On the Determination of Water Content in Biomass Processing
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On the Determination of Water Content in Biomass Processing Jane W. Agger & Pål J. Nilsen & Vincent G. H. Eijsink & Svein J. Horn
Published online: 26 October 2013 # Springer Science+Business Media New York 2013
Abstract Processing of lignocellulosic materials to fuels such as methane and bioethanol may involve several processing steps including pretreatment, saccharification, fermentation, and anaerobic digestion. The amounts of substrate used in these processes are usually based on dry matter content, and the processes themselves typically lead to a change in dry matter content. Thus, it is of great importance to be able to measure dry matter accurately. Dry matter content is commonly determined by measuring loss of water during oven drying. We have used Karl Fischer (KF) titration to measure the water content in a wide range of biomass fractions and have compared these data to results obtained by oven drying. This revealed considerable differences for all tested materials. For lignocellulosic materials, oven drying tends to overestimate dry matter content for untreated material. On the other hand, oven drying generally underestimates dry matter content in pretreated materials due to loss of organic volatiles. These differences have major consequences for the calculation of mass balances and yields in bioprocessing. The KF method gives more accurate water determination than oven drying due to the unique selectivity of the analysis. The method is suitable for the analysis of lignocellulosic biomasses and is particularly useful for determination of water content in pretreated materials, where oven drying usually underestimates the dry matter content due to loss of volatiles. Keywords Water Determination . Karl Fischer . Loss on Drying . Biomass . Biogas . Biofuel J. W. Agger : V. G. H. Eijsink : S. J. Horn (*) Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway e-mail: [email protected] P. J. Nilsen Cambi AS, P.O. Box 78, 1371 Asker, Norway
Introduction Generally, the term “dry matter” (DM) denotes the mass of something when completely dried, i.e., the mass of all constituents except water. The dry matter content (also known as dry weight or total solids) is an important parameter to monitor in biomass conversion processes, and is essential for calculations of mass balances and yields. Biomass processing generally involves several steps where the amount of biomass used is based on a pre-determined DM content. Additionally, the processes themselves usually lead to changes in DM content. Water content indirectly determines the content of DM, which comprises the organic and inorganic material in the biomass sample. The amount of organic matter (commonly referred to as volatile solids, VS) is often determined indirectly as the difference between DM and inorganic matter (ash). Biased water determination will cause inaccurate estimation of organic material, hence, incorrect estimation of, e.g., processing yields. Unfortunately, water determinatio
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