Managing livestock manure for sustainable agriculture
A workshop was held in the Netherlands in November 2010 aiming to promote exchange of information on manure management among member states of the European Union, with special focus on manure processing.
The presentations, workshop and excursions showed that many manure processing techniques are available (from low-tech separation to high-tech reverse osmosis techniques).
Site-specific conditions and farm structure define the optimal combination of techniques, as well as the constraints found at regional level (e.g. the nitrogen surplus).
Economic analyses showed that large scale high-tech processing techniques are expensive and can only be affordable for high-income farmers or in regions with high livestock density, where all alternative solutions for manure management are even more expensive. In these instances, the cooperation of several farmers in the processing facility is necessary.
It is clear that, since the pressure on the environment by intensive livestock farming systems is high, the environmental legislation, both at European and national level, has put on them many obligations, such as strict (manure) nitrogen application standards and measures to reduce ammonia and greenhouse gas emissions. Manure processing techniques could be seen as the response to these legislative constraints as well as the consequence of increasing environmental protection awareness by all stakeholders. In addition, particularly for those regions with intensive use of livestock manure, the differences in nitrogen/phosphorus ratio of raw manure and the nitrogen/phosphorus ratio of crops may incite farmers to process manure in order to redistribute the nitrogen and phosphorus nutrients over different fractions.
It was stressed that manure processing is part of the solution to improve the use of nutrients in manure and to decrease emissions to the environment in regions with intensive livestock farming systems. In regions with extensive livestock systems, simple manure separation techniques may help to increase nutrient use efficiency and can be used for energy generation on the farm scale. Many other tools are available to improve manure management and would need to be better enforced at all scales (nationally/regionally, through better legislation; locally, through implementation on field). The results of the different oral and poster presentations indicate that there is still much room for improving nitrogen use efficiency in agriculture. Improvement of nitrogen use efficiency of livestock farming systems includes also the optimization of the feed composition. The whole chain from feed to manure application should be considered.
Various barriers to implement manure treatment have been indentified, such as high investment and operational costs for high-tech manure processing techniques, legislation (e.g. permits to built manure treatment installations, conditions for export/import of processed products), acceptance by society, and possible risks associated with their operation. These barriers limit implementation of manure processing in practice.
Manure processing techniques affect nitrogen emissions to water and air, the phosphorus inputs to soil, and greenhouse gas emissions, both during the process itself and through the use of the end and by products. An integrated system analysis is needed for an overall assessment of the environmental performances of these techniques, taking both nitrogen and phosphorus into account, as well as greenhouse gases emissions.
Further testing and optimization of currently available manure processing techniques are needed, taking into account the local situation. Moreover, innovation and further developments of new techniques (e.g. Alum, Annamox, and acidification) is desirable. In many countries, research is carried out on manure management and manure processing techniques. It is important to improve the pace of information exchange, so that results of the different projects can be used to optimize manure management and increase nutrient use efficiency in the EU.
The global rock phosphate resources are decreasing. This requires systems using less rock phosphate-based fertilizers and in which phosphorus in manure and other residues is fully reused as a fertilizer. Increased attention to phosphorus sustainability issues is needed. This is a big job of political awareness worldwide. The European Commission announced that it is working on a reflection paper on sustainable use of phosphorus within the context of resource efficiency and its intention to promote further awareness on phosphorus limited resources and best options to improve its use at sustainable levels.
Summarizing, the major conclusions of the manure workshop are:
• There is an increasing interest in manure treatment;
• System approaches (integrated system analysis) are needed for an overall assessment of performances of manure treatment techniques;
• Site-specific conditions and farm structure define the optimal combination of techniques;
• Many techniques are available, but further testing and optimization are needed;
• There are legal driving forces for manure processing, but other socio-economic driving forces may be needed. Further innovation and new techniques will be desirable;
• New generations techniques are for example Alum, Annamox, and acidification;
• Various barriers (legal, social, economic) have been indentified, which limit implementation in practice;
• There is still much room for improving nitrogen use efficiency in agriculture;
o Differences between countries have been identified
o Whole feed-chain analysis needed for improving
o Pace of information exchange needs to be improved
• Nitrogen and phosphorus must be combined in system analysis;
• Increased attention to phosphorus sustainability issues is required; requiring greatly increased political awareness worldwide.
Read the whole report here