Promise of combined hydrothermal/chemical and mechanical refining for pretreatment of woody and herbaceous biomass

Abstract

Production of advanced biofuels from woody and herbaceous feedstocks is moving into commercialization. Biomass needs to be pretreated to overcome the physicochemical properties of biomass that hinder enzyme accessibility, impeding the conversion of the plant cell walls to fermentable sugars. Pretreatment also remains one of the most costly unit operations in the process and among the most critical because it is the source of chemicals that inhibit enzymes and microorganisms and largely determines enzyme loading and sugar yields. Pretreatments are categorized into hydrothermal (aqueous)/chemical, physical, and biological pretreatments, and the mechanistic details of which are briefly outlined in this review. To leverage the synergistic effects of different pretreatment methods, conducting two or more pretreatments consecutively has gained attention. Especially, combining hydrothermal/chemical pretreatment and mechanical refining, a type of physical pretreatment, has the potential to be applied to an industrial plant. Here, the effects of the combined pretreatment (combined hydrothermal/chemical pretreatment and mechanical refining) on energy consumption, physical structure, sugar yields, and enzyme dosage are summarized.

Erratum to: Promise of combined hydrothermal/chemical and mechanical refining for pretreatment of woody and herbaceous biomass

“…Unfortunately, after publication of this article [1], it was noticed that the capturing of Table 4 during the production process introduced several items in the ‘Sugar Yields’ column listed in the wrong row. The corrected table can be seen in this erratum (Table 4).…”

Valorization of lignin and cellulose in acid-steam-exploded corn stover by a moderate alkaline ethanol post-treatment based on an integrated biorefinery concept

“…These pretreatment technologies can be classified into biological, physical, chemical, and physicochemical methods, including dilute acid, steam explosion, hot-compressed water, organosolv, ammonia fiber explosion, and aqueous lime or alkali pretreatments [8–13]. All of the pretreatment methods have limitations; therefore, the synergistic benefits of combined methods should be considered [14]. …”

Nutritional value and in situ degradability of oak wood roughage and its feeding effects on growth performance and behavior of Hanwoo steers during the early fattening period

“…Lignocellulosic biomass such as wood and agricultural residues requires pretreatments to make cellulose and hemicellulose more accessible to the enzymes that convert the carbohydrate polymers into fermentable sugars. There are various methods of pretreatment using steam, chemicals, mechanical milling and combinations of these treatments [4]. Hydrothermolysis using steam or hot compressed water (>160°C) is generally regarded as an effective pretreatment of agricultural and hardwood biomass, whereas softwood requires harsher conditions such as the presence of acid catalysts during the steam pretreatment [4,16].…”

“…Hydrothermolysis using high pressure and temperature (150°C to 180°C is known to have a significant effect on wood and agricultural residues [4]. Previous results [5] suggest that the thinning woods from oak and pine forests treated with the steam-digestion process may be used as roughage sources by comparing chemical composition and in situ degradability.…”

“…More efficient utilization of woody materials could be realized by pretreatments using steam, chemicals, mechanical milling and combinations of these treatments. Researches have been mainly conducted for bioethanol production to increase the yield of fermentable products by using heat treatment in combination with chemical treatment [4]. However, the products are not environmentally friendly, must be neutralized prior to feeding and may result in a decrease in available nutrients due to excessive solubilization of hemicellulose.…”