Abstract
The composition of biomass feedstock and pyrolysis parameters, such as temperature, heating rate, and residence
time, are key factors that affect the distribution and properties of pyrolysis products and are among the most exten
sively studied. However, the pyrolysis atmosphere also plays a crucial role in determining process efficiency and prod
uct quality. This review examines the effects of various pyrolysis atmospheres on biochar yields and properties,
and also considers impacts on pyrolysis gases and liquids. While nitrogen is commonly used in research, the demand
for biochar with specific properties like increased porosity and functionality has led to exploring alternative atmos
pheres such as steam, oxidative, pyrolysis gas, carbon dioxide, methane and ammonia. These alternatives can produce
biochar with the desired characteristics in a single step, bypassing the need for multiple modifications. This review
provides an overview of these pyrolysis atmosphere options, their applications, advantages, and potential challenges.
Future research directions are also identified and highlighted, offering a roadmap for advancing biochar production
technology