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Bull-Driven Stone Ghani (Kolu) Oil Press

The ghani (also called kolhu in Hindi, chekku in Tamil and kolu in parts of South India) is a traditional Indian oil press constructed as a mortar-and-pestle assembly, historically driven by yoked bullocks walking in a circular path. It cold-presses oilseeds at low rotational speed and low temperature, preserving flavour, antioxidants and aromatic compounds.

Function

Seeds (typically sesame, groundnut, mustard or copra) are loaded into the wooden or stone mortar; the long pestle, attached to a yoke driven by one or two bullocks at approximately one to two rotations per minute, presses and macerates the seed mass. Oil seeps from the crushed seed and is collected through an opening at the base; the residual cake is removed by hand.

Design and specifications

Traditional ghanis are built from a single block of stone or hardwood (often tamarind or sal) with a vertical mortar cavity. Modernised motor-driven kolus retain the wooden pestle geometry but use a gear motor in place of the bullock to ensure consistent rpm and to comply with municipal animal-welfare norms; capacity is typically 5-15 kg of seed per batch.

Operation

Because the operation runs at low temperature, the press is classified as cold-pressing. Throughput is low compared with screw expellers, but conversion efficiency on high-oil seeds such as sesame and copra is acceptable, and the residual cake retains higher protein and is sold as livestock feed.

Subsidy and adoption

FAO records show that around the start of the 20th century India operated roughly 500,000 ghanis that crushed an estimated 97% of the country's oilseeds. The share fell to 28% by the 1940s as power presses and solvent-extraction plants spread. The Khadi and Village Industries Commission (KVIC) supports modernisation of village ghanis through PMEGP-linked loans and capital subsidy, and markets the resulting oils under village-industry certification.

See also: Cotton Ginning Mill, Solar Drying Tunnel.

References

  1. Ghani: A traditional method of oil processing in India. Food and Agriculture Organization of the United Nations.
  2. KVIC Cold-Pressed Coconut Oil Project Profile. Khadi and Village Industries Commission.