Compost quality

Keywords Agronomic value of composting Anaerobic digestion Biowaste Compost quality Composting process Maturity... 

The collected and treated amounts of organic material differ much in the European Union (EU) countries. Around 35% of the estimated 49 million tons biowaste is presently collected separately (ECN 2008). In Germany, 30% of the household waste insists of biowaste and between 1990 and 2004 the highest increase is also documented for biowaste from two million tons in 1990 to around eight million tons in 2004. The German Federal Compost Quality Assurance Organisation (BGK) assumes the amount in 2007 to 9-10 million tons, but in this year alone six million tons biowastes were delivered to composting plans connected to the BGK. 

Compost quality parameters, such as C/N ratio, degradable amounts of C and N fractions... 

Although a united compost quality system of the European Union does not exist, the European Compost Network (ECN), as an initiative of the ORBIT Association developed a Quality Assurance System providing the necessary background information and documentation to build up a European Quality Assurance System (ECN-QAS). Product definitions and characterizations of this system are shown in Table 12.7. 

Silva MTB, Menduina AM, Seijo YC, Viqueira FD-F (2007) Assessment of munidpal solid waste compost quality using standardized methods before preparation of plant growth. Waste Manage Res 25 99-108... 

Boelens, J. De Wilde, B. De Baere, L. Comparative study on biowaste definition effects on biowaste collection, compost process and compost quality. Compost. Sci. Util. 1996, 4, 60-72. 

Disintegration in pilot-scale composting test using specimen of maximum thickness Analysis of compost quality... 

Typical parameters and nutrient levels for assessment of compost quality are shown in Table 5.2. These are combined values from a variety of sources, including Bertoldi eta/. (1987), and are merely intended to help in setting up analytical procedures. 

Table 5.2. Typical parameters and nutrient levels for assessment of compost quality.

The certification programme for compostable biodegradable plastic products has been set up by experts responsible for waste recycling and compost quality assurance. The members are as follows ... 

Bundesgiitegemeinschaft Kompost (German association for compost quality assurance)... 

M. De Bertoldi, The Control of the Composting Process and Quality of End Products. In Composting and Compost Quality Assurance Criteria. D.V. Jackson, J.M. Merillot, P. I Hermite. (Eds.), CEC publisher, Luxembourg (1992). 

Compostable plastics may have a niche role to play where its use contributes to better compost quality by minimizing the plastic residue in the product... 

In the United States, there is no one standard approach to assessing stabihty. In recent work by the California Compost (Quality Coimcil (CCQC) in conjunction with the California Integrated Waste Management Board (CIWMB), Woods End Laboratory and other peer-reviewers. 

Compost quality guidelines are relatively new, dating to the mid-1980s [24]. There has been a steady progression of definitions of contaminant limits when considering compost quality. The very first published limits pertained to heavy metals and were seen in the late 1970s in Europe. These standards include ... 

Table 5.5. Minimum compost quality for general use according to BSI PAS 100 [8]...

Chapter 5 gives an overview of the composting process and methods, including up-to-date standardized guidelines for evaluating compostabihty of polymer materials. It also contains information about compost quality standards as well as the description of certification systems for compostability used in different regions in the world (Eirrope, USA, Japan). 

Standard practice for preparing residual solids obtained after biodegradability standard metiiods for plastics in solid waste for toxicity and compost quality testing... 

No negative effects on compost quality and in particular no toxic effects of the compost and leachates to the terrestrial and aquatic organisms. 

Nevertheless, the interpretation of differences between the two batches could be very difficult. How should a change in the pH value (e.g., from 7.9 to 8.2), or in the plant available fractions of nutrients in relation to their total content be interpreted A more readily applied result could be obtained from bioassays, since any decrease of the germination rate of the seed or any reduction of plant growth (production of green plant biomass) could easily be declared as a loss of compost quality, independent of the chemical composition. 

EN 13432 No toxic or harmful substances Minimum 50% organic material Heavy metals limits relative to compost quality criteria European national standards for chemical composition Ecotoxicity tests with two plant species... 

The term compost quality should not be limited to physical and chemical parameters. While such analysis could describe the contents of nntrients and the presence of a small number of selected pollutants very well, the appearance of unidentified metabolites and residues could be detected more reliably by the application of biotests. In particular, artificial polymers may contain ingredients or certain monomers which may resnlt in critical metabolites or intermediates upon biodegradation. 

Results from ecotoxicological investigations of biodegradable polymers after composting are rare. Biotest design and the evaluation of results should focus on the detection of influences on compost quality that predestine its possible application and specific use. Special laboratory composting test systems, for example, based on an inert mineral matrix, can be used if there is a demand for the analytical detection of toxic metabolites or residues. 

W. Hartl in Proceedings of the Austrian Compost Quality Assurance Symposium, Austrian Compost Quality Assurance Association, Vienna, 1996. 

The norms of compostability specifications can be considered as umbrella norms in which various necessary characteristics are summarised, along with the test methods on how to check these and the necessary pass levels to be met. An overview of the main characteristics is given in Figure 5.7. Two main characteristics are related to environmental safety, which in the case of composting falls back to compost quality chemical analyses and ecotoxicity. Two other characteristics are related to degradation biodegradation and disintegration. 

Reliability of NIR in the evaluation of compost quality, contents of total nitrogen, total phosphorus, organic matter, total carbon, moisture, copper, potassium, and sodium, has been investigated (32). NIR spectra of dried and ground compost samples were measured in an InfraAlyzer 500 diffuse reflectance NIR spectrophotometer from 1100 to 2500 nm at 2-nm intervals. MLR and PLS were conducted between raw and first-derivative optical data and the concentrations of each comonent in the compost. Good results were obtained for the contents of total nitrogen (SEP = 0.085%), total carbon (1.12%), moisture (0.11%), and copper (0.048%). 

This Australian standard specifies requirements regarding compost quality, soil conditions, and mulch. It is based on the superordinate standards AS 4736 and AS 5810. 

ISO/CD 14855 Respirometric test disintegration of the material during fermentation phase, no negative effects on compost quality... 

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