Progress report for FNE21-979
This project plans to measure two low tech composting systems--windrow, and low cost/low tech aerated static pile (ASP)--side by side and compare them, both in terms of cost (labor, fuel, equipment usage and wear and tear), time and quality of finished compost (nutrient content, biological activity, pH, moisture, etc.). Initial piles will be assembled at the same time, utilizing the same volume of materials and the same “recipe”, including C:N ratio. Our objectives are stated via the questions we seek to answer:
- What cost savings are possible with ASP versus windrow composting (labor, equipment, fuel)?
- What amount of feedstock can be processed and what quantity of finished compost can be produced in a year utilizing ASP versus windrow composting?
- What are the physical, biological and chemical properties of compost produced using ASP versus windrow composting?
Problem: The region where Honey Brook Organic Farm is located produces a lot of organic materials currently not being recognized for their value as compost feedstocks. There is an overabundance of horse manure and bedding not being managed in an ecologically sound and sustainable manner. Instead, these materials are either landfilled or stockpiled on the farms where they originate, potentially generating odors, attracting pests and contributing to ground and surface water pollution through loss of valuable nutrients.
In addition, soils in the region where Honey Brook Organic Farm is located include a significant percentage of sandy loams and loamy sands that are typically low in organic matter and Cation Exchange Capacity (C.E.C.). A low C.E.C. means the soil has reduced capacity for holding onto applied nutrients, which can lead to more leaching of fertilizers into groundwater or running off into surface water.
Honey Brook Organic Farm applies between 6 and 10 tons of compost per cropped acre each year in an effort to correct these soil deficiencies. With approximately 110 acres in production, this amounts to a seasonal need of about 880 tons of finished compost.
As with many organic farms, composting has played a critical role in the farm’s vegetable production system. The farmers have used a traditional windrow method of composting, turning piles with a large wheel loader. Compost feedstock consists mostly of horse manure in sawdust bedding but can also include municipally-collected leaves and woodchips. This material is very active, heating readily and requiring frequent turning to introduce oxygen into the system and to check excessive heat generation in the composting materials. With the demands of, at times, an overwhelming amount of other farm work and the difficulty of finding loader-savvy staff, it can frequently be difficult to turn piles at optimal times. Additionally, this composting method typically takes 6-12 months to produce finished compost, and requires the utilization of a large area (approximately 3 acres), which could be used for active cultivation. This is especially relevant since Honey Brook Organic Farm plans to decrease the acreage farmed at other sites.
Although the farm has breathable textile covers which, when deployed, shield the composting materials from excessive rainfall, the frequent turning requirement and labor shortages mean that the covers are not used until the final turning. This can result in more leachate formation than is ideal.
Solution: Kinsel proposes to pilot the development of a low cost, low tech Aerated Static Pile (ASP) composting system for processing of horse manure/bedding, leaves and wood chips. The ASP system will be compared side-by-side with the windrow system to determine which is most efficient, economical and ecological. The ASP system also offers the advantages of rapid 30 day cycle time to finished compost, on a smaller area footprint without turning that will make it easier to protect the materials from potential leachate runoff.
Beyond the benefits provided to Honey Brook Organic Farm, this project will demonstrate to the local farming community the efficiencies that can be obtained when working cooperatively to address what is essentially a solid waste problem, and opportunity. It should be noted that the area where Honey Brook Organic Farm is located contains the highest percentage of permanently preserved farmland in the state of New Jersey. New Jersey in general has a large number of horse farms, and with the average horse generating 51 lbs. of feces and manure and up to 15 lbs of spoiled bedding per day, effective manure management is a pressing issue and one that, through research for this grant it has been discovered, though acknowledged as a problem has received scant research attention.
A successful demonstration project, particularly one that is low cost and low tech, will encourage other landowners and farmers in the area to use readily-available feedstocks and to potentially install their own ASP composting systems, thereby enhancing their farms’ economic and ecological viability. Once this happens, a variety of local options will become available for producers/generators of horse manure and wood chips, solving a currently-existing logistical problem of long delivery distances via large truck. This will increase time and cost efficiencies, and also decrease carbon emissions. This management approach will also have the effect of decreasing water pollution through loss of nutrients. These are all valuable elements, particularly in light of the system vulnerabilities exposed by Covid-19 and global warming.
- - Technical Advisor
The primary goal of this project is to compare the current system of windrow manure composting to manure composting done via an ASP system. Achieving compost processing efficiencies would allow the farm to utilize more of its land for crop production, to save time and money on labor and fuel and to return larger quantities of compost to the fields in a quicker turnaround time, which will boost soil resiliency.
The initial windrow and batch one of the ASP will be constructed at the same time, using the same quantities and mixtures of material. The footprint for each will be approximately 40 feet long by 26 feet wide. Pile height will be approximately 7.5 feet. We will utilize homogenous manure and bedding material, assuring the proper Carbon to Nitrogen (C:N) ratio of between 20-30:1. Each pile will consist of 170 yards of material, with the ASP piles containing an additional 40 yards of woodchips to act as a biofilter. Piles will be aerated with a positive air flow system using a continuous timed blower. It is anticipated that 170 yards of manure and bedding feedstock material will be composted in every ASP cycle. Woodchip biofilter material will be recovered and reutilized. Cycles are anticipated to take 60 days (30 days in the active phase on air, and 30 days to cure). This process might take longer in the colder months. It is anticipated that new batches will be constructed on the ASP system every 30 days, weather permitting.
In both windrow and ASP systems moisture, density and temperature will be assessed, assuring that the Process to Further Reduce Pathogens (PFRP) threshold of 55oC (131oF) or higher for a minimum of 3 days, is achieved. Temperature will be taken 3 times a week using either a continuous temperature probe or manual probes. Temperatures will be taken at different heights and depths in the pile.
The following information will be recorded for each batch: Date pile was assembled, C:N ratio and total material volume, labor (time) spent assembling, monitoring and managing the batch, temperature (two probes in each pile), moisture content using squeeze test, density using field density test, electricity use and cost (if possible). Plans are to test finished compost (one composite sample per pile) as follows: For the ASP piles, Batch 2 and will be tested for standard compost nutrient analysis (Total N, Organic N, P, K), pH, %OM, Respiration (Solvita), Stability/Maturity, EC, Na, Cl and pathogens. If batch 2 and 3 are consistent, testing will be done again at Batches 5, 9 and 12. If they are inconsistent testing will be repeated for Batch 4, then again at Batches 6 and 8 and 12. 503 metals will be tested in the final Batch. The windrow compost will be tested at 12 months, using the same parameters.
Education & Outreach Activities and Participation Summary
The New Jersey Compost Council presented a course focusing on learning the fundamentals of ASP (Aerated Static Pile) Composting on September 8 & 9, 2021. The course was designed for Farmers, Compost Operators, municipalities, consultants and others and allowed participants to understand if ASP was a good fit for them, how it works and what is needed to either get started or improve their current processes. A hands-on site demonstration was conducted of Honey Brook Organic Farm's ASP composting project.
Participants earned Rutgers Continuing education credits and USCC Compost education credits and was live-streamed over Zoom. The course lecturer was Peter Moon, our ASP composting consultant. Peter has over 35 years of consulting experience, over two decades of which is specific to organics waste management. Peter started O2Compost in 1996 and since that time, has designed and constructed over 500 aerated compost systems for municipal, institutional and agricultural facilities. He is a licensed civil engineer in the State of WA. O2Compost has evolved over the years to become a recognized leader in training owners/operators on the Aerated Static Pile method of composting. Course participants were also entitled to a free consult with Peter Moon to answer any additional/specific questions they hadn't had the opportunity to ask during the course.
As part of its monthly Grower & Farmer Speaker Series, Jim Kinsel shared information about our ASP demonstration pilot for composting of manure, wood chips and leaves on our certified-organic produce farm. The October 18, 2021 NOFA-NJ tour was posted on YouTube, which can be viewed here.
Lastly, American Farm Publications published an article in its January 15, 2022 edition about Honey Brook Organic Farm's ASP composting system.
We did not specifically request that participants to either of the two workshops report feedback, however two farmers who farm for a non-profit organization offered that they hadn't previously realized how easy and inexpensive the ASP system could be.
James Kinsel, the lead farmer in this project, came to appreciate the following:
- The extended period of high temperatures generated by the composting material.
- The difficulty of achieving proper moisture content for the duration of the composting period.
- The special equipment requirements for drawing hot humid air from the pile instead of exhausting air into it.
- The simplicity of simple windrow composting and forgiving nature of the compost materials when composted using the simple windrow method.
We are still evaluating ASP composting for the feedstock available to us. The ASP pile was still very hot and active after two months, which is a much slower turn-around than anticipated.
Farmers traditionally compost what is readily and cheaply available. This will impact what farmers are prepared to do to optimize the parameters (ie C/N ratio, porosity, density) that influence the compostability of feedstocks. The ASP project was conducted in Chesterfield, NJ where we have been receiving what appears to be consistently uniform horse manure in sawdust bedding from a large equine training facility for several years. To date, we had composted this material without any additions, using a traditional windrow system which involved turning the piles several times over the course of a 10 month period and then making field applications at the end of that time. The windrows typically heat to excess of 160 degrees F fairly quickly and then stay above 150 degrees for an extended period, with the temperature dropping as the material dries out during the late summer. We do not irrigate the piles, but instead wait for fall and winter precipitation to reactivate the piles, which they do and heat again to 140 degrees. The windrows dry down in late summer despite longitudinally overlapping the windrows during a late summer turning to capture precipitation and minimize any leachate formation.
Although Peter Moon advised against the efficacy of attempting to irrigate the feedstock during ASP composting, we did make the effort using multiple runs of drip irrigation with partial success. As Peter Moon advised, we will add water to the feedstock during the formation of the next ASP pile which we are currently constructing.
My preliminary assessment of the ASP system, is that ASP may be more appropriate for some high density, high moisture feedstocks like food waste, some animal manures without bedding and leaves (for ensuring a high enough temperature to kill grass seeds). However, the horse manure in sawdust bedding which is available to us at no cost composts readily using the traditional windrow system with periodic turning. We do this turning using a 2-yard loader, which staff has been easily trained to use. The feedstock is also so forgiving that these turnings can occur when time is available, which eases labor management. ASP requires much tighter management and greater expertise, which complicates labor management. Since we have accepted and planned that finished material will take 10 months to finish, this means the faster composting time for ASP is not an asset to our operation. There is no discernible difference in compost quality, although we still need to send samples for analysis. Space for composting is also not a constraint for us.
We expect to run several more ASP cycles before project completion. These will focus on time and labor cost features for comparative purposes.
One obvious observed benefit to ASP composting for our farm is the potential use of the massive amounts of heat for a prolonged period generated by the process. We experimented with an inexpensive higher volume inline blower which pulled heat out of the pile with impressive results, although the blower failed from the heat and humidity in less than a week.
We are changing our farming operation to include high tunnels of in-ground cold-tolerant fig trees as well as figs in media-filled Macrobins which will be overwintered in a greenhouse with propane heat. We would like to minimize propane use for environmental as well as cost reasons. We are currently running a secondary experiment with an ASP pile where we are constructing the pile with a heat extractor added above the aeration pipes in the feedstock. Although possible to directly vent the ASP air system into a greenhouse, we have decided that this heated air would be too high in humidity and may cause problems with plants in the greenhouse. The heat extractor consists of 11 runs of 1" PE pipe running the full length of the ASP pile with 4" manifolds at both ends with each manifold conducted through 4" pipe into an adjacent 30' x 96' greenhouse with an attached blower. We will provide results for this experiment along with the final report.