A systems analysis of biodiesel production from wheat straw using oleaginous yeast: process design, mass and energy balances

Research output: Contribution to journalArticle

Abstract

Background: Biodiesel is the main liquid biofuel in the EU and is currently mainly produced from vegetable oils. Alternative feedstocks are lignocellulosic materials, which provide several benefits compared with many existing feedstocks. This study examined a technical process and its mass and energy balances to gain a systems perspective of combined biodiesel (FAME) and biogas production from straw using oleaginous yeasts. Important process parameters with a determining impact on overall mass and energy balances were identified and evaluated. Results: In the base case, 41% of energy in the biomass was converted to energy products, primary fossil fuel use was 0.37 MJprim/MJ produced and 5.74 MJ fossil fuels could be replaced per kg straw dry matter. The electricity and heat produced from burning the lignin were sufficient for process demands except in scenarios where the yeast was dried for lipid extraction. Using the residual yeast cell mass for biogas production greatly increased the energy yield, with biogas contributing 38% of total energy products. Conclusions: In extraction methods without drying the yeast, increasing lipid yield and decreasing the residence time for lipid accumulation are important for the energy and mass balance. Changing the lipid extraction method from wet to dry makes the greatest change to the mass and energy balance. Bioreactor agitation and aeration for lipid accumulation and yeast propagation is energy demanding. Changes in sugar concentration in the hydrolysate and residence times for lipid accumulation greatly affect electricity demand, but have relatively small impacts on fossil energy use (NER) and energy yield (EE). The impact would probably be greater if externally produced electricity were used.

Details

Authors
  • Hanna Karlsson
  • Serina Ahlgren
  • Mats Sandgren
  • Volkmar Passoth
  • Ola Wallberg
  • Per Anders Hansson
Organisations
External organisations
  • Swedish University of Agricultural Sciences
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Industrial Biotechnology
  • Chemical Engineering

Keywords

  • Biogas, Diesel, Lignocellulosic materials, Microbial oil, Systems perspective
Original languageEnglish
Pages (from-to)1-13
Number of pages13
JournalBiotechnology for Biofuels
Volume9
Issue number1
Publication statusPublished - 2016 Oct 25
Publication categoryResearch
Peer-reviewedYes