Agricultural Wastes最新文献

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.

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.

One competitive solution to the slurry handling problem of some intensive pig houses is described. The system is based on mechanical and chemical separation techniques. The solids produced are easy to store until they can be spread on neighbouring land and their smell is inoffensive. The liquids produced are greatly reduced in bulk, by evaporation, and in polluting potential, thereby reducing the problems of their eventual disposal.

A treatment plant has operated for 3 years in a 500 place finishing piggery in such a way that slurry was flushed from the channels hourly and passed through a mechanical separator to remove the coarse particles. Separation enabled a high rate biological filter to treat the separated liquid reliably without blockages and also increased the pump life tenfold. The treated separated liquid was then flocculated, and the conbined effect of the mechanical separation and the flocculation was to leave up to 40% of the input slurry as a semi-solid at 15% dry matter (DM) together with a clear filtrate liquid, much of which was evaporated by diverting air from the ventilation system around the treatment plant and through an air scrubber/evaporator. Thus, only 30% of the original slurry had to be discharged as liquid. With design modifications to the treatment plant and close control of water wastage this figure 30% can be reduced to zero, i.e. an output of solids only can be attained.

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.

Waste from a local hatchery was processed by cooking it with water at a ratio of 2 waste to 1 water and then dehydrating the product (‘processed hatchery waste’, PHW). PHW was subjected to proximate, mineral and amino acid analyses: it was found to contain 22·8% crude protein 21·48% true protein, 22·64% Ca and 2706 kcal kg⁻ metabolizable energy. The product was incorporated at 2·5% and 5·0% levels in broiler rations and at 4%, 8% and 12% in laying hen diets as a substitute for soyabean meal, meat meal and ground limestone. In the broiler trials, body weight gains, feed consumption and feed efficiency were comparable for birds on all diets. The optimal inclusion level of PHW in broiler rations is around 2·5%. In the laying hens trial, body weights, egg production rates, feed consumption and efficiency, and egg size were not adversely affected by including PHW in diets.

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.

Farmers are increasingly concerned to maximise the fertiliser potential of slurry applied to pasture. The availability of the nitrogen in cow slurry for grass growth has been investigated by a number of workers and values from 14% to 84% have been reported for the season after application. Results are presented for 7 field experiments undertaken in southern England on four different farms in the harvest years 1977–1979. Spring and summer slurry applications were 25–30% as effective as ammonium nitrate in promoting dry matter yield of ryegrass swards and winter applications somewhat less at around 15%. When combined with applications of ammonium nitrate the average response was similar but there were appreciable differences in responses between sites. The apparent recovery of slurry nitrogen in herbage was 13% averaged over all treatments.