International Journal of Recycling of Organic Waste in Agriculture
Volume:2 Issue: 1, Autumn 2012

Comparative effects of untreated olive mill wastewater (UOMW), treated olive mill wastewater (TOMW) and bioaugmented olive mill wastewater (BOMW) on soil properties, on seeds germination and on plants growth were investigated. The water holding capacity, the salinity, the organic carbon content, humus, total nitrogen, phosphate and potassium increased when the spread amounts of UOMW (50, 100 and 200 m3 ha-1.year-1) or TOMW increased. TOMW increased the total mesophylic number while the number of fungi and nitrifiers decreased. Actinomycetes and spore-forming bacteria were neither sensitive to TOMW nor to UOMW. The total coliforms number increased with higher doses of TOMW and UOMW. Hazard assessments of toxicity were conducted for UOMW, untreated olive mill wastewater organic extract (UOE), TOMW, treated olive mill wastewater organic extract (TOE) and extracts of soils amended with UOMW (SUOMW) and with TOMW (STOMW). Results showed an increase in the germination index when seeds species were cultivated with TOMW. Plants irrigated by TOMW showed an improvement in biomass, spike number, plants growth and a similar or even better dry productivity than plants irrigated with water.

The profitable use of the large amounts of olive oil mill wastes produced in Greece, as source of soil organic matter, might be probably beneficial to soil microorganism activity.

A high rate of organic matter biodegradation was observed in soil samples amended with the liquid form of olive mill wastewater, whereas the vice versa results were obtained with the solid form. When the soil was amended with a mixture of both olive mill waste forms, liquid (L) and solid (S), the organic matter of the solid waste (S) showed a well-improved biodegradation; the available forms of P, K, Zn, Mn, and Cu were increased, especially in treatments where the olive mill wastewater, liquid form, was threefold in comparison to the solid form. Moreover, the soil amended with the solid (S) form of olive mill waste reduced bacterial growth significantly, and both waste forms act negative impacts to soil-borne fungi belonging to the genus Rhizopus.

The results of this work demonstrated the high potential of olive mill waste, solid or liquid form, added to sandy loam soil in an incubation experiment in vitro. The better results for soil quality were obtained when a combining mixture of these materials was added in the ratio 1:3 (solid/liquid).

Moringa oleifera tree is indigenous and highly abundant in Indonesia and its seeds are widely known to be used as a natural coagulant for treating wastewater. Wastewater from tapioca starch industry, particularly in Indonesia, which contains high organic matters, was revealed by high biochemical oxygen demand (BOD) and chemical oxygen demand (COD) value. In this study the combination of powdered M. oleifera seed and natural filter media was studied. A laboratory scale of tapioca starch wastewater (TSW) treatment was designed using a continuous two-stage clarifier tanks filled with sand or coconut fibre combined with the addition of powdered M. oleifera seed.

A significant improvement on both the physical and chemical characteristics of the effluent quality, showing a clearer colour and a greater reduction in BOD, COD and total suspended solid values; while pH was in the acceptable range for effluent disposal. In terms of the microbial characteristics, all treatments gave slightly higher counts of total coliform in the range of 26 to 40 MPN 100 ml−1 .

The combination of two-stage clarifier tank with natural filter media and the use of M. oleifera as natural coagulant gave a significant improvement in the quality and appearance of TSW final effluent.

Abundant uses of chemical fertilizers have adversely affected the soil. The large production of livestock dung is recorded in India annually. The presence of abundant agrowastes and animal dung causes serious problems to animals as well as to human beings, due to the improper management of these wastes. Due to the presence of different physicochemical parameters, these agrowastes and animal dung as food source influence not only the earthworm population but also affect their growth and reproduction during vermicomposting. The effect of agrowastes (wheat straw, banana pills) and bran (barley, rice, and gram bran) with cow and goat dung as tertiary combinations (1:1:1) on the growth and reproduction of E. fetida was investigated.

The significant (P < 0.05) highest cocoon production was 5.92 ± 0.01/worm/2 weeks observed in CWRr. The reproduction rate as the number of hatchling emerged per cocoon was also significantly the highest (P < 0.05) in CWBr as 1.9 ± 0.03. The maximum biomass gained was up to 898.67 ± 2.04 mg/worm, and significant growth rate was 7.32 ± 0.02 mg/worm/day in CWGr combination. There was a significant decrease in pH, C/N ratio, TOC, and EC while there was a significant increase in TKN, TK, TAP, and TCa in different tertiary combinations of final vermicompost when compared to the initial feed mixture.

The tertiary combinations of dung and bran with agrowastes used were effective and efficient culture media for the large-scale production of E. fetida, which will be important for the production of vermicompost.

Palm oil mill effluent and palm press fiber are problematic wastes generated by the palm oil mill industries in Malaysia. This study has endeavored to assess the possibility of the vermicomposting of residue from the palm oil mills using epigeic earthworms Lumbricus rubellus under laboratory conditions. The study was conducted over 50 days using four combinations in three replicates of each treatment as palm oil mill effluent: palm press fiber in 50:50 ratio (T1), palm oil mill effluent/palm press fiber/cow dung in 50:25:25 ratio (T2), palm oil mill effluent/palm press fiber/cow dung/lawn clipping in 50:20:15:15 ratio (T3), and only palm press fiber (T4). Twenty healthy adult L. rubellus with average weight of 3.92 g was introduced.

Results showed that T3 has a significant decrease in C/N ratio (14.81 ± 0.07) compared to the other treatments. The presence of cow dung and lawn clipping in the mixtures makes it more suitable for vermicomposting process as early compost productions were recorded in T2 and T3.

The study showed that the major polluting problem in palm oil mills can be tackled through vermicomposting technique. Based on the results, vermicompost is found suitable for agriculture purposes as an organic fertilizer as well as soil conditioner.

Cassava waste pulp from the tapioca industry is abundant in Indonesia. However, there have been few Indonesian or international papers describing research on the possible use of cassava waste pulp as a superabsorbent after modification. The goal of this work was to increase the added value of cassava waste pulp by converting it into a superabsorbent. This conversion was carried out by a graft copolymerization of cassava waste pulp using acrylamide, ammonium persulfate, and N,N′-methylene-bisacrylamide as a monomer, an initiator, and a crosslinker, respectively. The copolymerization was conducted at 70°C for 3 h and saponified with 1 M NaOH for 2 h.

The superabsorbent had a maximum water absorption capacity of 1,014 g/g at pH 7.3; the absorbency was affected by the salinity of the medium. The rate parameter for absorption in distilled water was 5.4 min. The formation of a superabsorbent was confirmed by FTIR spectroscopy, as the spectra exhibited all characteristic bands of both cassava waste pulp and acrylamide.

Cassava waste pulp has a great potential to be used as a superabsorbent, which could give added value to cassava

The lack of electricity and water supply in rural abattoirs in developing nations prevents the adoption of waste-processing technologies practiced in economically advanced countries. This research attempts to recycle waste blood and rumen digesta generated in rural slaughterhouses as organic fertilizer, thus promoting sustainable agriculture.

The values of 5-day biochemical oxygen demand, chemical oxygen demand, total Kjeldahl nitrogen, concentrations of oil, grease, total suspended solids, total solids, and total phosphorus characterized blood and rumen digesta as highly polluting wastes. Waste blood and rumen digesta were mixed in 1:1, 2:1, and 3:1 ratios and dried to obtain ‘bovine-blood-rumen-digesta-mixture’ (BBRDM). The efficacy of the organic fertilizer was compared with diammonium phosphate (DAP) in a pot cultivation of tomato, chili, and brinjal. Five grams of BBRDM (N/P/K = 30.36:1:5.75)/kilogram of soil applied at the second and sixth weeks produced earlier fruiting by 2 weeks and yielded (in terms of total fruit weight) higher by 130% for tomato, by 259% for chili, and by 273% for brinjal in BBRDM (3:1)-cultivated plants compared to DAP. BBRDM-applied soils showed higher C, N, and P concentrations than DAP. High-nitrogen-containing BBRDM mineralized rapidly, and nitrogen and phosphorus were available within 6 days of drying. Although high nitrogen concentration caused toxicity when applied at the time of planting to young plants, BBRDM enhanced the yield and productivity when applied to mature plants after 15 days of plantation. Higher numbers of Azotobacter, phosphate-solubilizing bacteria, fungi, and amount of chlorophyll were isolated from soils treated with BBRDM than with DAP. Carbohydrate, protein, and fat contents of the vegetables were comparable to DAP-grown vegetables.

Highly polluting abattoir wastes could be gainfully utilized, promoting a healthy environment around rural slaughterhouses. The application of BBRDM to crops of marginal returns is an attractive proposal.

Chicken processing results in the production of a lot of blood which if disposed on land poses environmental hazards in terms of land pollution. The aim of the study was to develop an aerobic composting process for chicken blood to produce a nitrogen-rich soil amendment for use in agriculture. The study involved composting of blood and maize stover of different proportions (10%, 30%, 70% and 100% maize stover) in compost bins over 72 days and determining which proportions would yield compost with greater potential to support plant growth.

The performance of the different compost mixtures was evaluated by monitoring internal temperature, mineral N (NH4 + -N and NO3 − -N), C/N ratio, pH, electrical conductivity and total cations. The concentration of ammonium N decreased by 8.75%, 50.5%, 33.5% and 18.8% for the 10%, 30%, 70% and 100% stover treatments, respectively, with composting time. Nitrate N peaked to 1.93 and 1.06 mg/kg for the 30% and 70% treatments, respectively, on day 43, while it peaked to 1.54 and 0.54 mg/kg for the 10% and 100% treatments, respectively, on day 50. The C/N ratios decreased significantly (p < 0.001) for all treatments.

The 10% and 30% treatments had better composting performance than the 70% and 100% treatments as they reached and maintained thermophilic temperatures for at least 8 days. The 10% and 30% treatments appeared to have the greater potential of supporting crop growth.

Vermicomposting has recently been recognized as one of the most appropriate methods to stabilize organic waste. In terms of a system for waste management, vermicomposting is sustainable, economically viable, and without detrimental effects to human health or to the environment. The aim of this study was to evaluate the process of vermicomposting using an indigenous species of earthworms (Eisenia fetida) on a small domestic scale as a system for waste management.

This study was carried out as an experiment using the following procedure: a plastic container was prepared for vermicomposting; then, a bed was prepared in a ready container with a layer of initial bedding, sieved garden soil, and compostable waste. It was inoculated with Eisenia fetida earthworms. Samples were taken after 30 and 90 days of vermicomposting, and measurements were taken for the following parameters: percentage of organic matter, phosphorus, total carbon, total nitrogen, moisture content, ash, electrical conductivity, and pH. Results for percentage of organic matter, phosphorous, ash, total carbon, total nitrogen, carbon/nitrogen ratio, electrical conductivity, moisture content, and pH of mature compost after 90 days were 42 ± 2.8, 53 ± 0.17, 22 ± 0.170, 1.12 ± 0.003, 20 ± 0.25, 2.8 ± 0.6, 1, 200 ± 200 cSu, 56 ± 5.5%, 8.3 ± 0.2, respectively, and all these parameters except moisture content were compared with the standards.

According to these results, vermicomposting of municipal biodegradable waste by homeowners can be recommended as the best and most suitable method for solid waste disposal. This determines small-scale domestic vermicomposting as a suitable method for solid waste management. Reducing domestic waste at the source is an effective way to implement the main priorities of a waste management system in terms of its economy and its impact on the environment.

To prevent the interruption of the carbon cycle by the disposal of waste to landfills, organic kitchen waste requires proper treatment such as composting to reduce its uncontrolled degradation on disposal sites and subsequent greenhouse gases, odour emissions and nutrient losses. This study investigated the effects of bulking agent, newspaper and onion peels, composting waste load sizes of 2 and 6 kg, or the use of starter culture on kitchen-waste composting consisting of nitrogen-riched substrates, vegetable scraps and fish processing waste in an in-vessel system. The optimised formulation of kitchen waste mixture was used for a 30-day composting study, where the temperature profiles were recorded and the carbon-to-nitrogen ratios were measured as an indication of compost maturity. The kitchen-waste composting process was conducted in parallel in two fabricated kitchen waste composters.

It was found that the onion peels were more suitable in producing matured compost where the carbon-to -nitrogen ratio reduced to 10 within 16 days of composting. A smaller kitchen waste load size of 2 kg gave a shorter composting time by half when compared to the 6 kg. The use of a microbial cocktail consisting seven types of bacteria and eight types of fungi isolated from soils as a starter culture for this kitchen-waste composting did not show advantages in accelerating the composting process.

The results suggest that the in-vessel kitchen-waste composting can be efficient with a minimal load of about 2 kg using onion peels without additional starter culture.

Livestock excretions containing high concentration of nutrient, pig liquid fertilizer, and cattle manure were applied to agricultural land. The characteristics of nutrient transport were examined in surface runoff and groundwater by an artificial rainfall event at real scale field site. Also, the effects of the artificial rainfall event on the characteristics of residual soil after the rainfall and phosphorus adsorption capacity were evaluated in the lab.

As results from the field experiments, nitrogen concentration was decreased by the repeatable precipitation in surface runoff, but the nitrate concentration in groundwater was gradually increased by biological metabolism, especially with pig liquid fertilizer. Phosphorus was mostly adsorbed into the soil, and its reduction was affected by the soil drainage due to surface runoff in summer. The adsorption capacity of the phosphorus via a jar test was determined as 0.7 mg P/kg of soil.

The soil adsorption capacity would be an important factor for the optimum level of nutrient application that is required for agricultural performance and minimal environmental impact.

Nowadays, management and recycling of industrial by-products are one of the most important issues in developing and developed countries. Beef tallow is one of these residues produced in slaughter houses and primarily is utilized in soap production industry. However, when this industry is overloaded, the extra fats are usually incinerated or disposed in a sanitary landfill. However, beef tallow may be consumed in biodiesel production. Therefore, in this work, the process of biodiesel production in a pilot plant has been studied using beef tallow as raw material with methanol and potassium hydroxide as catalyst. The quality of the produced biodiesel is evaluated using Fourier transform infrared spectroscopy (FTIR) method.

FTIR analysis showed that the final product contains ester compositions which can be used as biodiesel fuel in diesel engines. The viscosity of natural beef tallow was very high, and actually, it was solid; however, after transesterification the viscosity of the final product decreased, and it became liquid. The viscosity of the final product measured at 40°C was 5.3 mm2 s −1 , and the comparison of this biodiesel with the data of ASTMD-445 standard resulted in the similarity of this product with petroleum diesel (3 to 12 mm2 s −1 ).

Alkaline transesterification of beef tallow with methanol decreases the viscosity of the final synthesized product and produces a high quality biodiesel for diesel engines. Beef tallow is one of the low cost residual materials available in slaughter houses. Therefore, the slaughter houses can be considered as one of the available sources to produce biodiesel. In this research, the process of biodiesel production from beef tallow was validated, but the economical viability must be improved by recovering methanol and glycerol.

The relationships between the density of the biomass pellet and the related variables are very complicated and highly nonlinear, which make developing a single, general, and accurate mathematical model almost impossible. One of the most appropriate methods to solve these problems is the intelligent method. Shankar and Bandyopadhyay and Shankar et al. successfully used genetic algorithms and artificial neural networks to understand and optimize an extrusion process.

The results showed that a four-layer perceptron network with training algorithm of back propagation, hyperbolic tangential activation function, and Delta training rule with ten neurons in the first hidden layer and four neurons in the second hidden layer had the best performance for the prediction of pellet density. The minimum root mean square error and coefficient of determination for the multilayer perceptron network were 0.01732 and 0.972, respectively. Also, the results of statistical analysis indicate that moisture content, speed of piston, and particle size significantly affected (P < 0.01) the density of pellets while the influence of die length was negligible (P > 0.05).

The results indicate that a properly trained neural network can be used to predict effect of input variable on pellet density. The ANN model was found to have higher predictive capability than the statistical model.

The composting process of peri-urban household wastes, changes that occur during composting, and the properties of the composting products that are of importance for use as soil amendments were studied. Seven different composting mixtures were made in large piles consisting of fallen tree leaves and fresh vegetable leaves mixed with grass or maize straw (0%, 10%, 30% and 50% w/w), wastes common in peri-urban areas of Harare.

The highest temperature peaks of the mixtures with 0% and 10% straw were in the range of 68°C to 72°C. Mixtures with 30% straw had temperature peaks of 50°C (maize) and 52°C (grass). The mixture with 50% grass straw reached a peak of 50°C, while the corresponding mixture with maize straw did not reach thermophilic temperatures. pH ranged from between 6.2 and 6.8 before composting to between 7.4 and 7.8 after composting. The ammonium concentration peaked at various times but declined to negligible concentrations at day 140. The concentration of nitrates increased with composting up to day 97 and decreased gradually thereafter. There was a general increase in nitrogen concentration from 0.9% to 2.3% as composting progressed. Decreases in organic C% and C/N ratio with composting were also observed, signifying mass loss.

The results of this study indicated that household wastes with 50% straw or less can be composted but with measures being taken to achieve temperatures greater than 55°C for at least 3 days to destroy weed seeds and pathogens. The composts with 30% straw mixture had the greatest potential as a soil amendment in peri-urban areas of Harare as they effectively reduced nitrogen losses.

Vermicompost (VC) made from cattle dung as raw material was used as soil supplement in the plots of size 4.5 x 4.5 m. Five treatments were given viz. Soil (control), VC@5 t/ha, VC@10 t/ha, VC@20 t/ha and NPK (recommended by PAU, Ludhiana) in triplicates in a Randomized Block Design (RBD). A total of 50 plants were selected randomly for the assessment of growth and yield of wheat Triticum aestivum L..

Most of the growth, yield and quality parameters were found to be maximum in NPK treatment. All the growth, yield and quality parameters in vermicompost treatments varied significantly from control though differences within various vermicompost treatments were not found to be significant.

It has been observed that there is no significant difference on applying higher doses of vermicompost and lowest dose (5 t/ha) is as effective as higher doses. So, vermicompost application is cost effective.

Different substrates have several materials which could have direct and/or indirect effects on plant growth and development. The use of different organic and inorganic substrates allows that plants have best nutrient uptake and sufficient growth and development to optimize water and oxygen holding. This work was carried out using a completely randomized design with six treatments and six replications. The treatments were pure palm peat, pure rice hull, soil + 5% (weight) palm peat, soil + 5% (weight) rice hull, soil + 5% (weight) palm peat + 5% (weight) rice hull and pure soil. During plant growth Papadopolus formula with fertigation method was used for nutrient solution. Selected physiochemical properties of culture media and selected growth indices of plants were measured at the end of growth period. Results showed that amount of porosity, water holding capacity (WHC) and cation exchange capacity (CEC) in date-palm peat was higher than soil and rice hull but amount of bulk density in date-Palm peat was lower than the others. Also The results showed that many growth parameters were affected by the culture media. Most amount of yield and plant height in each was related to palm waste (100%) and had significant difference at 5% level as compared with the others. Results showed that plant growing indices for cucumber plant were sufficient when cultured only in date Palm waste and rice hull substrates and when this materials were added to the soil, although it amended physiochemical properties of media but decreased the plant growing indices.

Adsorption of methylene blue by the sieved biomass of Cicer arientinum is conducted in batch mode. The effect of different parameters such as contact time, sorbent dose, pH, and temperature has been studied. The adsorption rises substantially as pH is increased from 2 to 4, and then with the increase to pH 10, there is slight decrease in the percentage of adsorption. This may be due to the electrostatic forces of attraction between [MB]+ cations and the OH− ions which are greater at low pH in the solution. In the highly acidic medium, there are an ample number of H+ ions. These can neutralize the negative sites on biosorbent surfaces, leading to a lesser adsorption. The Langmuir model fit and Hall separation values indicate favorable adsorption. Thermodynamic parameters via KD and ΔG have also been calculated: the ΔG value at 15°C is −943 J/mole, while at 45°C, the value of ΔG is −4,010 J/mole. At the higher concentration, KD values decrease and the ΔG values become positive in the same temperature range, indicating the spontaneity of the process. Kinetics of biosorption results shows that the sorption process is well explained by a pseudo-second-order model with determination coefficients of 0.4841 to 0.9962 for S-II under all experimental conditions. The sorption mechanism was determined by the Weber and Morris intraparticle diffusion model. For the initial concentration of 79.9 mg/L and material dose of 500 mg/L, the value of Kid and the intercept was found to be 4.359 and 22.557, respectively, indicating that the foundry layer is sufficiently thick. The low-cost, easily available agro-waste of C. arientinum was found to be a good adsorbent for the methylene blue dye.

The present study was undertaken to evaluate the efficiency of combined technology involving ceramic microfiltration and biosorbent for the treatment of tannery effluent from different streams, viz. composite effluent, effluent from primary clarifier and secondary clarifier. The membranes were prepared from a cost-effective composition of alumina and clay.

The effluents had high organic loading of 12,895, 3,890 and 410 mg/L, respectively, in terms of chemical oxygen demand (COD). Apart from these, the effluents consisted of toxic heavy metals, turbidity, biochemical oxygen demand (BOD), etc. It was observed that COD reduction was about 96.5% for effluent 1, 96.6% for effluent 2 and 96.9% for effluent 3. Considerable reduction in suspended solids, total nitrogen, and total organic carbon was obtained. Turbidity for all three types of effluent was below 1 NTU. The average flux value for effluents 1, 2 and 3 was about 13, 19 and 24 L/m2 /h (LMH), respectively. Response of the antioxidative defences of Euphorbia hirta was observed which resulted in considerable decrease in the activity of peroxidase, superoxide dismutase and catalase.

The treatment resulted in the reduction of toxicity thereby restoring normal activity when compared to control values. Changes in various biochemical parameters like protein, amino acid, carbohydrate, DNA, RNA and chlorophyll content were observed.

Vermicomposting is a biological process which may be a future technology for the management of animal excreta. This study was undertaken to produce vermicompost from cow dung and biogas plant slurry under field conditions. To achieve the objectives, two vermicomposting units containing cow dung (CD) and biogas plant slurry (BPS) were established, inoculated with Eisenia fetida species of earthworm and allowed to be vermicomposted for 3 months.

After 3 months, the vermicompost was harvested and characterized. The results showed that the vermicompost had lower pH, total organic carbon (TOC), organic matter (OM) and carbon/nitrogen ratio (C/N ratio) but higher electrical conductivity (EC), nitrogen, phosphorous and potassium (NPK) content than the raw substrate. The heavy metal content in vermicomposts was higher than raw substrates.

During vermicomposting, the CD and BPS were converted into a homogeneous, odourless and stabilized humus-like material. This experiment demonstrates that vermicomposting is an environmentally sustainable method for the management of animal excreta.

In light of existing regulations regarding the use of nematicides coupled with the global loss of agricultural outputs due to nematodes, new strategies are needed to ensure soil ecosystem health while promoting crop production without the use of potentially dangerous chemicals. Proof of concept methodologies can be used by soil/agricultural scientists interested in identifying potential shortcomings of a given strategy and to identify additional parameters for future work. Using this limited approach allows for the dissemination of information in a stepwise fashion so that changes in research strategies can be initiated prior to final ‘definitive’ results. This work tests the viability of using coal fly ash, stabilized biosolids, or a mixture of the two to manage plant-parasitic nematode populations and increase carrot yield.

The fly ash and biosolids chosen for this work did not alter soil pH or metal content enough to impact significantly on nematode populations. Data on all parameters were combined to see overall trends. The soil and amendments are basic in nature with pH values close to 8 and only fluctuating between 0.2 (season 1) and 0.4 (season 2) pH units from baseline to harvest. Fly ash played a minor role in B and Fe increases, and biosolids contained slightly more Ca, Cu, K, Mg, P, and Zn than the soils, but none of these elements were present in concentrations that affected nematode ontogeny. Fly ash was more important in altering electrical conductivity than biosolids and had the greatest impact on nematode population changes. Biosolids were most important for increasing carrot yields either alone or in mixtures.

Not all fly ash or biosolids are equal. The choice of these materials as soil amendments, or natural nematicides, should be based on pre-examination of the soils and the raw materials. Subsequently, ratios and application rates should be chosen so that the physicochemical and microbiological conditions favor nematode management. Biosolids and biosolids mixed with fly ash are capable of enhancing carrot yield significantly at the ratios and application rates tested in this study but had little effect on nematode populations.

The common practice of clearing pineapple (Ananas comosus) residues for land preparation for cultivation is by burning, an unsustainable agricultural practice that causes environmental pollution. Chicken manure produced from the poultry industry is also increasing. Inappropriate disposal or treatment can pose harm to the environment and humans. In order to reduce environmental pollution, pineapple leaves and chicken manure slurry were co-composted to obtain high-quality organic fertilizer. The shredded pineapple leaves were thoroughly mixed with chicken manure slurry, chicken feed and molasses in polystyrene boxes. Co-compost temperature readings were taken three times daily.

Nitrogen and P concentrations increased whereas C content was reduced throughout the co-composting. The CEC increased from 32.5 to 65.6 cmol kg−1 indicating humified organic material. Humic acid and ash contents also increased from 11.3% to 24.0% and 6.7% to 15.8%, respectively. The pH of the co-compost increased from 6.14 to 7.89. The final co-compost had no foul odour, low heavy metal content and comparable amount of nutrients. Seed germination indices of phytotoxicity test were above 80% of final co-compost. This suggests that the co-compost produced was phytotoxic-free and matured.

High-quality co-compost can be produced by co-composting pineapple leaves and chicken manure slurry and thus have potential to reduce environmental pollution that could result from poorly managed agricultural wastes.