The use of NG in the transportation sector is becoming an appealing option to diesel and gasoline fuels, presenting higher benefits. ANG technology offers a secure, cost-effective, energy-efficient strategy for the storage of NG in porous sorbents at reasonable gas densities. The major goal for its extensive utilization is the requirement of effective storage materials under practicable conditions. Recently, there has been increased attention in utilizing bio-wastes for the preparation of microporous carbons. In this contribution, our growing knowledge on the use of biobased materials and the processing strategies in an effort to predictively produce effective porous carbons appropriate for ANG technology have been reviewed. By careful literature selection, different precursors with different alternative processes to convert low-cost bio-wastes into porous carbons and achievements in methane storage are presented. To gain deeper insight into the technology, the correlation between the structural and chemical properties of materials and the factors affecting the storage performance are highlighted. The utilization of bio-wastes for the development of microporous carbons with facile methods emerged to be encouraging, which would be significant in larger scale applications. Bio-waste processing for ANG storage is valued over many other techniques, and the products are able to store substantial levels of methane. This review could help improve researchers’ evaluation of the methods as a guideline for ANG. Further studies for achieving an accomplished interconnection between the structural characteristics and the methane storage capacities with different bio-wastes and optimization strategies would be beneficial.

Current overview of the valorization of bio-wastes for adsorbed natural gas applications
    Abstract
        Graphical abstract
    1 Introduction
        1.1 Energy problem, renewable and environmentally sustainable energy
        1.2 Natural gas
        1.3 Methane
        1.4 Natural gas storage
        1.5 Adsorbed natural gas (ANG)
        1.6 Aim of this contribution
    2 ANG storage targets and materials
        2.1 ANG storage targets
        2.2 Methane storage materials
            2.2.1 Activated carbon
            2.2.2 Correlation between the microporous structure and methane storage
            2.2.3 Activated carbon precursors
            2.2.4 Advantages of biomass
            2.2.5 Production of activated carbon
            2.2.6 Biomass sources
    3 Conducted experimental studies
        3.1 Precursors, materials
        3.2 Material preparation
            3.2.1 Pretreatment
            3.2.2 Carbonization, activation
            3.2.3 Posttreatment
        3.3 Characterizations
            3.3.1 Determining packing and helium densities
            3.3.2 Nitrogen adsorption measurements
        3.4 Methane uptake measurements
            3.4.1 Volumetric and gravimetric analysis
            3.4.2 Methane adsorption measurement range
    4 Research findings
        4.1 Impact of activation methods and pore structure
        4.2 Impact of operational parameters
        4.3 Adsorption mechanisms
        4.4 Limitations of ANG technology
    5 Conclusions
    6 Future directions
    References

• Turkan Kopac(Department of Chemistry, Zonguldak Bülent Ecevit University, 67100 Zonguldak, Turkey)