Life Cycle Assessment of rice husk as an energy source. A Peruvian case study

Energy consumption linked to non-renewable resources such as fossil fuels contributes to greenhouse gas emissions and increases resource depletion. In this context, the use of agricultural solid residues such as rice husk, coffee husk, wheat straw, sugar cane bagasse, among others, has been widely studied as an alternative energy source in order to decrease the use of fossil fuels. In Peru, up to 693,308 metric tons of rice husk is generated annually and at present, 85% is burned in the open air or disposed in rivers, harming human health and contaminating our environment. On the other hand, official Peruvian energy policy is to incorporate the use of renewable energy sources, such as agricultural residues. Consequently, the aim of the study is to perform a technical and environmental assessment of the production of energy from rice husk as an alternative energy source to coal in Peru. Rice husk from Peru was characterized to identify its physical properties and chemical composition. In order to perform the environmental assessment, a Life Cycle Assessment (LCA) was employed. LCA is a standardized methodology to identify and quantify the environmental impacts from initial obtention of materials, through production, distribution and use to final disposal (ISO 14040, 2006 and ISO 14044, 2006). Four scenarios were evaluated, varying in paddy rice yield and dryer efficiency. The results show that the environmental impacts to obtain 1 MJ from rice husk, including elements in the global warming, acidification and eutrophication categories, are less than that from 1 MJ obtained from coal, 97%, 88% and 80% less, respectively. However, the opposite was found in water depletion, with the use of coal to generate heat having a 98% better impact over rice husk.