This is just a quick post about an interesting new archaeobotany article by Erica Rowan. We did our DPhils together at Oxford, and Erica is now doing great research into Greek and Roman foods at Exeter. Carbonised olive stones are found quite often at archaeological sites in the Mediterranean. Rowan argues that much of this waste comes from the burning of olive pressing waste or ‘pomace’ as fuel. Pomace consists of olive flesh, stones, skin and seeds which are left over after olives are pressed for olive, and can be used for fertilizer, fodder or fuel. Pomace is still used as fuel today.
The tricky thing is how do we know that charred olive stones are evidence for the use of pomace as fuel, as opposed to burnt food waste or the remains of ritualised offerings. Rowan argues that the key factors are quantity and context. So, large quantities of charred olive stones in individual contexts or areas of an archaeological site. An example of a high density find is 100 items per L of soil floated for plant remains from the Cardo V sewer in Herculaneum. A high degree of fragmentation is also evidence for fuel use – more fragments of olive stones than intact pieces. Contexts which can indicate the use as pomace as fuel are given as places near kilns or domestic dwellings.
After establishing these criteria, Rowan goes on to summarise the current evidence for pomace use in the pre-Roman, Roman and Late Antique Mediterranean. Unsurprisingly, the Roman period is highlighted as one where archaeobotanical evidence for pomace fuel is found more often, especially in industrial and urban contexts. The identification of pomace as a common Roman fuel has big implications for modelling the fuel requirements of the Roman economy.
It would have been great to have some clearer recommendations about how to identify pomace use archaeobotanically, such as the number of samples needed within an archaeological site phase to reliably identify pomace use and the broad ranges of densities which indicate evidence of pomace as opposed to table waste and/or ritualised deposits. Either way, this paper is a great example of the more detailed approaches recently taken to the taphonomy of plant remains, be it digestive waste (O’Meara 2014), crop-processing (Antolin 2011), ritualised deposition (Lodwick 2015) and now fuel. Perhaps more importantly, it shows that archaeobotanical data can make major contributions to understanding something as heavily debated as the Roman economy.
Antolín, F., & Buxó, R. 2010. Proposal for the systematic description and taphonomic study of carbonized cereal grain assemblages: a case study of an early Neolithic funerary context in the cave of Can Sadurní (Begues, Barcelona province, Spain). Vegetation History and Archaeobotany, 20(1), 53–66. doi:10.1007/s00334-010-0255-1
Lodwick, L. (2015). Identifying ritual deposition of plant remains: a case study of stone pine cones in Roman Britain. In T. Brindle, M. Allen, E. Durham, & A. Smith (Eds.), TRAC 2014: Proceedings of the Twenty-Fourth Annual Theoretical Roman Archaeology Conference (pp. 54–69). Oxford: Oxbow.
Rowan, E. 2015. Olive Oil Pressing Waste as a Fuel Source in Antiquity American Journal of Archaeology Vol. 119, No. 4 (October 2015), pp. 465–482. DOI: 10.3764/aja.119.4.0465 (£).
O’Meara, D. (2014). Ruminating on the Past: A history of digestive taphonomy in experimental archaeology. In J. Reeves Flores & R. Paardekooper (Eds.), Experiments past: histories of experimental archaeology (pp. 131–145). Leiden: Sidestone Press. Link