Filières de gestion des effluents d'élevages bovins : impact environnemental de la production et du stockage

Livestock manure management : environmental impact of the production and stocking phases

Context

Agriculture has a significant impact on environmental resource preservation. In Walloon Area, it is responsible for the emission, in the atmosphere, of around 9 % of the greenhouse gases and of around 23 % of the acidifying gases.

Beef production systems are well represented in Walloon area. Nevertheless, as other cattle production systems, it could be linked to gazes emissions such as CH₄, during rumination process, and N₂O or NH₃, during manure stocking phase. A good knowledge of these phenomena and of the utilisation value of these manure are essential to optimise their agronomical valorisation while limiting their environmental impact.

Objectives

The first aim of this research is to quantify greenhouse (GHG) (CO₂, CH₄, N₂O) and acidifying (NH₃) gazes emissions during the manure production, under cowshed, and the manure stocking phases. More especially we want to determine the impact of different parameters on these emissions : (1) the cowshed type (free and tying stall), (2) the straw supply levels (low and high) and (3) and the type of stored manure managements (composted or not).The second aim is the characterisation of the manure produced with the definition of the N, P and K balances in order to optimise the valorisation of these nutrients.

Expected results

In order to support these first results, the experimentations are repeated during the 2006-2007 season.

At the end, we aim to determine the best practices to apply in order to reduce GHG emission and to reduce the negative environmental impacts linked to farm manure valorisation.

Results obtained

During the winter 2005-2006, some measurements have been performed in 3 experimental cowsheds including, each, 4 Belgian Blue heifers. During this period of time, the main GHG produced, without taking into account the CO₂, was the methane (> 95 % in CO₂ equivalent) and this whatever the cowshed type or the straw supply levels.Nevertheless, GHG emissions levels were 28 % higher in free stall types than in tying types, with daily manure removal. NH₃emissions were similar among the different modalities tested. We also recorded the daily emission cycles for these different gases. These cycles can be directly linked to the animal feeding period an this more especially for NH₃ production cycle. During manure stocking phase, after winter, lower CO₂ and N₂O emission levels were observed for the manure obtained in the tying stall type. While CH₄emissions were higher in this stall type and this, whatever the straw supply level. For the manure obtained in the free stall type, the composting process had led to a reduction of N₂O and CH₄emissions of, respectively, 50 and 30 %. From the nutrients balance point of view, we observed, after the summer stocking phase, a reduction of 30 % of the N injected in the system through the use of feedstuff, straw, … These losses were mainly due to gazes emissions during the manure stocking phase. P balance was at equilibrium while some K losses were recorded.

Contribution

To reach these targets, the Farming System Section mobilises its competencies in terms of livestock feeding and manure managements together with its experimental cowsheds.

Partners

Center of Michamps, UCL, Belgium.

CRAW off coordinator

Dr. Ir. Richard Lambert Centre de MichampsMichamps, 1B-6600 BastogneTél. : +32 (0)61 21 08 20Fax : +32 (0)61 21 08 40E-mail : lambert@ecop.ucl.ac.be Dr. Ir. Didier Stilmant CRA-W – Section Systèmes agricolesRue de Serpont, 100B-6800 Libramont-ChevignyTél. : +32 (0)61 23 10 10Fax : +32 (0)61 23 10 28Email : stilmant@cra.wallonie.be