Elsevier

Biomass and Bioenergy

Volume 35, Issue 9, October 2011, Pages 3859-3864
Biomass and Bioenergy

Optimization of microwave pretreatment on wheat straw for ethanol production

https://doi.org/10.1016/j.biombioe.2011.04.054Get rights and content

Abstract

An orthogonal design (L9(34)) was used to optimize the microwave pretreatment on wheat straw for ethanol production. The orthogonal analysis was done based on the results obtained from the nine pretreatments. The effect of four factors including the ratio of biomass to NaOH solution, pretreatment time, microwave power, and the concentration of NaOH solution with three different levels on the chemical composition, cellulose/hemicellulose recoveries and ethanol concentration was investigated. According to the orthogonal analysis, pretreatment with the ratio of biomass to liquid at 80 g kg−1, the NaOH concentration of 10 kg m−3, the microwave power of 1000 W for 15 min was confirmed to be the optimal condition. The ethanol yield was 148.93 g kg−1 wheat straw at this condition, much higher than that from the untreated material which was only 26.78 g kg−1.

Highlight

► An orthogonal design was used to optimize the microwave pretreatment on wheat straw for ethanol production. ► Four factors with three different levels were investigated. ► An optimal condition was achieved based on the orthogonal analysis. ► Ethanol yield from microwave-treated wheat straw was 5 times than that from the untreated.

Introduction

In order to make the lignocellulose easily hydrolyzed by cellulase and further converted to ethanol, pretreatment is necessary to break down the recalcitrant structure of the raw materials [1], [2]. A lot of attempts have been done in this area including physical, biological and chemical technologies [3], [4], [5], [6], [7], [8], [9].

Among all the technologies, microwave has been one of those which have a long history in pretreating biomass. It was first introduced in 1984 by Ooshima to pretreat different hardwoods and softwoods [10]. But there was almost no development in 1990s due to the maturity of the dilute acid pretreatment [11], [12], [13], [14], [15], [16], [17]. Until recently, microwave pretreatment was re-used by several investigations [18], [19], [20]. But most of them were mainly focused on enhancing enzymatic digestibility of the biomass pretreated by microwave.

In the present study, the microwave pretreatment condition was optimized for ethanol production.

Section snippets

Raw material

Wheat straw (Hattrick) was grown in Denmark. It was harvested by reaper in September, 2007 and the wheat straw (without chaff) was then pressed to big bales. After the ear of the wheat were removed, chopped corn stover was baled by the windrow binder. After being sent to the pilot plant at Risø-DTU, the wheat straw was milled to a particle size ≤2 mm for the pretreatment experiments with Wiley mill, standard Model No. 3. The dry matter (DM) content was 92.25%. Cellulose, Hemicellulose (the sum

Effect of different factors/levels on the chemical composition of wheat straw after pretreatment

The four factors, A (Ratio of raw material to NaOH solution), B (Pretreatment time), C (Microwave Power), and D (Concentration of NaOH solution) with 3 levels for each one had different influence on the Cellulose, Hemicellulose and Lignin content after pretreatment. The orthogonal analysis is shown in Fig. 1 and the R values are listed in Table 3.

Compared with raw wheat straw, the cellulose content in the pretreated wheat straw was increased for all the factors at different levels. Both the

Acknowledgments

The work was financially supported by HTF project (10077-1). We like to thank Tomas Fernqvist, Ingelis Larsen, and Annette Eva Jensen in Risø-DTU for the technical assistance.

Cited by (75)

  • Waste-based bioethanol production by using food, fruit, and grain wastes

    2023, Value-Addition in Agri-Food Industry Waste through Enzyme Technology
  • Insight into the recent advances of microwave pretreatment technologies for the conversion of lignocellulosic biomass into sustainable biofuel

    2021, Chemosphere
    Citation Excerpt :

    In contrast to the conventional heating pretreatment method, microwave-assisted pretreatment is believed to produce high power densities, thus resulting in the increase in production rate and the reduction of costs. Xu et al., (2011) reported that microwave power had a positive effect on the recovered glucose yield from the alkali-based pretreatment of wheat straw. However, increasing microwave power in the pretreatment of sugarcane bagasse through the combination of microwave–acid methods changed sugar yields insignificantly (Fig. 7).

View all citing articles on Scopus
View full text