Rice Straw and Sugarcane Straw Agrowaste for Energy Production: Physico-chemical Characteristics and Prediction of their Thermal Behaviour (#1584)

Authors

Assureira, Estela

Assureira, Marco

Abstract

The growth in population leads to higher food and energy requirements, along with increased waste and greenhouse gas emissions. To create a sustainable environment, utilizing agricultural waste as an energy source is crucial. This option offers a consistent supply, widespread presence, and helps reduce environmental harm caused by burning practices and CO2 emissions. Sugarcane and rice, crops of global importance, annually generate around 0.6*109 tons of sugarcane straw (SCS) and 1.3 *109 tons of rice straw (RS). Due to their low nutritional value, they are not used as livestock feed, and their accumulation in crop fields causes the proliferation of vectors, which is why these agrowastes are burned or thrown into rivers, generating pollution. The valorization of SCS and RS for their use in energy generation, will have a profound impact as it will contribute positively to the incorporation of new energy alternatives, as well as to waste management and the reduction of emissions. The present research work, of an experimental nature, focuses on the energy production process from SCS and RS, having carried out the characterization and energy analysis of these agrowastes for their use in combustion.The heating value for the SCS and the RS were 17.4 MJ kg-1 and 14.9 MJ kg-1 respectively, while the moisture was less than 12% in both cases. The high content of K and Na determines the low melting temperature of the ashes. The percentage of S and Cl exceed the recommended values, which will lead to corrosion and emissions of SOx and HCl.The prediction of ash deposition on the surfaces of heat transfer equipment has been carried out based on the results of the ash composition of these agrowastes and the application of a set of indices. The values of the Base/Acid Index (B/A) and the Fouling Index (Fu) indicate an average tendency towards ash deposition for both agrowastes, which was corroborated by the deformation temperatures (DT) and hemisphere temperatures (HT) estimated by using ternary diagrams. The DT values were less than 1100°C in both cases, and the estimated HT temperature for the case of the RS was between 1200 and 1400°C, while for the SCS it was less than 1200°C. The total emissions estimated were 1229 gr kg-1 and 1396 gr kg-1 for RS and SCS respectively, in both cases corresponding more than 93% to CO2 emissions, which is favorable as they will be absorbed during the photosynthesis process. The low density observed for SCS indicates the need to cut, bale, or compact SCS in order to reduce transportation and storage costs.This research work provides information on the properties and energetic behaviour of SCS and RS for their use as fuel in thermochemical process, as well as guidelines to enhance their thermal properties through the application of pre-treatments, such as water leaching, to reduce the percentage of alkali metals, Cl and S, in order to increase the values of the ash fusion temperatures and thus reduce the risk of slagging and fouling in thermal equipment.