Agricultural Wastes最新文献

Two samples of spent coffee grounds were examined in the laboratory, using sheep to determine their potential as a ruminant feed. Analyses showed a high cell wall content (74–77% DM). In vivo digestibility coefficients for organic matter (0·22·0·48) were rather low and coefficients for gross energy were very low (0·02·0·17). The very low digestible energy (0·5·4·3 MJ kg⁻¹ DM) and negative metabolisable energy contents indicate that coffee grounds are worthless as a ruminant feed.

From a number of yeast strains capable of fat biosynthesis on a medium with beet molasses, Candida curvata D was selected as being most efficient. The optimum conditions for fat biosynthesis by C. curvata D were pH, 5·4; temperature, 30°C; sucrose content of the medium, 25 g litre⁻¹.

Cultivation of C. curvata D on a medium with beet molassed and whey gave food fat and biomass fields. The biomass, preserved separately or together with the spent medium, could be used as a fat-protein component of feeds for poultry, pigs or cattle.

Parallel aerated lagoons were operated for almost 2 years at various organic loads. The feed consisted of wastewater from a large piggery-farm pretreated in anaerobic lagoons. First-order kinetic models were developed for substrate removal and biomass generation. The constants from these models were: removal rate k = 0·0014 litre day⁻¹ mg⁻¹, biomass yield Y = 0·5 and decay coefficient k_d = 0·02 day⁻¹. It was found that lagoon performance should be interpreted against volumetric organic load rather than against hydraulic residence time or surface load. A load removal kinetic expression of the type S/S₀ = exp(− K/L) is proposed. The lagoon data interpreted according to this formula showed that the organics removal occureed sequentially. Two rates were defined. In the case of BOD removal there was a high rate (K₁ = 0·6 kgm⁻³ day⁻¹) down to a load of L = 0·6 kg m⁻³ day⁻¹; and a low rate period $\text{(K}{}_2\text{= 0·06 kg m}{}^{\mathrm{-3}}\text{day}{}^{\mathrm{-1}}\text{) below L = 0·6 kg m}{}^{\mathrm{-3}}\text{day}{}^{\mathrm{-1}}$. The turning point occurred at about HRT (hydraulic residence time) =3·2– 4·0 day. The proposed load interpretation allows for optimising the lagoon design into a series of high- and low-rate reactors, where the total volume will always be lower than the volume of one lagoon for the same treatment level.

Steam-treated bagasse, alone or with maize cob and paddy straw, untreated bagasse and mahua cake, and paddy straw compost (PSC), were evaluated, after pH adjustment with charcoal or charcoal and lime, as carriers for Azospirilum brasilense and Azotobacter chroococcum in terms of bacterial survival. Three of the materials supported a good population of both bacteria, but A. chroocuccum did not survive on PSC. All materials had good water-holding capacity, porosity and bulk density.

This paper proposes a scheme for the inhibition of thermophilic methane digestion processes by high ammonia concentrations. Ammonia acts as a strong inhibitor of the formation of methane from H₂ and CO₂. It has only a minor effect on the formation of methane from acetate, as indicated by the independence of the specific growth rate of acetate-consuming methanogens from the ammonia concentration (up to 4500 mg NH₄⁺-N per litre). On the basis of thermodynamic considerations it is shown that the inhibition of the hydrogen consumption leads to an inhibition of propionate breakdown. Accumulated propionate, in turn, acts as an inhibitor of the acetate-consuming methanogens. This scheme explains the discrepancy between the observed acetate accumulation in thermophilic methane digestion systems with high ammonia levels and the independence of acetate mediated methanogenesis from high ammonia concentrations under laboratory conditions.

This paper deals with the pyrolysis of coconut shell in experimental conditions at different temperatures for varying time periods, to determine the suitable range for obtaining maximum percentage yield of charcoal. Pyrolysis under field conditions has been done to compare the percentage yield efficiency of charcoal with experimental results. The efficiency of pyrolysis in experimental conditions at a temperature of 300°C and 180 s time duration is 70%, while in field conditions the efficiency recorded is 27%. Coconut shell with a yield potential of 2 tonnes per hectare per year in India can fulfil the cooking and heating requirements of two families, with five members each, in rural sectors.