Agricultural Wastes最新文献

A soil incubation experiment was conducted to determine nitrate N(NO₃−N) accumulation rates and available N (AAN_t) values for stored liquid manures from dairy cattle and swine, various poultry manures and a municipal sewage sludge applied to Norfolk and Cecil soils. Potentially available N (PAN_t) in the manures and sludge was also estimated by chemical tests which included an acid permanganate extraction, weak acid extraction, strong acid extraction and pepsin digestion. The resulting PAN_t values were compared to the AAN_t values from the soil incubation study.

The rates in which NO_3-N accumulated in soils treated with waste were described using first-order kinetics. The rate constants were highest for soils treated with poultry manure which contained high initial concentrations of ammonia N (NH₃-N) and rapidly mineralizable ORG-N. The lowest rate constants were for soils treated with municipal sludge which contained low concentrations of NH₃-N.

Incubation tests showed significant reductions in inorganic N (IN-N) in the first 2 weeks, which suggested immobilization and/or possibly denitrification or NH₃-N volatilization. After 26 weeks' incubation, AAN_t varied with waste type and soil type, being from 40% to 67% of total Kjeldahl N (TKN) applied to a Norfolk sandy soil and from 17% to 38% for a Cecil sandy loam.

An original analytical model of the biochemical behaviour of an anaerobic digester and its thermal balance under steady-state conditions is presented and described. It is based on the fundamental equations for hydrolysis, acidogenesis and methanogenesis and determined by several kinetic parameters. The thermal balance is investigated to define the optimum working temperature in relation to several operating parameters (outdoor temperature, geometry, insulation, etc.), from the maximum net energy content and the energy used to heat the fermenting system, bearing in mind the strongly temperature-dependent biogas productivity of the mesophilic bacteria.

Applications of pig slurry were made to pasture at frequent intervals over a 4-year period. Earthworm populations were assessed after the last treatments had been applied. Total numbers—and those of deep-burrowing species—were greater on the high-slurry plots (5528 m³ per hectare) than on controls receiving inorganic fertiliser. Approximately 212 kg per hectare of copper and 150 kg per hectare of zinc were applied by this high rate of slurry.

Cassava leaf meal (CLM), prepared from leaves remaining after the harvest of cassava roots, contained (dry basis): 20·1% crude protein, 30·3% acid detergent fibre, 4·6 Mcal kg⁻¹ gross energy, 1·16% calcium, 0·39 phosphorus and 84·0 mg kg⁻¹ hydrocyanic acid. It was also found to be a good source of essential amino acids, except for methionine, and of trace minerals.

Two feeding trials were conducted to study the effects of feeding CLM on the growth of rabbits. In each trial, 24 six-weeks-old crossbred rabbits were individually fed diets containing 0%, 20% and 40% CLM substituted for equal amounts of coconut oilcake in a 16% protein control diet. The results suggest that CLM could be used up to the 40% level in growing rabbit diets without any adverse effects on growth performance or carcass characteristics.

Results of laboratory studies of anaerobic lagoon performance have been analyzed to yield kinetic data applicable for design. None of the models currently used fitted the data. A novel interpretation has been proposed based on the dependence of effluent quality on volumetric organic loading. It is suggested that the removal takes place in consecutive stages at a progressively decreasing rate (expressed in kg m⁻³ day⁻¹). In the case of dilute piggery wastes from large farms the first stage of rapid sedimentation takes only a few hours and achieves some 55% removal of COD. The second stage, biochemical removal, proceeds at 1·7 kg COD m⁻³ day⁻¹ for about 3 days HRT and then the removal rate drops down to 0·2kg COD m⁻³ day⁻¹

A comparative study of a bench-scale and a pile composting showed that the C/N, ash percentage and alakaline phosphatase activity were potentially useful parameters for estimating the maturation of cattle manure compost. The values of these parameters were nearly constant during a simulated poor composting, whereas they changed significantly during an optimal process. Other parameters—decomposition degree, chemical oxygen demand, invertase and Rusch number—were less sensitive indicators of composting. The use of these data for agricultural compost samples has shown that high alkaline phosphatase activity and No₃⁻/NH₄⁺ ratio were correlated with compost maturity.