Biological Wastes最新文献

Pollard and bran were fermented by a selection of filamentous fungi to increase the protein content and availability for use as animal feed. Aspergillus terreus produced a product containing 32·6% crude protein (CP) after 16 days. Under identical environmental conditions, shallow-layer solid-state fermentations achieved higher CP yields than did tumbled or packed-column systems. When crude xylanase was added with A. terreus inoculum, a 5-day reduction in fermentation time was achieved resulting in a maximum CP content of 27%. A. terreus, Chaetomium virescens, Schizophyllum commune or Trichoderma reesei, in dual culture with one another or in combination with Phanerochaete chrysosporium, did not achieve higher final CP yields (after 16 days) than A. terreus alone. P. chrysosporium in combination with T. reesei and with S. commune resulted in the most rapid CP development of 26·1% and 26·4%, respectively, during the first 10 days.

Laboratory experiments were carried out to compare the controlled and uncontrolled start-up of the anaerobic treatment of natural-rubber effluent. It was found that a pH-controlled start-up was much more promising than an uncontrolled one. The biogas production was higher and a shorter period for stabilization was required in pH-controlled systems.

A comprehensive literature review was conducted on psychrophilic anaerobic digestion and design of anaerobic digesters for treating animal manures. Anaerobic digestion of caged layer manure was studied in the laboratory at low temperatures (14–23°C). The digesters were operated to determine combinations of temperature and loading rate that gave acceptable methane yield. Acceptable methane yield was obtained for loading rates ranging between 0·15 kg VS/m day and 0·57 kg VS/m³ day for temperatures of 14°C and 23°C, respectively. The resulting data along with that taken from similar tests documented in the literature was found to approximate the van't Hoff-Arrhenius equation. This equation is then suggested as a technique for determining suitable loading rates for psychrophilic digesters based on data for digesters operated at higher temperatures.

Newly-hatched larvae of the green hover fly Ornidia obesa (Diptera: Syrphidae) were allowed to grow on coffee pulp that had started to decompose for two days and taken from the anaerobic portion of a heap. This substrate was maintained in Petri dishes at room conditions (25 ± 5°C, 43·0 ± 12.9% air relative humidity) so as to obtain a better understanding about the larval growth of the above species on coffee pulp. A sigmoid model indicated that the maximum larval growth rate was 16·8 mg (wet basis) day⁻¹ at 13·9 days after hatching, that the period of most rapid growth was 10·0–18·9 days and that the larvae reached almost their full development 25 days after they emerged from eggs. It was also found that a comparatively slight decrease of substrate moisture caused a lowering of larval weight.

Feedlot wastes contain the essential elements for plant growth. Effective utilization of feedlot wastes as a source of fertilizer for crops is a function of the nutrient content in the manure, the mineralization rates of the organically combined molecules in the manure, and the cost associated with the management, hauling, and spreading of manure. This study, using simulation approach, evaluates the simultaneous effect of these variables in determining the economic potential of feedlot waste utilization in agricultural production. Least cost manure application is determined for various crops in four rotation systems and for three different nutrient content and mineralization rates.

The results show that the cost associated with the management, hauling, and spreading of manure to satisfy the nutrient requirements for the crops considered in the four rotation systems is significantly less than the cost of commercial fertilizer. Depending on the mineralization rate and the rotation system considered, the cost of applying manure ranges between 20 and 35 per cent of the cost of commercial fertilizer. The results also show that the maximum distance of transferring manure from the feedlot to the field that will equate the cost of applying manure with cost of commercial fertilizer ranges between 10·0 to 78·4 km.

A set of ten upflow sludge blanket digesters was examined as five pairs (one control and four test reactors) to assess the way in which controlled nutrient variations affected the performance of the reactors in treating a simulated ice-cream wastewater. An alternative carbon source was used and additional concentrations of calcium and cobalt were examined. The results show that the waste itself is capable of being treated by the UASB process, with granulation commencing after 60–70 days. However, of the supplements, only calcium had any significant effect.

A heat exchanger-type furnace suitable for agricultural wastes like sugarcane bagasse, cotton stalk, coconut shell, etc., as fuel has been developed. A maximum of 90°C hot air temperature was obtained at 25·4 m³/min air flow rate at 18 kg/h of feed rate with sugarcane bagasse as fuel. With an increase in air flow, the hot air temperature decreased. It took 10·2 h to reduce the moisture content of paddy from 22·4% (wb) to 13·87% (wb) at 63°C and 33 m³/min air flow rate and 24 h for coconut (copra) from 50% (wb) to 7% (wb) at 65°C and 53·5 m³/min air flow rate in the mechanical dryer to which the furnace was supplying the hot air. There is provision to regulate the temperature of hot air by mixing in atmospheric air.

The solid substrate fermentation (SSF) of urea-treated wheat straw (UTWS) with Coprinus fimetarius inoculation under non-sterile conditions can bring about an increase in crude protein, digestability and digestible protein. The significant increase in the chitin and the biomass content of fermented straw correlated with the good growth of the C. fimetarius, which resulted in dry matter loss of 19·32% on day 10 of the SSF. The inoculated mould comprised 65% of the fungal isolates and from among the other native fungi identified, only Aspergillus flavus showed toxin production in pure culture. Hence, the SSF of the UTWS with C. fimetarius, as a two-stage process, can be practised at ambient temperature under non-sterile conditions.