Evaluation of High Solids Alkaline Pretreatment of Rice Straw

Abstract

Fresh-harvested, air-dried rice straw was pretreated at a water content of 5 g H2O/g straw using sodium hydroxide (NaOH) and compared to pretreatment at 10 g H2O/g straw by hydrated lime (Ca(OH)2). Full factorial experiments including parallel wash-only treatments were completed with both sources of alkali. The experiments were designed to measure the effects of alkaline loading and pretreatment time on delignification and sugar yield upon enzymatic hydrolysis. Reaction temperature was held constant at 95°C for lime pretreatment and 55°C for NaOH pretreatment. The range of delignification was 13.1% to 27.0% for lime pretreatments and was 8.6% to 23.1% for NaOH pretreatments. Both alkaline loading and reaction time had significant positive effects (p < 0.001) on delignification under the design conditions, but only alkaline loading had a significant positive effect on enzymatic hydrolysis. Treatment at higher temperature also improved delignification; delignification with water alone ranged from 9.9% to 14.5% for pretreatment at 95°C, but there was little effect observed at 55°C. Post-pretreatment washing of biomass was not necessary for subsequent enzymatic hydrolysis. Maximum glucose yields were 176.3 mg/g dried biomass (48.5% conversion efficiency of total glucose) in lime-pretreated and unwashed biomass and were 142.3 mg/g dried biomass (39.2% conversion efficiency of total glucose) in NaOH-pretreated and unwashed biomass.

Chemical Pretreatment Methods for the Production of Cellulosic Ethanol: Technologies and Innovations

“…Mild alkali pretreatment of biomass favours enzymatic hydrolysis especially for materials that have relatively low lignin content. Sugar degradation and corrosion problems are less severe in alkali processes than in acid pretreatment [57,102] and mild conditions (55 ∘ C) may not require posttreatment washing since enzyme inhibiting compounds are generally low [103].…”

Düşük Sicaklik Düşük Zaman Alkali̇ Ön İşlemleri̇ni̇n Findik Kabuğunun Bi̇leşi̇mi̇ Ve Enzi̇mati̇k Hi̇droli̇zi̇ Üzeri̇ne Etki̇si̇ni̇n İncelenmesi̇

“…Ancak fındık kabuklarının içermiş oldukları lignin yüzdesi diğer zirai kabuklu biyokütlenin kabuklarında bulunan değerler ile benzerlik göstermektedir. Literatürde lignin yüzdesinin, badem kabukları için %20-28 [27], [29,30], hindistan cevizi kabuğu için %28-34 [30,28], brezilya fındığı için %59 [31] 2 kullanılması durumunda göre daha yüksek sıcaklıklara ihtiyaç duyulmaktadır buda enerji verimliliği ve maliyet açısından NaOH kullanılmasının daha uygun olduğunu göstermektedir [32]. Bizim çalışmamızda sabit sıcaklık ve sürede farklı alkalilerin etkinliği araştırıldığı için NaOH ön işlemi daha etkin sonuçlar vermiştir.…”

Combined sodium hydroxide and ammonium hydroxide pretreatment of post-biogas digestion dairy manure fiber for cost effective cellulosic bioethanol production

“…The second most important parameter affecting the overall process was the residence time [65]. This suggests that longer treatment times reduce fiber recalcitrance that limits sugar degradation [66] and improve energy utilization.…”