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.

The oil-synthesizing capacity of Candida curvata D was evaluated with different pH, temperature and carbon sources. The microbial oil contained a wide range of fatty acids, ranging from C₁₂ to C₂₂. The proportion of lipid fractions, as well as fatty-acid composition of the cells, varied with temperature, pH and medium. Under all conditions the studied oils were rich in octadecenoic, stearic and linoleic acids.

Urea at five levels (0, 1, 2, 4 and 6%) and NaOH at two levels (2 and 4% of dry matter to each of 2 and 4% urea level) were added to a mixture consisting of seven parts distillers grain solubles, two parts pressed pig slurry solids and one part ground wheat straw, on a fresh weight basis.

After a fermentation period of 42 days at ambient temperature in 100-litre capacity silos, the pH dropped in the unsupplemented wastelage (3·90), but it increased after urea and NaOH supplementation (up to 7·14). Ammonia and acetate concentrations in wastelage were enhanced with urea addition. Increase of acetate and butyrate concentration was observed when NaOH was added.

In sacco degradability increased from 49·0% (untreated sample) to 67·0% when 2% urea and 4% NaOH were added. The rumen dry matter degradability of wastelages was significantly higher when sheep consumed a diet rich in roughages (57·5%) rather than a concentrate ration (50·1%). Sheep consumed about 1 kg dry matter daily when unsupplemented or when 1% urea-added wastelage was fed. Higher levels of chemicals decreased dry-matter intake.

Chemically-treated wastelage replaced about a half of wilted grass silage without any negative effect on daily weight gain in short-term feeding experiment with growing bulls.