Biomethanation of Rice Straw: A Sustainable Perspective for the Valorisation of a Field Residue in the Energy Sector

Rice straw represents a field waste. Indeed, only 20% of the rice straw produced is used in the pulp and paper industry. The larger amount of this field residue is burned or left in the field, which has very important environmental consequences. Recently, analogous to a barrel of oil, a metric approach to rice straw, the rice straw barrel, was introduced in order to assign economic value to this waste. In this paper, potential annual biomethane production from anaerobic digestion is evaluated, resulting in a range of biomethane created for each rice straw barrel depending on volatile solid (VS) content as a percentage of total solid (TS) content and on biomethane yield: 23.36 m3 (VS=73.8%TS, 92 L kg−1VS), 26.61 m3 (VS=84.08%TS, 186 L kg−1VS), 29.27 m3 (VS=95.26%TS, 280 L kg−1VS). The new concept of the rice straw barrel is improved based on a new indicator for sustainability, the Thermodynamic Human Development Index (THDI), which was introduced within the last three years. The improvement in sustainability by using rice straw barrels for different countries is analysed based on the THDI.