The application of the olivine–spinel aluminum exchange thermometer to natural samples is limited by the restricted experimental data set on which it was calibrated. Here, we present a new data set of 46 high-temperature crystallization experiments and 21 reanalyzed published experiments, which we used to extend the calibration to higher and lower temperatures. The final calibration data set spans a range of conditions relevant to crustal and upper mantle processes: 1174–1606°C, 0.1–1350 MPa, QFM − 2.5 to QFM + 7.2 (oxygen fugacity, fO2, reported in log units relative to the quartz–fayalite–magnetite buffer, QFM), and 0–7.4 wt % H2Omelt. We propose three new models. The first is thermodynamically self-consistent, based on spinel Fe, Mg, Al, and Cr compositions and Al exchange between olivine and spinel. The second and third are empirical models that consider fewer elemental exchanges: the second uses only Al exchange and spinel compositions, whereas the third considers olivine–spinel Al and Cr exchange. All models include the modest effect of pressure on olivine-spinel equilibrium chemistry, whereas fO2 and water content have negligible effects. In general, as fewer elements are considered in the olivine–spinel exchange, the fit to experimental data worsens. Conversely, the associated decrease in model complexity improves their robustness against systematic errors when applied to natural crystal pairs: the thermodynamic model may underestimate crystallization temperatures in natural samples due to spinel subsolidus re-equilibration, whereas the empirical models (independent of Fe and Mg in spinel) are less sensitive to re-equilibration but yield temperatures with larger uncertainties. We applied a statistical test to select the most appropriate model for application to natural samples. When applied to lavas from mid-ocean ridges, Iceland, Skye, Emeishan, Etendeka, and Tortugal, our new temperature estimates are 30–100°C lower than previously proposed. The lower temperature estimates cause a lower mantle melting temperature and significant impacts on the mantle lithology constraints.

The Skaergaard intrusion is a layered, ferrobasaltic intrusion emplaced during the Early Eocene into the rifting volcanic margin of East Greenland. The magma chamber crystallised in response to cooling from the roof and margins upwards and inward, forming upper, marginal and bottom series, the latter referred to as the Layered Series. The phase layering in the bottom series suggests an evolved, olivine-normative tholeiitic melt saturated in plagioclase and olivine, followed by augite, and then simultaneously by ilmenite and magnetite forming primocrysts. Pigeonite appears in the lower parts and continues until the centre of the series. Apatite appears in the upper part concurrently with liquid immiscibility. Cryptic variations of the individual primocrysts record a systematic upward increase in iron and decrease in magnesium for the mafic minerals and a systematic increase in sodium and decrease in calcium for plagioclase. The appearance of pigeonite is caused by reactions and crystallisation in the trapped melt and by subsolidus adjustments without this phase reaching liquidus saturation. The high mode of olivine at the base of the upper part with the appearance of apatite is interpreted to mark the onset of liquid immiscibility. This may have led to the separation of conjugate melts with granophyre migrating upward and the basic component largely staying stationary or sinking. Petrologic and geochemical observations indicate differentiation in the lower part of the intrusion, principally controlled by crystal fractionation with the efficiency of fractionation controlled by the evolution and escape of liquid from the solidifying mush. During the final stages of solidification, the onset of liquid immiscibility and termination of melt convection impeded differentiation. Modelling by perfect Rayleigh fractionation shows that major and included trace elements conform reasonably to observations, while excluded elements deviate from model predictions. This decoupling is caused by the mobility of a granophyre component formed in the trapped melt and in the main residual magma chamber. Consequently, the sampled gabbros may not be representative of the final solid-melt mush. By restoring the gabbros to their original mush compositions, it is possible to constrain granophyre migration pathways. We suggest that the granophyre formed in the trapped melt in the lower part of the intrusion mostly migrated laterally through pressure release pathways to form lenses and pockets with only limited upward migration into the main magma reservoir. Near the end stage of differentiation, the residual magma exsolved and formed complex mixtures of ferrobasaltic and granophyric melts. Estimates predict that a substantial amount of the granophyric melt penetrated as sills into the downward crystallising, upper part of the body as well as into the host rocks. The redistribution of granophyric melts within the solidifying crystal mush complicates predictions of trapped-melt content and mass-balance calculations but helps to explain apparent decoupling of included and excluded trace elements, especially towards the end stages of evolution. Final crystallisation was controlled mostly by in situ crystallisation leaving complex mixtures of ferrodiorite and granophyre components.

The Skaergaard intrusion is one of the most thoroughly studied layered mafic intrusions on Earth and an exceptional example of (near) closed-system magmatic differentiation. We report new Fe isotope data for whole rocks, and magnetite and ilmenite separates through the layered series (LS) and upper border series (UBS) of the intrusion. d56Fe values for gabbroic rocks range from 0.033 parts per thousand to 0.151 parts per thousand with an abrupt step increase at the base of Lower Zone c (LZc) within LS with the appearance of cumulus magnetite and subsequent decline accompanying FeTi oxide fractionation. The lowest d56Fe values are found near the Upper Zone b (UZb) to c (UZc) boundary followed by a sharp rise across UZc approaching the Sandwich Horizon. Magnetiteilmenite separates straddle bulk rock compositions with fractionation factors (? 56Fe) of 0.081 parts per thousand to 0.239 parts per thousand, consistent with subsolidus equilibration. Granophyric rocks occurring as pods, sheets and wispy layers from the upper zone and UBS equivalents and having unradiogenic Sr similar to gabbroic rocks of Skaergaard, are isotopically heavier than their host ferrodiorites (? 56Fe?=?0.1 parts per thousand) reaching a maximum d56Fe of 0.217 parts per thousand in UBS. A fused xenolith from UBS has d56Fe ?=?0.372 parts per thousand This range in d56Fe spans much of that reported for terrestrial igneous rocks, and like the global dataset, shows a pronounced increase in d56Fe with inferred silica content of modeled Skaergaard liquids. Forward modeling of closed system fractional solidification was undertaken to account for Fe isotope systematics, first by testing published liquid lines of descent (LLD), and then by exploring improvements and considering the impacts of liquid immiscibility, crustal contamination, fluid exsolution and diffusional processes. Our modeling relies on published Fe+2 and Fe+3 force constants for magmatic minerals and silicate glasses, and the most reliable estimates of the average bulk composition and mass proportions of the well-defined subzones of the intrusion. We show that the increase in d56Fe across the LZbLZc boundary is readily explained by the increased incorporation of Fe+3 into the crystallizing solid including magnetite. We further demonstrate that the classic Fenner LLD, involving strong Fe enrichment at nearly constant silica, does not lead to a rise in d56Fe toward the end stages of evolution, while a Bowen-like LLD, with little Fe enrichment and strong Si enrichment, also underestimates enrichment in heavy Fe isotopes in the ferrodiorites of UZc. A LLD following an intermediate path involving modest Fe and Si enrichment, followed by Fe depletion best explains the observations. We predict similar to 3.5% (by mass) residual liquid after crystallization of UZc having a composition similar to felsic segregations in pegmatitic bodies found in the intrusion. While liquid immiscibility may have been encountered within fractionating mush at the margins of the intrusion, the Fe isotope systematics do not support liquid phase separation of the bulk magma. Crustal contamination, fluid exsolution, hydrothermal alteration and thermal diffusion are also shown to have no resolvable effect on the Fe isotope composition of the gabbroic and granophyric rocks. We conclude that the Fe isotope systematics documented in the Skaergaard intrusion reflect the dominant role of fractionating Fe-rich minerals from gabbroic through ferrodioritic to rhyolitic liquids. The success of our model to account for the observed Fe isotope systematics for Skaergaard demonstrates the utility of Fe+2 and Fe+3 force constants determined at ambient conditions to model magmatic conditions and gives critical insights into plutonic processes fractionating Fe isotopes complementary to the volcanic record.

We report a compilation of new and published whole-rock major and trace element analyses for 646 samples of the Skaergaard intrusion, East Greenland. The samples were collected in 14 stratigraphic profiles either from accessible and well-exposed surface areas or from drill core, and they cover most regions of the intrusion. This includes the Layered Series, the Upper Border Series, the Marginal Border Series and the Sandwich Horizon. The geochemical data were obtained by a combination of X-ray fluorescence and inductively coupled plasma mass spectrometry. This data set can, for example, be used to constrain processes of igneous differentiation and ore formation.

The geochemical signatures of a 12-year-old experimental bioreactor at a California landfill are used to identify elemental concentrations and ratios that characterize the landfill and relate it to the age and state of technology of the deposited waste. The bioreactor was constructed and sealed with a synthetic liner during 2001–2002 and operated and monitored as an anaerobic digester to enhance methane production. In 2013, the bioreactor was sampled and trace element concentrations of the extracted fine fractions were determined. The concentrations normalized to a regional soil composition, reveal systematic peaks for transition metals, alkali metals, heavy metals, and various metalloids and non-metals. A group of potential solder elements (Cu, Zn, Cd, In, Sn, Pb, Bi, and Sb) shows moderate to strong co-variations and is largely attributed to household electronic components and other similar products, while elements that correlated well with rare-earth and other elements are related to the diluting effect of a soil component used as cover. Batteries show modest to little effects on the overall concentrations. Circulating fluids (recycled leachate) in the controlled reactor did not completely redistribute and homogenize the elemental signatures within the time frame of the bioreactor. It is concluded that the present experimental landfill defines an Anthropocene marker identifiable by building material (plaster), PVC plastic, and household electronic components (Pb–Sn solder). These marker elements and ratios are variably diluted by soil components identified by alkali metals, rare-earths, and high field-strength elements (Hf, Zr, Nb, and Ta).

Escalating demands for infrastructure materials and energy worldwide necessitate exploration of means to efficiently utilize resources to support growing consumption. This work evaluates the potential symbiotic relationship between cultivation of an agricultural product (namely, rice), energy conversion, and utilization of bioash in the production of cement-based materials to improve the sustainability across multiple industries. Primarily, leaching methods of biomass that benefit energy conversion are evaluated as a means to simultaneously improve ash properties for use in cement-based materials. Specifically, this study considers water leaching and H3PO4 leaching of rice hulls and rice straw, which were subsequently ashed at three different temperatures, 600, 850, and 1100 degrees C. The effects of leaching on the ash characteristics, on the performance of ash-cement mortars, and on the greenhouse gas (GHG) emissions from both the mortars and energy produced are quantified. Findings showed that while acid leaching led to higher GHG emissions for electricity generation, leaching decreased concentrations of undesirable alkali metals and chlorides in the ash. Regardless of treatment and ashing temperature, the inclusion of bioash delayed the early strength development of the cement-based mortars. Yet, several permutations of treatment, feedstock type, and ashing temperature were found to contribute to the later-age strength development of cement-based materials while reducing related GHG emissions. Specifically, after 28 days of curing, mortars containing 15% cement replacement with unleached ash prepared at 600 degrees C had 1-5% lower compressive strength, and after 56 days, mortars with leached rice hull ash prepared at 600 degrees C had 5-6% lower compressive strengths. Further, the use of unleached and water-leached ashes in mortar led to reductions in GHG emissions up to 15%. Hence, this work shows that pretreatment methods applied to rice biomass residues may contribute to desirable cobenefits for energy and materials production.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Agricultural residues and energy crops often contain high contents of alkali metals, chlorine, silica, and other elements that promote slagging, fouling, corrosion, and gas emission during thermochemical conversion (e.g., combustion and gasification). Water leaching is a common method, but not always effective to reduce such elements. Bioleaching by adding microbes to water leaching was introduced to leach cellulosic biomass in this study. Three microbial species including two fungi (Fusarium oxysporum and Aspergillus niger) and one bacterium (Burkholderia fungorum) were selected to leach four lignocellulosic feedstocks such as corn stover, wheat straw, switchgrass, and sorghum. Among three microbes, A. niger was found the most efficient to remove most elements by 80% in 48 h, and sorghum was relatively more amenable to bioleaching. With A. niger, the bioleaching with water to feedstock (w/w) ratio of 25 for 6 h was sufficient to leach K (85%), Cl (90%), Mg (60%), and P (70%) from sorghum. Overall, bioleaching is more efficient than water leaching except for Na. Studies on bioleaching mechanism indicated that the acidification resulted from organic acids produced by A. niger during bioleaching might contribute to the higher leaching efficiency over other microbial species and water leaching.

Experiments were performed on a laboratory scale fluidized bed gasifier to characterize the gasification products of almond shell and hull removed in nut processing operations and to determine the effect of gasifying media on bed agglomeration. The higher heating value of syngas during air gasification of almond biomass ranged from 4 to 6 MJ m(-3) while gas concentrations ranged from 14 to 18% H-2, 3-4% CH4, 43-50% N-2, 16-19% CO, and 16-17% CO2. For steam gasification, higher heating value was 10-12 MJ m(-3) and gas concentrations were 35-40% H-2, 5-7% CH4, 17-21% N-2, 18-21% CO, and 16-18% CO2. The high level of potassium in the almond shells led to strong corrosion and bed agglomeration due to flue gas transport of potassium compounds. These resulting pervasive kalsilite reactions were significantly worse under air gasification than under steam gasification. As a result of prolonged duration and elevated temperature approaching 1,000 degrees C, the corrosinal reaction changes to formation of an adhesive potassium distillate melt locally forming strong bonds. This latter is interpreted as a result of aerosol transported of melt particles.

The composition, mineralogy, and textures preserved in scoria from ancient fires provide constraints on the firing temperature, the source and nature of the fire, and its potential social and cultural implications. Analyses of four scoria fragments preserved in a posthole of an Iron Age longhouse at Store Tovstrup, West Denmark, by scanning electron microscopy, electron microprobe, and laser ablation ICP-MS show these to consist of rounded quartz and orthoclase grains, gas vesicles, and carbonaceous material bonded together by a silicate- and potassium-rich (SiO2 67-69 wt% A and K2O 11-14 wt%) melt (now glass). Given the presence of vesicles and carbonaceous material, the fire is indicated to have occurred under restricted air-flow and to have involved decomposition of biomass and soil. The initiation of melting occurred during what was presumably an event of short duration. Simplified ternary phase equilibria point to localized melting initiated around 700-800 degrees C and continuing to about 1000 degrees C. The main structure succumbed to char at lower temperatures. Calculations suggest that a mixture of 50% sandy soil, 41% barley straw, and 9% oak branches best explains the low Al2O3 , Fe2O3 , and Na2O concentrations in the melt phase. The scoria at Store Tovstrup most likely originated from a short duration burning with restricted air-flow resulting in the collapse and charring of daub walls. The fire was intentional and set after the house had been cleared of household goods.

The use of a differential thermal analyzer with an on-line inductively coupled plasma mass spectrometer allows continuous and near-synchronous analysis of mass loss and elemental release patterns during pyrolysis of biomass and other feedstock. Applied to a mixed-conifer softwood, the results show that the released elements can be divided into those that are dominantly released during decomposition (250–475°C) and those that are dominantly released at high temperature (900–1300°C), thus reflecting their different roles in the organic matrix. Production and analysis of a 950°C pyrolysis wood ash allows the bulk partition between flue gas (including entrained particles) and solid char to be evaluated, mass balance to be demonstrated, and a semi-quantitative calibration to be suggested. Our exploratory experiment demonstrates that the present approach can provide reliable insight and semi-quantitative modeling tools useful for elucidating the role and behavior of many elements during thermal treatment of biomass.

Marsh (Contrib Miner Petrol 166:665–690, 2013) again claims that crystal-free basalt magmas are unable to differentiate in crustal magma chambers and regards layered intrusions as primarily due to the repeated emplacement of crystal suspensions. He ignores an earlier critique of his unconventional inferences (Latypov, J Petrol 50:1047–1069, 2009) as well as a wealth of petrographic, geochemical and experimental evidence supporting the dominant role of fractional crystallization in the solidification of layered intrusions. Most tellingly, the cryptic variations preserved in the Skaergaard and many other basaltic layered intrusions would require an exceedingly implausible sequence of phenocrystic magmas but are wholly consistent with in situ fractional crystallization. A major flaw in Marsh’s hypothesis is that it dismisses progressive fractional crystallization within any magma chamber and hence prohibits the formation of crystal slurries with phenocrysts and melts that change systematically in composition in any feeder system. This inherent attribute of the hypothesis excludes the formation of layered intrusions anywhere.

Characterization of biomass relevant to thermochemical conversion processes and other applications is critical to the design and proper operation of energy conversion, biorefining, and other facilities, especially in regard to estimating critical problems related to fouling and slagging from ash constituents. Residue feedstock from almond production was obtained from seven huller and sheller facilities located throughout the Central Valley of California. Results of proximate (moisture, ash, volatile and fixed carbon content), ultimate (C, H, N, S, O composition), heating value, major and trace elements, and melting behavior analyses (all reported on a wt.% dry basis) reveal many similarities and also differences that potentially affect their utilization. The moisture content of air-dried feedstock is an average of 9.7% with only the separated hull material having a higher value (12.2%) and the fine component (<2mm) a lower value (8.2%) on an as received basis. The volatile matter is relatively constant (72–76%). The ash content reflects a variable soil component in most fractions with a low average in shell of 3.5% and increasing to 22% in the fine fraction. The elemental C/O ratio is constant at about 1.15 and only appears slightly higher in the woody fraction (1.21). Nitrogen (0.4–0.8%) and sulfur (0.2–0.3%) are elevated compared to many other types of biomass, with the large variation in N probably related to irrigation water source and fertilization practices. Chlorine is generally low (<0.05) and varies without KCl control in both the crude feedstock and the ash. The ash of the almond biomass is very high in K, varying between 18–36% and only S, Ca, and P reaching substantial amounts. The trace element concentrations are mostly well below local soil compositions with only Ga, Sr, and Cu well above and thus suggest few, if any, regulatory utilization challenges. The elevated feedstock concentrations of S and N may be sufficient to cause some environmental concern for certain types of thermal conversion processes, mostly in relation to NOx and SOx emissions. The high ash content together with the very high K content can cause adverse bed behavior, corrosion, and fouling in boilers, despite the relatively high ash melting temperatures (>1100°C) suggested by pellet fusibility test.

Basaltic glasses from the three alkalic areas of Iceland: Snaefellsnes Volcanic Zone, Sudurlend Volcanic Zone and Vestmannaeyjar Volcanic Area contain plagioclase, olivine, clinopyroxene, chromian spinet and titanomagnetite as phenocryst phases. The glasses are nepheline to hypersthene normative alkali basaltic with FeO/MgO ratios between 1.44.7. Olivine range in composition from Fog0 to Fo55 , plag1oclase from An90 to An50and clinopyroxene from En45 Fs10wo45 to En40Fs17wo43• Clinopyroxene reveals systematic Ti:AL metastable crystallization trends related to the composition of the enclosing glass. Two types of phenocryst are present in most glasses showing a bimodality in size and composition. Microphenocrysts is the phase most Likely to have crystallized from the enclosing glass, while macrophenocrysts may have crystallized from a liquid of a slightly less evolved composition. The glasses show complex phenocryst-glass relations which can be related to a polybaric effect. The normative glass compostions are related to divariant surfaces in the basalt tetrahedron and define the position of the four phase cotectic Line. In general with increasing FeO/MgO in the glass the phenocryst assemblages vary from clinopyroxene, olivine and plagioclase along a clinopyroxene-olivine surface to olivine and plagioclase along a olivine-plagioclase surface. A deflection is seen in the normative glass compositions from clinopyroxene containing glasses to clinopyroxene free glasses. The appearance of plagioclase together with clinopyroxene and olivine can be explained in the Light of experimental investigations of the effect of pressure on phase relations. The major element variation of the glasses is interpreted as representing mantle derived magma batches

Siliceous scoria droplets, measuring from 1 to 10 mm, from one late Pleistocene and four early Holocene archaeological sites in northern Syria are compared to similar droplets previously suggested to be the result of a cosmic impact at the onset of the Younger Dryas global cooling event. The findings demonstrate that the presence of siliceous scoria droplets are independent of age and thus are not specific to the beginning of the Younger Dryas. Occurrences have not been reported from natural deposits, but are instead associated with buildings destroyed by fire and thus appear to be restricted to archaeological sites. We therefore conclude that melting of building earth in ancient settlements can occur during fires reaching modest temperatures. There is no evidence to suggest that siliceous scoria droplets result from very high temperature melting of soil and are the result of a cosmic event. (C) 2014 Elsevier Ltd. All rights reserved.

Modification of fuel compositions can reduce ash fouling and slagging, corrosion, and environmental impacts for thermochemical conversion systems. Leaching was used as a feedstock pretreatment to improve the properties of selected agricultural, forestry, and energy crop biomass, including rice straw, wheat straw, corn stover, switchgrass, Miscanthus, Jose tall wheatgrass, and Douglas fir wood. Crude and leached solids were characterized for changes in ash fusibility, heating value, major element concentrations, and other properties. Leachates were analyzed for major and trace elements and organic species. Ash contents were in all cases significantly reduced although simultaneous inorganic and organic material extraction led to more complex outcomes in fuel properties due to possible changes in the composition of residual solids. Declines in ash concentrations were therefore not always accompanied by increases in heating value or improvements in initial ash melting temperatures, although melt flow temperatures in all cases increased, in some cases by more than 500°C. The trends in melt behavior are generally predicted from phase equilibria using reduced ash compositions. Sugars (1.5–103.5mg/g dry matter) and organic acids (0.6–57.6mg/g dry matter) constituted the major fractions of the identified organic extracts and may have potential for coproduct recovery.

Trace element concentrations on a dry ash basis in saline-irrigated biomass feedstock from the San Joaquin Valley are investigated using multi-element spectroscopic techniques. The results show high concentrations of both Na and K compared to local baseline soil. The content of Na is higher than observed for nonsaline-irrigated biomass reflecting the salinity of the drainage water. The alkali earth elements as well as other alkali trace elements are, however, not markedly affected by the salinity of the irrigation water. The transition elements Cu and Zn are enriched only in the herbaceous feedstock compared to nonsaline biomass. Sulfur, chlorine, and phosphorus are markedly enriched in the saline feedstock. The ash content of toxic elements invariably exceeds the concentrations in the baseline soil for Cu, As, Se, Cd, Sb, and Pb. Compared to nonsaline biomass ashes, Cu is relatively enriched in the herbaceous feedstock ashes, As only in eucalyptus wood, and Cd, Sb, and Pb in woody feedstock. Selenium is relatively enriched in all saline feedstock. Only the concentrations of Cd in woody saline-irrigated feedstock may potentially exceed environmental guideline concentrations and may, thus, warrant caution for using saline biomass for soil amendment.

Knowledge of the inorganic components of biomass feedstock is important for process control and for handling coproducts and wastes resulting from energy and fuel utilization of biomass. Analytical survey of forestry thinnings (wood chips), agricultural residues (rice straw, wheat straw, corn stover), and dedicated perennial grass crops (switchgrass, wheatgrass, and miscanthus) shows that, potentially, the whole periodic table may be present in biomass. The main effect of ashing is bonding of oxygen in the ash mainly as silicate, oxides, hydroxides, phosphates, and carbonate residual minerals. Carbon is partially retained as carbonates and graphite (char). Nitrogen is dominantly released to the flue gas, while sulfur is mostly retained in the ash as sulfates. Small losses (similar to 19%) for both sulfur and chlorine were detected during ashing at 575 degrees C. The majority of the alkali metals (Li, Na, K, and Rb) will substantially modify soil if applied as a fertilizer. Only Mg, Ca, and Sr of the alkali earth metals, Mn, Cu, and Zn of the period 4 transition metals, and Mo and Cd of the period 5 transition metals may exceed regulatory limits if used as a fertilizer. The heavy elements occur in concentrations too low to cause concern with the exception of Se. The high alkali content of some biomass ash thus makes them good candidates for use as fertilizers provided that they are applied in low proportions (<50%) to soil. Ash of wood material is a carrier of many of the alkali elements (Li, K, Rb, Mg, Ca, Sr, Ba) and some transition elements (Mn, Cu, Zn, Mo, Ag, Cd). In contrast, ash of herbaceous plant material is in addition to K only variably enriched: Li, Na, Se, and Mo in wheatgrass, Mg, and Ca in switchgrass, Mg, Ca, and Cd in corn stover, Mn in rice straw, Mo in wheat straw, and Mn and Cd in miscanthus. Water leaching results in significant losses for anionic chlorine and sulfur as well as for most of the alkali metals, thus making resulting ash from such treated feedstock less attractive as K fertilizers although fuel properties are enhanced for thermal conversion.

Author Summary: Proper execution of representative sampling and laboratory mass reduction procedures are critical for the validity and reliability of chemical analyses of highly heterogeneous biomass fuels. In the study reported by Thy et al., it was demonstrated that faulty sampling had resulted in apparent ash compositions that differed from the true compositions by factors of two to three for many major oxides. Analytical results based on non-representative samples may thus not be representative for the specific fuel and processes being studied. Despite the general acceptance that accurate and representative compositions is a critical prerequisite for understanding reactions and elemental fractionation, the biomass energy community appears largely to have ignored the critical issues surrounding representative primary sampling. This can have resulted in misleading or faulty conclusions and may have restricted reliable predictive modelling.