Journal of Scientific & Industrial Research Vol. 77, October 2018, pp. 587-591 Application of Rice Husk and Maize Straw Biochar for Carbon Sequestration and Nitrous Oxide Emission Impedement B Tesfamichael 1 , N Gesesse 2 and S A Jabasingh 3 * 1,2,3 Process Engineering Division, School of Chemical and Bio Engineering, Addis Ababa Institute of Technology, Addis Ababa University, Addis Ababa, Ethiopia Received 22 January 2018; revised 14 June 2018; accepted 23 August 2018 The aim of this study is to produce biochar from rice husk and maize straw by pyrolysis and to determine their carbon sequestration and CO 2 reduction potential. Studies leading to the incorporation of these biochars in the soil indicated their ability to sequester on an average of 148.67g of carbon/kg of RHB and 132.67g of carbon/kg of MSB, respectively. The potential of RHB and MSB to control the nitrous oxide emissions from the urea-fertilized soil is also investigated as a stride towards the abatement of Green House Gases (GHG). Keywords: Biochar, Sequestration, Rice Husk, Maize Straw, Sugar Cane, Green House Gases Introduction Ethiopia’s contribution to GHG emissions is very low on a global scale. However, the current practices may double the GHG emissions from 150 Mt CO 2 e to 400 Mt CO 2 e by 2030 1 . Half of the GHG emission in the country comes from the agriculture sector, primarily due to the open burning of the agricultural wastes. Though many the conventional methods including planting of trees, management of organic soils, and degraded land restoration have been in practice, to curb the CO 2 emission, most of them have a limited carbon- sink duration 2,3 . The present study adopts for the incorporation of biochar, whose resistant towards microbial and physical decay, allows for carbon sequestration by establishing a prolonged carbon sink, leading to a 20% net carbon withdrawal from the atmosphere 4-6 . The study deals with the biochar production from sustainable resources, the rice husk and maize straw, and their application to the soil, with the scope of improvising the soil quality by reducing the emission of nitrous oxide, (N 2 O), a greenhouse gas, which emanates from the fields, due to the usage of nitrogen based fertilizers. N 2 O contributes to nearly, 3Gt CO 2 e, which is about 7.9 % of the global GHG emission 7-10,13 . Materials and Methods Pretreatment of agricultural residue Rice husk (RH) and maize straw (MS) were air dried at ambient atmospheric temperature 6 . They were rinsed thoroughly using distilled water to remove dust and/or other sediments. Their particle size were reduced and passed on to a 2 mm sieve to ensure even distribution during its processing 9 . RH and MS were then oven dried at 105°C for 2h, until the moisture content was reduced to less than 10% 5,11 . Biochar production Biochar was produced from RH and MS by a slow pyrolysis process employing the lab-scale pyrolysis set up 10,19 . The biochars were produced from the agricultural residues at three different pyrolysis temperatures of 350, 450 and 550°C. The biochars produced from RH and MS were named as rice husk biochar (RHB) and maize straw biochar (MSB), respectively. Biochar characterization The percentage yield of biochar from each experimental run was calculated using                … (1) The moisture content was determined as the weight loss following the oven drying of 1g of biochar in a ceramic crucible at 105°C for 24 h 5,11 . Volatile matter —————— *Author for Correspondence E-mail: anu3480@gmail.com