A review on commercial-scale high-value products that can be produced alongside cellulosic ethanol

Abstract

The demand for fossil derivate fuels and chemicals has increased, augmenting concerns on climate change, global economic stability, and sustainability on fossil resources. Therefore, the production of fuels and chemicals from alternative and renewable resources has attracted considerable and growing attention. Ethanol is a promising biofuel that can reduce the consumption of gasoline in the transportation sector and related greenhouse gas (GHG) emissions. Lignocellulosic biomass is a promising feedstock to produce bioethanol (cellulosic ethanol) because of its abundance and low cost. Since the conversion of lignocellulose to ethanol is complex and expensive, the cellulosic ethanol price cannot compete with those of the fossil derivate fuels. A promising strategy to lower the production cost of cellulosic ethanol is developing a biorefinery which produces ethanol and other high-value chemicals from lignocellulose. The selection of such chemicals is difficult because there are hundreds of products that can be produced from lignocellulose. Multiple reviews and reports have described a small group of lignocellulose derivate compounds that have the potential to be commercialized. Some of these products are in the bench scale and require extensive research and time before they can be industrially produced. This review examines chemicals and materials with a Technology Readiness Level (TRL) of at least 8, which have reached a commercial scale and could be shortly or immediately integrated into a cellulosic ethanol process.

Keywords: Bio-based chemicals; Biofuel; Bioproducts; Biorefinery; Cellulosic ethanol; Commercial production; Lignocellulose.

Fig. 1

Process diagram to produce bioethanol from sugar and starch feedstocks, and lignocellulose including biochemicals and biomaterials with potential to be produced alongside bioethanol (red lines)

Fig. 2

Process diagram for the production of second-generation bioethanol from lignocellulose. Production routes to produce biochemicals from glucose that are industrially produced (red lines)

Fig. 3

Process diagram for the production of second-generation bioethanol from lignocellulose. Production routes to produce biochemicals from ethanol that are currently produced industrially (red lines)

Fig. 4

Process diagram for the production of acetone–butanol–ethanol (ABE) from lignocellulosic biomass. 2G ethanol process stages (black lines) and integrated ABE stages (red lines)

Fig. 5

Diagram for the co-production of 2G ethanol and MFC from lignocellulose

Fig. 6

Process diagram for the production of 2G ethanol and integrated process options for the production of xylitol from (red line): xylose and glucose