Algal biofuels

The world is facing energy crisis and environmental issues due to the depletion of fossil fuels and increasing CO₂ concentration in the atmosphere. Growing microalgae can contribute to practical solutions for these global problems because they can harvest solar energy and capture CO₂ by converting it into biofuel using photosynthesis. Microalgae are robust organisms capable of rapid growth under a variety of conditions including in open ponds or closed photobioreactors. Their reduced biomass compounds can be used as the feedstock for mass production of a variety of biofuels. As another advantage, their ability to accumulate or secrete biofuels can be controlled by changing their growth conditions or metabolic engineering. This review is aimed to highlight different forms of biofuels produced by microalgae and the approaches taken to improve their biofuel productivity. The costs for industrial-scale production of algal biofuels in open ponds or closed photobioreactors are analyzed. Different strategies for photoproduction of hydrogen by the hydrogenase enzyme of green algae are discussed. Algae are also good sources of biodiesel since some species can make large quantities of lipids as their biomass. The lipid contents for some of the best oil-producing strains of algae in optimized growth conditions are reviewed. The potential of microalgae for producing petroleum related chemicals or ready-make fuels such as bioethanol, triterpenic hydrocarbons, isobutyraldehyde, isobutanol, and isoprene from their biomass are also presented.     

Bonkers about biofuels

Biofuels have been touted before, but failed to deliver. What's needed to get it right this time around?     

Bioprocessing for biofuels

While engineering of new biofuels pathways into microbial hosts has received considerable attention, innovations in bioprocessing are required for commercialization of both conventional and next-generation fuels. For ethanol and butanol, reducing energy costs for product recovery remains a challenge. Fuels produced from heterologous aerobic pathways in yeast and bacteria require control of aeration and cooling at large scales. Converting lignocellulosic biomass to sugars for fuels production requires effective biomass pretreatment to increase surface area, decrystallize cellulose and facilitate enzymatic hydrolysis. Effective means to recover microalgae and extract their intracellular lipids remains a practical and economic bottleneck in algal biodiesel production.     

The ethics of biofuels

The rapid development and adoption of biofuels has been driven by a wide range of targets and other policy instruments, but first‐generation biofuels have been widely criticized. In light of the development of new biofuel technologies that aim to avoid the problems of the past, the Nuffield Council on Bioethics conducted an 18‐month inquiry on the ethical, social and policy issues raised by both current and future biofuels. The Council concludes that many biofuels policies fail to take consideration of important ethical principles, such as protecting human rights, environmental sustainability, climate change mitigation, just reward, and equitable distribution of costs and benefits. It proposes an overarching ethical standard for biofuels, enforced by a certification scheme for all biofuels produced in and imported into Europe and ideally worldwide.     

The Brazilian biofuels industry

Ethanol is a biofuel that is used as a replacement for approximately 3% of the fossil-based gasoline consumed in the world today. Most of this biofuel is produced from sugarcane in Brazil and corn in the United States. We present here the rationale for the ethanol program in Brazil, its present 'status' and its perspectives. The environmental benefits of the program, particularly the contribution of ethanol to reducing the emission of greenhouse gases, are discussed, as well as the limitations to its expansion.     

Using microorganisms to brew biofuels

Interest in alternative fuel sources has grown in recent years in response to a confluence of factors, including concerns over our reliance on and increasing demand for fossil fuels as well as the deleterious environmental effects of fossil fuel extraction and utilization. The use of microbe-derived fuel alcohols is a viable alternative, as they are renewable, emit fewer greenhouse gasses, and require little augmentation of current energy infrastructure as compared to other sustainable transportation options such as electric vehicles and fuel cells. Here, we present a brief overview of candidate substrates for alcohol production with a focus on lignocellulosic sources, relevant microorganisms under research for industrialization and the biotechnological techniques used to improve alcohol production phenotypes.     

How biotech can transform biofuels

For cellulosic ethanol to become a reality, biotechnological solutions should focus on optimizing the conversion of biomass to sugars.     

Engineering microbes to produce biofuels

The current biofuels landscape is chaotic. It is controlled by the rules imposed by economic forces and driven by the necessity of finding new sources of energy, particularly motor fuels. The need is bringing forth great creativity in uncovering new candidate fuel molecules that can be made via metabolic engineering. These next generation fuels include long-chain alcohols, terpenoid hydrocarbons, and diesel-length alkanes. Renewable fuels contain carbon derived from carbon dioxide. The carbon dioxide is derived directly by a photosynthetic fuel-producing organism(s) or via intermediary biomass polymers that were previously derived from carbon dioxide. To use the latter economically, biomass depolymerization processes must improve and this is a very active area of research. There are competitive approaches with some groups using enzyme based methods and others using chemical catalysts. With the former, feedstock and end-product toxicity loom as major problems. Advances chiefly rest on the ability to manipulate biological systems. Computational and modular construction approaches are key. For example, novel metabolic networks have been constructed to make long-chain alcohols and hydrocarbons that have superior fuel properties over ethanol. A particularly exciting approach is to implement a direct utilization of solar energy to make a usable fuel. A number of approaches use the components of current biological systems, but re-engineer them for more direct, efficient production of fuels.     

生物燃料的发展现状与前景

利用储量巨大的生物质能发展可再生的清洁型生物燃料可以帮助缓解世界能源危机,扭转由于石化燃料的大量使用而造成的全球环境日益恶化的趋势.拟对现代生物燃料的3种生产转化途径、相应产品及其在世界范围内的生产和应用情况作一介绍,分析生物燃料的优、缺点和所面临的挑战,进而探讨我国能源结构的现状以及发展利用生物燃料的前景.发展生物燃料不能单纯地考虑能源,而应该在可持续科学的框架下进行,须建立多样化、多功能的景观格局和生产体系,高度整合资源、环境、社会和经济诸方面,从而促进可持续发展的长远目标.     

Implementing biofuels on a global scale

Is the introduction of renewable biofuels a simple problem of technology development and diffusion or does it require an industrial revolution?     

Harnessing xylose pathways for biofuels production

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Technoeconomic analysis for biofuels and bioproducts

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