Screening tests for N sorption allow to select and engineer biochars for N mitigation during biomass processing.

Area of Science:

• Agricultural Science
• Environmental Science
• Material Science

Background:

• Biochar amendment in biomass processing offers ecological and economic advantages by reducing greenhouse gas and ammonia (NH₃) emissions.
• Biochar's capacity for ammonium-nitrogen (NH₄⁺-N) and NH₃ sorption is key to its benefits, influenced by its characteristics.
• Understanding the link between biochar properties and nitrogen sorption allows for optimized biochar production and selection for enhanced N sorption.

Purpose of the Study:

• To develop rapid screening methods for assessing biochar's potential to sorb NH₄⁺-N and NH₃.
• To investigate how feedstock, pyrolysis temperature, biochar characteristics, and treatments affect nitrogen sorption.
• To establish a predictive model for NH₄⁺-N sorption based on biochar properties.

Main Methods:

• Development of fast screening tests for NH₄⁺-N and NH₃ sorption.
• Analysis of biochar characteristics including nutrient content and cation exchange capacity.
• Experimental evaluation of feedstock, pyrolysis temperature, and post-production treatments (grinding, washing) on nitrogen sorption.
• Development of a general linear model to predict NH₄⁺-N sorption.

Main Results:

• NH₄⁺-N sorption ranged from 0 to 1.54 mg/g, with highest sorption observed in manure-based biochars produced at lower temperatures (300-450 °C).
• Grinding and washing treatments enhanced NH₄⁺-N sorption for some biochars.
• NH₃ sorption showed a positive linear correlation with NH₄⁺-N sorption, moisture retention, and cation exchange capacity; pyrolysis temperature and feedstock type had no significant impact on NH₃ sorption.

Conclusions:

• Fast screening tests can effectively estimate biochar's nitrogen sorption potential.
• Biochar properties, particularly those of manure-based biochars from lower temperature pyrolysis, are critical for maximizing N sorption.
• The developed model and understanding of biochar characteristics enable targeted selection and production for improved nitrogen management in biomass processing.