29.01.2013
Leaching of nitrogen and phosphorus from intensive pig productioncan be reduced if the large quantities of manure are used for biogasproduction and if the digestate is spread in springtime when the cropsgrow and utilize the natural fertilizer efficiently. According to a newreport from BalticSea2020, the right setup of technologies for biogasproduction and proper treatment of the digestate can benefit both waterquality and climate.
The study aims to reduce leaching of nutrients to the Baltic Seafrom intensive pig production. The strategy is to identify and describebest available technologies to digest pig manure and efficientlyrecirculate the nutrients as fertilizer to the crop production.Digestion makes nitrogen better available for the plants and a moreefficient fertilizing can be achieved, provided that dosage of nutrientsis according to plants need.
According to Thorkild Qvist Frandsen from AgroTech, nutrient flowcalculations show that the readily available nitrogen in one ton of pigmanure increases from 2,6 kg to 3,4 kg during digestion. More nitrogencan therefore be taken up by the plants and less leaches to surroundingwaters. The risk for leaching of nutrients to air and water increases ifmanure is spread during autumn when the plant uptake is less efficient.The risk increases a bit with digested manure.
Lena Rodhe from JTI - the Swedish Institute for Agricultural andEnvironmental Engineering argues that covered storage is needed to avoidemissions of ammonia, and large enough to allow for spreading thedigestate in springtime. She states that a spreading technology whichquickly incorporates the digestate into the soil should be used.
The report also recommends separation of slurry or digestate inorder to facilitate dosing of nutrients in accordance to crop needs. Theresulting solid fraction should be stored as short time as possible incovered containers to reduce the risk for evaporation of ammonia andlaughing gas (N2O). Knud Tybirk from Agro Business Park states thatan efficient use of the valuable nutrient resource in livestock manurerequires the right dosage of the digestate to the fields. This requiresstandard values for the concentrations of nutrients in livestock manure.Though, he stresses that these are unfortunately not yet available inall countries around the Baltic Sea.
The report ?Best Available Technologies for pig manure biogasplants in the Baltic Sea Region? was produced in collaboration betweenexperts from AgriFood Research - Finland, Agro Business Park - Denmark,AgroTech ? Denmark and the Swedish Institute for Agricultural andEnvironmental Technology. The project is initiated and financed byBaltic Sea 2020.
For the full report click at: Best Available Technologies for Pig Manure Biogas Plants in the Baltic Sea Region.
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