A good number of composting methods have been suggested/published in the literature on quick or fast composting. In practical terms, how fast one can generate/produce good quality compost for use in urban horticulture or agriculture?
Difficult question since it depends on several factors: moisture, C:N ration, raw material composition, aeration, to name a couple. But if you want some approximation, here it goes: around 20 - 40 days for the main breakdown to take place (highest biological activity) and then 5 - 10 months for ripening.
I think, if you can maintain the C:N ratio at the beginning (near 30:1) and have optimum moisture condition throughout ( between 50 and 75% WHC ) and have a substrate having less lignin content and can add some cellulolytic and lignolytic microorganisms like Tricoderma viride, Trichurus spiralis, Paeciliomyces fusisporus etc , maintain the temperature between 28-32 degree Celcius throughout and with occasional rotating of the materials, then you may expect good compost within 45 days time.
Use microorganisms and moderate c/ n ration under anaerobic conditions
Dear colleagues,thank you for your good responses. One can bring the organic material/residue break down period within say 30-45 days or even less.But the slow or maturation period (ripening) requires long time (5-10 months as mentioned by Dr.Rafael).In that case how to reduce the time of composting to one month or even less ? Can some body highlight the minimum time frame required for maturation or curing or humification of manure?
As already suggested by colleagues, you can boost composting by lowering C/N ratio (10-15) and adding microbial consortium to end by 25-35 days. But maturation needs more time especially with fast thermophile phase (T>50°C up to 3 days). There is another way to fast compost wastes with high quality management: I mean In-Vessel composting technology, which is rotating composting drum that could be industrialized (small or big size unit) or home made unit. The industrial one is of course with gaz and multi-parameters probes with sometimes online quality checking. The advantage is continuous feeding with compost production within 20 days, but the gap is the high operational and investments costs. You can choose now between doing fast and doing right. Here after you can find a paper that deals with start up parameters along with monitoring and quality:
Article Composting parameters and compost quality: a literature review
Dr. Rao, if you use a controlled bioxidative process that involves a heterogeneous organic substrate in the solid state, evolves by passing through thermophillic phase with a temporary release of phytotoxins and then leads to the production of carbon dioxide, water, minerals and stabilized organic matter i.e. compost. Factors such as C:N ratio, moisture content, aeration, pH and temperature determine the prevalence and succession of microbial population during composting. Compost making includes three important and vital scientific principles namely the narrowing down of the C:N ratio, the total destruction of harmful pathogens and weed seeds ensured by high temperature evolved during decomposition, and stabilization. If you can control the entire thing, then I expect the maturity of compost within 40 days. The maturity of the compost can be judged by studying several indices such as BOD (biological oxygen demand), VFA ( volatile fatty acids), CEC, nitrate-N, ratio of reducing sugar, C:N ratio etc.
Dr.Khalid,in short-term mechanical composting systems,how maturity of compost is ensured? It seems to me that humification may not be possible under such conditions. Dr.Tarafdar mentions that maturity can be attained in around 40 days.We have also to ensure that the weed seeds and pathogens are killied during the composting process.I shall go through the paper you attached.
As R. Raabe has concluded a stabilized compost can be generated in less than 30 days under optimized conditions. However as A. Rao has stated this will not necessarily be recolonized with the most beneficial mesophilic microbes. In high temperature compost the proliferation of a thermophilic microbial microflora is somewhat constricting. The use of earthworms process organic materials under low temperatures and the casts are superior to high temperature compost in nutrient composition and in the microbial microflora which is dominated by mesophilic microbes. Rather than depend on high temperature the use of small invertebrates are ideal for both speeding up the organic matter transformation and producing a premium product which is superior to high temperature compost. Earthworm castings are manure with the greater amounts of quickly available nutrient. The use of castings and high temperature compost can give early vigorous growth and prolonged support of plant nutrition. An earthworm can produce 5 kg of casting in one year of activity. In well manured pastures earthworms can exceed 1,000,000 earthworms per hectare. My conclusion is that we should never understand the life underneath our feet to resolve some of our most pressing agricultural constraints.
Thank you Dr.Happerly for your enlightening comments.Your conclusion is worth thinking and action especially by young colleagues.Thank you Dr.Khalid for sending soft copy of your review.
Dr. Paul is absolutely right. Beside earthworm, soil biota are involved directly or indirectly in various soil functions. For example, microbes weather rocks to yield primary and secondary mineral particles through biological, chemical and physical weathering resulted betterment of plant growth. Earthworms consume all type of organic matter, retain 5-10% for their growth and excrete the mucous-coated undigested matter called vermicast that has undergone physical and chemical breakdown by the activity of muscular gizzard present in their intestine. It is a cost effective and efficient process of recycling non-toxic animal, industrial and agricultural wastes which are rich in N, P, K, Ca, Mg, vitamins, enzymes and plant growth promoting substances.
There are some popular or well known fast composting methods which may take 2-3 weeks (Berkeley method of Robert D.Raabe) and 3-4 weeks (North Dakota method authored by Ronald C.Smith and reviewd by Tom Kalb).The latter method has three compartments (bins) -the raw material Bin 1, Bin 2 for decomposition and Bin 3 for maturatio or humus formation.However , the time taken for maturity of compost is not exactly mentioned in the methods referred to above. I find an interesting document of ' The composting Council of Canada'.The document specifies some criteria for arriving at or reaching maturity stage. I find two interesting criteria for compost maturity-1. Compost must be' cured 'for a minimum of 21 days and must not reheat upon standing to greater than 20o C above ambient temperature and 2. Compost must be' cured' a minimum of 21 days and organic matter must be reduced by at least 60% by weight. Of course, chemical criteria mentioned by Drs Tarafdar and Khalid are known tools but takes time and effort. It will be interesting if quality/maturity of quick/fast composts is judged by chemical methods and validated.
The following references ( pdfs ) are available on internet.
1. Rapid composting method by Robert D.Raane,Berkeley,University of California.
2. Composting practices reviewed by Tom kalb NDSU
3.The composting process:compost maturity. The composting Council of Canada.
Dr.Naveen, thank you for your input.It is the same method developed by Dr.Raabe.The main concern is whether compost maturity is achieved in rapid composting methods or not.
Since the thermophilic nature of rapid composting does not lead to recolonization with beneficial mesophilic microflora the way for getting both rapid composting and the disease suppression desirable in compost would be letting the compost get to a point where it no longer reheats under turning moisture and aeration and then to inoculate with beneficial mesophilic organisms which can colonize plant roots. Hoitnick suggests this inoculation would include Trichoderma harzianum and Flavobacterium spp. A final inoculation with a beneficial mesophilic consortium would be recommended for testing this ability to get both rapid results and consistency of results in many soil environments where compost would be beneficial.
The fastest way is the use of microbial consortium in Anaerobic digester , where the digestate becomes biofertilizer and biogas is use for alternative energy source within the duration of less than 30 days including curing before application for crop production.
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I think if you can maintain your waste mixture at the optimum conditions from the beginning you can end with good quality compost within 45 days. these conditions are C:N ( 1:30), moisture ( 65%), particle size ( < 5 cm) which I think is very important factor . In addition to periodic turning.
Drs.Ayodele and Maria ,thank you for your comments.One should compare and contrast the qualities of aerobically well decomposed manure and anaerobic biodigested slurry.Can some body highlight the possible humus formation and maturity criteria in biodigested slurry?Also,what is the quality criteria for the biodigested slurry?
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