In-vessel composting of household wastes Srinath R. Iyengar * , Prashant P. Bhave 1 Civil and Environmental Engineering Department, V.J. Technological Institute, H.R. Mahajani Road, Matunga, Mumbai 400 019, India Accepted 30 June 2005 Available online 8 September 2005 Abstract The process of composting has been studied using five different types of reactors, each simulating a different condition for the formation of compost; one of which was designed as a dynamic complete-mix type household compost reactor. A lab-scale study was conducted first using the compost accelerators culture (Trichoderma viridae, Trichoderma harzianum, Trichorus spirallis, Asper- gillus sp., Paecilomyces fusisporus, Chaetomium globosum) grown on jowar (Sorghum vulgare) grains as the inoculum mixed with cow-dung slurry, and then by using the mulch/compost formed in the respective reactors as the inoculum. The reactors were loaded with raw as well as cooked vegetable waste for a period of 4 weeks and then the mulch formed was allowed to maturate. The mulch was analysed at various stages for the compost and other environmental parameters. The compost from the designed aerobic reactor provides good humus to build up a poor physical soil and some basic plant nutrients. This proves to be an efficient, eco-friendly, cost-effective, and nuisance-free solution for the management of household solid wastes. Ó 2005 Elsevier Ltd. All rights reserved. 1. Introduction The collection and disposal of solid wastes is rapidly becoming one of the major unsolved problems of urban areas in India. For the small community located well outside the large metropolitan area, disposal of an aver- age of 0.2–0.3 kg of refuse per person per day presents less of a problem than its collection. For the large metropolitan cities like Mumbai, however, the problem of disposal as well as collection is subject to a multiplier that in most cases is in millions. It is estimated that about 48 million tonnes of urban municipal solid wastes is generated daily in the country (Agarwal et al., 2005). Per capita waste generation in major cities ranges from 0.20 to 0.60 kg per day (Central Public Health and Envi- ronment Engineering Organization, 2000). This situation has urged the need to develop and study various alternative technologies like composting. Composting can be defined as the controlled biological decomposition of organic substrates carried out by suc- cessive microbial populations combining both meso- philic and thermophilic activities, leading to the production of a final product sufficiently stable for stor- age and application to land without adverse environ- mental effects. For composting to be accepted as a viable alternative to landfilling and to other methods of MSW treatment such as incineration, effective separation of the organic fraction needs to be achieved. It is possible to practice the separation of the degradable materials at the source of generation, i.e., the individual houses. Moreover, early separation of the waste flows and their decentralised recy- cling could contribute to reducing the waste quantities to be transported by the city and to free capacities which can be used elsewhere (Zurbru ¨ gg et al., 2004). The scope of the study included the design and testing of a household compost reactor working aerobically, which was inoculated with compost accelerating micro- organisms to achieve substantial and rapid volume reduction of the biowastes by producing compost. Anal- 0956-053X/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2005.06.011 * Corresponding author. E-mail addresses: [email protected](S.R. Iyengar), [email protected](P.P. Bhave). 1 Tel.: + 91 22 9869414814/251 2670767. www.elsevier.com/locate/wasman Waste Management 26 (2006) 1070–1080
Transcript
www.elsevier.com/locate/wasman
Waste Management 26 (2006) 1070–1080
In-vessel composting of household wastes
Srinath R. Iyengar *, Prashant P. Bhave 1
Civil and Environmental Engineering Department, V.J. Technological Institute, H.R. Mahajani Road, Matunga, Mumbai 400 019, India
Accepted 30 June 2005Available online 8 September 2005
Abstract
The process of composting has been studied using five different types of reactors, each simulating a different condition for theformation of compost; one of which was designed as a dynamic complete-mix type household compost reactor. A lab-scale studywas conducted first using the compost accelerators culture (Trichoderma viridae, Trichoderma harzianum, Trichorus spirallis, Asper-
gillus sp., Paecilomyces fusisporus, Chaetomium globosum) grown on jowar (Sorghum vulgare) grains as the inoculum mixed withcow-dung slurry, and then by using the mulch/compost formed in the respective reactors as the inoculum. The reactors were loadedwith raw as well as cooked vegetable waste for a period of 4 weeks and then the mulch formed was allowed to maturate. The mulchwas analysed at various stages for the compost and other environmental parameters.
The compost from the designed aerobic reactor provides good humus to build up a poor physical soil and some basic plant nutrients.This proves to be an efficient, eco-friendly, cost-effective, and nuisance-free solution for the management of household solid wastes.� 2005 Elsevier Ltd. All rights reserved.
1. Introduction
The collection and disposal of solid wastes is rapidlybecoming one of the major unsolved problems of urbanareas in India. For the small community located welloutside the large metropolitan area, disposal of an aver-age of 0.2–0.3 kg of refuse per person per day presentsless of a problem than its collection. For the largemetropolitan cities like Mumbai, however, the problemof disposal as well as collection is subject to a multiplierthat in most cases is in millions. It is estimated thatabout 48 million tonnes of urban municipal solid wastesis generated daily in the country (Agarwal et al., 2005).Per capita waste generation in major cities ranges from0.20 to 0.60 kg per day (Central Public Health and Envi-ronment Engineering Organization, 2000).
This situation has urged the need to develop andstudy various alternative technologies like composting.
0956-053X/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.
Composting can be defined as the controlled biologicaldecomposition of organic substrates carried out by suc-cessive microbial populations combining both meso-philic and thermophilic activities, leading to theproduction of a final product sufficiently stable for stor-age and application to land without adverse environ-mental effects.
For composting to be accepted as a viable alternativeto landfilling and to other methods of MSW treatmentsuch as incineration, effective separation of the organicfraction needs to be achieved. It is possible to practicethe separation of the degradable materials at the sourceof generation, i.e., the individual houses. Moreover, earlyseparation of the waste flows and their decentralised recy-cling could contribute to reducing the waste quantities tobe transported by the city and to free capacities which canbe used elsewhere (Zurbrugg et al., 2004).
The scope of the study included the design and testingof a household compost reactor working aerobically,which was inoculated with compost accelerating micro-organisms to achieve substantial and rapid volumereduction of the biowastes by producing compost. Anal-
ysing the mulch/compost thus formed at various stagesand assessing the efficiency of the reactor also formeda part of the study.
2. Materials and methods
The process of composting was studied using five dif-ferent types of reactors, each simulating a different con-dition for the formation of compost. A lab-scale studywas conducted first using the compost accelerators cul-ture (Trichoderma viridae, Trichoderma harzianum, Tri-
chorus spirallis, Aspergillus sp., Paecilomyces
fusisporus, Chaetomium globosum) grown on jowar (Sor-ghum vulgare) grains as the inoculum mixed with cow-dung slurry, and then by using the mulch/compostformed in the respective reactors as the inoculum. Theculture was obtained from the Plant MicrobiologyDepartment of Mahatma Phule Krishi Vidyapeeth (anAgricultural University) located at Pune, India. Thereactors were loaded with raw as well as cooked vegeta-ble wastes which were homogenised by cutting the mate-rial to approximately 5–8 cm in length. The loading wascarried out for a period of 4 weeks, of which the last 2weeks were for shock loading, and then the mulchformed was allowed to mature. The mulch was analysedat various stages for the essential parameters.
The Central Public Health and Environment Engi-neering Organization (2000) specifies that the nitrogen,phosphorous and potassium (NPK) contents for com-post should be more than 1% each. The nitrogen shouldbe in the form of nitrates for proper utilization by theplants. The C/N ratio should be between 15 and 20.Hence the qualities of the composts produced in the dif-ferent reactors were compared in the light of the aboverecommended properties.
For the wet compost/mulch samples, moisture contentwas immediately analysed and pH was measured. All ofthe other properties were evaluated after samples weredried at 105 �C and finely ground. Moisture was deter-mined using the �percent of dry weight� method by dryingat 105 �C to constant weight and total organic carbon(TOC) by loss on ignition (600 �C for 2 h). The pH(1:50 (w/v)) was measured using a pH electrode, totalphosphate (acid digest) and soluble phosphate (distilledwater extraction) using vanadomolybdophosphoric acidmethod, sulphur (acid digest) using barium sulphate pre-cipitation method, and soluble nitrate (distilled waterextraction) using nitration of phenol disulphonic acidmethod by employing UV–Vis spectrophotometry (Sys-tronics) at 420 nm. Total potassium (acid digest), sodium(acid digest) and soluble potassium (distilled water extrac-tion) were determined using flame photometry (Systron-ics) fitted with element specific filters. NH4–N (aciddigest) was measured using UV–Vis spectrophotometry(Systronics) at 650 nm.
The reactors based on the conditions maintained inthem were as follows:
2.1. The complete-mix type aerobic reactor (‘‘CM’’
Reactor)
This is basically a dynamic type of reactor havingprovisions for the mixing of the compost/mulch beingformed and functioning aerobically (Fig. 1).
The loading of the reactor was performed by initiallyspreading a layer of dried leaves at the bottom of the in-ner container. These leaves were sprinkled with water toimpart some moisture within the reactor. A layer of soil(approximately 2.5–3.0 cm) was placed over the leaves.The reactor was then loaded 5 days per week with rawvegetable/cooked food waste. On the second day ofloading, 30 g of compost accelerator microorganismsgrown on jowar grains mixed with 1 L of cow-dung slur-ry was added to the reactor. The loading of 0.5 kg wascontinued for a period of 2 weeks followed by 2 weeksof shock loading of 1 kg.
The mulch formed was mixed daily. Sampling andanalysis of the mulch were carried out twice per week,starting after 1 week of loading was completed. Afterloading was complete, the mulch in the reactor was re-moved and kept for maturation for a period of 30 days.A small portion of the mulch (0.5 kg) was left in thereactor to act as an inoculum for the second loading.Daily temperature of the mulch was also monitored.
2.2. The facultative type reactor (‘‘F’’ Reactor)
Loading of this reactor was conducted in the samemanner as that of the complete-mix type reactor men-tioned before; however, no mixing of the vegetablewaste was done. The primary idea was to have an aero-bic type reactor initially, which eventually would be-come anaerobic at the bottom layers when the depthof load increased (Fig. 2). The top layers being aerobicwould contribute to capturing odorous compounds.The lid was always kept closed.
The daily temperature of the mulch was monitored.After 1 week of loading, the sampling and the analysisof the mulch were carried out twice per week. Like thecomplete-mix type reactor, after the loading was com-plete, the mulch in the reactor was removed and keptfor maturation.
2.3. The anaerobic type reactor (‘‘A’’ Reactor)
This reactor was dimensionally similar to the �F Reac-tor� with the only difference being that no perforationswere made on the reactor body. The complete 4-weekloading of 15 kg was conducted at one time in a mannersimilar to that mentioned earlier. Once loaded and inoc-ulated with the compost accelerator microorganisms
Fig. 1. The complete-mix type aerobic compost reactor (�CM Reactor�).
mixed with cow-dung slurry, the reactor was not openedat all. The mulch formed in this reactor was also removedand kept for maturation.
The sampling and the analysis of the mulch/compostdeveloped within this reactor was carried out only oncefor the comparison of the results, along with the last setof sampling for the other reactors. Daily temperature ofthe mulch was also monitored through three airtightports on the reactor which were placed at differentheights from the base.
2.4. The aerobic/facultative type reactor (only compost
accelerators as inoculum and occasional mixing of waste)
(‘‘BS’’ Reactor)
This reactor was similar to that of the facultative typereactor in terms of the structure, dimensions and
arrangement. The loading differs in two ways than thefacultative type reactor discussed previously:
(a) There is a layer of coarse aggregates mixed withsoil above the dry leaf layer, having more depth(about 5 cm).
(b) The vegetable waste was inoculated only with thecompost accelerator microorganisms (approxi-mately 30 g) unlike in the other reactors, whereincow-dung slurry was mixed together beforeaddition.
The contents were mixed occasionally, i.e., once perweek. The mulch from this reactor was sampled andanalysed once per week. The temperature of the reactorwas monitored only during sampling. The reactor waskept closed all the time.
Fig. 2. The facultative type compost reactor (�F Reactor�).
2.5. The aerobic/facultative type reactor (compost
accelerators in cow-dung slurry as inoculum and
occasional mixing of waste) (‘‘H’’ Reactor)
The arrangement for this reactor was similar tothat of the anaerobic type reactor (i.e., a plasticdrum without any perforations). In this case, theloading was conducted in a similar manner as thatfor the complete-mix type aerobic reactor. The lidof the reactor was kept open during the daytimeand during the night time the lid was kept closedto minimize the presence of flies, larvaes, and otherinsects in the reactor. Energy from the sun contrib-uted to the evaporation of some of the leachate thatwas generated.
The contents were mixed occasionally, i.e., once perweek. The mulch from this reactor was sampled and
analysed once per week. The temperature of the reactorwas monitored when sampled.
3. Results
The comparison of the results for mulch/compostanalysed after the first and second loadings, which werecarried out for a period of over 60 days each, is shown inTable 1 for the five different types of reactors studied:�CM Reactor�, �F Reactor�, �A Reactor�, �BS Reactor�,and �H Reactor�.
3.1. Analysis of leachate generated
The leachate generated from the �CM Reactor�, �FReactor�, and �A Reactor� were analysed, and the resultsof the analysis are tabulated in Table 2.
Table 1Comparison of the final quality of mulch/compost formed in the reactors during the first and second loadings
a Since there is no drainage for the leachate from the anaerobic type reactor, the leachate generated due to the decomposition of the wasteaccumulates and fills up all the voids within the mulch. The initial aerobic process then turns anaerobic and the process is slowed down. If theleachate is drained and the process is continued, more leachate would be formed after sometime, leading to the same anaerobic condition. Hence, theactual volume of the leachate generated in case of the �A� Reactor was difficult to estimate.
b The MPN Index was observed to reduce with successive loading hence the values are presented in decreasing order.
The volume reduction observed in three of the reac-tors studied after the first and second loadings is pre-sented in Table 3. In the �CM Reactor�, the volumereduction was observed to be more than 90% duringthe loadings under laboratory conditions. It would beworth mentioning that in actual situations, the volumechange may differ depending upon the inputs to thereactor and in most cases would be less than or at mostequal to the laboratory achieved values.
Table 3Volume reduction achieved in three reactors
Loading no. Reactor type % Volume reduction
1 CM 92.31F 81.64AN 28.18
2 CM 91.91F 83.5AN 12.58
4. Comparisons and discussion
Although the study was made of five different reac-tors, the variations in the parameters during the stageshave been documented graphically for three reactorswherein good results were obtained, viz. �CM Reactor�,�F Reactor� and �BS Reactor�. Additionally, these varia-tions in the parameters during the loadings followed asimilar trend and hence have not been separately dis-cussed. The variations of the different parameters duringthe lab-scale study of the composting process are as dis-cussed below:
Physical parameters – The compost formed in all thereactors except the �A Reactor� had a musty/earthyodour, brown to brownish black colour and soil-liketexture after the maturation period. The mulch fromthe �A Reactor� showed a decaying odour, brownishgreen colour and appeared to have a soggy texture be-cause of its high moisture content; even after the matu-ration period.
C/N – Decomposition of organic matter is broughtabout by microorganisms that use the carbon as a
source of energy and nitrogen for building cell struc-ture. More carbon than nitrogen is needed. If the ex-cess of carbon is too great, decomposition decreaseswhen the nitrogen is used up and some of the organ-isms die (Polprasert, 1996). The stored nitrogen is thenused by other organisms to form new cell material. Inthe process more carbon is used. Thus, the amount ofcarbon is reduced to a more suitable level while nitro-gen is recycled. In general, a drop in the C:N was ob-served for mulch formed in all the reactors. In thecase of the anaerobic reactor, the final C:N ratiowas found to be much higher than the recommendedvalues. The compost from the anaerobic reactor wouldnot be suitable for land application since the excesscarbon would tend to utilize nitrogen in the soil tobuild cell protoplasm, consequently resulting in lossof nitrogen in the soil on which it would be applied.On the other hand, the low C:N in the compostformed in �BS Reactor� would not help to improvethe soil structure (Bhattacharyya et al., 2001).
Temperature – Heat generation results from micro-bial activity, so the composting process experiences aninitial rise in temperature followed by declining and sta-bilized temperatures as microbial activity decreases dueto lower levels of available organic matter (Hagertyet al., 1973). It was observed (Fig. 3) that the variationof temperature with respect to the ambient/room tem-perature was less in the case of the �CM Reactor� dueto the mixing arrangement. The heat generated wasspread by mixing and did not remain localized. More-
20
22
24
26
28
30
32
34
36
38
40
42
44
0 5 10 15 20 25 30
Number of days after the load
Tem
per
atu
re (
oC
)
Ambient / Room Temperature
Fig. 3. Variation of temperat
over the enclosed design of the complete-mix type reac-tor minimized the heat loss from the mulch formed. Incase of the anaerobic reactor, there is no place for theleachate to escape; hence the leachate accumulated inthe lower portion of the reactor thus increasing themoisture content and thereby lowering the temperatureof the reactor.
pH – The pH of the composting material droppedduring the initial weeks of composting due to the forma-tion of organic acids, i.e., amino acids and other volatilefatty acids (Hagerty et al., 1973). After this period, thepH tends to move towards neutral again when theseacids have been converted to carbon dioxide by themicrobial action. This drop in pH values was observedfor the days of loading due to daily addition of biode-gradable organic matter, which is in agreement withthe observations made by Seo et al. (2004); then duringthe maturation phase, the pH subsequently rose (Fig. 4).
Ammonia nitrogen content of the mulch decreased(Fig. 5) while the Nitrate showed a rise with time(Fig. 6). The major loss of nitrogen due to volatilizationof ammonia during composting is through turning/mix-ing, i.e., increased aeration which agrees with the resultsof Verma et al. (1999) and Korner et al. (2003), while inthe anaerobic type reactor most of the nitrogen is con-tained in the mulch. During the curing phase, the ammo-nia is nitrified to become nitrates in the mulch formed inthe reactors (Polprasert, 1996).
Of all the other parameters, Potassium is the only ele-ment that is present in a form that can be easily leached
35 40 45 50 55 60 65
ing of the reactor commenced
CM Reactor F Reactor
ure within the reactors.
5
5.5
6
6.5
7
7.5
8
8.5
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Number of days after the loading of the reactor commenced
pH
CM Reactor F Reactor BS Reactor
Fig. 4. Variation of pH in the mulch analyzed at various stages.
0
0.05
0.1
0.15
0.2
0.25
0.3
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Number of days after the loading of the reactor commenced
% A
mm
on
ia N
itro
gen
co
nte
nt
CM Reactor F Reactor BS Reactor
Fig. 5. Variation of ammonia nitrogen content in the mulch analyzed at various stages.
out (Polprasert, 1996). The low potassium content in thecompost (0.05–0.167%), compared to the recommended1% for composts, may be attributed to its draining outin the form of leachate. The total potassium contentwas found to increase during the period of composting(Fig. 7), and the soluble potassium content also showedsimilar trends. Effective use of some fibrous material likestraw or wood chips, which can absorb relatively largequantities of water and still maintain their structuralintegrity and porosity, could prevent the loss of potas-sium from the compost formed.
Phosphorous content gradually increased during thecomposting process (Fig. 8). As shown by Asija et al.(1984), the water solubility of phosphorous decreasedwith the humification thereby showing that phospho-rous solubilised during the decomposition was subjectedto further immobilization by the compost acceleratormicroorganisms (Fig. 9).
Sulphur has been recognized as the fourth majorplant nutrient along with nitrogen, phosphorous, andpotassium (NPK). In sulphur deficit soil, applyingNPK rich manure cannot ensure high yields unless sul-phur is also applied. Hence the sulphur content in themulch was also analysed along with the other parame-ters (Tandon, 1999). The sulphur content like theNPK content shows an increasing trend.
Application of cooked food to the reactors forcomposting along with the possible end use of the ma-
ture compost as soil conditioners indicated the need toanalyse the mulch for Sodium content. It has beenshown that accumulation of sodium (Na+) in a soilcauses numerous adverse phenomena, such as changesin soil exchangeable ions and soil pH; destabilizationof soil structure; deterioration of soil hydraulic prop-erties; increased susceptibility to crusting, runoff, ero-sion and aeration; and osmotic and specific ioneffects on plants (Quadir and Schubert, 2002). Thetrend for sodium was similar to that of NPK and sul-phur content, but was observed to be present in verylow amounts.
The leachate generated could be used as compost tea
since it was found to be rich in dissolved nutrients andmicroorganisms. A part of the leachate could also berecycled through the reactor to improve the efficiencyof the process. Another possibility would be to evapo-rate the leachate during maturation and the remainingsolids could be scraped and added to the compostmulch. The generation of leachate from the �CM Reac-tor� could be minimized by employing a layer of soiland coarse aggregates/crushed stones in the space be-tween the stand and the outer drum where the leachateis collected (as in the case of �BS Reactor�). This layerwould act like an absorbing and filtering media forleachate.
The MPN index does not differentiate between the col-iforms of faecal and non-faecal origin, i.e., soil coliforms
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Number of days after the loading of the reactor commenced
% P
ota
ssiu
m c
on
ten
t
CM Reactor F Reactor BS Reactor
Fig. 7. Variation of potassium content in the mulch analyzed at various stages.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Number of days after the loading of the reactor commenced
% P
ho
sph
oro
us
con
ten
t
CM Reactor F Reactor BS Reactor
Fig. 8. Variation of phosphorous content in the mulch analyzed at various stages.
(Pelczar et al., 1993). Since soil was added in each of thereactors and at no point of time there was any contamina-tion of the mulch, it can be said that the MPN index de-picts quantitatively the soil coliforms leached out. It isfurther observed that this number also goes on decreasingwith the successive loading in reactors and the consequentdrainage of leachate from the reactors.
5. Conclusions
Based on the above comparison, it is evident that themulch produced in the reactors showed a low level ofpotassium content. The results also suggest that it maybe advisable to add potassium from an external sourceto improve the quality of the mulch. Leachate producedmay be recirculated into the reactor to improve the effi-ciency and quality of the compost. Cooked food wastesmay be washed before loading into the reactor to re-move the undesirable sodium content and to increasethe overall quality of the mulch produced in thereactors.
The anaerobic reactor failed to qualify as a house-hold reactor because of the poor quality of the mulchproduced, and low level of volume reduction.
The complete-mix reactor proved to be an idealhousehold reactor because of the following reasons:
� It is more efficient than the other reactors in terms ofthe quality of mulch/compost produced.� It can achieve 65–70% in volume reduction in the
organic fraction of the household wastes.� A small area is required for the installation and oper-
ation of the reactor.� The final stabilized compost from the designed aero-
bic reactor provides good humus to build up a poorphysical soil and gives some basic plant nutrients.� The problems of fly breeding, odour generation, and
rodents are eliminated because of the reactor�senclosed aerobic design.� Operation and maintenance of the reactor is very
simple.� The initial cost and maintenance cost of reactor are
low.
Thus the complete-mix reactor proves to be an effi-cient, eco-friendly, cost-effective, and nuisance-free solu-tion for the management of household solid wastes. Itcould be introduced in residential areas and the compostused to fertilize plants.
Agarwal, A., Singhmar, A., Kulshrestha, M., Mittal, A.K., 2005.Municipal solid waste recycling and associated markets in Delhi,India. Resources Conservation and Recycling 44, 73–90.
Asija, A.K., Pareek, R.P., Singhania, R.A., Singh, S., 1984. Effect ofmethod of preparation and enrichment on the quality of manure.Journal of Indian Society of Soil Science 32, 323–329.
Bhattacharyya, P., Chakrabarti, K., Chakraborty, A., Bhattacharyya,B., 2001. Microbial biomass and activities of soils amended withmunicipal solid waste compost. Journal of Indian Society of SoilScience 49 (1), 98–104.
Central Public Health and Environment Engineering Organization(CPHEEO), Government of India, 2000. Manual on MunicipalSolid Waste Management, New Delhi, India.
Hagerty, J.D., Pavoni, J.L., Heer, J.E., 1973. Solid Waste Manage-ment. Van Nostrand Reinhold Company, New York, USA.
Korner, I., Braukmeimer, J., Herrenklage, J., Leikam, K., Ritzkowski,M., Schlegelmilch, M., Stegmann, R., 2003. Investigation andoptimization of composting process – test systems and practicalexamples. Waste Management 23, 17–26.
Pelczar, M.J., Chan, E.C.S., Krieg, N.R., 1993. Microbiology. TataMcGraw-Hill, New Delhi, India.
Quadir, M., Schubert, S., 2002. Degradation processes and nutrientconstraints in sodic soils. Land Degradation and Development 13,275–294.
Seo, J.Y., Heo, J.S., Kim, T.H., Joo, W.H., Crohn, D.M., 2004. Effectof vermiculite addition on compost produced from Korean foodwastes. Waste Management 24, 981–987.
Tandon, H.L.S., 1999. Organic Fertilisers and Biofertilisers: ATechno-Commercial Source Book. FDCO Publication, New Delhi,India.
Verma, L.N., Rawat, A.K., Rathore, G.S., 1999. Composting processas influenced by the method of aeration. Journal of Indian Societyof Soil Science 47 (2), 368–371.
Zurbrugg, C., Drescher, S., Patel, A., Sharatchandra, H.C., 2004.Decentralised composting of urban waste – an overview ofcommunity and private initiatives in Indian cities. Waste Manage-ment 24, 655–662.
