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7.1 Yong Hou – University of Copenhagen

ReUseWaste > Thesis abstracts > 7.1 Yong Hou

WP 7.1: Integrated assessment of manure management chains in EU-27, Yong Hou, WUR

Livestock manure contributes considerably to global emissions of ammonia (NH3) and greenhouse gases (GHG), especially methane (CH4) and nitrous oxide (N2O). Various measures have been developed to mitigate these emissions, but most of these focus on one specific gas and/or emission source.  The objective of this study was to increase the understanding of the agronomic, environmental and social-economic performances of the animal manure management chains in Europe at country scales, and to examine options for improving performances of the integrated system.

For paper 1, we conducted a meta-analysis and integrated assessment of the effects of mitigation measures on NH3, CH4 and (direct and indirect) N2O emissions from the whole manure management chain. We analysed the effects of mitigation technologies on NH3, CH4 and N2O emissions from individual sources statistically using results of 126 published studies. Whole-chain effects on NH3 and GHG emissions were assessed through scenario analysis. Significant NH3 reduction efficiencies were observed for i) housing via lowering the dietary crude protein (CP) content (24-65%, compared to the reference situation), for ii) external slurry storages via acidification (83%) and covers of straw (78%) or artificial films (98%), for iii) solid manure storages via compaction and covering (61%, compared to composting), and for iv) manure application through band spreading (55%, compared to surface application), incorporation (70%) and injection (80%).

Acidification decreased CH4 emissions from stored slurry by 87%. Significant increases in N2O emissions were found for straw-covered slurry storages (by two orders of magnitude) and manure injection (by 26-199%). These side-effects of straw covers and slurry injection on N2O emission were relatively small when considering the total GHG emissions from the manure chain. Lowering the CP content of feed and acidifying slurry are strategies that consistently reduce NH3 and GHG emissions in the whole chain. Other strategies may reduce emissions of a specific gas or emissions source, by which there is a risk of unwanted trade-offs in the manure management chain. Proper farm-scale combinations of mitigation measures are important to minimize impacts of livestock production on global emissions of NH3 and GHG.

In paper 2, we report on N excretion factors for a range of animal categories in policy reports by Member States of the European Union (EU). We discuss also the guidelines and methodologies for the estimation of N excretion factors by the EU Nitrates Directive, the OECD/Eurostat gross N balance guidebook, the EMEP/EEA Guidebook and the IPCC Guidelines. Our results show that N excretion factors for dairy cattle and other cattle, pigs, laying hens, broilers, sheep, and goats may differ significantly between policy reports and between countries. Part of these differences may be related to differences in animal production, size/weight of the animals, and feed composition, but partly also to differences in the aggregation of livestock categories and estimation procedures. The methodologies and data used by Member States are often not well described. There is a need for a common, harmonized methodology and procedure for the estimation of N excretion factors, to arrive at a common basis for the estimation of manure N, N balances, and ammonia (NH3) and nitrous oxide (N2O) emissions across the EU.

In paper 3, we present a transparent and uniform methodology for estimating annual feed use and N excretion per animal category for all countries of the EU-27, based on the energy and protein requirements of the animals and statistics of feed use and composition, animal number and productivity. The calculated total feed use in the EU-27 was 506 Tg dry mass in 2010. Dairy cows used 29%, other cattle 34%, pigs 17%, chicken 9%, sheep and goats 8%, and other animal categories 3% of the total feed use. Grass and annual forages were mainly used by dairy cows (30 and 49%, respectively) and other cattle (55 and 44%); pigs used most of the feed cereals (53%); protein-rich feed (e.g., soybean meal) were mostly used by pigs (34%) and chicken (24%). Differences between countries in feed use were large, mainly related to variations in national feed supply and animal productivity. Total N excretion of the animals amounted to 9.7 Tg in 2010, and varied between countries from 14 to 291 kg ha-1 of utilized agricultural land. The present study provides a uniform and transparent approach for evaluating feed use and N excretion in all countries of the EU-27. Our results underline the significant differences in N excretions between EU countries as a result of feed use variations, suggesting the need for basing N excretion estimations on feed use data. The dataset present in this study may serve as a basis for such efforts, also to improve national inventories of N emissions.

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