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Additives and other pre/1st treatments

Set of processes which objective is the preparation of the material for a further purpose or treatment.

The descriptions of these livestock manure processing technologies were based on 'Flotats, Xavier, Henning Lyngsø Foged, August Bonmati Blasi, Jordi Palatsi, Albert Magri and Karl Martin Schelde. 2011. Manure processing technologies. Technical Report No. II concerning “Manure Processing Activities in Europe” to the European Commission, Directorate-General Environment. 184 pp."

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Short description

Application of lime resulting in a raised pH, which may be desired for the inactivation of pathogens and/or the precipitation of phosphates.

Best Available Technique: Not indicated
Objective

To stabilize manure and reduce the contents on pathogens. Liming is also applied to increase the pH in view of the application of other treatment processes such as N-stripping or nutrient precipitation.

Level of complexity

Usual scale

Innovation stage

General diagram

Applied to







Typical technology combinations 6-37-12 (for subsequent calcium phosphate precipitation 40)
Pictures

Illustration of liming for phosphorous removal in Tyndall Farm (North Carolina, USA)

Theroetical fundamentals and process description

Slaked lime (Ca(OH)2) is usually added to liquid streams in order to favour posterior treatments such as N-stripping or nutrient precipitation. When it is considered, a thorough mixing with liquid manures is needed. Buffering capacity of the system will determine lime requirements needed to regulate the pH, being highly dependent on the total content of inorganic carbon and the equilibrium HCO3-/CO2. Reduction of such requirements may be achieved by removing CO2 from the system by stripping or nitrification. Quicklime (CaO) is normally used for the solidifying of dewatered materials. By mixing CaO with solid materials, the temperature rises exothermically to between 55ºC and 70ºC. Temperature and pH increase has a detrimental effect on the viability of pathogens. The reactive lime used in the process is serving as a source of energy for the drying, as a sterilizing agent for all bacteria and viruses (pathogens) present in the manure, and as a liming agent changing soil pH.

Environmental effects

Effects on air (emissions):

If such process is not well controlled then it may result in an undesired volatilization of ammonia.

Effects on water/soil (and management):

The increase of pH is a conditioning process applied when planning P-recovery by precipitation or N-recovery by stripping. Obtained products can enhance the capability of manure/slurry management. Solid fractions (struvite) or liquid by-products (ammonia salts) can be more easily exported to areas with low livestock density, reducing problems derived from nutrient surplus, whereas liquid fractions can be used or further processed in situ.

Other effects:

Temperature and pH increase has a detrimental effect on the viability of pathogens.

Biosecurity aspects Not indicated
Technical indicators

Conversion efficiency:


NA

  • Net energy consumption - explanation:

    ~ 0.4 kWh/m3 of input slurry (Vanotti et al., 2009)

  • Reagent 1 - explanation:

    Lime unslaked (quicklime, calcium oxide, CaO), Lime slaked (calcium hydroxide, Ca(OH)2), The amount of reagent needed to attain a given pH is linked to the alkalinity of the manure. Treatments such as nitrification or CO2 stripping may help in reducing such reagent requirements.

Observations

Observations: Recommendations for selection of concrete should be followed. Also lime manipulation should be performed under safety protocols.

Economic indicators (Economic figures are rough indications, which cannot be used for individual project planning)
  • Non economically quantifiable benefits:

    Hygienization is favoured by increasing pH. Combined with a nitrification-denitrification stage, the addition of Ca(OH)2 to the treated effluent (pH 9.5) has been reported to result in an increase in the reduction of the number of pathogens from 2.6-log units to 4-log units (Vanotti et al., 2009).

Literature references
  • Szogi A.A., Vanotti M.B. (2009). Removal of phosphorus from livestock effluents. J. Environ. Qual. 38, 576-586. DOI:10.2134/jeq2007.0641.
  • Vanotti M.B., Szogi A.A., Millner P.D., Loughrin, J.H. (2009). Development of a second-generation environmentally superior technology for treatment of swine manure in the USA. Bioresour. Technol. 100, 5406-5416. DOI:10.1016/j.biortech.2009.02.019.
Real scale installation references
  • Tyndall farm Sampson Co., NC, USA Super Soil Systems
Examples of suppliers