Problem statement: Yellow mealworms of different sizes (4.8-182.7 mg) were grown in a medium of wheat flour and brewer's yeast (95:5 by weight) to evaluate their potential as a protein source. Approach: There was an initial adjustment period (3-9 days) observed during which the younger larvae (4.8-61.1 mg) grew slowly while the older ones (80.3-182.7 mg) lost weight. After this initial period, the younger larvae (4.8-122.1 mg) increased in weight while the older ones (139.6-182.7 mg) continued to lose weight as they entered the pupal stage. For efficient production of larvae, they should be harvested at a weight of 100-110 mg. The moisture issue in the medium presents an important management problem for commercial production. Results: A system in which eggs are separate from adults and hatched in separate chambers would alleviate the danger of losing the larval population due to microbial infection. The moisture, ash, protein and fat contents were 58.1-61.5, 1.8-2.2, 24.3-27.6 and 12.0-12.5%, respectively. Yellow mealworms seem to be a promising source of protein for human consumption with the required fat and essential amino acids. Further research into raising them on a variety of low quality substances/wastes such as saw dust, waste paper, corn starch and potato flour is recommended. Conclusion/Recommendations: The future research should also investigate the nutrition content of the medium (minerals, protein, fat, carbohydrates and vitamins) and the effect of environmental parameters (temperature, humidity, production of CO 2 and heat) on protein yield and quality. This information will aid in the design of an economically viable large scale production system.
Problem statement: Protein deficiency is one of the major nutritional problems in the developing world. The most disastrous consequences occur in children where protein malnutrition manifests itself in forms of two notorious diseases: Marasmus and kwashiorkor. Expansion of present agricultural practices into marginal lands is expected to solve this chronic protein shortage. The process of photosynthesis is the only non depletable protein source and can supply some essential amino acids as well as provide adequate nitrogen in the diet for synthesis of non essential amino acids in addition to vitamins and minerals. Approach: The aim of this study was to assess the nutritional values of common plant leaves and determine the feasibility of using them as a protein supplement. Six plants were cultivated and tested for their nutritional quality: amaranth, cowpea, sugar been, pumpkin, sweet potato and cabbage. Results: Pumpkin leaves recorded the highest protein yield (11.75%) followed by amaranth (10.5%) The protein contents in the leaves of sweet potato, cowpea, cabbage and sugar been were much lower (7.85, 6.95, 5.60 and 3.45%, respectively). Conclusion: Except for sugar bean, all plants had higher extractable protein content than cabbage. Proper use of the growing season can achieve high protein yield. Clean cutting will ensure that the leaves do not deteriorate within a few hours when kept in cool place and freezing leaves can improve protein extractability. The test plants should be given a trial as protein sources for human. Plant leaves have vitamins, minerals and essential amino acids and when consumed in adequate amounts they can supplement protein especially in areas where the environment is very hostile to livestock keeping or where fish protein is lacking. The optimum harvest age, fertilizer requirements and the possibility of combining two or more plants together to improve protein content should be studied. The amino acid, minerals and vitamins profiles should also be determined
Energy produced from plant residue composting has stimulated great interest in heat recovery and utilization. Composting is an exothermic process often controlled through temperature measurements. However, energy analysis of the overall composting system, especially the rotary bioreactors, is generally not well known and very limited. This study presents detailed energy analysis in a laboratory-scale, batch-operated, rotary bioreactor used for composting tomato plant residues. The bioreactor was considered as a thermodynamic system operating under unsteady state conditions. The composting process was described, the input generated and lost energy terms as well as the relative importance of each term were quantitatively evaluated, and the composting phases were clearly identified. Results showed that the compost temperature peaked at 72 h of operation reaching 66.7 • C with a heat generation rate of 9.3 W•kg −1 of organic matter. During the composting process, the accumulated heat generation was 1.9 MJ•kg −1 of organic matter; only 4% of this heat was gained by the composting material, and 96% was lost outside the bioreactor. Contributions of thermal radiation, aeration, cylindrical, and side-walls surfaces of the reactor on the total heat loss were 1%, 2%, 69%, and 28%, respectively. The information obtained is applicable in the design, management, and control of composting operations and in improvement of bioreactor effectiveness and productivity.
The effectiveness of in-vessel thermophilic composting on the inactivation of Botrytis cinerea was evaluated. The bioreactor operated on an infected mixture of tomato plant residues, wood shavings, and municipal solid compost (1:1.5:0.28). Tap water and urea were added to adjust the moisture content and C:N ratio to 60% and 30:1, respectively. Used cooking oil was added as a bioavailable carbon source to compensate for heat losses from the system and extend the thermophilic composting stage. The controlled thermophilic composting process was successful in inactivating B. cinerea. During all experiments, the average reactor temperature increased gradually, reaching its peak after 31 h of operation. Temperatures in the range of 62.6-63.9 degrees C were maintained during the thermophilic stage by the intermittent addition of used cooking oil. The results of the enzyme-linked immunosorbent assay test indicated that the initial concentration of B. cinerea in the compost samples (14.6 mug of dried mycelium/g of compost) was reduced to 12.9, 8.8, and 2.4 mu/g after 24, 48, and 72 h of thermophilic composting, respectively. Plating assay indicated that the mold was completely inactivated in samples after 48 h of thermophilic composting. No significant reduction in B. cinerea was observed during the transient phase (first 30 h of rising temperature) because the temperature reached the lethal level of 55 degrees C after 23 h, thus allowing only 7 h of exposure to temperatures higher than 55 degrees C during this phase. The relatively short time required for complete inactivation of B. cinerea was achieved by maintaining a constant high temperature and a uniform distribution of temperature and extending the duration of the thermophilic stage by the addition of the proper amount of bioavailable carbon (used cooking oil).
The active phase of conventional static composting systems varies dramatically, ranging from several weeks to several months. Therefore, this study was to examine the effect of a combined continuous aeration-rotation process on shortening the active phase of composted material. A mixture of tomato plant residues with 20%-chicken manure ( v / v ) was composted in two identical pilot-scale bioreactors. One of them was static, and the other was continuously rotated at 3 rpm; each was supplied with continuous aeration. Compost temperatures ( T c ) were measured throughout the composting process; the moisture content ( MC ) and carbon/nitrogen ratio ( C/N ) were measured at the beginning and end of the experiment. The quality and stage of compost were evaluated at the end of the experiment using Dewar, Solvita, and visual tests. Continuous aeration-rotation significantly reduced the active phase period to 4.5 days, increased the compost temperature ( T c ) to 60°C after 3 days of operation, and remained at 50–65°C for approximately 3 consecutive days (thermophilic stage). In contrast, compost in the static bioreactor remained in the mesophilic stage ( T c < 45°C). During the composting process, the C/N ratio was reduced from 30/1 to 23/1 in the rotating bioreactor, while it remained at 30/1 in the static bioreactor, indicating that the nitrogen content was not a limiting factor affecting the composting process. The MC was within the optimum range for microorganisms (58–61%) for both bioreactors. After the active phase had ended in the rotating bioreactor, the compost was inactive and ready for further maturation, while compost from the static bioreactor was still immature and active. These results show that the proposed method can be done on a commercial scale to significantly reduce the composting period and to enhance the compost stability and productivity.
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