Optimal and cost-effective industrial biomethanation of tobacco

Extremadura is a Spanish south western region located by the Portuguese border. For decades, tobacco has been traditionally cultivated in Caceres, the north province of such region. As a result, farmers in the area have extensive experience with this crop, and a fresh tobacco annual production is therefore guaranteed. This way, tobacco plant appears as an excellent candidate as energy crop. The present work reports on the economic viability of the anaerobic digestion of tobacco plant under the two following scenarios: 1) biogas generated in the biological process to be used as fuel to produce heat, thus avoiding the consumption of any other fossil fuel; 2) electric and thermal power generated by the anaerobic digestion plant to be self-consumed or sold to nearby industries. The mesophilic anaerobic digestion experiments carried out in semicontinuous mode yielded the highest methane production (53.84 +/- 15.48 Nm(3)CH(4)/t fresh tobacco) for substrate composition 15% fresh tobacco/85% water and 16 days degradation period. However, such methane yield by anaerobic digestion was seen not to meet economic feasibility requirements. Instead, methane production rates should be increased up to 90 and 110 Nm(3) methane/t fresh tobacco (1500 (sic)/ha production costs) in order to achieve 8.91 and 9.08 years for investment return according to scenarios 1 and 2, respectively. (C) 2013 Elsevier Ltd. All rights reserved.