title: Biorefining of wheat straw: accounting for the distribution of mineral elements in pretreated biomass by an extended pretreatment-severity equation.
abstract: BACKGROUND
  Mineral elements present in lignocellulosic biomass feedstocks may accumulate in biorefinery process streams and cause technological problems, or alternatively can be reaped for value addition. A better understanding of the distribution of minerals in biomass in response to pretreatment factors is therefore important in relation to development of new biorefinery processes. The objective of the present study was to examine the levels of mineral elements in pretreated wheat straw in response to systematic variations in the hydrothermal pretreatment parameters (pH, temperature, and treatment time), and to assess whether it is possible to model mineral levels in the pretreated fiber fraction.
  
  
  RESULTS
  Principal component analysis of the wheat straw biomass constituents, including mineral elements, showed that the recovered levels of wheat straw constituents after different hydrothermal pretreatments could be divided into two groups: 1) Phosphorus, magnesium, potassium, manganese, zinc, and calcium correlated with xylose and arabinose (that is, hemicellulose), and levels of these constituents present in the fiber fraction after pretreatment varied depending on the pretreatment-severity; and 2) Silicon, iron, copper, aluminum correlated with lignin and cellulose levels, but the levels of these constituents showed no severity-dependent trends. For the first group, an expanded pretreatment-severity equation, containing a specific factor for each constituent, accounting for variability due to pretreatment pH, was developed. Using this equation, the mineral levels could be predicted with R(2) > 0.75; for some with R(2) up to 0.96.
  
  
  CONCLUSIONS
  Pretreatment conditions, especially pH, significantly influenced the levels of phosphorus, magnesium, potassium, manganese, zinc, and calcium in the resulting fiber fractions. A new expanded pretreatment-severity equation is proposed to model and predict mineral composition in pretreated wheat straw biomass.
authors.affiliation: DONG Energy, Kraftværksvej 53, DK-7000 Fredericia, Denmark ; Center for BioProcess Engineering, Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Duy Michael
authors.initials: DM
authors.lastname: Le
authors.affiliation: DONG Energy, Kraftværksvej 53, DK-7000 Fredericia, Denmark.
authors.forename: Hanne R
authors.initials: HR
authors.lastname: Sørensen
authors.affiliation: DONG Energy, Kraftværksvej 53, DK-7000 Fredericia, Denmark.
authors.forename: Niels Ole
authors.initials: NO
authors.lastname: Knudsen
authors.affiliation: Plant and Soil Science Section, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, DK-1871 Frederiksberg C, Copenhagen Denmark.
authors.forename: Jan K
authors.initials: JK
authors.lastname: Schjoerring
authors.affiliation: Center for BioProcess Engineering, Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Anne S
authors.initials: AS
authors.lastname: Meyer
keywords: Hydrothermal pretreatment; Lignocellulose; Minerals; Severity modeling; pH