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Resources, Conservation and Recycling 58 (2012) 69– 78

Contents lists available at SciVerse ScienceDirect

Resources, Conservation and Recycling

journa l h o me pa ge: www.elsev ier .com/ locate / resconrec

eview

ffective composting of oil palm industrial waste by filamentous fungi: A review

oor Mohammada, Md. Zahangir Alama,∗, Nassereldeen A. Kabbashia, Amimul Ahsanb

Bioenvironmental Engineering Research Unit (BERU), Department of Biotechnology Engineering, Faculty of Engineering, International Islamic University Malaysia, Jalan Gombak,3100 Kuala Lumpur, MalaysiaDepartment of Civil Engineering, Faculty of Engineering (Green Engineering and Sustainable Technology Lab, Institute of Advanced Technology), University Putra Malaysia, 43400PM Serdang, Selangor, Malaysia

r t i c l e i n f o

rticle history:eceived 19 October 2010eceived in revised form 24 October 2011ccepted 24 October 2011

eywords:

a b s t r a c t

Palm oil production is a major agricultural industry in Malaysia, in which palm oil mill effluent (POME)and oil palm empty fruit bunch (EFB) are considered as major waste products from the palm oil indus-try. These waste products create an environmental hazard and entail high disposal costs every year.Composting is a biologically based process which is practiced to stabilize the organic matter for soilamendment (producing compost) and to protect the environment from the detrimental effects of these

ompostinggro-industrial wastesmpty fruit bunchesalm oil mill effluentilamentous fungi

waste products. This study reviews the composting process of EFB and POME as a single substrate and/ortheir mixture by using potential filamentous fungi that are especially lignocellulolytic and antibiotic (ina matured stage) in nature within several effective parameters, for example, C/N ratio, moisture con-tent, pH, temperature, etc. Several studies record the mature composting process as being 60 days. Inmost cases, temperature and moisture content was maintained up to 70 ◦C and 60–75%, respectively. In

eview addition, this study reviews EFB and POME with their constituents for an efficient composting process.© 2011 Elsevier B.V. All rights reserved.

ontents

. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

. Composting of agro-industrial waste by the filamentous fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

. Major oil palm wastes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713.1. Oil palm empty fruit bunches (EFBs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

3.1.1. Constitutes of EFB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713.1.2. EFB as a fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

3.2. Palm oil mill effluent (POME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 733.2.1. Constituents of POME. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 733.2.2. POME as a fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

. EFB and POME for composting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

. Compost and plant pathogenicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

. Environmental and economic impacts of composting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

. Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

. Introduction the harmful accumulation of organic materials but it is also essen-

The problem of disposal of waste streams from a myriad ofndustries is increasingly acute in the world. Before industrializa-ion, the production and decomposition of organic materials wereasically in balance. Decomposition is not only important to avoid

∗ Corresponding author. Tel.: +60 3 61964571; fax: +60 3 61964442.E-mail addresses: zahangir@iium.edu.my, zahangir@yahoo.com (Md.Z. Alam).

921-3449/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.resconrec.2011.10.009

tial for recycling nutrients and organic matters. Soils and theirmicrobial organisms play an important role in these processes.Furthermore, the fertility of many soils is decreased due to an inad-equate supply of organic matter or improper management, such asthe occurrence of acidity due to ammonium producing fertilizers.

These issues have highlighted the necessity of developing alter-natives, of which composting is a promising one. Compostingis a controlled biological decomposition process, which convertsorganic wastes into humus-like materials. It may be defined as a

70 N. Mohammad et al. / Resources, Conservation and Recycling 58 (2012) 69– 78

Preproc essing High rate

Phase Curing Phase Postprocess ing

Amendment

Compos tables

New Bulking Materi als Recy cled Bulking Materials

Compo sts

Product Recycle

compo

boihpa(nbcsmena

tpdcre2iItg(ew(e(httiiMMeo

aglu222

o

Fig. 1. Generalized process diagram for

ioconversion process of an organic waste substrate into stablerganic end products (compost) (Molla et al., 2002a). The compost-ng process consists of some basic steps such as pre-processing,igh rate decomposition, recovery of bulking agents, curing andost-processing (Fig. 1) (Metcalf and Eddy, 2003). Composting is

successful strategy for sustainable recycling of organic wastesFermor, 1993; Tuomela et al., 2009). It is an ecological alter-ative to mass burning and land-filling of garbage. Solid-phaseio-oxidative stabilization of the organic fraction from such agri-ultural or urban residue, either source-collected or mechanicallyorted, represents a reliable technology for reducing the environ-ental impact of municipal solid waste management (Bazrafshan

t al., 2006). Benefits from composting are (1) conservation of plantutrients and (2) transformation of unsafe wastes into harmlessnd useful products (Liu, 2000).

Palm oil is one of the world’s most rapidly expanding equa-orial crops. Indonesia and Malaysia are the two largest palm oilroducing countries. They are rich with numerous endemic, forest-welling species (Rupani et al., 2010). Malaysia has a tropicallimate and is prosperous in natural resources. Oil palm cur-ently occupies the largest acreage of farmed land in Malaysia (Arift al., 2001). According to the Malaysia Palm Oil Board (MPOB,008), global production of palm oil and plantation area has been

ncreased. Malaysia contributes 41% of world production (Fig. 2).n Malaysia, the oil palm biomass (OPB) produces about 40 milliononnes per year (Baharuddin et al., 2009). This OPB can be cate-orized as a form of empty fruit bunches (EFBs), oil palm trunksOPT) and oil palm fronds (OPF), and the rest is palm oil mill efflu-nt (POME). Many studies are being conducted to manage theseastes, producing different by-products such as activated carbon

Alam et al., 2007), xylose (Rahman et al., 2006), cellulase (Alamt al., 2009), polyhydroxyalkanoates (Mumtaz et al., 2010), proteaseWu et al., 2006), hydrogen (Morimoto et al., 2004). Compostingas been considered to be one of the most suitable ways to solvehis problem where organic wastes are converted into productshat are beneficial for plant growth. Some compost manufactur-ng industries for residues from palm oil production are developedn various countries simultaneously. For example, Sime Darby in

alaysia is an encouraging composting plant situated at Lavang Oilill, utilizing empty fruit bunches (EFBs) and palm oil mill efflu-

nts (POMEs) from the oil mill to produce 26,000 tonnes of enrichedrganic fertilizer per year (MPOB, 2005).

Because composting is a microbial process, compost stabilitynd maturity depend on the results of microbial activity. Microor-anisms convert or break the constituents inside the substrates. Aot of filamentous fungi species are described in the literature to beseful for transforming organic wastes into compost (Molla et al.,001; Kalogeris et al., 2003; Brand et al., 2000; Fakhru’l-Razi et al.,

002; Guest and Smith, 2002; Alam et al., 2003a,b; Lacina et al.,003; Mannan et al., 2005; Fleury, 2007, etc.).

The objectives of this literature review are (1) to discuss the rolef filamentous fungi used for composting in agro-industrial wastes,

sting process (Metcalf and Eddy, 2003).

(2) to introduce oil palm empty fruit bunches (EFBs) and palm oilmill effluent (POME) as the potential raw materials for compostingand (3) to review the composting process of these materials withmicrobial systems (especially fungi) and process controls.

2. Composting of agro-industrial waste by the filamentousfungi

The ability of fungi to degrade lignocellulosic materials is dueto their highly efficient enzymatic system. Fungi have two typesof extracellular enzymatic systems: the hydrolytic system, whichproduces hydrolases that are responsible for polysaccharide degra-dation and a unique oxidative and extracellular ligninolytic system,which degrades lignin and opens phenyl rings (Sánchez, 2009). Lig-nocellulosic residues from wood, grass, agricultural and forestrywastes and municipal solid wastes are particularly abundant innature and are a valuable potential for bioconversion.

Fungi, especially thermophilic species, have often been reportedfrom composts (Cooney and Emerson, 1964). Waksman et al. (1939)were the first to demonstrate the importance of a thermophilicfungus in the decomposition of stable manure. Eastwood (1952)failed to isolate any thermophilic fungi from the composts of bar-ley straw and grass cuttings but as suggested in the study (Changand Hudson, 1967) this may have been due to their using unsuitableincubation temperatures. Henssen (1957), on the other hand, suc-cessfully isolated five thermophilic fungi from stable manure, anddemonstrated the ability of Humicola insolents to decompose cel-lulose and Sporotrichum thermophile to decompose hemicelluloseand pectin. Gregory et al. (1963) carried out an extensive investiga-tion on the microbial and biochemical changes in mouldy timothyand fescue grass hay. They concerned themselves with the changesin microbial population as well as changes in the volatile nitrogen,sugar content, lipids and ash in the hay.

Chang (1967) carried out ecological and biochemical studies onthe fungi of wheat straw composts, with special emphasis on thechanges in the major carbohydrate constituents of the compostingmaterial. An attempt was made to elucidate the roles fungi playedin bringing about changes in the composts and the properties thatenabled them to inhabit this special ecological function. Rhizopusmicrosporus, Mucor pusillus, Aspergillus fumigatus, Aspergillus niger,Aspergillus terreus, Aspergillus fiaous, Penicillium sp., Trichodermalongibrachiatum and an agaric., nine species of fungi were isolatedfrom the fungal succession on bagasse by Sandhu and Sidhu (1980).Pectin was utilized by all nine bagasse fungi, while cellulose wasutilized by all except R. microsporus and M. pusillus. Xylan was uti-lized by all except R. microsporus, while aconidendrin was utilizedonly by A. niger.

A survey of data on composition, properties, and possibilities of

disposal or treatment of fruit distillery wastes was presented byPerdih et al. (1991). Comparing different ways of treating distillerywastes, a bioconversion process using filamentous fungi seemedto be promising. Brand et al. (2000) studied the detoxification of

N. Mohammad et al. / Resources, Conservation and Recycling 58 (2012) 69– 78 71

duction in 2008 (MPOB, 2008).

coatmioite

ymBmybmetiaf

tohMrtccScPclp

sepfiheu(um

Table 1Fibrous compositions of major constituents in EFB (%).a

Components Sreekala et al. (1997) Khalil et al. (2007)

Lignin 25–35 21.2Cellulose 45–50 49.6Hemicellulose 25–35 18Ash – 2

Fig. 2. World palm oil pro

offee husk in solid state fermentation using three different strainsf Rhizopus, Phanerochaete, and Aspergillus sp. Using Rhizopusrrizus LPB-79, the best results on the degradation of caffeine andannins during a 6-day period were obtained with pH 6.0 and 60%

oisture. When Phanerochaete chrysosporium BK was used, max-mum degradation of caffeine and tannins within 14 days werebtained with 70.8 and 45%, respectively, with the coffee husk hav-ng 65% moisture and pH 5.5. The Aspergillus strain, isolated fromhe coffee husk, showed best biomass formation on coffee huskxtract-agar medium.

Raw citrus waste was predominantly colonized by mesophiliceasts (Heerden et al., 2002). It also contained low numbers of ther-ophilous bacteria and filamentous fungi, e.g. Bacillus licheniformis,

acillus stearothermophilus, A. fumigatus and Talaromyces ther-ophilus, as well as a few mesophilic actinomycetes. Mesophilic

east populations remained constant at a depth of 30 cm on day 3,ut mesophilic bacteria consistently outnumbered mesophylic fila-entous fungi during composting. Kalogeris et al. (2003) produced

xtracellular cellulolytic enzymes under solid state cultivation byhe thermophilic fungus Thermoascus aurantiacus and character-zed them. Elevated levels of endoglucanase and �-glucosidasectivities were produced simultaneously by optimization of growthactors.

Molla et al. (2004) conducted a study to evaluate the feasibility ofhe solid-state bioconversion (SSB) processes in the biodegradationf wastewater sludge using two mixed fungal cultures, Trichodermaarzianum with P. chrysosporium 2094 (T/P) and T. harzianum withucor hiemalis (T/M) and two bulking materials, sawdust (SD) and

ice straw (RS). The significant growth and multiplication of bothhe mixed fungal cultures were reflected in soluble protein, glu-osamine and color intensity measurement of the water extract. Aomposting process was developed by Kabbashi et al. (2006) usingSF for utilization of agro-industrial wastes. This study was con-erned with a simple composting process using selected substrates,OME and EFB plus wheat flour as a co-substrate. The strains of P.hrysosporium, T. harzianum, A. niger (A 106, S 101), and Penicil-ium isolated from POME were used for an effective compostingrocess.

Rhamnolipid biosurfactant was added to a rice straw hydroly-is system to enhance the production of reducing sugars (Zhangt al., 2009). Differing from the traditional method, on-siteroduction of rhamnolipid made the rice straw decomposingungus Trichoderma reesei ZM4-F3 and rhamnolipid produc-ng bacteria Pseudomonas aeruginosa BSZ-07 work together. T.arzianum NBRI-1055 was used as the fungal candidate tonhance the antioxidant activities of soybean matrix by mod-

lating polyphenolic substances during solid-state fermentationHarikesh et al., 2010). Trichoderma fermented soybean andnfermented soybean products were extracted with water andethanol.

a Results are shown as dry matter basis.

3. Major oil palm wastes

3.1. Oil palm empty fruit bunches (EFBs)

3.1.1. Constitutes of EFBAn average oil palm mill can handle about 100 metric tonnes

(mt) of fresh fruit bunches daily (Singh et al., 2010). At the millswhere oil extraction takes place, solid residues and liquid wastesare generated. As shown in Fig. 3, the solid residues, mainly EFB, aremore than 20% of the fresh fruit weight (Ma et al., 1993; Kamarudinet al., 1997; Lorestani, 2006). The EFBs are either incinerated orapplied to fields. These practices create environmental pollutionproblems as incineration and boilers emit gases with particulatessuch as tar and soot droplets of 20–100 microns and a dust load ofabout 3000–4000 mg/nm (Igwe and Onyegbado, 2007) and indis-criminate dumping of EFB causes additional methane emissioninto the atmosphere (Amal et al., 2008). To minimize pollution, anew usage for these wastes ought to be looked into. As shown inTable 1, these biomasses from palm oil mills contain 45–50% cel-lulose, 25–35% hemicelluloses and 25–35% lignin (Sreekala et al.,1997; Khalil et al., 2007). They are composed of a bundle of fibreswith an average size of about 1 mm long, 25 �m wide and 3 �mthick (Deraman, 1993).

However, the nutrient contents are variable, as can be seen fromthe findings of different researchers, shown in Table 2.

3.1.2. EFB as a fertilizerThe EFB is a suitable raw material for recycling because it is

produced in large quantities in localized areas. In the past, it wasoften used as fuel to generate steam at the mills (Ma et al., 1993).Researchers are now trying to utilize this cheap raw material in dif-ferent applications. Composting of EFB is being extended to farmersby the Department of Agriculture of Malaysia (Damanhuri, 1998).

Currently most of the EFB are used as mulch in plantations,almost wholly replacing incineration, which is now confined to onlya few mills. The usual application rate of EFB is 40–70 tonnes per

hectare. The trials are carried out in one of the Sabah Land Develop-ment Boar (SLDB) trials with EFB to evaluate the nutrient contentin one tonne of EFB (see Table 3).

72 N. Mohammad et al. / Resources, Conservation and Recycling 58 (2012) 69– 78

Table 2Approximate compositions of major constituents in EFB (%).a

Nutrients Amal et al. (2008) Suhaimi and Ong (2001) Hajar (2006) Rozainee et al. (2001)

C 48.8 43.7 42.0–43.0 50.09N 0.2 0.52 0.65–0.94 2.05C/N – 45–64 –P – 0.05 – –H 6.3 – – 7.16O 36.7 – – 40.16K – 1.34 – –S 0.2 0.07 – 0.06B – 4 9–11 –Ca – 0.19 – –Cu – 13 – –Mn – – – –Mg – 20 – –Zn – 21 – –Fe – 649 – –Ash 7.3 – 4.8–8.7 5.74Oil – – 8.1–9.4 –P2O2 – – 0.18–0.27 –K2O – – 2.0–3.9 –MgO – – 0.25–0.40 –CaO – – 0.15–0.48 –

a Results are shown as dry matter basis.

Table 3Fertilizer content of one tone EFB.

Fertilizer Amount (kg) December 2002 price (RMa) December 2002 price (RM/kg) Actual price as fertilizer (RM)

Urea 3.8 540–580 0.54 2.05Rock phosphate 3.9 550 0.55 2.15Muriate of potash 18.0 230–250 0.23 4.14Kieserite 9.2 340–400 0.34 3.13

Total price as fertilizer

a Ringgit Malaysia (RM).

Fresh Fruit Bunch (100 %)

Empty Fruit Bunch (20 %)

Bunch Ash (0.5 %) Crude Oil

(43 %) Nu(13

Fruits (70 %)

Water Evaporation

(20 %)

Pure Oil (21 %)

Mois(1 %

Shell (6 %)

Solids (Animal feed/fertilizer)

(2 % )

Fig. 3. Products from oil mill p

11.47

Evaporation (10 %)

ts %)

Pericarp (14 %)

ture )

Kernel (6 %)

Dry Fibre Fuel

(12 %)

Water Evaporation

(2 %)

rocess (Lorestani, 2006).

nserv

3

3

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3

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4

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N. Mohammad et al. / Resources, Co

.2. Palm oil mill effluent (POME)

.2.1. Constituents of POMEEffluent water discharged from the oil palm industry is known

s POME, which contains many soluble chemical materials thatre detrimental to the environment. Fig. 4 summarizes the stepsnvolved in the processing of oil palm for crude palm oil productionMumtaz et al., 2010). It includes various liquids, soiled materi-ls, residual oil and suspended solids which are shown in Table 4.pecifically, palm oil mill effluent (POME) is a general phrase refer-ing to the effluent from the final stages of palm oil production inhe mill (Igwe and Onyegbado, 2007). POME in its untreated form is

very high-strength waste, depending on the operation of the pro-ess that can involve informal, semi-formal and formal processes.OME is actually the sum total of liquid waste which cannot beasily or immediately reprocessed for extraction of useful products.

.2.2. POME as a fertilizerThe application of raw or digested POME as fertilizer on land was

nitially considered unreasonable because of the effluent wouldill vegetation and lead to the jamming of percolation and water-ogging, thus resulting in anaerobic conditions. Later, Wood et al.1979) reported that raw POME would readily cause clogging andater logging of the soil, but that these problems could be over-

ome by the controlled application of small quantities of POMEt a time. Ground water was tested after 6–12 months of trialpplications of raw POME as fertilizer and showed no substan-ial percolation of oxygen-demanding or other polluting elementsithout excessive run-off over the surface during wet weather

Wood et al., 1979). It was thus recognized that the water quality inhe applied areas was unaffected (Dolmat et al., 1987). Moreover,viasogie and Aghimien (2003) reconfirmed that a proper use ofOME in the land environment would directly improve soil fertil-ty. Their results showed an enrichment of the soils with regardo phosphorus, nitrogen, calcium, magnesium after the applicationf POME. Although zinc was particularly present in its exchange-ble form, copper, iron and lead were predominant in their organicorms.

The use of POME as a cheap organic fertilizer may offer an alter-ative to the excessive application of chemical fertilizers, especiallyhosphorus, for which cost is a severe economic limitation (Ta et al.,009). According to Wood et al. (1979), an application of POME at.5 × 106 mt per hectare (ha) was anticipated to represent a fer-ilizer application of around 30 kg ammonium sulphate, 7 kg rockhosphate, 52 kg potash and 18 kg kieserite per palm per year. Theutrient composition of the fertilizers is shown in Table 5.

. EFB and POME for composting

Composting of EFB is a possible way to convert the bulkyunches into a valuable, manageable product for use in thelantation or as a market product. Investigation of the rotting char-cteristic of empty fruit bunches (EFBs) during composting haseen conducted during the last decade (Lim, 1989; Darnoko et al.,993; Theo and Chia, 1993; Thambirajah et al., 1995; Goenadi et al.,998; Franke, 1998; Schuchardt et al., 1998, 1999, 2000).

Other materials are often added, particularly chicken manurend POME. However, POME has a high nutrient content (Zakariat al., 1994), and large oil palm plantations prefer to use it directlys a fertilizer. The POME is first treated to reduce the organic loadMa et al., 1993). The sediments left after treatment, which have

higher nutrient value than the slurry (Zakaria et al., 1994), areither recycled to the fields or sold to the public.

The effects of composting palm press fibre alone, palm pressbre supplemented with poultry layer deep-litter and urea, and

ation and Recycling 58 (2012) 69– 78 73

palm press fibre supplemented with poultry broiler floor-litterand urea were studied by Thambirajah and Kuthubutheen (1989).After 8 weeks of composting the C/N ratios of the mixtures werereduced significantly. The temperature in the heaps rose in thefirst 3 weeks of composting but stabilized after 8 weeks. The ratioof thermophilic to mesophilic fungi increased during composting,and even after the compost had cooled the thermophilic fungalcounts remained high. The mesophilic bacteria were not influencedby temperature fluctuation in the heaps, and bacterial numbersremained high even during the peak heating phase.

The composting of oil palm empty-fruit-bunches in supplemen-tation with either goat dung, cow dung or chicken manure wasstudied with varying different C/N ratios (Thambirajah et al., 1995).The rate of utilization of cellulosic material showed a positive cor-relation with the increase in the nitrogen (NH4) content of thecompost. Hamdan et al. (1998) studied the decomposition of EFBin oil palm plantations where EFB was spread in the field as mulchon top of nylon net, at a rate of 30, 60 and 90 mt/ha/year. At eachEFB application rate, spots were selected for nitrogen supplemen-tation to meet a C/N ratio of 15, 30 and 60. The EFB was found to becompletely decomposed after 10 months of application. Anotherstudy by Suhaimi and Ong (2001) examined the composting of EFBin open and closed composting systems. Mixtures of EFB, fermen-tation liquid waste (in form of POME) and chicken manure (open)and EFB, POME and chicken manure (closed) were the ingredientsfor composting. This resulted in irregular biological activity. Thecomposting process developed at a reasonable rate, being fasterfor the open than the closed system. A C/N ratio of about 16 wasachieved in about 50 days (open) and 85 days (closed). Compostingof EFB from oil palms with the addition of POME was carried outunder a wet tropical climate at Medan in Indonesia (Schuchardtet al., 2002). During the composting process the fresh POME wasadded (based on the evaporation rate) to balance the high waterevaporation. During the rotting process of 12 weeks the mass ofthe dry matter and the carbon decreased >60%, the volume and themass at about 50%, and the C/N ratio from 50 at the beginning wasreduced to 15.

Kabbashi et al. (2006) studied the composting process usingselected substrates, POME and EFB plus wheat flour as a co-substrate in a tray bio-reactor. The strains of P. chrysosporium, T.harzianum, A. niger (A 106, S 101), and Penicillium isolated fromPOME were used for an effective composting process. The com-posting time required to complete the process was two months.The C/N ratio and germination index (GI) achieved were 17 and95%, respectively. Yasmeen et al. (2008) investigated the efficiencyof rice straw and EFB of oil palm compost extracts, either fortified orunfortified with T. harzianum, on morpho-physiological growth andoccurrence of Choanephora wet rot of okra. Treatments tested werewater (control), rice straw (RST) compost extract, Trichoderma-enriched RST compost extract, EFB of oil palm compost extract,Trichoderma-enriched EFB compost extract, aqueous suspensionof Trichoderma, and a fungicide Dithane M-451. The experimentalresults were significantly higher in Trichoderma-enriched RST com-post extracts, followed by Dithane M-451, Trichoderma-enrichedEFB extracts, RST, EFB and aqueous suspension of T. harzianum inboth Choanephora inoculated and uninoculated (control) plots.

Microbial communities and cellulolytic enzymes activities wereanalyzed during the co-composting of EFB and partially treatedPOME on a pilot scale (Baharuddin et al., 2009). The diversityof the bacterial community was investigated using polymerasechain reaction-denaturing gradient gel electrophoresis. The results(Table 6) indicated that the composting process of EFB with par-

tially treated POME was dominated by uncultured bacteria species.Formation of compost from EFB and decanter cake slurry by theaddition of POME, with a regular turning operation, was investi-gated by Yahya et al. (2010). The addition of decanter cake slurry

74 N. Mohammad et al. / Resources, Conservation and Recycling 58 (2012) 69– 78

Table 4Approximate chemical constituents of POME (ppm).

Materials Palaniappan (1993) Ma et al. (1996) Sivapalan and Ripin (1997)

pH 4–7 4.7 4.89N 380–227 750 47P 180 –K 990–1542 2270 3365Ca 330–256 439 71Cu – 0.89 –Mg 242–247 615 442Mn – 2 –Zn – 2.3 –Fe – 46.5 –B – 7.6 –NO3 – 35 92SO4 – – 322Water – – –Oil – 4000 10,500SS 18,000 20,650TS 34,260–12,408 40,000 41,200TVS 34,000 –BOD 20,790–2240 25,000 35,100COD 50,000 6100

Fig. 4. Schematic diagram of oil extraction from oil palm and POME generation (dashed line represents byproduct/waste stream) (Mumtaz et al., 2010).

N. Mohammad et al. / Resources, Conservation and Recycling 58 (2012) 69– 78 75

Table 5Expected fertilizer values from POME (Ta et al., 2009).

Fertilizers Tonnes (×103) Price, December 2002 (RM/tonne) Price (RM in millions)

Ammonium sulphate 75.5 580.00 43.79Rock phosphate (CIRP) 19.5 545.00 10.63Muriate of potash 68.6 250.00 17.15Kieserite 59.6 400.00 23.84Total 95.41

Table 6Characterization of feedstock materials and composts after different durations of composting process (Baharuddin et al., 2009).

Sample Color Temperature (◦C) pH Moisture content (%) C/N ratio

EFB Brown 32.2 6.5 25 56.5

hawc

cs

5

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iastfma(sasit

aoace(lmU

te

POME Blackish 41.3

Compost (30 days) Dark brown 57.4

Compost (60 days) Blackish 35.3

ad speeded up the composting process of the EFB. The C/N ratiofter 51 days for the mature compost with the decanter cake slurryas 18.65, while that of the matured compost without the decanter

ake slurry remained high at 28.96.Table 7 shows a summary of the results available in the literature

oncerned with composting of EFB and POME in different microbialystems with controlling parameters.

. Compost and plant pathogenicity

Composting using a biologically based technique is recognizeds an environmentally sound method of waste management (Ishakt al., 1999; Liao et al., 1993). Simultaneously, the end product ofomposting has tremendous impact on nutritional values for plantrowth by conserving proper soil health (Georgacakis et al., 1996;ang et al., 1998). However, assessing the phytotoxicity of com-osts is one of the most important criteria being used to avoidnvironmental risks as well as plant growth before these compostsan be applied to agricultural land. Otherwise, they may cause ofevere economic loss in crop production and contamination of thenvironment by disseminating several diseases.

The process of composting is ecologically complex as it isnfluenced by a wide range of environmental variables. Moisturevailability appears to be a significant factor in composting systemsince water affects gaseous exchange. As water content increases,he rate of gas transfer decreases, and the rate of oxygen trans-er becomes insufficient to meet the metabolic demands of the

icroorganisms. The composting system will become restricted inctivity and eventually anaerobic (Miller, 1991). Frassinetti et al.1990) studied the changes in patterns of phytotoxicity of sewageludge compost as affected by the pattern of oxygenation (aerobicnd anaerobic conditions). The experimental results showed thatludge processed under anaerobic conditions had increased toxic-ty. In aerobic conditions, the microflora develops and is capable ofransforming organic matter and eliminating biological toxicity.

Plant seed germination and root elongation tests have been useds simple and sensitive techniques for detection of the toxicityf various environmental pollutants such as heavy metals (Wongnd Bradshaw, 1982), phenolic compounds (Wong, 1985), refuseompost (Wong, 1985), industrial effluents from heavy machin-ry, agricultural product utilization and special chemical industriesWang and Keturi, 1990). Many plant species, including cabbage,ettuce, carrot, cucumber, tomato and oats, have been recom-

ended for seed germination and root elongation tests (FDA, 1987;

SEPA, 1982).

The phytotoxicity of spent pig-manure sawdust litter (spent lit-er) was evaluated during composting (Tiquia et al., 1996). Aqueousxtracts of the spent litter were prepared by shaking the sample

7.6 95 13.68.3 65 24.67.8 60 12.8

with water and the toxicity of these extracts was determined onrelative seed germination, relative root elongation and germina-tion index. Phytotoxicity of the spent litter was only evident duringthe earlier stage of composting (first 14 days) and seed germina-tion and root elongation reached 100% (the same as the control)towards the end of the composting. Multiple regression analysis,Relative root elongation and GI were more sensitive indicators ofphytotoxicity than seed germination.

Tam and Tiquia (1994) determined seed germination and rootelongation of four plant species to evaluate the toxicity of the spentlitter. Compared with seed germination, root elongation was moresensitive to the toxicity of the spent litter. The study was under-taken to characterize the fungi on non-phytopathogenicity for cropproduction as well as the potential ability for bioconversion ofdomestic wastewater sludge by Molla et al. (2002b). Ten filamen-tous fungi adapted to domestic wastewater sludge (DWS) werestudied to assess their potentiality in terms of adaptation to highersludge-supplemented growing media and phytopathogenicity tothree germinating crops (Corn: Zea mays, Mung bean: Phaseolusaureus and Mustard: Brassica napus) seeds. The performances ofthe fungi in seed germination were evaluated based on the percentgermination index (GI) and infected/spotted seeds on the directfungal biomass (FBM) and the fungal metabolite (FM).

It has been reported that low concentrations of some trace met-als retard root elongation and delay seed germination for a largenumber of plants (Wong and Bradshaw, 1982; Wong and Lau,1983). Ammonia produced upon decay of animal manure can alsoinhibit seed germination and seedling growth of Brassica parachi-nensis (Ellis et al., 1991; Wong and Lau, 1983). Phytotoxicity ofimmature compost was much higher than of mature compost (Bacaet al., 1990; Garcia et al., 1992a; Zucconi et al., 1981a,b) because ofthe presence of toxins during decomposing organic material, NH3,high C/N ratio and the availability of heavy metals (Inbar et al.,1990). The phytotoxicity of organic wastes was also due to highelectrical conductivity, an excess of ammonia, phenolic substances,organic acids of low molecular weight and other phytotoxic organicmetabolites (Garcia et al., 1992b).

6. Environmental and economic impacts of composting

Composting, one of the most suitable technologies for treatingwastes can reduce the mass, destroy the weed seeds, provide a suf-ficient sanitization effect and produce valuable end products (Jianget al., 2001). In terms of its inexpensive costs and rather simplye

technique, composting was used widely, especially in develop-ing countries. For example, in China more than 17 million tonnesorganic fertilizer was produced from composting each year; andin the municipal solid waste and sewage sludge treatment field,

76 N. Mohammad et al. / Resources, Conservation and Recycling 58 (2012) 69– 78

Table 7Characterization of composting process with EFB and POME used for investigations in reviewed literature.

Substrates Microbial systems Controlling parameters References

Palm press fibre, poultry layerdeep-litter and broilerfloor-litter and urea

Inoculated by Bacteria andfungi

Temperature, moisture, C/N, etc. Thambirajah and Kuthubutheen (1989)

EFB, goat dung, cow dung andchicken manure

Inoculated by bacteria, fungal Temperature (70 ◦C), C/N (35:1), pH(5.4), etc.

Thambirajah et al. (1995)

EFB Natural degradationa C/N (30) Hamdan et al. (1998)EFB, fermentation liquid waste and

chicken manure and palm oilmill effluent

Natural degradation Moisture (56%), C/N (41, open; 56,closed), etc.

Suhaimi and Ong (2001)

EFB and POME Natural degradation Evaporation rate (3.5 m3/t), C/N (50),rainfall (2000 mm/a), etc.

Schuchardt et al. (2002)

EFB, POME and wheat flour Inoculated by P. chrysosporium,T. harzianum, A. niger andPenicillium

pH (5–7), moisture content (60–70%),temperature (30 ± 2 ◦C), etc.

Kabbashi et al. (2006)

Rice straw and EFB Inoculated by Trichodermaharzianum

Fortified or unfortified Yasmeen et al. (2008)

EFB and POME Inoculated by bacteria species Temperature (>50 ◦C), moisturecontent (65–70%), etc.

Baharuddin et al. (2009)

With/

tCphlgahaogdhCvt

7

iihiAwtgHuhttpdnoccaeol

EFB and POME Natural degradation

a Natural degradation indicates no inoculation of microbes.

he proportion of composting increased rapidly (Li et al., 2003).ompost from organic wastes is much cheaper than the fertilizerroduced in the industry. Compost also improves the soil water-olding capacity and provides better tilts. The use of compost is no

onger limited to its use as a soil amendment. Compost technolo-ies are emerging rapidly valuable tools in pollution preventionnd control. Compost is now being used in erosion control onighways, the clean up of contaminants in storm water runoffnd in the remediation of soils contaminated with heavy metalsr toxic organic compounds. With regard to the concerns aboutlobal warming, composting is playing a major role. The organicecomposition of wastes in anaerobic landfills and open lagoonsas methane as the major product, while the same process formsO2 in anaerobic composting. Since methane has 22 times the unfa-orable impact on global warming, composting materials abateshis problem (Ndegwa, 1999).

. Conclusions

Composting is commonly defined as a natural aerobic biochem-cal process in which microorganisms transform organic materialsnto a stable soil-like product. The process is well established andas been comprehensively documented in literature. Although this

s an old technique, its application in palm oil wastes is very limited.mong them, EFB as well as POME are not environmentally friendlyhen they are disposed of after the extraction of oil palm fruits. EFB

akes a long time to degrade, while the POME contaminates theround and reduces the soil fertility with excessive organic loads.owever, they may be a potential resource and value-added prod-ct if they are treated and managed properly. Numerous studiesave already regarded these issues. Current practices described inhe literature are time consuming: at least two months are neededo convert them; and they do not guarantee pathogen-free endroducts (composts). Moreover, most researchers are using naturalegradation without proper microbial systems. Their systems areot fully efficient because fungi were not deployed making full usef their enzymatic properties. Furthermore, application of mixedulture fungi in the composting system, especially in EFB and POMEomposting is limited. Proper microbial systems can be developed

nd used for the composting process to establish an efficient andffective composting process. Microbes would be selected basedn their enzymatic properties i.e. lignin, cellulose and hemicellu-ose degrading fungi that would be useful for the raw materials of

without decanter cake slurry Yahya et al. (2010)

lignocellulolytic based composting process. Mixed culture fungalsystems can accelerate the process and shorten the time.

Acknowledgements

The authors are grateful to the Research Management Center(RMC) and the Department of Biotechnology Engineering, Interna-tional Islamic University Malaysia (IIUM) for their financial support.

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