence time to transfer sufficient heat. Future trials should employ more loops and longer detention time to allow for better heat transfer. The process will work if heat is transferred from the exhaust to the water; the hotter the exhaust, the shorter the detention time. Additional design time should be spent to further investigate the time and temperature relationships required to drive off the water. 2.2 Thermodynamics DiscussionThe thermodynamics of the system set up at Cedar Grove did not allow for enough water to be driven off to concentrate the liquid very much. The system did not transfer as much heat to the water as was necessary. The air leaving the exhaust stack ranged from 100-115o F, and the black flexible PVC used to run the water through the stack did not transfer heat well. Future projects should use more loops inside the stack. This project used 4 loops, and a minimum of 12-15 should be used. In | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
