Steam explosion

Technology
Technology details
Name:	Steam explosion
Category:	Pre-processing (Physical processes and technologies), Post-processing (Physical processes and technologies)
Feedstock:	Garden and park waste
Product:	Lignocellulosic hydrolysate

Steam explosion is a physicochemical method to break the lignocellulose structure by using high-pressure steam to disrupt the bonding between polymeric components (lignin, cellulose) and decompression. It can be used to pre-treat the lignocellulosic biomass to improve subsequent processes, such as enzymatic hydrolysis.

Feedstock

Origin and composition

Steam explosion is used to pre-treat lignocellulosic biomass such as wood, straw and lignocellulosic wastes for industrial processes. Normally, the material enters the steam explosion process as chips, pellets or ground material.

Pre-treatment

• Sizing

Process and technologies

Lignocellulosic biomass, such as wood, exists of composite materials with high mechanical strength composed of cellulose fibres, lignin polymers as a matrix and hemicelluloses in a tightly packed cellular structure of fibres that form fibre bundles. Their natural function is to bear high mechanical loads, and to resist chemical and enzymatic degradation through microorganisms. Steam explosion breaks this structure down to enable these chemical and enzymatic conversions. It converts biomass in a steam atmosphere at elevated temperatures ranging from 140 to 240 °C. The steam pressure is rapidly reduced to atmospheric pressure, whereby a mechanical disruption of biomass occurs. In steam explosion, the lignocellulosic biomass is treated with a high-pressure, hot steam for some time and then the vessel is rapidly depressurised to atmospheric pressure. With this explosive decompression and high temperature it causes degradation of hemicellulose, which is extracted as a water-soluble fraction. The cellulose is largely preserved in its original form, and only slight depolymerisation occurs at mild reaction condition. The Lignin undergoes depolymerisation by cleavage of β–O–4 linkages, and condensation of the fragments occurs to form a more stable polymer.

Steam explosion was introduced and patented as a biomass pre-treatment process in 1926 by Mason et al. (1926). The patent describes a steam explosion process for the pre-treatment of wood where wood chips are fed from a bin through a screw loading valve. The chips are then steam heated at a temperature of about 285°C and a pressure of 3.5 MPa for about 2 min. The pressure is increased rapidly to about 7 MPa (70 bar) for about 5 s, and the chips are then discharged and explode at atmospheric pressure into a pulp. The sudden pressure release defibrillates the cellulose bundles, and this result in a better accessibility of the cellulose for hydrolysis or fermentation.

Product

Steam explosion is a pre-treatment process that makes biomass more suitable for following processes, such as enzymatic hydrolysis, acid hydrolysis or fermentation. Depending on residence time and temperature, steam explosion can result in anything from small cracks in the wood structure, to total defibrillation of the wood fibers.

Post-treatment

• Hydrolysis
• Fermentation

Technology providers

Technology comparison

Company name	Country	Technology category	Technology name	TRL	Capacity [kg/h]	Pressure [bar]	Temperature [°C]	Feedstock: Food waste	Feedstock: Garden & park waste
Company 1	[Country HQ location]	[Technology category (if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]			●	●
Company 2	[Country HQ location]	[(if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]			●	●

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Steam explosion provider

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Technology and process details
Technology name:		Technology category:	Pre-processing (Physical processes and technologies), Post-processing (Physical processes and technologies)
TRL:		Capacity:	kg·h-1
Cellulose yield:	%	Hemicellulose removal:	%
Pressure:	bar	Temperature:	°C
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Feedstock and product details
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