Slurry Acidification Research Articles

Ammonia volatilization from dairy farming systems in temperate areas : a review

Ammonia (NH3) emissions from dairy farm systems cause environmental problems. This paper reviews and quantifies the major loss routes of NH3 in dairy farms. Furthermore, management options are discussed that reduce NH3 losses. Losses of NH3 occur during slurry application, housing, slurry storage, grazing, fertilizer application and from crops, in descending order of importance. Animal waste is the major source in four of the six cases. This ranking varies between farms and between countries, depending on environmental conditions and management practices. Total NH3 losses range from 17 to 46 kg N cow yr-1, reflecting the variability in amount and composition of animal excreta (urine + faeces), management of the slurry and soil and environmental conditions. The amount and composition of urine and faeces depend on N tranformations in the digestive track of the cow. Of the major nitrogen compounds excreted urea has the highest potential for NH3 volatilization followed by allantoin, uric acid and creatinine in decreasing order. Creatine, xanthine and hypoxanthine have a low NH3 volatilization potential. Reducing the excretion of urea and urea like products by optimizing N Intake (NI) and N Retention (NR) is one way of decreasing NH3 losses. Improvement is possible since NR is about 20% of NI in practice, whereas 43% is theoretically possible. The second solution is to reduce the rate of NH3 loss by technical means like direct incorporation of slurry into the soil, dilution or acidification of slurry, covering of the slurry storage and/or acidification or dilution of slurry in the storage. These techniques have been known for a long time and now become available on a large scale in practice. Reducing the surface area per cow in the shed and sprinkling floors with water to remove and to dilute urine also decreases NH3 loss. Reducing NH3 loss requires a whole farm system approach, because it shows how intervening in one part may affect NH3 losses in other parts of the system. Reducing NH3 loss may increase nitrate leaching and denitrification. To prevent this, the achieved reduction in NH3 loss should lead to a reduction of total N input of fertilizers, concentrates and forage on the N budget of the farm, which is possible as a reduction of NH3 loss improves the N fertilizing value of slurry. Model calculations showed great scope for reducing NH3 losses on dairy farms by improved management. Up to three fold reductions in NH3 loss are possible together with marked reductions in mineral fertilizer usage. The rate at which improved management techniques, will be introduced in practice depends on legislation, the applicability of new techniques and the expected increase in net production costs. To comply with environmental targets requires a huge effort of farmers with associated high costs.

Deodorant compositions containing antibacterial zeolite and silicones

Livestock manure is a major contributor to ammonia and greenhouse gas emissions and treatment technologies such as slurry acidification can be used to reduce both. In this study, life cycle assessment was used to compare impact potentials of slurry acidification at either the pig housing or the field application stage with conventional slurry management. Furthermore, the effects of differences in environmental regulations concerning nitrogen application limits were analysed. The impact categories analysed were terrestrial eutrophication potential, climate change potential, marine eutrophication potential and toxicity potential. Slurry acidification reduced the terrestrial eutrophication potential by 71% for in-house acidification and by 30% for field acidification. Changes in regulatory plant-available nitrogen application limits resulted in changes in climate change potential and marine eutrophication potential, with lower limits favouring in-house acidification. Acidification can substantially reduce the environmental impacts of animal slurry, but the effect depends on the context of the regulatory regime.

Effects of diet and storage time on the concentration of sulphide in dairy-cow slurry

Hydrogen sulphide emission from animal slurries during storage, mixing, or treatment can create a health hazard. A laboratory experiment investigated the effect of diet and storage time on the total sulphide concentration in slurries from dairy cows. Four diets with varying proportions of silage and concentrates were fed at levels targeted to give the same milk production. The total sulphide concentrations in the resulting slurries stored anaerobically at 15°C were measured on nine occasions during twelve months. Diets containing 34% protein resulted in slurries with average sulphide concentrations of 53 mg S− litre−1 compared with 39 mg S− litre−1 in slurries from diets containing 17% protein. Total sulphide concentrations were highest at the start of the experiment and averaged 55 mg S− litre−1, and decreased to 31 mg S− litre−1 after twelve months' storage. Acidification of slurry to lower volatilization of ammonia and improve the utilization of slurry nitrogen by crops presents hazards from hydrogen sulphide evolution irrespective of the length of the slurry-storage period.

Effect of separation and acidification of cattle slurry on ammonia volatilization and on the efficiency of slurry nitrogen for herbage production

SUMMARYDuring the growing season of 1988 at the Agricultural Research Institute, Hillsborough, cattle slurry was kept whole or was separated through screens with mesh sizes of 5 mm, 3 mm, 0·25 mm and 0·015 mm. The resulting slurry liquids were either left unacidified or were acidified to pH 5.5 with 5M-H2SO4 prior to application at 75 kg NH+4-N/ha to perennial ryegrass in the field. Volatilization of ammonia was measured using ventilated enclosures. Plots treated with a range of rates of inorganic fertilizer N were used to construct response curves to assess the efficiency of N in slurry for herbage production compared with equinitrogenous inorganic fertilizer.On average over the season, acidification of cattle slurry decreased ammonia volatilization to < 15% of that from unacidified whole slurry. Compared with inorganic fertilizer N, the overall efficiency of NH+4-N was 96% in acidified slurries and 36% in unacidified whole slurry. Ammonia volatilization from separated slurries decreased with decreasing mesh size to 39% of that from whole slurry for a 0·015 mm mesh. The overall efficiency of NH4+-N in slurry separated through a 0·015 mm mesh was 76%. A highly significant linear relationship was found between NH3-N volatilized from all slurry treatments and N offtake in herbage at all three harvests.