Manure Processing

Objectives To convert surplus manure in products of higher value and/or products which are easier to transport. To reduce local manure surpluses. | Objectives Techniques Cost Targeted Livestock System Impact Context of Application Monitoring: EIA, Indicators References

Techniques

Many systems of manure processing have been researched, only few are used on any larger scale. Feasibility of large scale manure processing depends on the local circumstances (local legislation, fertilizer prices) and processing cost. The following techniques are available:

> Basic possibilities for manure processing (liquid manure mixture from pigs, poultry or cattle):

The liquid mixture (manure, urine and water with a dry matter content of 5 – 12 %) can be used for biogas production. This will not essentially change the composition of the manure from the environmental point of view. It is an energy production process. The dry matter content of the manure is increased a little bit, the smell is reduced but all the minerals (N.P and K are still in the manure mixture. Without or after biogas fermentation this mixture could be directly applied as fertilizer to agriculture land (crop land or pasture) | Manure tank for transportation and spreading of liquid manure

- The liquid manure mixture (with or without the biogas fermentation) could be separated in a liquid and a solid fraction.
Various techniques are available:

- separate a solid fraction with a DM content of less than 20 %, this mixture can still be pumped and applied to the field (either through spraying or direct injection in the soil).
- machinery to separate a solid fraction of 60 – 70 % DM.

- Solid fraction of 60 – 70 % DM. This could be used for composting, during the composting process considerable part of the nitrogen will evaporate as ammonia into the atmosphere. To prevent ammonia emissions the composting has to take place in tunnels to capture the ammonia. The compost could be used for fertilizer and for soil improvement. Supplementation with P and N might be necessary to improve the fertilizer value.
- Recovery of liquid ammonia from the liquid fraction. The liquid ammonia fraction could be used for fertilizer (injection in the soil), in the fertilizer industry or could be added to the compost to improve the fertilizer value.

- The liquid fraction could undergo a denitrification process. The nitrogen will be transformed into N2 and will escape in the air. The process will have to be very well implemented and monitored because there is a high risk that NOx will be formed in the process. NOx is a greenhouse gas 320 times stronger than CO2.

- The remaining liquid fraction contains mainly K and Cl, this could be spread on the field.

> Most processes require large quantities of manure and are generally not techniques suitable for on farm implementation. Some of the endproducts have to be produced in very large quantities and of a very reliable quality before they acceptable for the industry.

Other techniques:

- Further drying of the solid fraction (evaporation of water): this is an expensive process, very often requiring fossil fuel. The dried manure could be pelletized and used as fertilizer for special crops or in the hobby gardening (there is normally only a small marketing niche for this type of product).

- The dried fraction could be used for burning. This is frequently not cost efficient, the drying will require more energy than the effective energy gained from burning the product. Manure from broilers could be an exception because the original product is mixed with wood shavings and has a high DM content. The residual ash of the burning process contains P and K and can be used in the fertilizer industry. Again the fertilizer industry will only be interested in this product if it is available in large quantities of a confirmed constant quality. The residual ash could contain residues of heavy metals which make it unsuitable for further processing by the fertilizer industry.

| Click on the image to view a full-size version of this diagram

Costs

Most processes are expensive and cost between US$ 10 to 20 per ton of liquid manure.

Targeted Livestock System

Grazing System

LGA | LGS1 | LGS2 | LGS3 | LGH1 | LGH2 | LGH3 | LGT1 | LGT2 | LGT3
N | N | N | N | N | N | N | N | N | N

Mixed System

MCG | MCR | MCC | MFF | MEF
Y | Y | Y | Y | Y

Industrial System

IFP | IPL | IPG | IRM | IDU | ISL | ITN | IMP
N | Y | Y | Y | Y | Y | N | N

These techniques are applicable to the industrial livestock production systems and to the mixed cut and carry system and external feed resources, where manure is stored in the form of a liquid mixture and cannot be directly applied to the land

Impact

- Positive environmental impact
In most cases the volume of manure is reduced and the emissions to the environment are reduced.
The production of biogas reduces the need for fossil fuel
Composted manure has a higher value as organic fertilizer
The transport cost are reduced to bring manure from surplus areas to deficit areas
- Negative environmental impact
Most forms of processing of manure (drying and pelletizing, separation of solids and liquids) require fossil energy.
- Livestock productivity impact
Only an indirect effect of manure through improved fodder crop production

Context of Application

- Policy: Incentives for development and implementation of the various forms of manure processing

- Education/training: information on manure handling, storage and processing

Monitoring : EIA; Indicators

- Quantity of manure processed

References

Osei-Safo, C. Biogas utilization and its agricultural implications in Ghana. Click here to view Acrobat file

El Shimi, S. and Arafa, S. Biogas technology transfer to rural communities in Egypt. Click here to view Acrobat file

Savickas, J. and Klementavicius, A. Current initiations in biogas implementation. Click here to view Acrobat file

Turyareeba, P. Socio-economic implications associated with wider use of bio-energy and wind energy technologies. Click here to view Acrobat file

Biogas demonstration plant on a pig farm in Lithuania: http://www.folkecenter.dk/rokai/rokai.html

Burton, C.H. 1997. Manure management: Treatment strategies for sustainable agriculture. Silsoe Research Institute, Bedford UK. (ISBN: 0 9531282 0 2)

Mineral policy in the Netherlands; Dutch policy to reduce undesired effects of mineral losses to the environment. Published in 1999 by the Ministry of Agriculture, Nature Management and Fisheries and the Ministry of Housing, Spatial Planning and the Environment. Available from: Ministry of Agriculture, Infotiek, P.O. Box 20401, 2500 EK, The Hague, The Netherlands.

Prospects of manure fermentation on Dutch dairy farms, by J.M.A. Nijssen, S.J.F. Antuma, A.T.J. van Scheppingen. Publication 122 (in Dutch) of the Research Station for Cattle, Sheep and Horse Husbandry (PR), P.O. Box 2176, 8203 AD Lelystad, the Netherlands. E-mail: info@pr.agro.nl Internet: http://www.pv.wageningen-ur.nl/ukhome.htm

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