Determination of the Combustion Parameters of Nonwoody and Animal Biomasses via Thermogravimetric Analysis for Sustainable Energy Valorization

The present paper discusses differences in the theoretical behavior of nonconventional biomasses during combustion according to their combustion parameters, focusing on their potential for sustainable energy valorization and their contribution to sustainable development. Data were obtained through thermogravimetric analysis (TGA) of biomasses from the local Galicia–North Portugal Euroregion. The samples tested were raw, nonwoody biomasses, specifically kiwi waste and gorse, and animal-derived biomasses, poultry and turkey manure. A wood pellet was also included as a reference conventional biofuel. Nonwoody biomass samples containing kaolin and calcium carbonate were also tested. Thermogravimetric analyses were performed on each biofuel under an oxidative atmosphere at different heating rates. With these data, different combustion parameters were calculated. The TGA results showed that the mean ignition temperature observed for animal-derived fuels was about 15 °C lower than for nonwoody biomasses at every heating rate, which indicates that they start to burn at lower temperatures. These animal-derived fuels generally presented better combustion parameters, suggesting that their combustion behavior is better; however, their high ash and moisture contents are problematic. These issues would be aggravated in real facilities, making them more difficult to use as fuel. The proportion of additives used had no effect on the parameters at lower heating rates, although they started to modify their tendency at 30 °C/min. For instance, the ignition index for non-additivated kiwi waste was 174.32 (wt. %/min³) × 10⁻³ compared to 143.78 (wt. %/min³) × 10⁻³ for kiwi with CaCO₃.