http://drr.vau.ac.lk/handle/123456789/235 Sat, 04 Apr 2026 07:58:20 GMT 2026-04-04T07:58:20Z http://drr.vau.ac.lk/handle/123456789/1985 Utilization of Alligator Weed as Organic Liquid Fertilizer: A Comparative Study on Okra (Abelmoschus esculentus) Growth and Yield Kabisha, P.; Nanthakumaran, A. Alligator weed (Alternanthera philoxeroides) is a highly invasive species causing severe ecological and economic consequences by affecting water quality, hydrological flow, and the growth of native flora and fauna due to its rapid growth and dense mat formation. It thrives in both aquatic and terrestrial habitats and has become a significant ecological concern in Sri Lanka. In Trincomalee, a two-hectare farm pond in Anpuvalipuram has been infested annually, typically from November to May (up to 1.5-hectare level), disrupting fishing and irrigation activities. Although local communities have attempted control measures such as mulching and feeding it to poultry because of its high nutrient availability, these practices have further encouraged its spread into surrounding terrestrial areas. This study was conducted to evaluate the potential of alligator weed as an organic liquid fertilizer and to compare its effectiveness on the growth and yield of the okra crop with that of a conventional organic fertilizer mix and an inorganic fertilizer. Liquid fertilizers were prepared using four concentrations of alligator weed (25%, 50%, 75% and 100%). A traditional organic mixture of Gliricidia and neem leaves, an inorganic fertilizer treatment, and an untreated control were also included. The experiment was arranged in a Completely Randomized Design with four replicates. Fertilizer samples were analyzed for nitrogen, phosphorus, potassium (NPK), pH, and electrical conductivity (EC). Growth and yield performance were evaluated by measuring crop height, stem circumference, total pod number and total pod weight. Despite relatively low NPK concentrations, the 50% alligator weed liquid fertilizer treatment achieved the highest yield performance (1,145.26 g and 64 pods), which was comparable to inorganic fertilizer and superior to both the organic mixture and the control. Utilizing alligator weed not only provides a sustainable alternative to inorganic fertilizers but also offers an eco-friendly strategy for managing a problematic invasive species while recycling nutrients within agricultural areas. Wed, 01 Jan 2025 00:00:00 GMT http://drr.vau.ac.lk/handle/123456789/1985 2025-01-01T00:00:00Z http://drr.vau.ac.lk/handle/123456789/1984 Sustainable Biogas Production using Food Waste and Animal Excreta Kathusika, B.; Nanthakumaran, A.; Rathnasiri, P.G. The rising fossil fuel dependence and organic waste generation increase the need for sustainable energy such as biogas. In Sri Lanka, food waste and animal manure remain underutilized despite their potential for renewable energy and nutrient recovery. This study aimed to assess the feasibility of biogas production through co-digestion using food waste and animal excreta. Experiments were conducted in four separate trials for both substrates using a 500 mL batch anaerobic digester operated at mesophilic temperature (35–37 °C) with constant agitation at 200 rpm. Biogas volume was quantified by the water displacement method, with 9 N Sodium Hydroxide (NaOH) used as a Carbon Dioxide (CO2) scrubber to allow direct measurement of methane. Substrate quality was analyzed before and after digestion, including Total solids, Volatile solids, pH, COD removal efficiency, and C/N ratio. Methane yields were further modeled using the Modified Gompertz equation to assess kinetic performance. The results revealed that co-digestion significantly enhanced methane generation compared to mono-digestion. Buffalo dung with food waste in 2:1 ratio achieved the highest cumulative methane yield, with experimental values of 8.99 mL/g VS and a Gompertz fit of 9.03 mL/g VS (R2 =0.9893). The higher yield may result from buffalo dung’s stable buffering and rich microbial content. Followed by cow dung with food waste, yielding 7.25 mL/g VS experimentally and 6.85 mL/g VS by Gompertz fit (R2 = 0.9790), dung-only trials produced lower methane volumes. These findings confirm the superior biogas potential and stability of buffalo dung-based co-digestion. Future research is recommended to scale up biogas production systems using the ratio of buffalo dung with food waste in 2:1 and to improve slurry utilization, and expand large-scale applications to reduce food waste and animal manure while addressing local energy demands. Wed, 01 Jan 2025 00:00:00 GMT http://drr.vau.ac.lk/handle/123456789/1984 2025-01-01T00:00:00Z http://drr.vau.ac.lk/handle/123456789/1983 Optimization of Anaerobic Codigestion Process for Biogas Production by Treating Food Waste with Water Hyacinth Thadshayini, K.; Nanthakumaran, A.; Rathnasiri, P.G. Sri Lanka faces increasing challenges in waste management and renewable energy due to rising food waste generation and the proliferation of invasive Water Hyacinth (Eichhornia crassipes). This study investigated the optimization of biomethane production through co-digestion of food waste and pretreated water hyacinth, using cow dung as inoculum. Laboratory-scale experiments were conducted in 500mL batch digesters under mesophilic conditions (37◦C) with agitation at 200rpm. Biomethane volume was measured using the water displacement method, with carbon dioxide (CO2) absorbed using 9N sodium hydroxide (NaOH). Four trials were performed: cow dung alone, cow dung with food waste, cow dung with water hyacinth, and cow dung with food waste and water hyacinth. Cumulative biomethane production in the trials was 115, 158, 216, and 240mL, respectively. The highest methane yield of 11.04mL/gVS and maximum production rate of 1.288mL/gVS/h were observed in the co-digestion of all three substrates, with 21.74gVS added. Pretreatment of water hyacinth contributed to increased biomethane production. The Modified Gompertz model closely fitted the experimental data (R2 = 0.8847–0.9952), with minor deviations attributed to substrate heterogeneity and microbial adaptation. These results demonstrate that co-digestion enhances biomethane yield, production rate, process stability, and organic waste conversion efficiency. This study recommends adopting this approach in existing biogas systems to support sustainable energy recovery, effective control of invasive water hyacinth, and improved organic waste management in Sri Lanka. Wed, 01 Jan 2025 00:00:00 GMT http://drr.vau.ac.lk/handle/123456789/1983 2025-01-01T00:00:00Z http://drr.vau.ac.lk/handle/123456789/1982 Effect of Animal Fat on Anaerobic Co-Digestion and Process Optimization Nawagamuwa, N.G.B.S.M.; Rathnasiri, P.G.; Devaisy, S. One of the emergent challenges in meat processing industries is producing biogas with animal waste associated with high-fat content. This research attempts to find out the effect of animal fat (poultry) on anaerobic co-digestion and process optimization by means of food waste as the co-substrate and cow dung (CD) as the inoculum by considering the trend in biomethane production at different quantities of animal fat. A series of batch fermentations were carried out in a lab-scale batch reactor (>500mL) based on the VDI 4630 protocol. One control batch experiment was conducted with inoculum alone and five other dif ferent co-digestion experiments were implemented in triplicates with the proportions of rendered chicken fat emulsion:food waste at 0:100, 25:75, 50:50, 75:25, and 100:0 (w/w) in the presence of inoculum. The propor tion of substrates to inoculum was 100:300 (w/w) in all the co-digestion experiments. Each experiment was implemented for four (4) days continuously under mesophilic (35°C) conditions and at 200rpm mixing speed by ensuring continuous mixing. Experimental data proved that the highest total biogas potential is achiev able with co-digestion experiments incorporated with high quantities of food waste (0:100, 25:75), though a sudden process failure of acidification occurred eventually, along with minimal organic material conversion rate (mL/gCODremoval). Experiments utilizing relatively high quantities of fat emulsion showed relatively low total biogas production without any sudden process failure and with a high organic material conver sion rate. The highest pH reduction with high COD and volatile solid removal efficiencies were represented by high-quantity food waste incorporated batch experiments. The most viable co-digestion proportion was 50:50 (w/w) among the batch experiments incorporated by food waste with regard to the limited pH drop of the feedstock mixture. Another satisfactory fermentation was the co-digestion of animal fat associated with inoculum (cow dung) without using food waste (100:0), which produced continuous biomethane production with a high rate of organic material conversion. Continuous mixing and stable temperature at 35°C may optimize gas production efficiency, and pH adjustment will be a further optimization technique for achieving the highest possible biomethane production. Wed, 01 Jan 2025 00:00:00 GMT http://drr.vau.ac.lk/handle/123456789/1982 2025-01-01T00:00:00Z