International Journal of Recycling of Organic Waste in Agriculture
Volume:8 Issue: 1, Autumn 2019

Crop wastes are underused organic resources due to low heating value and slow decomposition rates. However, conversion to biochar through pyrolysis could offer agronomic and environmental benefits. The study compared the pyrolysis of biochar from crop wastes, assessed their physicochemical properties for the purposeful use to improve soil fertility, crop productivity and their carbon sequestration potential. Biochar was produced from crop wastes such as cassava residues, corncobs, rice husk, sawdust, coffee husk, and peanut using an Elsa barrel pyrolyser. Standard laboratory procedures were used to analyze pH, CEC, total carbon and nitrogen and exchangeable cations. The biochars were high in nutrients containing 4.17–18.15 g kg−1 N, 22.26–42.51 mg kg−1 P, 2.48–4.18 cmol kg−1 K and pH 7.78–10.81 units. It is evident that adding biochar to acidic soil containing 0.79 g kg−1 N, 7.41 mg kg−1 P, 1.42 cmol kg−1 K and pH of 5.68 could increase soil fertility and plant productivity. Carbon dioxide reduction potential ranged from 94.46 to 313.42 CO2 eq kg−1. This implies that the concept and technique of producing biochar could be a valuable way of reducing carbon emissions into the atmosphere thereby mitigating climate change. Crop wastes and by-products which constitute a nuisance could be used to produce a very useful by-product, biochar whose quality depends on the substrate from which it is produced. Recycling crop wastes to biochar is strongly recommended to smallholder farmers for use in agriculture to improve fertility and crop productivity due to their high nutrient content and soil fertility attributes.

The purpose of this study was to assess the efficacy of inorganic additives during the humification of poultry waste and rice husk. Poultry waste mixture was treated with aluminum sulfate 3% and rock phosphate 2% during co-composting of mixture in mechanical composter and evaluated the potential of humification and compost nitrogen mineralization in incubation and pot study. The mesophilic to thermophilic phase of composting mixture is prolonged due to the rise in temperature, pH and ammonia that steadily decrease near the maturation phase. The humification rate (HR), humification index (HI), degree of polymerization (DP) and cation exchange capacity (CEC) increased in enriched compost as compared to unenriched with the composting process. The germination index (GI) of enriched compost (C/N:10.8) was significantly greater than unenriched compost (C/N:23.43). These all maturity indices, i.e., C/N, CE, HI, DP, HR revealed the significant correlation with each other. In the incubation study, nitrogen mineralization was also evaluated and nitrogen was applied at the rate of 50 kg-N/ha using the enriched and unenriched compost and found high mineralization in enriched compost due to low C/N. A laboratory-scale pot experiment was also conducted, applied the compost at a rate of 100 kg-N/ha and recorded the encouraging results in growth and nutrition value of Abelmoschus esculentus plant. It was concluded that use of additives have a significant impact on humification of poultry waste.

The present research was conducted with the objective of exploring the vermicomposting process, which involves different stages such as building of a vermicompost station; import of a compost earthworm (Eisenia foetida); and production of vermicompost using dry grass clippings, rice straw and cow manure. The vermicompost produced can be of significant value to the end users like farmers for replacement of chemical fertilizers and procuring better prices for the organic produce using such composting material locally available at much lower cost. Vermicomposting was done using Eisenia foetida with three treatments [T1 (Rice straw), T2 (Rice straw + grass) and T3 (Grass)]. Temperature, humidity and pH were measured during the process. The population of earthworms, the production of vermicompost, and the chemical and microbial characteristics of the vermicompost were recorded after sixty (60) days and hundred twenty (120) days. The data were analyzed statistically using Sigma Plot 12.0. Results indicated that for all the three treatments the temperature was in the range of 0–35 °C, the humidity was between 80 and 100% and the pH fluctuated in the range of 5.5–7.0 and stabilized to near neutral on the 60th day. The combination of rice straw and grass had the highest rate of vermicompost production of 105 kg/m2 followed by grass and rice straw with 102.5 kg/m2 and 87 kg/m2, respectively, at the end of 120 days. The harvested vermicompost had an excellent nutrient status, confirmed by the chemical analyses, and contained all the essential macro- and micronutrients.

Nigeria produces large quantities of wastes per year, which are underutilised and constitute environmental nuisance. The effect of dietary mycomeat produced from ogi production wastes based on yellow maize using wild and mutant strains of Pleurotus sajor-caju was assessed based on chickens’ growth, haematology and histology. The wastes were air-dried for 72 h. The inoculum was developed by transferring loopful of inoculum into the prepared inoculum medium. Incubation was carried out at 37 ± 1 °C. 144 1-day-old chicks were used. The trial lasted for 21 days. The chicks were grouped into 4, each containing 36 1-day-old chicks. The animals were provided with fresh feed and water ad libitum. Feed intake and body weight were measured weekly, while the calculation of feed conversion ratio (FCR) and weight gain was based on the data obtained. Feed intake was lower for birds fed diets containing ogi production wastes and mycomeat produced from ogi production wastes using a mutant strain of P. sajor-caju. No significant differences were observed for body weight gain amongst the treatments. Mycomeat produced from ogi production wastes using a mutant strain of P. sajor-caju and ogi production wastes enhanced FCR, while those on wild strain of P. sajor-caju did not differ significantly from other treatments. Inclusion of mycomeat in the diet of broiler chicks is considered safe and could promote growth.

A lots of poultry litter (PL) is being generated every day from poultry industries and improper management leads to different environmental problems. Production of biochar from PL is a new management strategy of PL which is a nutrient-rich organic amendment for improving soil nutritional status. The experiment was aimed for the production of poultry litter biochar (PLB) from fresh PL to assess the important properties of both PL and PLB, and to observe the effects on plant growth. It also appraised the change of soil properties after PL and PLB application. Poultry litter biochar was produced from fresh PL heated at 300 °C temperature for 10 min in muffle furnace. Poultry litter was applied into the soil at 2.5, 5.0, 7.5 and 10 t ha−1 and PLB was applied at 1, 2, 3 and 4 t ha−1 along with control. Gima kalmi (Ipomoea aquatica) was grown as test plant. To assess the potentiality and residual effect, the same plant was grown consecutively after harvesting first crop. Post-harvest soil analysis was also carried out after harvesting the first crop. After pyrolysis pH, EC, organic carbon, available nitrogen, phosphorus, potassium, calcium, total phosphorus, potassium, calcium, magnesium, and iron were increased in PLB. A significant (p < 0.001) increase in plant growth and biomass production was observed and it was higher in PLB-treated soil than that of the PL-treated soil for both first and second crop. Poultry litter biochar might be a promising organic fertilizer with high nutrient composition than fresh PL. This also could be an ecofriendly management strategy for sustainable agriculture and long-term productivity.

Four different types of composts were assessed in two methods of application for their potential to support organic tomato yield. A 2-year experiment was conducted using four different soil conditioners: cow manure (CM), household compost (HC), spent mushroom compost (SMC), and vermicompost (VC). Three different application rates (10, 20, and 30 t ha−1 for all composts except VC and 3, 6, and 9 t ha−1 for VC) were included as a second factor. Two methods of fertilizer placement (as a row behind the root area and broadcast on the field) were considered as a third factor. The yield was influenced by different soil conditioners and placement method in the first year; in the second year, just interactions were significantly different. Treatments with CM showed significantly higher tomato yield in the first year (103 t ha−1) compared to other composts, but in the second year, SMC produced a higher yield (58 t ha−1). The experiment indicated that the treatment with CM in high level with broadcast application had higher dry matter (DM) production (3.1 t ha−1) in 2014, and treatment with CM in low rate and broadcast application had higher DM production (5.8 t ha−1) in 2015. Compost broadcast on the plots showed a higher yield production in case of similar rates and compost type. The proper rate of compost application is dependent on the method of compost placement.

Riparian zones are identified as mitigation areas of agricultural pollutants to river ecosystems. However, the mitigation mechanisms of these pollutants remain unclear mainly on the effects of different types of riparian vegetation and its organic matter content in the pollutants removal process. This study aims to assess the content of organic matter in soils composed of woody vegetation and grass and its effects on four pesticides adsorption. Adsorption studies were conducted in soil collected in riparian vegetation areas composed of grass and trees under the influence of an agricultural area. The analyses were performed in 21 shakers containing 100 g soil and a L of water previously contaminated with pesticide that were stirred for 30, 60, 120, 240, 360, 720, and 1440 min. A study was made of maximum adsorption capacity using the time 360 min and the concentrations of 5, 20, 40, and 50 μg L−1. The soils of woody vegetation areas had a higher concentration of organic matter as compared with grass areas, and time 360 min achieved the highest adsorption capacity with minimum values of 84% adsorption for the area of land made up of trees and 67% for grass areas. The soils of woody vegetation areas had a higher concentration of organic matter as compared with grass areas, time 360 min. The best adsorption capacity was obtained with minimal adsorption amounts of 84% to the area of soil composed of 67% for trees and grass areas.

Intensive agriculture activities in small holder farming systems are declining over all soil nutrient status. The present study is conducted to compare the soil health and plant growth attributes under rice cultivation among different organic amendments. Recycled waste of rice–wheat agrosystem is utilized to determine optimal sustainable solution for hilly areas. Randomly blocked design experiment was conducted with rice plants, each amended with organic inputs including rice straw residue (T1), rice biochar (T2), rice compost (T3), wheat straw residue (T4), wheat biochar (T5), wheat compost (T6), mix of wheat + rice compost (T7), green manure (T8) and control (no amendment). Soil samples were studied at each growth phase while plant growth attributes were measured at the harvesting stage of the crop. T6 and T7 have shown significantly higher magnitude of soil organic carbon, microbial biomass carbon, microbial quotient, available nitrogen, and enzymatic activities (dehydrogenase, alkaline phosphatase and urease) than biochar (T2 and T5) and crop residue amendments (T1, T4 and T8). An increase of up to 47% was obtained in cumulative growth attributes (plant height, total biomass, and a number of tillers, spikes, and spike length) of rice plant in T6 amendment. The principal component analysis revealed two components responsible for 54.17% of the variance in the organically treated soil. The experimental results imply that composting of crop residues could be the most reliable practice to improve soil nutritional quality as well as crop growth for sustainable rice–wheat cropping system in the hilly area.

This study assessed changes in bio-quality indices and plant available P released during aerobic–thermophilic co-composting of different mix ratios of non-reactive ground phosphate rock (GPR) with poultry and cattle manures. Aerobic–thermophilic co-composting of different mix ratios (5:5, 8:2, 7:3 and 9:1) of non-reactive GPR with poultry and cattle manures was carried out. Compost piles without GPR addition were included as control. Compost samples were taken at mesophilic, thermophilic, cooling–stabilization and maturing phases for microbial counts, enzyme activities and P assessment. Abundance of different microbial groups across the composting phases varied greatly (p < 0.001) mostly dominated by fungi that was generally more in the cattle than poultry manure-based phospho-composts. Fungi and actinomycetes counts in the composts were positively correlated with alkaline phosphatase and β-glucosidase. A strong inter-correlation between β-glucosidase and alkaline phosphatase (r = 1.000, p < 0.001) was observed, suggesting that both enzymes possess same origin. Alkaline phosphatase and β-glucosidase contents in the phospho-composts showed negative correlation with water soluble P (r = − 0.65, p < 0.001), and Bray P1 and Fe–P contents (r = − 0.15, p > 0.05) indicating inhibition of the P forms. Quantitatively higher P was obtained from poultry manure-based phospho-compost and in the 8:2 mix ratio at compost maturity. Microbial diversity and enzyme activity exerted positive impact on P mineralization and availability from the non-reactive GPR signifying the beneficial effect of co-composting. Co-composting of P-rich non-reactive GPR with organic wastes containing variable chemical composition promotes microbial diversity during composting and increases plant available P content and compost fertilizer value.

The purpose of this research was to evaluate the kinetics of anaerobic microbial culture during adaptation to pure and complex lignocellulosic substrates at low temperature. Six pairs of 1.0 L batch reactors maintained at 20 °C were fed pure (xylan and cellulose) and complex (cow manure and wheat straw) lignocellulosic substrate in three successive cycles of 35 days each. The biogas volume and composition, chemical oxygen demand, and volatile solids were monitored to evaluate the kinetics of the culture during the adaption. Anaerobic culture adapted to digest the pure and complex lignocellulosic substrates at 20 °C in relatively short period (105 days; 3 successive cycles of 35 days each) in batch reactor studies. The first-order model kinetics revealed that the average increase (day−1 cycle−1) in the reaction rate constant over the successive cycles was 0.0831 (xylan) > 0.0235 (cow manure) > 0.0207 (wheat straw) > 0.0123 (xylan:cellulose mixture) > 0.0041 (cellulose). The rates of the substrate degradation at 20 °C were: 0.085–0.093 day−1 (cellulose), 0.112–0.278 day−1 (xylan), 0.112–0.137 day−1 (xylan:cellulose mixture), 0.069–0.116 day−1 (cow manure), and 0.057–0.106 day−1 (wheat straw). Anaerobic mixed culture can be adapted to pure and complex lignocellulosic substrates and convert them to methane at low temperature (20 °C) in relatively short time (105 days) using a sequential procedure. The culture adaptation to wheat straw proceeded at a slower rate than that for cow manure.