i n d u s t r i a l c r o p s a n d p r o d u c t s 2 7 ( 2 0 0 8 ) 123–129 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / i n d c r o p Moisture-dependent physical properties of jatropha seed (Jatropha curcas L.) D.K. Garnayak a , R.C. Pradhan a , S.N. Naik a,∗ , N. Bhatnagar b a Centre for Rural Development and Technology, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India b Mechanical Engineering Department, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India a r t i c l e i n f o Article history: Received 21 June 2007 Received in revised form 31 August 2007 Accepted 1 September 2007 Keywords: Jatropha seed Physical properties Moisture content a b s t r a c t The study was conducted to investigate some moisture-dependent physical properties of jatropha seed namely, seed dimension, 1000 seed mass, surface area, sphericity, bulk density, true density, angle of repose and static coefficient of friction against different materials. The physical properties of jatropha seed were evaluated as a function of moisture content in the range of 4.75–19.57% d.w. The average length, width, thickness and 1000 seed mass were 18.65 mm, 11.34 mm, 8.91 mm and 741.1 g, respectively at moisture content of 4.75% d.w. The geometric mean diameter and sphericity increased from 12.32 to 12.89 mm and 0.66 to 0.67 as moisture content increased from 4.75 to 19.57% d.w., respectively. In the same moisture range, densities of the rewetted jatropha seed decreased from 492 to 419 kg m −3 , true density increased from 679 to 767 kg m −3 , and the corresponding porosity increased from 27.54 to 45.37%.As the moisture content increased from 4.75 to 19.57% d.w., the angle of repose and surface area were found to increase from 28.15 ◦ to 39.95 ◦ and 476.78 to 521.99 mm 2 , respectively. The static coefficient of friction of jatropha seed increased linearly against the surfaces of three structural materials, namely plywood (44.12%), mild steel sheet (64.15%) and aluminum (68.63%) as the moisture content increased from 4.75 to 19.57% d.w. © 2007 Elsevier B.V. All rights reserved. 1. Introduction India is the sixth largest country in the world in terms of energy demand, which is 3.5% of the world commercial energy demand and is expected to grow at the rate of 4.8% per annum of its present demand (M.S. Kumar et al., 2003).The growth in energy demand in all forms is expected to con- tinue unabated owing to increasing urbanization, standard of living and expanding population. In the Indian context, the estimated import of crude oil may go up from 85 to 147 MMT per annum by the end of 2006–2007, correspondingly increas- ing the import bill from $13.3 to $15.7 billion (Biofuel Report, 2003). ∗ Corresponding author. Tel.: +91 11 26591162; fax: +91 11 26591121. E-mail address: snn@rdat.iitd.ac.in (S.N. Naik). Jatropha curcas L. (physic nut or purging nut) is a drought resistant shrub or tree belonging to the family Euphorbiaceae, which is cultivated in Central and South America, South-East Asia, India and Africa (Mart´ ␫nez-Herrera et al., 2006). Jatropha hitherto considered as a wild oilseed plant of the tropics is now being credited as a most promising biofuel crop, ideally suited for growing in the wastelands of the country. Jatropha plants grow on poor degraded soils and are able to ensure a reasonable production of seeds with very little inputs. Jatropha plants start yielding from the second year of planting, but in limited quantity. If managed properly, it starts giving 4–5 kg of seed per tree production from the fifth year onwards and seed yield can be obtained up to 40–50 years from the day of 0926-6690/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2007.09.001