Waste valorization of rice straw as a building material in Valencia and its implications for local and global ecosystems

Abstract

The environmental implications of rice straw cultivation in the Spanish city of Valencia have generated controversy in recent decades. The paddy fields surround a natural park called Albufera, and the need to protect the local environment requires the cultivation to be as sustainable as possible. Every year over 75000 tons of rice straw generated after the harvest are burned or mixed with the soil. Both practices emit greenhouse gases and have huge effects on the surrounding areas’ population and environment. One way to avoid those emissions is to use rice straw as a raw material for building products. A building façade panel using rice straw as its main component is presented as an alternative to the conventional double-layered brick façades widely used in this area. This article describes the life cycle assessment (LCA) and the acoustic and thermal insulation of the rice straw façade compared to those of a conventional brick façade. Additionally, the surface and interstitial condensation have also been studied through a simulation. The LCA, conducted using the Environmental Footprint methodology, indicates that the rice straw façade has a lower impact on the environment in every studied category. The rice straw façade emits 78 % less CO2e than the benchmark typology. If the emissions of either burning the straw or mixing the straw with the soil are subtracted, each square meter of rice straw façade prevents the emission of 18.85 kg of CO2e and 52.64 kg of CO2e, respectively. The measured acoustic insulation is similar in both studied façades. The sound reduction index of the brick façade is 49 dB and the obtained with the rice straw façade is 47 ± 1.93 dB. Both results comply with the local building regulations. The thermal insulation of the rice straw façade (as measured by thermal transmittance) is 0.29 ± 0.08 W/m2°C, which doubles that of the benchmark typology (0.629 W/m2°C). The hygrothermal behavior also complies with the local building regulations. The straw façade shows no signs of Surface condensation since the interior surface temperature factor of the façade is 0.927, higher than the required by the conditions of the most restrictive month (0.430). Also, there is no risk of interstitial condensations in any month. These results indicate that the rice straw panels can be both a suitable sustainable alternative for the building industry in Spain and a viable solution to the environmental problems caused by rice straw mismanagement.