Biochar covering to mitigate the ammonia emissions from the manure storage tank: Effect of the pyrolysis temperature

Biochar has been recently investigated as an alternative to the floating cover applied during manure storage, for its interesting durability and hydrophobicity. Pyrolysis parameters play an important role in affecting physic-chemical biochar characteristics, such as pH, porosity, and specific surface. This paper aims at comparing the $\boldsymbol{\text{NH}_{3}}$ emissions that occurred after the application of two types of biochar, produced at 285 and $\boldsymbol{450^{\circ} \mathrm{C}}$ (namely under torrefaction and pyrolysis regime, respectively). Results showed that biochar at $\boldsymbol{285^{\circ} \mathrm{C}}$ emitted 42 % less $\boldsymbol{\text{NH}_{3}}$ than the other one. Generally, $\boldsymbol{\text{NH}_{3}}$ emissions rates were in accordance with the free $\boldsymbol{\text{NH}_{3}}$ in the liquid solution. On the other hand, the greater adsorption capacity of biochar at $\boldsymbol{\mathbf{4 5 0}^{\circ} \mathrm{C}}$ does not seem to have played a relevant role in reducing ammonia emissions, confirming that the “lid” action is prevailing in limiting the gaseous exchange.