Session- Compost Quality
Compost quality: an Italian approach
Fabrizio Adani
Ricicla Group DiProVe Universti degli Studi di Milano, Italy
Lombard Region (1999) (North Italy) has introduced, recently, guidelines for compost production and compost quality (Scaglia et al., 2000), representing it a first example of complete composting rules. Guidelines paid particular attention to compost quality using parameters, analytic methodologies and limits that came out from a collaboration between public administration (Region) and scientific institution (Ricicla Group of the Dipartimento di Produzione Vegetale - University of Milano) (http://users.unimi.it/~ricicla/ricicla.htm). Composting subjects such as stability, maturity and organic matter evolution, that well represent compost quality, has been defined and new analytical methods set up and proposed. Biological stability was defined as an index of the microbiological activity, therefore a direct determination of this activity should be the best methods for its measure. Respirometric test (oxygen uptake) well match this requirement. Respirometric methods can be divided in static (SRI) and dynamic (DRI) depending by the presence of absence of aeration during respirometric measure. Dynamic approach was developed by our group and included in the rules. Practical uses of DRI have been developed in the last years and results will be presented during the conference. Maturity has been defined as the absence of phytoxicity. Therefore biological methods such as germination and vegetation tests have been proposed in the past. Vegetation test developed for sewage sludge has been re-proposed for compost and included in the rules. Experimental design and results expression will be presented. Composting process proceeded by degradation and humification. These two moments represent the evolution of the organic matter and the Organic Matter Evolution Index (OMEI) is its measure. Many application of OMEI revealed the ability of this parameters to detect effectively how far is the evolution of the OM independently by composting time, becoming the OMEI a measure of the composting efficiency. Principle, experimental design, significance and limits of stability, maturity and OM evolution will be presented and discussed.
Analysis of Sampling Conditions, Test Variability and Quality of Composts On 30 Farms in New York State
Jean BONHOTAL (1), William F Brinton (2), Tom Fiesinger (3)
(1) Cornell Waste Management Institute (2) Woods End Research Laboratory (3)New York State Energy Research and Development Authority, USA
Prior to establishing compost quality marketing guidelines at the state level, compositional traits and variability of testing across a range of compost samples and types must be established. Many assumptions have been made about composition of composts. However, little work has been done specifically comparing the variability of compost traits pertinent to quality guidelines and setting limits for the reliability of sampling procedures among farmer-composters. In a preliminary compost use survey of commercial and home users, respondents indicated strong interest in reported quality of purchased composts. From this survey data the most frequently mentioned issues included product maturity, salt content, presence of weed seed, and physical and chemical contamination. Cornell Waste Management Institute and Woods End Research Lab examined thirty agricultural based composts in a multi-tiered study examining variability of test data with a focus on within-farm variability. Test traits examined included but were not necessarily limited to organic content, C:N, pH, conductivity, NPK content, maturity, phytotoxicity by cress test, fecal coliform content, Johne's disease, selected metals, and germinable and dormant weed seeds. In the first phase, 7 farmer composters were recruited and sampling instructions prepared using a combination of Woods End Laboratory and TMECC sampling and testing guidelines. Two sampling intervals within 2 weeks of each other using two samplers (trained University staff vs. farmer-composter) were introduced. Similarly, on selected farms, a re-sampling by the same sampler at a slightly later date from the same pile was undertaken. Finally, where bagging of composts was practiced on the farms, quadruplicate samples were drawn across a single batch of compost bags. To analysis the resulting data, we employed analysis of variance (ANOVA) which distinguished samplers, dates and farm.Farm compost piles are often of irregular shape and dissimilar dimensions, and therefore prescribed sampling procedures may not adequately reflect intrinsic problems of representativeness. Therefore, in a second phase study, variability of test data in dependence of depth into pile was undertaken. Three sample locations were established independent of exact pile size and were: core, 30cm above the pile center bottom, edge at 30cm from outside, and middle which was half-way between the outer and the core locations. The mean coefficient of variation (CV) for 20 analytes averaged by farm for all farms ranged from 2 to 115%. Within this same set, the CV for mineral and metal traits ranged from only 3 to 22%. Test data results in dependence on samplers did not differ by more than 10.9% for all 7 farms, excluding fecal and weed seed counts. Test data in dependence on date of sampling same batches varied somewhat more and up to 106% for zinc content, but generally less than 17%, excepting fecal counts and weeds, which varied by 181 and 171%, respectively. Weed seed tests are under development and may be essentially variable in nature. Similarly, fecal coliform counts are subject to order of magnitude variance, where a single aberrant value may throw off the arithmetic mean of the entire set very considerably. By using geometric mean transformation, we show average concentrations of all farms to present a different picture. Similarly, copper varied hugely across compost sites in apparent dependence on the practice of hoof-copper dips. Farms which bagged compost, exhibited astonishing variability in test data, which in many cases was greater than that observed across pile batch samples. A factor that affects variability of bagged compost traits is depth in pile, since farm operations in our survey tended to load baggers by bucket direct from piles. The variability of test data was significantly dependent on both depth of sampling with a statistically significant interaction of farm x depth. Samples drawn from pile cores exhibited higher pHs, lower nitrate, higher nitrite and higher salt contents than mid or edge samples. VOA, moisture, weed count and fecal counts varied across sample locations in dependence on farm. It is apparent in this data set that without controlling depth of sampling or accounting for stratification of piles obscured in the samples, basic traits like moisture, TKN, salts, density, weed count, and metals could not be established at CVs much under 20%. Johnes, a wasting disease in ruminants is of great interest to the dairy industry so a compost experiment was designed to look at where, when and how effectively Johnes is controlled in the process. Johnes free manure was inoculated and testing occurred weekly over a 6-week period. Results were not available at the time of preparation of this abstract. With the advent of CAFO regulations, many farmers are interested in moving some of their nutrients off farm. These farmers have expressed interest in or are selling composted product as a means to accomplish that. Results of this study are likely to help farmers, laboratories and regulators better understand compost composition and test result variability and therefore lead to providing more useful test information to their customers.
The CCQC Maturity Index
Buchanan, Mark (1), Brinton, Will (2), Shields, Frank (3), West, Jim (4), Thompson, Wayne (5), and COTTON, MATTHEW (6)
(1) Buchanan Associates, (2) Woods End Research Laboratory, (3) Soil Control Laboratory, (4) Soil and Plant Laboratory, (5) Edaphos International, (6) California Compost Quality Council, USA
Immature and poorly stabilized composts pose a number of problems during storage, marketing and use. Continued active decomposition may have negative impacts on plant growth due to reduced oxygen, available nitrogen or the presence of phytotoxic compounds. Compost maturity and stability are often used interchangeably. However, each refers to specific properties of these materials. Efforts continue to develop and refine methods which evaluate stability and maturity, but no universally accepted and applied method exists. A mature compost will exhibit characteristics that indicate completeness of the composting process and minimal potential for negative impacts on plant development. As maturity is not described by a single property, the maturity index, based on "passing" two or more specific tests will provide the greatest assurance to the producer and end-user. The CCQC Maturity Index characterization requires that the producer provide the C:N ratio of the finished product and reports at least one parameter from the Group A and B lists. Compost samples must pass the C:N ratio standard prior to consideration of results from tests in Group A and B. The results of Group A and B tests will determine compost to be very mature, mature or immature. No tests should be used to satisfy Group A and B requirements that have not resulted in generally agreed upon interpretation. These ratings are based on current standards established by experienced analytical specialists. However, at this time exact interpretation of the CCQC Maturity Index is not universally accepted by all laboratories and may be subject to additional refinement in the future.
Grappling with Compost Quality Downunder
WILKINSON, KEVIN G (1) and Paulin, Bob (2)
(1) Department of Natural Resources and Environment, Agriculture Victoria Knoxfield, Victoria, Australia. (2) Department of Agriculture Western Australia, Australia
The drive for a more sustainable, environmentally responsible agricultural sector represents a tremendous opportunity for composting. In Australia, these developments have come hand-in-hand with the adoption of quality assurance systems by growers for food safety reasons. However, in return, compost producers have been relatively slow in giving greater emphasis to compost quality and quality assurance. Research into the use of compost in horticulture has been conducted across Australia over the past several years. Research projects have mainly focused on using compost as a soil amendment in vegetable production, and as surface mulches for water conservation and weed suppression in viticulture. These projects have yielded mixed results. In Western Australia, some progress has been made in identifying important quality parameters for composts targeted for use on sandy soils for vegetable production. These relate mainly to the potential for nitrogen drawdown and the level of decomposition of the organic matter. Studies in Victoria have also confirmed that yield reductions can occur on heavier soils when quality control is compromised. The economic pressures of composting, a limited understanding of what defines compost quality and the lack of market-driven compost quality control threaten our ability to capitalise on the opportunities that are emerging in agricultural markets for compost. This paper will discuss the implications these issues have for researchers, the composting industry and the development of a sustainable compost-based agricultural production system in Australia.