International Journal of Recycling of Organic Waste in Agriculture
Volume:4 Issue: 2, Spring 2015

Phosphorus (P) ore is an expensive and limited resource that will be depleted in a few decades if the current global consumption rate continues. Japan, one of the most developed countries in the world, relies completely on imported phosphate rock for P. Potassium (K) ore, which is equally important for continuous development, is also becoming increasingly expensive. The recovery of P and K is therefore important for continuous and sustainable development. In this study, concentrated P (obtained from eluent) and K (obtained through alkali leaching of rice straw charcoal) were recovered as potassium magnesium phosphate (PMP) through the controlled addition of magnesium (Mg). A PMP crystal was produced when an equimolar (with respect to P) Mg solution was added to the leaching solution (rich in P and K) at a pH range of 11–12. Thus, the production of PMP in a crystalline form demonstrates the huge scope for the recycling of limited resources.

Background Macrophytes (fresh water plants) comprise a diverse group of the flora which play important roles in the maintenance of trophic food chains and biogeochemical processes, but are deleterious when present in excess. However, due to various anthropogenic activities, there is accumulation of nutrients in aquatic ecosystems resulting in massive macrophytic growth. These weeds do not possess any economic value and remain laid on lake shores after harvesting and become a source of odor problem, thus posing a challenge to the lake management authorities regarding their proper disposal. However, vermicomposting turns these macrophytes into materials useful in horticulture/agriculture for restoration of soil fertility, in addition to providing a solution to the nuisance of harvested weeds. Results The study was conducted to investigate the effect of different rates (2, 4 and 6 t/ha) of macrophyte-based vermicompost on germination, growth and yield of Solanum melongena under field conditions. The data revealed that different rates of vermicompost produced varied and significant effect (P\0.05) as compared to the control on germination, growth and yield parameters with maximum value recorded at 6 t/ha, followed by 4 t/ha and the least at 2 t/ha. The dose of 6 t/ha significantly (P\0.05) increased germination (22.56 ± 2.5 %), number of fruits per plant (3.55 ± 0.07) mean fruit weight (73 ± 5.0 g), yield per plant (1.48 ± 0.05 kg) and marketable fruits (28.66 ± 3.0 %) when compared with the control. The study suggests that macrophyte-based vermicompost as a potential source of plant nutrients for sustainable crop production. Conclusion Macrophyte-based vermicompost is an efficient quality yielder and economy enhancer for sustainable agriculture especially for the communities having vegetable gardens around lakes will benefit by using macrophyte vermicompost, a balanced and low-cost organic fertilizer.

The reuse of organic wastes in agriculture is an appropriate method of environment management. Most plants with ornamental leaves are cultivated in soilless media, in which peat is the basic medium; but the use of peat is questionable due to ecological damage to the environment and economic disadvantages to ornamental plant producers. Peanut shells as remained wastes of cultivating peanut has a considerable volume, compost of which can be used as available sources of ornamental plants medium. A pot experiment was conducted to investigate the possibility of using peanut shell compost in the appropriate bed in the cultivation of ornamental plants. Dracaena marginata was selected as the test plant. The control treatment consisted of a 2:1 ratio of peat to perlite, and peat was replaced by 15, 30, 45, 60 and 100 % v/v of peanut shell compost. The study was done based on a complete randomized design in three repetitions in the ornamental plants and flowers research station, Lahijan, Iran.

The results showed that the bulk density of the planting beds decreased with the addition of peanut shell compost in comparison to the control. Peanut shell compost increased total nitrogen and available phosphorus and potassium of the media. Peanut shell compost increased plant growth indices, but the growth was reduced in 100 % in the compost treatment. The compost led to increase in nutrient uptake by plants.

In conclusion, it became known that peanut shell compost is an appropriate alternative to peat as the growth medium of ornamental plants. Because of the favorable properties and high porosity, peanut shell compost can be mixed with low-porosity substrates and applied as a substitute to peat in the cultivation media. It is not suggested to increase peanut compost level by 60 and 100 %.

This study investigates changes in the microbiological community of two co-composting mixtures of activated sludge and date palm waste over a 6-month period. The use of the co-composting time extract medium to evaluate the abundance of cultivable indigenous microflora showed that the total microbial biomass was higher during the thermophilic phase. The mesophilic microflora was more abundant than the thermophilic bacteria, throughout the co-composting process. The proportion of mesophilic and thermophilic actinobacteria was high during the maturation phase especially for mixture A. However, thermotolerant fungal microflora increased during the thermophilic stage. Furthermore, correlating physico-chemical analysis of samples with bacterial diversity indicated that the bacterial communities underwent temperature changes. Enterococci and thermotolerant coliforms decreased significantly toward the end of the co-composting process which indicates the safety and sanitization of the end product.

Cellulase is one of the enzymes commonly used in several agricultural, industrial and sewage sludge treatment processes. The present study aimed to investigate the potential use sludge generated from sewage treatment plants as a production medium for cellulase by B. megaterium strain that was isolated from a sewage treatment plant. The production of cellulase in the sludge medium was compared to different cellulosic materials: cotton, filter paper, bagasse and sawdust as well as to galactose, fructose, lactose, maltose, mannitol, mannose, ribose, sucrose and xylose. The production of cellulase was conducted at optimum conditions (0.4 mL of the bacterial inoculum, 45 °C, 72 h, pH 6.5 and citrate phosphate buffer) that were determined in this study.

The sludge medium has induced the cellulase production by B. megaterium strain compared to cotton, filter paper, bagasse and sawdust. However, B. megaterium produced high cellulase in the presence of carbohydrate compounds as carbon source. More cellulase was produced in the sludge medium containing low concentrations of Ni2+, Zn2+ and Cu2+ ions.

The ability of B. megaterium strain to produce cellulase in the sewage sludge medium was due to that the strain has acclimatized to resist heavy metals and produce the enzyme genetically. Moreover, B. megaterium has an important environmental role for reuse of sewage sludge as production medium for cellulase that could be used in many of applications, including production of animal feed, formulation of detergents, juice clarification, paper industry and wine production.

Novel biomass-processing technologies have been recently used for conversion of organic wastes into valuable biofuels like bio-hydrogen. Agricultural wastes are available and renewable energy resources to supply energy demand of the future. The purpose of this study is to investigate the production of hydrogen-rich syngas from wheat straw, walnut shell, and almond shell.

Supercritical water gasification is a promising technology to convert biomass into useful fuels. Non-catalytic conversion of wheat straw, walnut shell, and almond shell into the hydrogen-rich gas in supercritical water media was performed using homemade batch microreactor system.

Hydrogen gas yields of 6.52, 4.26 and 4.1 mmol per 1 gram of wheat straw, walnut shell, and almond shell were observed, respectively. In addition, hydrogen and carbon gasification efficiencies equal to 42.6 and 46.9 % were calculated from gaseous products and elemental analysis of wheat straw, which were higher than other feedstocks’ gasification efficiencies.

Wheat straw had the highest and walnut shell had the lowest total gas and hydrogen gas yields. Taking into account the structural analysis, it was recognized that feedstocks with higher cellulose and hemicellulose and lower lignin contents were better gasified due to their easier hydrolysis and higher solubility in water.

Application of different chemical fertilizers and manures is a major source of ammonia (NH3) emission. The rate and total amount of NH3 emission are related to different parameters such as climatic conditions, soil characteristics and kind of fertilizer. The current study has indicated the NH3 emission from bovine slurry, pig slurry and ammonium nitrate fertilizer after application on two soils. Two different methods were used to measure NH3 emissions: the method that use acid traps and the method that use photoacoustic infrared gas analyzer.

In both soils the rate of NH3 emission was the greatest from the denser bovine slurry, declined in the pig slurry followed by the ammonium nitrate treatment and the control. The rate of soil infiltration could be the main factor that explained these differences. For all treatments the amount of total NH3 losses reduced in the more acidic soil. For all fertilizers the highest NH3 fluxes were measured in the first hours after spreading. A good agreement observed between the two methods is used for determining of NH3 emission. The use of a multi-gas monitor (MGM) is simple and accurate and produces a continuous series of NH3 concentration in time.

The rate and amount of NH3 emission was related to the kind of fertilizers and interaction of these treatments with soils. The results of current study confirmed that comparison of chemical fertilizers and slurry for NH3 emission is difficult because the reaction of these two groups of fertilizer is totally different.

Vermicomposts (VC) improve plant growth and development beyond that normally observed from just soil nutrient transformation and availability. These increases in plant productivity have been attributed to improved soil structure and soil microbial populations that have higher levels of activity and greater production of biological metabolites, such as plant growth regulators. Although there have been many studies on the benefits of VC as a fertilizer source, little research has focused on the effects and/or interactions of soil type and VC application rates on vegetable crop productivity. This paper identifies optimum application rate(s) of VC on tomato growth responses for three different textural classes of soils (loamy sand, silt loam, and silty clay).

Soils with high VC rates (0.4 and 0.8 g/g) produced taller plants with more leaf and flower numbers, higher leaf chlorophyll content, greater plant biomass, and more total leaf area compared to soils with low VC rates (0.05, 0.1, and 0.2 g/g). Tomato growth increases were also observed at the low VC soil amendment rates compared to the nontreated control. Tomatoes grown in the sandy soil amended with VC generally had the greatest growth responses (plant height, leaf and flower number, and leaf chlorophyll content) compared to the clay or silt loam soils, with the silt loam soil generally providing the least response.

This research indicated that VC is a suitable alternative fertilizer for tomato, with approximately 0.5–0.6 g/g VC added to soil resulting in optimal tomato plant growth. Moreover, this rate provided tomato growth results similar to the standard inorganic fertility program. The sandy soil with VC amendments generally increased tomato plant growth parameters the most compared to the clay and loam soils, with the loam soil generally providing the least.

Composting of harvested Salvinia natans weed of Loktak lake of Manipur, India can protect the precious lake from the unwanted growth of the weeds but there is a need to assess the total amount and bioavailable forms of heavy metals and minerals of the final compost before application as a soil conditioner.

Studies were conducted on the transformations of the physico-chemical parameters and the total amount, bioavailable and leachable forms of heavy metals and minerals during agitated pile composting of S. natans with rice husk and cattle manure in five different combinations [trial 1 (5 S. natans: 4 cattle manure: 1 rice husk), trial 2 (6 S. natans: 3 cattle manure: 1 rice husk), trial 3 (7 S. natans: 2 cattle manure: 1 rice husk), trial 4 (8 S. natans: 1 cattle manure: 1 rice husk) and trial 5 (10 S. natans: 0 cattle manure: 0 rice husk)].

The highest temperature (52.2 °C) was monitored in trial 2 having 30 % cattle manure during the process. Highest reduction of moisture content and volatile solid in trial 2 corroborated the temperature profile. Total concentrations of heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr), total concentration of nutrients (Na, K, Ca, and Mg) and the water-soluble forms of the nutrients were enhanced significantly. The water-soluble, plant-available and leachable metals decreased favorably with maximum reduction observed mostly in trial 2. The study also revealed that the total concentrations of Zn (211–254 mg/kg), Ni (310–345 mg/kg) and Pb (805–891 mg/kg) of the final composts were higher than that of Cr (140–207 mg/kg) but the water-soluble forms of Zn (3.6–4.7 % of total Zn), Ni (NIL) and Pb (0.7–1.0 % of total Pb) were lower than that of Cr (13.3–19.3 % of total Cr) indicating that Cr in the composts had higher toxicity potential. The leachable heavy metals were within the threshold limits prescribed for agricultural application.

Composting of S. natans biomass with appropriate proportion of cattle manure reduced the bioavailable and leachable forms of the heavy metals in the biomass.