Sven G. Sommer

Ammonia Emission from Mineral Fertilizers and Fertilized Crops

Abstract A thorough understanding of the physical and chemical processes involved in NH 3 emission from inorganic N fertilizers and fertilized crops is required if reliable and operational NH 3 emission factors and decision support systems for inorganic fertilizers are to be developed, taking into account the actual soil properties, climatic conditions and management factors. For this reason, the present review focuses on processes involved in NH 3 volatilization from inorganic nitrogen fertilizers and the exchange of ammonia between crop foliage and the atmosphere. The proportion of nitrogen lost from N fertilizers due to NH 3 volatilization may range from ≈0 to >50%, depending on fertilizer type, environmental conditions (temperature, wind speed, rain), and soil properties (calcium content, cation exchange capacity, acidity). The risk for high NH 3 losses may be reduced by proper management strategies including, e.g., incorporation of the fertilizer into the soil, use of acidic fertilizers on calcareous soils, use of fertilizers with a high content of carbonate-precipitating cations, split applications to rice paddies or application to the soil surface beneath the crop canopy. The latter takes advantage of the relatively low wind speed within well-developed canopies, reducing the rate of vertical NH 3 transport and increasing foliar NH 3 absorption. Conversely, NH 3 is emitted from the leaves when the internal NH 3 concentration is higher than that in the ambient atmosphere as may often be the case, particularly during periods with rapid N absorption by the roots or during senescence induced N-remobilization from leaves. Between 1 and 4% of shoot N may be lost in this way.

Solid-liquid separation of animal slurry in theory and practice: a review

Animal slurry contains plant nutrients that are essential for crop production. However, intensive livestock production may lead to a surplus of plant nutrients on farms and, as a consequence, discharge or emission to the environment. In order to ensure that the slurry applied to fields matches the nutrient requirements of the crops, techniques have been developed to reduce the nutrient content of slurry by means of separation. This review discusses the separation technologies used for animal slurry treatment and the physical and chemical processes involved in separation. These processes need to be understood before efficient, reliable and cheap separation technologies that take into account the actual properties of slurry and the likely end-use of the separation products can be developed. A simple separation efficiency expression can be used to assess the efficiency of slurry separation. It is indeed important to measure the amount and composition of the slurry before treatment, the dry-matter-rich fraction and the liquid fraction. The separation efficiency of mechanical separators for the removal of dry matter and phosphorus (P) is ranked as follows: centrifugation > sedimentation > non-pressurized filtration > pressurized filtration. In general, the separation of total N and NH4+4 follows the same pattern, but the separation efficiency is lower than for dry matter and P. Treatment with a flocculant before separation improves separation efficiency significantly. Of the polyacrylamide polymers tested, high-molecular-weight, linear cationic polymers with a medium charge density (20–40 mol%) were found to be the most efficient flocculants. The best mechanical separation techniques for flocculated slurry are screens or filter belts. The separation efficiency of polyacrylamide-treated slurry can be improved by adding a multivalent ion to coagulate particles and for precipitation of phosphorus. Aluminium sulfate (Al2(SO4)3) or ferric chloride (FeCl3) seem to be very efficient for improving the mechanical separators. Alternatively, the mineral struvite (MgNH4PO4) may be formed by changing the slurry characteristics, such as by the addition of magnesium (Mg) or by increasing the pH to 9. The struvite crystals are removed during solid-liquid separation. The products of the solid—liquid separation may be further treated by evaporation, membrane filtration or ammonia stripping in order to obtain the desired end-products; however, low-maintenance and/or cost-efficient operation of these post-treatments has not yet been demonstrated. The separation should be developed as a whole-system approach, paying attention to parameters such as the value of end-products, environmental consequences and economy.

A detailed ammonia emission inventory for Denmark

Abstract This paper describes the method used to create an ammonia inventory for Denmark and presents the emission factors used and their justification. The total Danish emission for 1996 was 92,700xa0t NH4+–N, with agriculture accounting for nearly 99%. Emissions from animal manure accounted for 76% of agricultural emissions. We conclude that there will be a continued demand for inventories based on emission factors, despite their lack of physical and chemical realism, but that they will become more complex. This will place increased demands on the statistical information available and on the knowledge of the underlying science.

A SIMPLE PASSIVE SAMPLER FOR MEASURING AMMONIA EMISSION IN THE FIELD

A new type of passive sampler for the determination of NH3 emission from land surfaces and manure storages was tested in a micrometereological mass balance method. The sampler consists of 2 glass tubes, each with a length of 10 cm and an internal diameter of 0.7 cm. The two glass tubes are connected in series, with one end fitted with a thin stainless steel disc having a 1 mm hole in the center. The inner surface of each glass tube is coated with oxalic acid. The results show that the passive flux sampler can be used to give accurate determinations of NH3 emission. The passive flux sampler makes gas washing bottles, pumps, flow meters, anemometers, and electricity unnecessary and ammonia loss can be determined easily and cheaply without the requirement of a large labor force.

A simple model of pH in slurry

Ammonia volatilization from stored slurry or surface-applied slurry in the field is strongly affected by pH. Thus a simple, iterative model was developed to predict pH changes in slurry. Concentrations of NH 4 + /NH 3 , CO 2 /HCO 3 - /CO 3 2- and volatile fatty acids were input data to the model. The model was validated by titrating 17 slurry samples collected from four cattle farms, seven pig farms and three biogas plants. Predictions of pH agreed well for 14 slurries with titration data in the pH interval from 4 to 10. Simulations indicated that microbial degradation of VFA to methane and carbon dioxide resulted in a pH increase if the carbon dioxide produced was lost to the atmosphere. There was little change in pH if the produced carbon dioxide dissolved in the slurry.

Animal manure recycling: treatment and management.

A rapidly changing and expanding livestock and poultry production sector is causing a range of environmental problems on local, regional and global scales. Animal Manure Recycling: Treatment and Management presents an accessible overview of environmentally friendly technologies for managing animal manure more efficiently and in a sustainable manner. The book describes the physical and chemical characteristics of animal manure and microbial processes, featuring detailed examples and case studies showing how this knowledge can be used in practice. Readers are introduced to the sustainable use of animal manure for crop fertilisation and soil amelioration. Environmentally friendly technologies for reducing emissions of ammonia, odour and the greenhouse gases nitrous oxide and methane are presented, and reduction of plant nutrient losses using separation technologies is introduced. Finally and most importantly, the book describes methods to commercialise and transfer knowledge about innovations to end-users.

Best available technology for European livestock farms : Availability, effectiveness and uptake

Concerns over the negative environmental impact from livestock farming across Europe continue to make their mark resulting in new legislation and large research programs. However, despite a huge amount of published material and many available techniques, doubts over the success of national and European initiatives remain. Uptake of the more cost-effective and environmentally-friendly farming methods (such as dietary control, building design and good manure management) is already widespread but unlikely to be enough in itself to ensure that current environmental targets are fully met. Some of the abatement options available for intensive pig and poultry farming are brought together under the European IPPC/IED directive where they are listed as Best Available Techniques (BAT). This list is far from complete and other methods including many treatment options are currently excluded. However, the efficacies of many of the current BAT-listed options are modest, difficult to regulate and in some cases they may even be counterproductive with respect to other objectives ie pollution swapping. Evaluation of the existing and new BAT technologies is a key to a successful abatement of pollution from the sector and this in turn relies heavily on good measurement strategies. Consideration of the global effect of proposed techniques in the context of the whole farm will be essential for the development of a valid strategy.

Nitrogen turnover and loss during storage of slurry and composting of solid manure under typical Vietnamese farming conditions

A high proportion of plant nutrients present in animal feed are excreted and therefore animal manure can be an important source of nitrogen (N) for crop production if losses of plant nutrients to the environment during storage and processing are minimized. The present study examines gaseous N losses from stored pig slurry and during composting of solid manure as affected by protein and fibre content in the feed and manure management. Two slurry storage treatments (with and without cover) and three additives to solid manure composting (straw only, straw + lime and straw + superphosphate) were examined for three common types of pig feed in Vietnam (low-protein high-fibre, medium-protein medium-fibre and high-protein low-fibre). Feed type was found to affect the N content in pig slurry or manure and thus potential N losses. The fraction of N loss caused by N emission from covered slurry storage was 0·25―0·30 of initial N content, while that from uncovered slurry was 0·60―0·70. After 90 days of storage, 1·15―1·20 times the initial ammonium-N (NH 4 -N) was found in the covered slurry and 0·40―0·50 in the uncovered. The fraction of N lost during composting with superphosphate was 0·25―0·35 of initial total N, while with lime or straw the total N loss was 0·45―0·55. With added superphosphate, 1·25―1·60 times the initial NH 4 -N in manure was found in the compost after 80 days compared with only 0·11―0·22 for lime and 0·22―0·36 for straw only. Covering stored slurry and addition of superphosphate when composting solid pig manure are thus important methods for Vietnamese farmers to minimize N losses and produce compost with a high content of plant-available N.

A comprehensive model to estimate the simultaneous release of acidic and basic gaseous pollutants from swine slurry under different scenarios

Swine slurry is a source of atmospheric pollutants. Emissions of basic and acidic compounds from slurry are largely dependent on the surface pH. In a storage system, the pH at the surface layers changes over time due to the volatilisation of ammonia (NH3), carbon dioxide (CO2) and acetic acid (HAc). In this article, a comprehensive gas emission–pH (GE–pH) coupled model is proposed to describe the simultaneous release of acidic and basic gaseous pollutants from swine slurry. The model was applied to describe the release of NH3, CO2, HAc and hydrogen sulphide (H2S) from standard slurries stored in animal houses, outside storage tanks and lagoons. The modelled results agreed well with values reported in the literature and could be reasonably interpreted. The key parameters affecting the release of gases were: initial pH, initial concentration of total ammonium nitrogen and inorganic carbon, slurry temperature and air velocity. This study suggests that future modelling studies on gas emissions from animal slurry should consider the concentration of inorganic carbon and the frequency in which the slurry surface is mixed or altered, because they affect the surface pH and the release of gaseous pollutants from slurry.

Ammonium removal from high-strength aqueous solutions by Australian zeolite

ABSTRACT Removal of ammonium nitrogen (NH4+-N) particularly from sources which are highly rich in nitrogen is important for addressing environmental pollution. Zeolites, aluminosilicate minerals, are commonly used as commercial adsorbents and ion-exchange medium in number of commercial applications due to its high adsorption capacity of ammonium (NH4+). However, detailed investigations on NH4+ adsorption and ion exchange capacities of Australian natural zeolites are rare, particularly under higher NH4+ concentrations in the medium. Therefore, this study was conducted to determine NH4+ adsorption characteristics of Australian natural zeolites at high NH4+ concentrations with and without other chemical compounds in an aqueous solution. Results showed that initial NH4+ concentration, temperature, reaction time, and pH of the solution had significant effects on NH4+ adsorption capacity of zeolite. Increased retention time and temperature generally had a positive impact on adsorption. Freundlich model fitted well with adsorption process of Australian natural zeolites; however, Langmuir model had best fitted for the adsorption process of sodium (Na+) treated zeolites. NaCl treatment increased the NH4+ adsorption capacity of Australian zeolites by 25% at 1000 mg-N, NH4+ solution. The maximum adsorption capacity of both natural Australian zeolites and Na+ treated zeolites were estimated as 9.48 and 11.83 mg-N/g, respectively, which is lower than many zeolites from other sources. Compared to the NH4+ only medium, presence of other competitive ions and acetic acid in the medium (resembling composition in digested swine manure slurries) reduced NH4+ removal of natural and Na+ treated zeolites by 44% and 57%, respectively. This suggests detailed investigations are required to determine practically achievable NH4+ -N removal potential of zeolites for applications in complex mediums such as animal manure slurries.