Abstract
Ethanol production from cellulosic material is considered one of the most promising options for future biofuel production contributing to both the energy diversification and decarbonization of the transport sector, especially where electricity is not a viable option (e.g., aviation). Compared to conventional (or first generation) ethanol production from food and feed crops (mainly sugar and starch based crops), cellulosic (or second generation) ethanol provides better performance in terms of greenhouse gas (GHG) emissions savings and low risk of direct and indirect land-use change. However, despite the policy support (in terms of targets) and significant R&D funding in the last decade (both in EU and outside the EU), cellulosic ethanol production appears to be still limited. The paper provides a comprehensive overview of the status of cellulosic ethanol production in EU and outside EU, reviewing available literature and highlighting technical and non-technical barriers that still limit its production at commercial scale. The review shows that the cellulosic ethanol sector appears to be still stagnating, characterized by technical difficulties as well as high production costs. Competitiveness issues, against standard starch based ethanol, are evident considering many commercial scale cellulosic ethanol plants appear to be currently in idle or on-hold states.
Highlights
Ethanol production from cellulosic material such as agricultural residues and energy crops is considered a highly promising option for future ethanol production, helping the energy diversification and decarbonization of the transport sector
The main purpose of this review is to provide a comprehensive overview of the status and different aspects of cellulosic ethanol production both inside and outside the EU, highlighting technical and non-technical barriers that still limit its production at commercial scale
Cellulosic ethanol production can be summarized in four main steps: pretreatment, hydrolysis, fermentation, and product recovery (Figure 1)
Summary
Ethanol production from cellulosic material such as agricultural residues (e.g., wheat straw and corn stover) and energy crops (e.g., switchgrass and miscanthus) is considered a highly promising option for future ethanol production, helping the energy diversification and decarbonization of the transport sector. Compared to conventional (or first generation) ethanol production from food and feed crops (mainly sugar and starch based crops), cellulosic (or second generation, 2G) ethanol is considered to provide better performance in terms of greenhouse gas (GHG) reduction and low risk of direct and indirect land-use change impacts. Those advantages have led to the promotion of cellulosic ethanol in the legislation around the globe. Advanced biofuels are defined by the directive as ‘biofuels that are produced from the feedstock listed in Part A of Annex IX’ that includes among others, agriculture and forestry residues as well as energy crops Those biofuels will continue to count double towards the targets.
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