Chemical characterization of volatile organic compounds emitted by animal manure.

Overview

• This study analyzes the volatile organic compounds (VOCs) emitted by different types of animal manure to understand their chemical composition and environmental impact.
• The research uses advanced laboratory techniques to identify and quantify VOC emissions from cow, horse, sheep, and goat manures under controlled conditions.

Introduction and Importance

• Animal manure is widely used as an organic fertilizer because it enriches soil nutrient content and supports plant growth.
• Besides its agricultural benefits, manure releases VOCs that affect atmospheric chemistry, contributing to air pollution, odor problems, and potential harm to human health and ecosystems.
• Understanding the precise makeup of VOC emissions from manure is essential to evaluate and mitigate their environmental effects.
• Both laboratory and field studies are necessary: laboratory experiments provide detailed chemical data to complement field measurements, filling knowledge gaps in the literature.

Experimental Design and Methods

• Samples were collected from four types of animal manures—cow, horse, sheep, and goat—from a farm near Paris, France (Grignon).
• Experiments were conducted in controlled atmospheric simulation chambers to replicate environmental conditions while enabling precise measurement.
• Two complementary analytical techniques were employed:
  • Proton Transfer Reaction-Quadrupole ion guide-Time-of-Flight Mass Spectrometry (PTR-QiTOF-MS): allowed detection and quantification of 368 individual VOCs within the samples.
  • Thermal Desorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS): helped improve identification and characterization of the VOCs.

Key Findings on VOC Composition

• The study identified a diverse range of VOC chemical groups emitted from the manures, including:
  • Oxygenated compounds such as ethanol, cresol, and acetaldehyde.
  • Nitrogenated compounds such as ammonia and trimethylamine.
  • Sulfur-containing compounds such as methanethiol and dimethyl sulfide.
  • Aromatic compounds including phenols and indoles.
  • Terpenes like isoprene and D-limonene.
  • Halogenated compounds.
• Among the manures tested:
  • Cow manure had the highest total VOC emission fluxes.
  • Goat manure had the second highest, followed by sheep and horse manures.
• Oxygenated VOCs were the main contributors to the total VOC flux across all manure types.

Statistical Analysis and Emission Profiles

• Distinct VOC profiles were identified for different manure types:
  • Cow manure emissions were dominated by oxygenated and nitrogenated compounds.
  • Goat manure was unique for having high emissions of compounds containing both oxygen and nitrogen atoms (e.g., CHNO molecular formulas).

Environmental Implications and Applications

• The detailed chemical dataset provides a valuable reference inventory for VOC emissions from various animal manures, useful for environmental monitoring and regulatory purposes.
• Identification of odor-causing compounds and VOCs that can act as precursors to atmospheric aerosols helps in understanding air quality issues related to manure management.
• The results can guide future research toward evaluating manure treatment methods aimed at reducing VOC emissions and promoting sustainable agricultural practices.