Nutrient Losses during Winter and Summer Storage of Separated and Unseparated Digested Cattle Slurry

Abstract

Management factors affect nutrient loss during animal manure slurry storage in different ways. We conducted a pilot-scale study to evaluate carbon (C) and nitrogen (N) losses from unseparated and digested dairy slurry during winter and summer storage. In addition to season, treatments included mechanical separation of digestate into liquid and solid fractions and bimonthly mixing. Chemical analyses were performed every 2 wk for the mixed materials and at the start and end of storage for unmixed materials. The parameters examined allowed us to estimate C and N losses and examine the factors that determine these losses as well as emission patterns. Gas measurements were done every 2 wk to determine the main forms in which gaseous losses occurred. To evaluate the effect of separation, measured losses and emissions of separated liquid and solid fractions were mathematically combined using the mass separation efficiency of the mechanical separator. Nutrient losses were mainly affected by climatic conditions. Losses of C (up to 23%) from unseparated, unmixed digestate and of N (38% from combined separated fractions and from unseparated digestate) were much greater in summer than in winter, when C and N losses were <7%. Mixing tended to significantly increase N losses (P < 0.1) only in winter. Mechanical separation resulted in lower GHG emissions from combined separated fractions than from unseparated digestate. Results indicate that to maximize the fertilizer value of digested slurry, dairy farmers must carefully choose management practices, especially in summer. For separated digestates, practices should focus on storage of the liquid fraction, the major contributor of C and N losses (up to 64 and 90% of total losses, respectively) in summer. Moreover, management practices should limit NH 3 , the main form of N losses (up to 99.5%). Nutrient Losses during Winter and Summer Storage of Separated and Unseparated Digested Cattle SlurryFrancesca Perazzolo,* Gabriele Mattachini, Elisabetta Riva, and Giorgio Provolo M anure slurries from dairy and other livestock production systems are valuable sources of plant nutrients and carbon (C) and are thus a resource for crop producers. Slurry use as fertilizer should be based on its nutrient and C content (considering potential nitrogen [N] and C losses during on-farm storage) to reduce negative environmental impacts . Losses of N and C as ammonia (NH 3 ), nitrous oxide (N 2 O), and methane (CH 4 ) during slurry storage are particularly relevant (Chadwick et al., 2011;Dinuccio et al., 2012) and should be evaluated and minimized via cost-effective mitigation methods.Using the integrated modeling tool MITERRA-EUROPE, Oenema et al. (2007) estimated that in the EU almost 30% of the N excreted in dairy barns is lost during storage. Approximately 63% of the loss was via NH 3 emissions; 23% was lost following nitrification or denitrification as nitric oxide (NO), N 2 O, and N 2 ; and 13% was lost due to leaching and run-off. However, the differences in mean N losses from manure...

The effect of acidogenic and methanogenic conditions on the availability and stability of carbon, nitrogen and phosphorus in a digestate

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Effects of pH, Total Solids, Temperature and Storage Duration on Gas Emissions from Slurry Storage: A Systematic Review

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