Tobacco as a promising crop for low-carbon biorefinery

Abstract

Energy crops play a vital role in meeting future energy and chemical demands while addressing climate change. However, the idealization of low-carbon workflows and careful consideration of cost-benefit equations are crucial for their more sustainable implementation. Here, we propose tobacco as a promising energy crop because of its exceptional water solubility, mainly attributed to a high proportion of water-soluble carbohydrates and nitrogen, less lignocellulose, and the presence of acids. We then designed a strategy that maximizes biomass conversion into bio-based products while minimizing energy and material inputs. By autoclaving tobacco leaves in water, we obtained a nutrient-rich medium capable of supporting the growth of microorganisms and the production of bioproducts without the need for extensive pretreatment, hydrolysis, or additional supplements. Additionally, cultivating tobacco on barren lands can generate sufficient biomass to produce approximately 573 billion gallons of ethanol per year. This approach also leads to a reduction of greenhouse gas emissions by approximately 76% compared to traditional corn stover during biorefinery processes. Therefore, our study presents a novel and direct strategy that could significantly contribute to the goal of reducing carbon emissions and global sustainable development compared to traditional methods.

Graphical abstract

Figure 1

Main advantages of tobacco compared to five common biomasses (A–C) Analysis of the significant substances after being treated by autoclaving at 115°C for 30 min. (A) The water-soluble component (SCM) analysis. (B) The water-soluble carbohydrates (WSC) analysis. (C) The nitrogen analysis. (D–F) Analysis of the significant substances of biomass itself. (D) Lignin analysis. (E) Cellulose analysis. (F) Hemicellulose analysis. Tobacco leaves contained a substantially larger amount of SCM, WSC, and nitrogen and a smaller amount of lignocellulose compared to other biomasses. Error bars represent standard deviations (n = 3).

Figure 2

Main chemical components of tobacco leaves treated by autoclaving (A) The composition of the aqueous solution. Ash is calculated from the results of raw and treated tobacco leaves, which mainly includes some salts. In addition, others include a small amount of sugar, a relatively large proportion of acids and phenols, and amino acids, which can be used as helpful factors for the growth of microorganisms. (B) The composition of solid residue. Others include some sugars, acids, phenols, amino acids, etc., that are not dissolved in the aqueous solution. (C) Main sugars and nitrogen contents in SCM. (D) The fermentation inhibitors in SCM. Error bars represent standard deviations (n = 3).

Figure 3

Tobacco medium for prokaryotic and eukaryotic growth and bioconversion (A) Growth of three E. coli strains, BL21(DE3), BW25113, and JM109(DE3), in the tobacco medium compared to other common media. (B) Growth of three yeast strains, S. cerevisiae S288c, P. pastoris GS115, and Y. lipolytica Po1h, in the tobacco medium compared to other common media. (C) Production of farnesene by engineered E. coli strain in control medium, tobacco medium, and tobacco addition medium. (D) Production of farnesene by engineered S. cerevisiae strain in control medium, tobacco medium, and tobacco addition medium. (E) Production of ethanol by S. cerevisiae S288c in control medium, tobacco medium, and tobacco addition medium. (F) Production of 2,3-BD by wild Bacillus amyloliquefaciens T4 in control medium, tobacco medium, and tobacco addition medium. Error bars represent standard deviations (n = 3). Statistical significance: ∗p > 0.05, ∗∗p < 0.05, ∗∗∗p < 0.001, and ∗∗∗∗p < 0.0001 based on two-way ANOVA.

Figure 4

The global barren/very sparsely vegetated land for tobacco plants (A) The distribution of global barren/very sparsely vegetated land. (B) The annual average temperature of existing global barren/very sparsely vegetated land in 1990–2010. (C) The annual average precipitation of existing global barren/very sparsely vegetated land in 1990–2010.

Figure 5

Life cycle assessment of tobacco and corn stover to bioethanol Life cycle greenhouse gas emissions (A and B) and energy consumption (C and D) of tobacco and corn stover to bioethanol. (B) and (D) represent the comparison of the greenhouse gas emissions and energy consumption from the chemicals and energy of bioconversion stage.