The general principles of green chemistry guide the design of environmentally benign products and processes. It is known that the efficient utilization of carbon resources and carbon recycling are of great importance for the sustainable development of our society, and there are many related challenging scientific issues to be solved. Herein we attempt a holistic view on carbon resource processing, utilization, and recycling, and we call this “green carbon science”. We will discuss the definition and the four key principles of green carbon science and highlight some related fields including petroleum refining, the production of liquid fuels and chemicals from coal and methane, and transformations of CO2 and biomass into fuels and chemicals.

Green Carbon Science: Scientific Basis for Integrating Carbon Resource Processing, Utilization, and Recycling

A review on water in low rank coals: The existence, interaction with coal structure and effects on coal utilization

Lignocellulosic materials are among the most promising alternative energy resources that can be utilized to produce cellulosic ethanol. However, the physical and chemical structure of lignocellulosic materials forms strong native recalcitrance and results in relatively low yield of ethanol from raw lignocellulosic materials. An appropriate pretreatment method is required to overcome this recalcitrance. For decades various pretreatment processes have been developed to improve the digestibility of lignocellulosic biomass. Each pretreatment process has a different specificity on altering the physical and chemical structure of lignocellulosic materials. In this paper, the chemical structure of lignocellulosic biomass and factors likely affect the digestibility of lignocellulosic materials are discussed, and then an overview about the most important pretreatment processes available are provided. In particular, the combined pretreatment strategies are reviewed for improving the enzymatic hydrolysis of lignocellulose and realizing the comprehensive utilization of lignocellulosic materials.

The role of pretreatment in improving the enzymatic hydrolysis

a b s t r a c t This paper primarily presents an overall review of the use of microalgae as a biofuel feedstock. Among the microalgae that have potential as biofuel feedstock, Chlorella, specifically, was thoroughly discussed because of its ability to adapt both to heterotrophic and phototrophic culture conditions. The lipid content and biomass productivity of microalgae can be up to 80% and 7.3 g/l/d based on the dried weight of biomass, respectively, making microalgae an ideal candidate as a biofuel feedstock. The set-up of the system and the biomass productivity of microalgae cultivated in an open pond and a photobioreactor were also compared in this work. The effect of the culture condition is discussed based on the twostage culture period. The issues that were discussed include the light condition and the CO2, DO and N supply. The microalgal productivities under heterotrophic and phototrophic culture conditions were also compared and highlighted in this work. The harvesting process and type of flocculants used to aid the harvesting were highlighted by considering the final yield of biomass. A new idea regarding how to harvest microalgae based on positive and negative charges was also proposed in this work. The extraction methods and solvents discussed were primarily for the conventional and newly invented techniques. Conversion processes such as transesterification and thermochemical processes were discussed, sketched in figures and summarized in tables. The cost–benefit analysis of heterotrophic culture and the cultivation system was highlighted at the end of this work. Other benefits of microalgae are also mentioned in this work to give further support for the use of microalgae as a feedstock for biofuel production.

Conversion of microalgae to biofuel

Increased demand for liquid transportation fuels coupled with gradual depletion of oil reserves and volatile petroleum prices have recently renewed interest in coal-to-liquids (CTL) technologies. Large recoverable global coal reserves can provide liquid fuels and significantly reduce dependence on oil imports. Direct coal liquefaction (DCL) converts solid coal (H/C ratio ≈ 0.8) to liquid fuels (H/C ratio ≈ 2) by adding hydrogen at high temperature and pressures in the presence or absence of catalyst. This review provides a comprehensive literature survey of the coal structure, chemistry and catalysis involved in direct liquefaction of coal. This report also touches briefly on the historical development and current status of DCL technologies. Key issues, challenges involved in DCL process and directions for the future research are also addressed.

Zhicai Wang

Papers

Molecular structure characterization of low-medium rank coals via XRD, solid state 13C NMR and FTIR spectroscopy

Thermal dissolution of Shenfu coal in different solvents

Effect of hydrothermal treatment on the extraction of coal in the CS2/NMP mixed solvent

Kinetic analysis and modeling of coal pyrolysis with model-free methods

Co-liquefaction behavior of a sub-bituminous coal and sawdust