International Journal of Recycling of Organic Waste in Agriculture
Volume:3 Issue: 2, Spring 2014

Background Disposal of vegetable waste in landfills and illegal sites leads to emission of greenhouse gases and leachate production, thereby imposing major environmental issues. As an alternative, this waste can be successfully recycled for its high nutrient content using composting process. Results Five trials were made with the ratio of 6:3:1 of trial 1 (50 kg), trial 2 (70 kg), trial 3 (90 kg), trial 4 (120 kg) and trial 5 (150 kg) by adding 10 kg of dry leaves in each of the trials as bulking agent. Due to active microbial population and high biodegradable organic matter in vegetable waste, early thermophilic phase was observed within 18–24 h of the composting process in all of the trials with a maximum of 61.4 C in trial 3. Total mesophilic heterotrophs were observed in the range of 7.1 9 1011 CFU g-1 and gradually reduced to 2.65 9 106 CFU g-1 at the end of 20 days, which was considered due to prolonged thermophilic phase maintained in trial 3. An average of 54–56 C temperature was maintained for 7 days in trial 3, with spore-forming population in the order of 3.82 9 109 CFU g-1 contributing to higher organic destruction. The populations of fungus, actinomycetes and streptomycetes were observed to reduce during thermophilic phase and remained in the order of 2.85 9 104 , 3.8 9 106 and 4.1 9 105 CFU g-1 , respectively, at the end of 20 days. CO2 evolution and OUR were in the order of 0.89 and 0.32 mg g-1 VS d-1 , respectively, in trial 3 denoting maximum degradation of organic matter and stabilization of compost. Indicator organisms were found well with the standard limits due to elevated temperature. Conclusions Combinations of waste materials played a major role in favoring microbial succession. Temperature in the compost system had major effect on the survival of the microbial populations. Elevated temperatures favored higher degradation of organic matter, thereby stabilizing the compost within proposed time of composting and also destructing the indicator pathogens.

Soil incorporation of cereal straw to avoid burning and air pollution may influence the availability of Zn, a critical micronutrient in cereal production. Field experiment was carried out to evaluate the effect of zinc sulphate application and the cyclic incorporation of cereal straw on the yields, tissue concentration and uptake of Zn by rice and wheat crops and availability of Zn in soil.

Application of 25 kg ZnSO4 ha-1 to I year rice crop increased the grain yields of rice by 24.3 and 56.3 % over control during I and II year, respectively. Application of 25 kg ZnSO4 ha-1 to I year rice crop ? cyclic incorporation of 1.5 t straw ha-1 increased the grain yields of rice by 21.4 and 87.4 % over control during I and II year, respectively. In I year, the grain yield of wheat crop was not significantly influenced by the different treatments while in II year the highest wheat grain yield was recorded with 25 kg ZnSO4 ha-1 to I year rice crop ? cyclic incorporation of 6.0 t cereal straw ha-1 . Application of 25 kg ZnSO4 ha-1 to I year rice ? cyclic incorporation of 1.5 t straw ha-1 resulted in a significant increase in the concentration of Zn in the plant tissues of both rice and wheat crops. The cyclic incorporation of 1.5–3.0 t cereal straw ha-1maintained better availability of ZnSO4 applied to I year rice crop to the subsequently grown crops.

Soil application of 25 kg ZnSO4 along with incorporation of 1.5 t cereal straw ha-1 prior to I year rice transplanting followed by cyclic incorporation of cereal straw in subsequent crops ensures higher availability of Zn in soil and higher yields in rice–wheat rotation.

The objective of this study was to develop a consortium of effective microorganisms to hasten the composting process and to reduce the composting period.

An efficient microorganism (EM) consortium was developed using Candida tropicalis (Y6), Phanerochaete chrysosporium (VV18), Streptomyces globisporous (C3), Lactobacillus sp. and enriched photosynthetic bacterial inoculum for rapid composting of paddy straw. Paddy straw was amended with poultry droppings to narrow down its C:N ratio for faster degradation. Composting was carried out in open pits with EM consortium and compared with compost inoculant (CI) consisting of Aspergillus nidulans (ITCC 2011), Trichoderma viride (ITCC 2211), Phanerochaete chrysosporium (NCIM 1073) and A. awamori (F-18). Changes in biochemical and physiochemical parameters like C:N ratio, pH, EC and humus were studied over a period of 60 days to test compost maturity and stability along with microbial and extracellular hydrolytic enzyme activities. Paddy straw amended with EM and CI hasten the composting process by bringing C:N ratio down to 15:1 and achieving a total humus content of 4.82 % within 60 days. High activity of hydrolytic enzyme carboxymethyl cellulase (CMCase) (0.43 IU/g) and microbial activity in terms of dehydrogenase (158.64 μg TPF/g/day) was observed in this treatment. The activity of xylanase was positively correlated (r = 0.987) with alkali-soluble carbon.

This study illustrates the importance of microbial bioaugmentation to hasten the composting process of paddy straw to produce quality compost.

Water hyacinth (Eichhornia crassipes) is one of the worst weeds in the world. Composting is one of the most economical ways for the treatment and final disposal of water hyacinth, because it combines material recycling and biomass disposal. A major restriction of land application of water hyacinth compost is the possible high heavy metal concentration in the final product. Zeolites may be useful as metal scavengers in metal-rich water hyacinth compost. The speciation of heavy metals (Zn, Cu, Mn, Fe, Pb, Ni, Cd and Cr) was done according to Tessier’s sequential extraction method during water hyacinth composting mixed with cattle manure, sawdust and natural zeolite. The water hyacinth, cattle manure and sawdust were taken in the 6:3:1 ratio with 5, 10 and 15 % natural zeolite, respectively.

The temperature was measured in the range of 48.6–56.2 °C in control and zeolite treatments. Higher reduction of exchangeable (F1) and oxidizable (F4) fractions of Zn was observed about 72.8 and 79.6 %, respectively, in zeolite 1 treatment but higher reduction of carbonate (F2) and reducible (F3) fractions was observed about 70 and 37 %, respectively, in zeolite 2 treatment. The F1, F2, F3 and F4 fractions of Cu and Fe were reduced in the control and all zeolite treatments. The F1, F2, F3 and F4 fractions of Mn were reduced significantly in the all zeolite treatments in comparison to control. The bioavailability factor (BF) of Zn, Cu, Mn, Fe, Ni, Cd and Cr was reduced significantly in zeolite treatments in comparison to control. There was no significant change observed with BF of Pb in zeolite treatments. The total concentration of Pb was higher than Zn, Cu, Mn, Ni and Cr but its BF was lowest among the all these metals.

Addition of optimum percentage of natural zeolite was successful for enhancing degradation of organic matter and reducing bioavailability of heavy metals during water hyacinth composting mixed with cattle manure and sawdust. The bioavailable fractions of heavy metals were effectively correlated with pH and TOC in control and zeolite 1 treatment as compared to zeolite 2 and 3 treatments.

Ruminants have low efficiency of nitrogen utilisation; unutilised nitrogen is being excreted in the faeces and urine. The most effective way to minimise nitrogen losses in ruminant production is through efficient feeding strategy. Ruminant manure is an inevitable consequence of its production. All these have adverse environmental effects. Composting and vermicomposting have been suggested as efficient tools for recycling manure, these bring a stabilised and sanitised end product for agriculture. Composting process is an accelerated aerobic degradation of fresh organic matter by microorganism to mature compost. Nevertheless, it may bring some environmental problems by releasing gases which include ammonia, methane and nitrous oxide, reduce the agronomic value of the manure and increase the cost of composting through turning of the compost to ensure aeration. To overcome the cost of composting and produce high quality products, vermicomposting is being recommended. Vermicomposting involves the bio-oxidation and stabilisation of organic material by the joint action of earthworm and microorganism. Moreover, the combination of composting and vermicomposting has been considered as a way of achieving stabilised substrates. Ensiled cattle manure treated with straws has been used to improve nutritional quality of ruminant feed and the result was encouraging. Vermicast, an end product of vermicomposting has higher nutrients content compared with manure or composted manure. Therefore vermicomposting of ruminant manure with rice/wheat straws might have the potential of being used as feed supplement to small ruminant. The likely benefit will be an increase in feed intake, increase in microbial protein supply, increase in fibre digestibility and possibly an increase in weight gain. The aim of this review is to discuss nitrogen losses in ruminant production and manure management and to provide an insight on the possibility of using vermicast as feed supplement to ruminants and as probiotic for treating fibrous feed.

Biocontrol of nematode agents to decrease the hazardous impacts of chemical pesticide application including problems of public health and environmental pollution is a priority. In this study, solid (Vermicompost) and liquid products (Liquid Vermicompost, Vermiwash and Coelomic fluid) of the earthworm species Eisenia fetida were tested against root-knot nematode, Meloidogyne javanica in vitro and greenhouse conditions.

Results showed that Liquid Vermicompost, Coelomic fluid and Vermiwash had the greatest effect on egg hatching inhibition, respectively, and Coelomic fluid, Vermiwash and Liquid Vermicompost had the highest effect on mortality of larvae (J2), respectively, in vitro. All earthworm-based products were added to the cucumber pots and then a root-knot disease as well as plant growth indices was recorded. Results showed that all products could reduce the number of nematode juveniles and gall index in greenhouse conditions. The best combination for controlling disease was Vermicompost + 10 % Liquid Vermicompost and the highest rates of growth related to plants were treated with Vermicompost + 10 % Vermiwash.

It is concluded that earthworm products have a remarkable potential as control agents against root-knot nematode and improving host plant health.

A study was carried out to determine the effects of organic, inorganic fertilizers and integrated soil fertility management and irrigation levels (1,000, 750 and 500 ml per planting station) on coffee growth. There were no significant differences (p > 0.05) in girth, number of leaves and number of primaries due to the different soil fertility management options. Significant differences (p < 0.05) due to soil nutrient sources were observed in coffee height where inorganic fertilizer treatment resulted in tallest coffee plants (47.4 cm) and integrated soil fertility having the shortest coffee trees (42.8 cm) after 1 year. The highest irrigation level of 1,000 ml had the tallest plants with thickest stems while the lowest level had the shortest and thinnest plants (p < 0.05). No significant differences were observed in the number of leaves and number of primaries due to irrigation treatments. Results indicate that inorganic fertilizers are the most effective at high irrigation levels while organic manure performs better than inorganic fertilizers under low irrigation water levels.

Vegetable crops generate a large amount of crop residues after harvesting of economic part. These potentially nutritious residues are soft, succulent and easily decomposable and instead of disposing or damping, it can be used as source of organic residues for utilizing the embedded nutrients through compost production. In the present study, diverse vegetable wastes were recycled for vermicomposting and their effects were evaluated in field experiments in organic carrot production.

The result showed that among different vegetable wastes, substrate combining mixture of non-legume and legume wastes at 2:1 emerged best considering the nutrient contents, C/N ratio, earthworm biomass and vermicompost recovery. Use of such vermicompost recorded highest root length (19.26 cm), root volume (73 cm3 ), root weight (68.43 g) and root yield (16.07 Mg ha-1 ) of carrot. The quality of the root as judged by beta carotene and total soluble solids content was also found highest by the same vermicompost.

The findings established the potentiality of earthworm for quality vermicompost production from vegetable wastes, and through intended selection and judicious mixture of different vegetable wastes the cast quality can be improved. The study demonstrated that vermicompost produced from the substrate, combining mixture of non-legume and legume vegetable waste at 2:1 will provide the major nutrients in more balanced proportion compared to sole individual family waste vermicompost (vermicompost obtained from the waste of one single plant family). The findings can be promoted as a sound vegetable wastes recycling technology for organic carrot production to conserve natural resources and to minimize the deleterious impact of vegetable wastes on mother earth.

Making powder from whey is one of the most challenging parts of whey processing. The present study investigates the performance of a spray dryer for the preparation of whey powder. Its main objective is to categorize unknown samples using analysis of discrimination function between the operating variables and powder properties in two or more naturally occurring groups. In this work, spray drying was performed in a pilot-scale co-current spray dryer. The amount of solid content, inlet, and outlet air temperature was chosen as independent variables. The titratable acidity, PH, EC, TDS, analytical elements, particle size diameter, ingredients, and morphology were the response variables that quantify the powder quality.ResultsThe PH of whey powder with 15 % solid content was lower than the PH of whey powder with 30 % solid content. Furthermore, the PH of the whey dried at inlet (outlet) air temperature of 180 °C (106 °C) was lower than the whey dried at 145 °C (87 °C). Substances with higher acidity had higher electrical conductivity (EC) as well. The mean particle diameters of the powders produced by pilot-plant spray dryer were in the range of 11.26–18.23 µm. SEM picture showed that in pilot-plant spray dryer, there were a few shallow holes on the particle surfaces as well as a few wizened particles.ConclusionsIt was observed that in the materials with higher acidity, the EC was high and the PH was low. More solid content caused higher viscosities in the feed, which increased the droplet size and consequently, the particle size. By increasing the temperature and heating duration, the amount of PH reduced and the diameter of the particles increased. Moreover, by increasing the percentage of the solid content, the PH increased, while the solid mass carried away by the outlet air decreased. Small particles sprayed by the two-fluid nozzles, led to less amount of TDS. From the morphological point of view, as the industrial samples were exposed to heat longer as compared to pilot-plant samples, they produced spherical and smoother particles.