Fuel, Fire and Heat: an experimental approach to highlight the potential of studying ash and char remains from archaeological contexts

Braadbaart, Freek; Poole, Imogen; Huisman, Hans; Os, Bertil van

doi:10.1016/j.jas.2011.10.009

Cited by 84 publications

(60 citation statements)

References 47 publications

(63 reference statements)

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“…The reflectance measured on all these areas shows a temperature of around 500°C. It is noted that the reflectance values measured on the charred remains of a COPR fuel, even when later used as a fuel for the preparation of food at lower temperatures, will still show the higher reflectance values related to 500°C, since only the highest temperature ever reached in charred material is measured (Braadbaart et al 2012). Based on these observations it is tentatively concluded that the recovered fragments of charred fragmented olive stones from Poros and Tell Tweini derive from a COPR fuel.…”

Section: Heating Conditionsmentioning

confidence: 90%

“…A water content of 50 % in, for example, fresh wood will reduce the HHV to around 8 MJ kg -1 . Simple air drying to around 15 % by weight water is a very effective means to significantly improve its heating potential to about 17 MJ kg -1 (Braadbaart et al 2012). The ash content of both olive stones and OPR is of the order of 1 % and therefore the effect on the heating potential is negligible.…”

Section: Fuel Characteristics Of Olive Pressing Residuesmentioning

confidence: 99%

“…It was shown that these fuels, with their compact fibre structure, have a lower rate of combustion relative to wood with its relatively open structure. This renders the former fuels more efficient since they require less fuel for an equivalent heat yield than wood, as extensively explained in Braadbaart et al (2012). Apart from simple air drying the HHV of the OPR can be further upgraded by thermal degradation, a process also used to convert wood into charcoal, whereby the carbon content is substantially increased from around 50-70 % by weight or higher (Table 2).…”

Section: Fuel Characteristics Of Olive Pressing Residuesmentioning

confidence: 99%

“…This latter mainly consists of aromatic compounds and as a result the carbon component increases from 50 to 70 wt% (for details see Braadbaart et al 2012). This particular process occurs independently of the presence or absence of air.…”

Section: Fuel Characteristicsmentioning

confidence: 99%

“…Once a heat source has been introduced to the fuel, heat is absorbed and the heated fuel begins to increase in temperature. When a temperature of 280-300°C is reached, a complex chemical reaction starts that leads to the thermal degradation of the organic constituents of the fuel, producing volatile gases and a charred residue (Rein 2009;Braadbaart et al 2012). Only then, and with enough air, will both products oxidize, which is a highly exothermic process, meaning that heat will be generated and released.…”

Section: Introductionmentioning

confidence: 99%

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Charred olive stones: experimental and archaeological evidence for recognizing olive processing residues used as fuel

Braadbaart

Marinova

Sarpaki³

2016

Veget Hist Archaeobot

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After extracting oil from olives a residue is left usually referred to as the olive oil processing residue (OPR). This study explores the way in which ancient societies may have used OPR as fuel for fires to generate heat and the various issues that are related to the residues of this fuel. After drying, the high heating value and structure of OPR makes it an excellent and efficient fuel. Upgrading OPR further, through thermal conversion or charring, provides an even more efficient fuel (COPR), with a hotter and smoke free flame, a higher heating value and which is lighter in mass and thus easier to transport. After a fire is extinguished two types of remains of the fuel are left i.e. char and ash. Analyses on both remains, recovered from archaeological deposits, could be used as a source of information on fuel utilization. Laboratory experiments on charred modern OPR and stones show that by measuring their reflectance and analyzing their structure under reflected light microscopy, OPR and COPR can be distinguished in the charred material recovered from three archaeological sites in Greece and Syria. Based on these investigations it is suggested that on the three sites COPR was used as fuel. Ash, sampled together with the char, provides the possibility of investigating if other types of fuel were used, apart from OPR or COPR. On the investigated sites no ash was collected, but the analysis of the modern OPR showed that the properties of its ash could be used to distinguish it from other types of fuel. Ash from modern OPR and olive stones showed the presence of phytoliths. The often discussed issue related to the sharpness and smoothness of the edges of charred fragmented olive stones was investigated. The results showed that this is not a reliable criterion for recognizing olive oil production. It is recommended that in addition to the identification of the botanical material more properties of the remains of fuels should be analysed. To prevent destroying and losing char and ash as a result of excavation activities such as flotation and sieving, special measures have to be taken. The results show that analysing char and ash may provide valuable information on the (pyro)technology practised in ancient societies.

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Section: Heating Conditionsmentioning

confidence: 90%

Section: Fuel Characteristics Of Olive Pressing Residuesmentioning

confidence: 99%

Section: Fuel Characteristics Of Olive Pressing Residuesmentioning

confidence: 99%

Section: Fuel Characteristicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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