Biomass, particularly agro-industrial wastes, is a renewable fuel and the fourth largest following coal, oil and natural gas. Compared with these fossil fuels, it has the advantages of being neutral concerning the emissions of the greenhouse gas carbon dioxide, as this participates in biomass growth through the photosynthesis reactions, and reducing pollutant species generation, given the low sulfur and nitrogen contents. Bio-wastes can create major environmental problems if not properly handled.

On the other hand, one of the most important economic activities in the Cuyo Region, Argentina, is the agroindustry, this sector produces a significant environmental impact in specific geographical areas. These wastes generated have significant amounts of lignocellulosic materials.

The recent Argentine political, are strongly encouraging the use of biomass for energy purposes, mainly owing to three targets economic and social development of countryside, elimination of wastes and reduction of CO₂ emissions.

The more developed technologies for obtaining energy or fuels from biomass are those based on thermochemical treatments, namely, pyrolysis, gasification and combustion.

The moisture content of biomass wastes is an important property in the thermal treatment since the moisture levels may affect its performance and reliability. As is well known, the first step of pyrolysis and combustion corresponds to water evaporation, which requires energy and reduces overall process efficiency.

After the forced drying at 378K until constant weight, for example, the moisture content of biomass can decrease between 2 at 5%. Numerous pyrolysis and combustion studies have used this dry-basis biomass for experimental research and kinetic analysis.

High moisture content has a much lower net energy density by mass, owing to the weight of the water, but also by volume due to the energy required to evaporate the water. Consequently, drying pretreatment of biomass to thermal treatment is usually desirable and in some cases essential, in order to minimize the effect of moisture on the treatment.

The kinetic modeling of the drying stage is crucial for an accurate prediction of the material’s behavior under different working conditions. Investigation of this stage kinetics and its parameters contributes to further information of heat and mass transfer.

As biomass is linear heating in the thermogravimetric analyzer, the moisture continuously absorbs energy and then evaporates. However, not all water molecules can be turned to vapor and released. Only the water molecules that have obtained sufficient energy for gasification can undergo the transition. This level of gasification energy can be regarded as the activation energy required for biomass to dry. The higher the drying activation energy the more heat requirement in the drying process.

The aim of this study is the determination of nonisothermal drying kinetics of marc, stalk and peach pits from Argentine agro-industry. Different models were applied at obtained TG data of water evaporation under inert and oxidative atmosphere. The activation energy was determined using integral and differential methods applied at the model with better fit.