By the start of the 21st century, biobutanol attracted interests as a drop-in liquid fuel that can be produced from renewable carbohydrate resources. A wide range of research studies dedicated to reviving the old acetone-butanol-ethanol (ABE) fermentation. ABE fermentation has been widely utilized all over the world at commercial scale during World War I and World Ward II for its acetone production but lost its economic vitality in the competition with petrochemical industry. In the search for a sustainable route from renewable resources to liquid biofuels, ABE fermentation attracted interests for n-butanol production. With such a unique industrial background, ABE fermentation has been targeted by some companies to be revived as an industrial process. Furthermore, the development of recombinant stains for the production of isobutanol had promising results and commercialized by two American companies. In this chapter, different aspects of microbial production of n-butanol and isobutanol are presented.
Alcohols have high potential as fuels, solvents, and building blocks for the production of a wide range of chemicals. To become a proper fuel, candidates should pass several assessments based on the physical properties such as density and viscosity and chemical properties such as combustion energy. The primary aliphatic alcohols between C3 and C7, the so-called higher alcohols, have recently attracted interest owing to their possible production from renewable carbohydrate resources through microbial pathways. In this chapter, different features of the higher alcohols are discussed to assess their potential as liquid fuels, reagents in synthetic chemistry, or solvents in industry. The considerable potentials of higher alcohols justify the enormous research efforts on developing synthetic pathways for their efficient microbial synthesis.
One of the most current discussions in the transportation sector is air pollution caused by diesel engines. In fact, even with the advances in engine technologies, the combustion of diesel in internal combustion engines leads to the significant release of toxic gases into the atmosphere, such as particulate matter and nitrogen oxide, posing threats to human health and the environment. Although researchers proposed replacing petroleum-based diesel with bio-based diesel, technical, environmental, and economic challenges make their sustainability questionable. In line with that, more sustainable techniques have been introduced to reduce the toxic gas emissions from diesel combustion. Modifying diesel properties using fuel additives or reformulation is a straightforward and economical alternative among these techniques. Various additives, such as oxygenated, cetane number improvers, metal-based compounds, antioxidants, lubricity improvers, and cold flow improvers, are commercially used to improve diesel properties. Among these, higher alcohols as oxygenated additives due to their higher oxygen content and latent heat than diesel can shift the combustion process toward lower temperatures, lowering particulate matter and nitrogen oxide emissions. Despite the promising results offered by higher alcohols as fuel additives for diesel, the sustainability of their production from an environmental, economic, and social point of view should not be neglected. In better words, the decision-making process should not focus on the effects of higher alcohols on exhaust pollutants only, but also it should consider the principles of sustainable development in the background process of higher alcohols, that is, a cradle-to-grave approach. Life cycle sustainability assessment is a valuable tool to address this problem through systematical evaluation of environmental, economic, and social background processes or production of higher alcohols. This chapter aims to better understand the environmental, economic, and social aspects of higher alcohol production based on a life cycle sustainability assessment approach.
Glycolipids are microbial surface-active molecules that are composed of a carbohydrate unit linked to a single or multiple fatty acid(s). They are receiving increased research interest due to their green production pathways and their environmental and application benefits. Rhamnolipids, trehalolipids, sophorolipids, and mannosylerythritol lipids are among the most well-characterized glycolipids. Their antibacterial and emulsifying properties impart great potential to glycolipids in areas such as cleaning, cosmetic, and food preservation and can serve as sustainable substitutes for many synthetic surfactants. In addition, the valorization of food wastes through their use as fermentation feedstocks to produce glycolipid biosurfactants has received considerable attention because the process allows the bioconversion of inexpensive renewable by-products to value-added compounds, which may help to decrease production costs. This chapter focuses on the status and future perspectives related to the economical production of glycolipid biosurfactants and their potential application in foods.
Concerns about carbon emissions and global warming have mobilized the world toward decarburization through various strategies, such as using zero or low-carbon products. One of the most important current strategies in decarburization is to eliminate or reduce the use of fossil fuels as one of the world's largest sources of carbon emissions. In line with this, biofuel utilization is expected to expand worldwide due to its potential to solve carbon emissions. It is well documented that biodiesel is a promising alternative to overcome inherent problems attributed to petrodiesel in carbon emission. Despite biodiesel's merits, its production depends on various materials and energy resources responsible for different environmental impacts. This fact might be questioned the sustainability of biodiesel production. Although maintaining the sustainability of biodiesel on a laboratory scale because of strict control of conditions can be successful, small-scale production cannot be used commercially and enter the competitive market. Accordingly, efforts should go toward commercializing biodiesel and expanding its use in the real world. Nevertheless, commercial biodiesel production in the real world can be problematic and challenging in terms of sustainability because of the large scale. Life cycle thinking (LCT) is a powerful approach to studying the sustainability of various products. More specifically, this approach can focus on three main pillars of sustainability, that is, environmental, economic, and social. Traditionally, environmental life cycle assessment is widely accepted to evaluate the environmental impacts of products during their life cycle. Recently, social life cycle assessment that addresses the social performances of products has also been developed. Accordingly, these approaches can help to address challenges and concerns associated with the sustainability of commercial biodiesel production. In light of the above, the current chapter scrutinizes the sustainability of commercial biodiesel production on the industrial scale based on the LCT approach from environmental and social points of view.
