The recovery of large quantities of fragmented carbonized olive stones from archaeological sites around the Mediterranean indicates that olive oil pressing waste (pomace) was used as a domestic and industrial fuel source throughout antiquity. Olive pomace burns at a high and constant temperature, making it an ideal fuel for heating and cooking as well as firing pottery and lime kilns. The Roman period is characterized by an expansion in pomace use both quantitatively and geographically. Beginning in the first century C.E., pomace fuel was introduced into new urban markets and began to play a larger role in industrial production. This article highlights the history of pomace use in antiquity, focusing primarily on the changes that took place during the Roman period. The article also seeks to establish a set of identification criteria that will enable archaeologists to distinguish pomace residue from other sources of carbonized olive stones, including ritual and table waste. 1 introduction While wood and charcoal were undoubtedly the most widespread and commonly used fuels in antiquity, they were not the only sources of fuel, nor were they always the least expensive or the most favored. Cereal chaff, dung, coal, and animal fats, among others, were also used. 2 There is growing scholarly recognition of the use of secondary fuels in the ancient world, particularly with reference to the production of a specific good, such as pottery. 3 Olive oil pressings-so-called press cake, or pomace, 4 the solid material that remains after the oil is collected-provide an underrated yet highly archaeologically observable example of these secondary fuels. The carbonization process turns material into a mass of carbon that does not decompose, is impervious to microbial attack, and does not react with other minerals and chemicals. 5 Thus, the burning of pomace leaves behind fragments of carbonized olive stone, which are durable and invulnerable to decay. 1 I thank especially Andrew Wilson for his continued assistance, as well as Mark Robinson and the anonymous reviewers for the AJA for their helpful comments on an earlier draft of this article. I am grateful to Nicolas Monteix and Robyn Veal, who shared their research with me and offered valuable advice. An audience at the "Fuel and Fire in the Ancient Roman World" conference at the British School at Rome provided useful feedback on the presentation of an early version of this paper, as did discussions with Anaya Sarpaki and C. Margaret Scarry at the 2013 International Work Group for Palaeoethnobotany conference in Thessaloniki. Finally, I would like to thank the Herculaneum Conservation Project and the Soprintendenza Speciale per i Beni Archeologici di Pompei, Ercolano e Stabia for allowing me to study their material and Maxine Anastasi for the creation of the fig. 3 map. The opinions expressed here and any remaining errors are my own. Figures are my own unless otherwise noted.