Direct microbial transformation of carbon dioxide to value-added chemicals: A comprehensive analysis and application potentials

Bioresource Technology 288 (2019) 121401

Contents lists available at ScienceDirect

Bioresource Technology journal homepage: www.elsevier.com/locate/biortech

Review

Direct microbial transformation of carbon dioxide to value-added chemicals: A comprehensive analysis and application potentials

T

Muhammad Irfana,c, Yang Baia, Lei Zhoua, Mohsin Kazmia,c, Shan Yuana, Serge Maurice Mbadingaa, Shi-Zhong Yanga, Jin Feng Liua, Wolfgang Sandd,e, Ji-Dong Gub, ⁎ Bo-Zhong Mua,f, a

State Key Laboratory of Bioreactor Engineering and School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China b School of Biological Sciences, University of Hong Kong, Pokfulam Road, Hong Kong, China c Department of Chemical, Polymer and Composite Materials Engineering, University of Engineering and Technology, KSK Campus, Lahore 54890, Pakistan d Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China e Biofilm Centre, University of Duisburg-Essen, Essen, Germany f Engineering Research Center of MEOR, East China University of Science and Technology, Ministry of Education, Shanghai 200237, China

GRAPHICAL ABSTRACT

ARTICLE INFO

ABSTRACT

Keywords: Carbon dioxide Direct microbial transformation Utilization Electron donors Green biotechnology Value-added products

Carbon dioxide storage in petroleum and other geological reservoirs is an economical option for long-term separation of this gas from the atmosphere. Other options include applications through conversion to valuable chemicals. Microalgae and plants perform direct fixation of carbon dioxide to biomass, which is then used as raw material for further microbial transformation (MT). The approach by microbial transformation can achieve reduction of carbon dioxide and production of biofuels. This review addresses the research and technological processes related to direct MT of carbon dioxide, factors affecting their efficiency in operation and the review of economic feasibility. Additionally, some commercial plants making utilization of CO2 around the globe are also summarized along with different value-added chemicals (methane, acetate, fatty acids and alcohols) as reported in literature. Further information is also provided for a better understanding of direct CO2 MT and its future prospects leading to a sustainable and clean environment.

⁎

Corresponding author at: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China. E-mail address: [email protected] (B.-Z. Mu).

https://doi.org/10.1016/j.biortech.2019.121401 Received 23 February 2019; Received in revised form 27 April 2019; Accepted 29 April 2019 Available online 30 April 2019 0960-8524/ © 2019 Elsevier Ltd. All rights reserved.

Bioresource Technology 288 (2019) 121401

M. Irfan, et al.

above have some limitations in different respects related to scale-up of facility, immaturity of technology, large investment and consumption of energy. The better alternative is to use carbon dioxide for the production of some useful chemicals i.e., carbon dioxide capture and utilization (CCU) and carbon dioxide capture, utilization and storage (CCUS). These are also termed as valorization of carbon dioxide and have the dual benefit of carbon dioxide mitigation and production of the valuable compounds. These are environment-friendly and economically more feasible than the sequestration techniques. There are three types of processes used mainly for valorization of carbon dioxide: chemical conversion of carbon dioxide into useful chemicals, biotransformation of carbon dioxide into useful chemicals (Cantrell et al., 2008; Thakur et al., 2018; Varjani, 2017) and its use in different indirect applications. Chemical conversions convert carbon dioxide into useful chemicals using some specific chemical catalyst provided that the required amount of energy is supplied. These consist of three types, i.e. thermo-chemical/photochemical, electrochemical and a hybrid approach. Indirect applications utilize carbon dioxide in production of the chemicals, which can further be employed in different applications, such as use of carbon dioxide in beverages, fire extinguishers and solvent extraction process, etc. (Bacik et al., 2011). Biotransformation of carbon dioxide makes use of biocatalysts (enzymes or microorganisms) under comparably mild conditions of temperature and pressure and require energy less than chemical conversions. As the result of less energy requirement for the biotransformation of carbon dioxide, the biological conversions of carbon dioxide are more feasible than the chemical conversions (Joshi, 2014). These also have advantages for easy incorporation of innovation and process modifications (Cantrell et al., 2008; Clomburg et al., 2017; Thakur et al., 2018). Fig. 1 summarizes different techniques in use for sequestration and utilization of carbon dioxide. In short, it is an urgent need of the present time to reduce the increasing concentration of carbon dioxide from atmosphere and focus on green energy and renewable fuels to decrease dependency on conventional fuels. One of the useful strategies in this respect is to focus on conversion of carbon dioxide into valuable chemicals and fuels. Linear non-polar geometry and inert nature of carbon dioxide under normal conditions make the chemical conversions energy intensive. On other hand, the energy requirement is less for methods involving biotransformation of carbon dioxide rendering it more preferred and feasible than chemical conversions. Biotransformation of carbon dioxide is currently under investigation worldwide in different respects, but limited literature is presently available about the operational, technoeconomic and scale-up aspects of the potential processes of direct microbial transformation (MT) of carbon dioxide, which is thus the focus of this review. With this aim, this contribution first presents a brief comparison of different technological processes for biotransformation of carbon dioxide and then addresses different aspects of the direct microbial transformation of carbon dioxide in detail. Discussion on

1. Introduction Environmental safety is one main concern nowadays as global warming is an urgent issue to all societies (Durmaz, 2018; Kumar et al., 2018; Liu et al., 2019). The Swedish physicist Svante Arrhenius first described the phenomenon of global warming in 1896. According to him, the increasing concentration of carbon dioxide contributes to greenhouse effects leading to global warming (Salmiati et al., 2015; Liu et al., 2019). It is pertinent to mention that power sector using fossil fuels is a major contributor towards greenhouse emissions (Li et al., 2015). The others include land use, biomass, transportation fuels, waste disposal and treatment, agriculture products, residential, commercial and different industrial processes (Chen et al., 2008). In short, different adverse environmental changes causing an increasing concentration of carbon dioxide are a consequence of the different factors by the use of fossil fuels, industrial operations and human activities. According to the International Energy Agency (IEA), carbon dioxide emission is predicted to be 63% higher in 2030 as compared to that in 2004 (Ganesh, 2014). The IEA states that if continued in this way carbon dioxide emissions can reach to 40.2 Gt. by 2030 (Rossi et al., 2015). Thus, it is indispensable to reduce the use of fossil fuels so that the harmful emissions, the increasing global temperature (De Silva et al., 2015) and increasing ocean acidity (Farrelly et al., 2013) can be controlled. The main reasons for these consequences are increasing population and the use of traditional wastewater and organic waste treatments on one side (Rosso and Stenstrom, 2008) while the globalization, the rapid economic growth and availability of less renewable energy sources on the other side (Alshehry and Belloumi, 2015). Keeping in view the whole scenario, it is necessary to reduce carbon dioxide emissions and energy demand and to switch to low carbon and renewable fuels. The Organization of Economic Cooperation and Development (OECD) also aims to implement high carbon taxes and technological advancements leading to bio-based fuels, solar and wind energy usage and eventually low carbon emissions (Zhang and Mabee, 2016). Different technologies currently in use for carbon dioxide capture and storage (CCS) have the following three main steps: capturing; transportation and storage (Huntley and Redalje, 2007). The two techniques used for sequestration are ocean and geo sequestration. Yet major drawbacks of these include: high transportation cost, public anxiety due to increased associated ocean acidity and danger of leakage back into the atmosphere (Huang and Tan, 2014; Fernandez et al., 2015; Liu et al., 2019). Other options are: chemical absorption and desorption, enhanced oil recovery (EOR) and enhanced coal bed methane recovery (ECBM) (Ziobrowski et al., 2016). Cryogenic separation and gas permeation are also in use for carbon dioxide capture from its mixture with different gases (Pires et al., 2011; Thakur et al., 2018). One newly developed technique in this respect is termed hydrate based gas separation (Babu et al., 2015). Table 1 summarizes the promising features and drawbacks of these techniques. All processes mentioned Table 1 Comparison of different carbon dioxide sequestration and separation techniques. Name

Promising features

Drawbacks

References

Geo-sequestration

Danger of leakage, High cost, Public anxiety

(Huang and Tan, 2014; Fernandez et al., 2015; Thakur et al., 2018)

Chemical adsorption

Massive storage capacity, Mature technology, Long retention time High storage capacity, Prolonged residence time Efficiency of 90%

Membrane separation Cryogenic separation

High packing density, Easy installation Efficiency of 99.9%

Hydrate based gas separation

Clean process, Suitable for industrial flue gases, High storage capacity Enhanced oil recovery of 8–15% Enhanced methane recovery

Oceanic sequestration

EOR ECBM

Damage to sea life Loss of solvent by evaporation, Poor thermal stability of solvent, High cost required High cost required Energy intensive, High cost, Scale-up of the facility needs further research Large equipment required for processing, High cost, Technological immaturity Energy intensive process. Energy intensive process

2

(Durmaz, 2018; Thakur et al., 2018) (Pires et al., 2011; Durmaz, 2018; Thakur et al., 2018) (Babu et al., 2015; Thakur et al., 2018) (Ziobrowski et al., 2016; Thakur et al., 2018)

Bioresource Technology 288 (2019) 121401

M. Irfan, et al.

Fig. 1. Different ways of sequestration and utilization of carbon dioxide.

ongoing for artificial photosynthesis with different semiconductor materials. This process does not contributes to a large extent for carbon dioxide reduction, but its importance cannot be ignored due to increasing concentration of carbon dioxide in the environment and the need to reduce it (Ampelli et al., 2015). The technologies may make get breakthrough in the near future. Microalgae are also an option for indirect biotransformation of carbon dioxide (Cheng et al., 2013; Alaswad et al., 2015; Dong et al., 2019; Li et al., 2019; Onumaegbu et al., 2018). Microbial carbon capture cells (MCCs) also make use of this technique and have the added advantage of carbon capture along-with power generation and wastewater treatment (Pandit et al., 2012). Microalgae have more potential for bio-fixation/indirect biotransformation of carbon dioxide than terrestrial plants. The liquid and gaseous biofuels reported to be produced by this technique include fatty acid methyl esters, biodiesel, bioethanol, acetone, ethanol, organic acids, biobutanol, biogas, biohydrogen and biomethane (Wang et al., 2015; Mehrabadi et al., 2017; Zhu et al., 2017; Amiri and Karimi, 2018; De Bhowmick et al., 2018). Indirect carbon dioxide bio-fixation/biotransformation for production of chemicals follows Calvin Benson cycle and is the most important biosynthetic process in nature because it is responsible for the consumption of 7 * 106 g carbon on the annual basis (Thauer, 2008). Indirect carbon dioxide biotransformation is only briefly discussed here because a lot of literature data already available on this topic.

technological processes available for direct microbial transformation of carbon dioxide and factors affecting their efficiency in operation is presented. It is followed by an analysis made for different value-added chemicals including methane, fatty acids, acetate and alcohols, produced by this technology. Afterwards, technoeconomic feasibility analysis for scaling-up the production of useful chemicals (ethanol, oxalic acid and acetic acid) by using this process and its comparison with previous reports are presented. Companies around the globe working on commercial level for carbon dioxide capture and utilization directly or indirectly are also enlisted along with their product applications. Finally, process challenges and future research directions related to this field are provided to yield a better understanding of the processes and insights into the bright future towards green, clean and sustainable environment. 2. Biotransformation of carbon dioxide There are two types of biotransformation of carbon dioxide: indirect biotransformation of carbon dioxide and direct biotransformation of carbon dioxide. They are further discussed in more details in the followings. 2.1. Indirect biotransformation of carbon dioxide Indirect biotransformation of carbon dioxide involves techniques which make use of carbon dioxide indirectly to produce useful chemicals. Photosynthesis is one type of indirect carbon dioxide biotransformation likely by microbial transformation or by bio-fixation/ bio-fixation using plants. This process produces biomass. Biomass is also used for medical and pharmaceutical purposes besides being foodstuff for humans and animals. There are many technologies available for the production of solid, liquid and gaseous fuels from biomass. The main steps of these technologies are: harvesting; pre-treatment; hydrolysis; fermentation and purification. Bioethanol, bio-char, syngas, biogas and biodiesel are some examples of products from these techniques (Zhang and Mabee, 2016; Oh et al., 2018; Sivaramakrishnan and Incharoensakdi, 2018; Hassan et al., 2018; Lane et al., 2018; Li et al., 2019). Due to its significance, research and development are also

2.2. Direct biotransformation of carbon dioxide In this process carbon dioxide is converted to valuable chemicals directly using biocatalysts. This process has much more potential than the indirect carbon dioxide biotransformation/bio-fixation towards carbon dioxide reduction and value-added chemicals production due to its operational setup and other connected benefits. The biological pathways that are used for direct carbon dioxide biotransformation are reductive TCA cycle and Wood Ljundahl cycle (Berg, 2011). Carbon dioxide is used as substrate in this process. Source of hydrogen, physical setup and biocatalyst are the additional requirements. Depending on biocatalysts (enzymes or microorganisms) it can be further identified as direct microbial or direct enzymatic transformation of carbon dioxide.

3

4

Products examples

Nature of process Cost Process response Environmental impact Optimum temperature range (◦C) Working ability with flue gases from different industries Complexity of process Nature of technique Requirement of arable land Potential to mitigate CO2 Factors affecting efficiency of process Biofertilizers, Biogas, Biohydrogen, Biomethane, Biodiesel, bioethanol, acetone, ethanol, organic acids and biobutanol

Complex process Old Yes Low Algal species, Temperature, Light intensity, etc.

Natural Microalgae

Bioreactor

Simple process Old No Low Intensity of sunlight, level of nutrients, etc. Bioethanol, biochar, syngas, biogas and biodiesel

Gasifier, Distillation column, etc. for processing biomass Natural Microorganisms

Equipment used

3–8%

Green process Costly Fast Environment friendly 15–35 Yes

0.5%

Photosynthetic Efficiency

Calvin Benson cycle

Indirect CO2 Biotransformation by Microalgae

Green process Cheap Slow Environment friendly 15–35 No

Calvin Benson cycle

CO2 fixation pathway

CO2 capture phenomenon Catalysts

Indirect CO2 Biotransformation by Plants

Parameter

Table 2 Comparison of direct and indirect carbon dioxide biotransformation.

Simple process New No High Type of microbial consortia, Applied voltage, Time of operation, etc. Methane, Acetate, Ethanol, Butanol, Fatty acids

Synthetic Microorganisms, Enzymes, Microbial community Green process Costly Fast Environment friendly Depends on the microbial culture used Yes

Reductive TCA cycle and Wood Ljungdahl cycle High Columbic efficiency is desirable in this case Bio-electro-synthesis cell

Direct CO2 Biotransformation/Microbialelectro-synthesis

(Fernandez et al., 2015; Cheah et al., 2016; Goli et al., 2016; Thakur et al., 2018; Li et al., 2019)

(Cheah et al., 2016; Venkata Subhash et al., 2017; Yadav and Sen, 2017; Thakur et al., 2018; Li et al., 2019)

References

M. Irfan, et al.

Bioresource Technology 288 (2019) 121401

Bioresource Technology 288 (2019) 121401

M. Irfan, et al.

Table 2 presents a comparison of different parameters for direct and indirect biotransformation of carbon dioxide. It is evident that direct biotransformation of carbon dioxide has more potential to mitigate carbon dioxide as compared to indirect biotransformation of carbon dioxide and is the focus of this review with respect to use of microorganisms as the biocatalyst i.e. direct MT as mentioned before. 2.3. Different processes for direct microbial transformation of carbon dioxide Processes for direct microbial transformation of carbon dioxide can be divided into different types depending upon the use source of reducing power. Fig. 2 shows the different strategies for this. The different sources of hydrogen are: molecular hydrogen; organic and inorganic substances including minerals and zero valent metals; substances for Interspecies electron transfer and electricity. With regard to the different sources of hydrogen, processes of direct microbial transformation of carbon dioxide are classified into two major categories: processes with the use of electricity and processes without the use of electricity. Processes without the use of electricity make use of different types of electron donors, interspecies electron transfer substances or molecular hydrogen. With the use of electricity, the processes involve an external source of electricity for electrolysis, interspecies electron transfer substances can be used additionally. There are three types of processes involving electricity, having some operational setup differences and these are: microbial fuel cells (MFCs); microbial electrolysis cells (MECs) and microbial electro-synthesis (MES).

Fig. 3. Simplified description of microbial electro-synthesis with simple anode and biocathode.

dioxide mitigation as well as high-value chemicals production (Szuhaj et al., 2016). A simplified process of a microbial electrosynthesis is shown in Fig. 3.

Fig. 2. Different sources of CO2 reduction to produce value-added chemicals.

Microbial fuel cells (MFCs) make use of a bio-anode and function by using the activity of microorganisms and organic materials to produce the electricity (Yasin et al., 2015; Saba et al., 2017). In microbial electrolysis cells (MECs) with a bio-anode is involved, but some electricity is supplied from external sources. It is used mostly in wastewater treatment and chemical production applications. The third process termed as microbial electro-synthesis is mainly used in direct carbon dioxide biotransformation applications. It incorporates a bio-cathode in the assembly. External electron/electricity is supplied for electrolysis and the reduction of carbon dioxide takes place at the bio-cathode. A bio-cathode can also be used in combination with the microbial electrolysis cell for the microbial electrosynthesis. Systems containing a membrane between anode and cathode are mostly used. This technique has the dual benefit of surplus electrical energy storage and carbon

2.4. Efficiency of direct microbial transformation of carbon dioxide Efficient operation of different direct CO2 MT processes is linked to certain factors such as flow and pressure of hydrogen and temperature of operation etc. These parameters must be optimized with respect to the microbial catalyst involved. The conditions suitable for one type of microorganism may not be for other microorganisms. Certain factors affecting the efficiency of different processes of direct microbial transformation are discussed first and then some factors specifically related to microbial electro-synthesis (MES) from carbon dioxide are mentioned separately due to different physical setups and operational parameters involved. Fig. 4 shows different factors affecting the efficiency of direct MT of carbon dioxide.

5

Bioresource Technology 288 (2019) 121401

M. Irfan, et al.

the use of external electricity and have a positive effect on the overall process by facilitating direct interspecies electron transfer (DIET) (Dong et al., 2019). Both the electron donors and redox mediators have a positive effect on the process of direct microbial transformation. 2.4.4. Operational time If time of direct CO2 MT is increased, the production increases probably due to the growth of the microorganisms until it achieves the maximum level if favorable conditions are provided (Marshall et al., 2013). This cannot be generalized for all the microbial synthesis processes, as there also exist certain other limiting factors such as aqueous chemistry, activity of microorganism, etc. in a specific process besides the type of biocatalyst affecting the time of the operation. 2.5. Efficiency of microbial electro-synthesis of carbon dioxide Different factors, in addition to those mentioned in the previous section, affecting the performance of microbial electro-synthesis from carbon dioxide are discussed separately mainly due to the different type of the setup involved in this process from other processes of direct microbial transformation of carbon dioxide. 2.5.1. Electrode materials Platinum (Kundu et al., 2013), nickel (Escapa et al., 2015) and carbon based electrodes with the doping of carbon nanotubes (Jourdin et al., 2016) have been used as cathode materials. Inexpensive carbon based cathode with the doping of materials such as palladium have also been reported to be useable (Escapa et al., 2015). While selecting a cathode for a typical application, one should consider both the efficiency in the relevant application and the cost, and an optimization should be made for all the operational parameters. Stainless steel and Ni alloys are a better choice keeping in mind the efficiency and cost (Kundu et al., 2013). Materials used for cathode effects the production rate, So, it must support the attachment of microbial culture to the electrode surface. Hydrogen is reported to be produced at a rate of 2.2 m3 m−2 per day using a graphite paper cathode in the presence of a mixed microbial culture (Jeremiasse et al., 2012). Another paper reported hydrogen production of 2.4 m3 m−2 per day with a graphite felt cathode with a mixed microbial culture (Croese et al., 2014). It depicts that production of hydrogen is also dependent on the colonization a cathode by the microbial culture on the cathode under the same conditions (LaBelle et al., 2014). Sometimes a microbial culture changes the properties of electrode and effects the production of the desired chemicals. Therefore, the material for the bio-cathode and the microbial culture should both be given due consideration during the process. A new technique of an inversion of a bio-anode after the biofilm development to bio-cathode has also been reported in the literature (Geelhoed and Stams, 2011). For anode, carbon is usually used because it is inexpensive. Carbon electrodes coated with carbon nanotubes are also reported to be efficient (Tsai et al., 2009). Graphene sponge due to its low cost and carbon felt because it produces high current densities due to its large surface area also used (Qiao et al., 2008; Desloover et al., 2012).

Fig. 4. Different factors affecting the efficiency of technological processes of direct microbial transformation of carbon dioxide.

2.4.1. Different types of microbial cultures and operational conditions Microorganisms can and be used in two different forms, either as pure culture or as mixed culture of different microbial community. Each of them can be more effective than the other depending on the process application used, but usually mixed culture offers more flexibility towards operational parameters such as substrate selection and substrate utilization, etc. (Freguia et al., 2010). Mixed culture adapts to the conditions of the bioreactor. Depending on the conditions, enrichment may be required and affects the process performance. The factors that play a vital role in this phenomenon are composition of the microbial community, type of the substrate used (Zhan et al., 2014), and type and configuration of the bioreactor. Type of the bioreactor is dependent upon the reactor design, if the single chamber is used for a reaction there might be some competing reactions that interfere with the product production, in the double chamber same reaction might yield better product (Pasupuleti et al., 2015). Such type of phenomenon must be taken into consideration in studying the performance of the process. 2.4.2. Type of the substrates The substrates and synthesis buffer used also affect the microbial community (LaBelle et al., 2014). A lot of literature is presented using different organic substrates and carbon dioxide as the carbon source for the process for microbial transformation (Jourdin et al., 2016). Microbial transformation using direct carbon dioxide as the only substrate is considered in this review article.

2.5.2. Electrode pretreatment A pretreatment of electrodes can have positive effect on the performance of the process. Surface area and material surface properties of the electrodes are the main electrode properties, which affect the operation (Qiao et al., 2008). The results of the use of different cathode materials for checking the effect of the surface area on different operational parameters have been shown in the literature. The surface area has a positive effect (Zhang et al., 2012). Different techniques for the pre-treatment of electrodes are: solvent cleaning; vacuum heat treatment; laser treatment; plasma treatment; electrochemical treatment. Solvent cleaning helps to remove contaminants, provides an active surface for further modification, but without creation of new active sites. Vacuum heat treatment and laser treatment provide new active sites but have the disadvantage of deactivation of the surface due to the formation of

2.4.3. Role of electron donors and mediators Some microorganisms and microbial consortia cannot take up electrons directly from the electron acceptor for their metabolism. Two options available in such cases are, either some microorganisms can produce redox mediators that are used by themselves or by other microorganisms present in the community involved or external mediators need to be added (Wang et al., 2013). In this way, coupling of electron transport with production of the desired product can be realized. It has been reported that chemicals other than redox mediators can be added for the purpose of electron transfer such as conjugated electrolytes (Yan et al., 2015; Park et al., 2018). Inorganic electron donors like magnetite are also used in microbial electro-synthesis. Electron donors are helpful for the microorganisms in their metabolism, increase the growth of the microorganisms even without 6

Bioresource Technology 288 (2019) 121401

M. Irfan, et al.

oxides on the surface from surrounding environment. Electrochemical and plasma pre-treatment are useful for the electrodes. Electrochemical pretreatment is a simple and cost-effective technique which not only cleans the electrode but also provides new active sites with a high density of electronic states (Rana et al., 2019). Plasma treatment is a safe technique, and used to enhance surface attachment properties of inorganic materials (PoncinEpaillard and Legeay, 2003). It changes the surface properties (hydrophilic properties) which impacts the cell attachment. In this way, start-up time is reduced, and current density is increased. When comparing the treatment of the electrodes with nitrogen, oxygen and argon, the nitrogen treatment is found to have better results (Cheng and Logan, 2007; Flexer et al., 2013). Ammonia treatment of the electrode is also reported to have positive results (Cheng and Logan, 2007). By using the electrode pretreatment, the efficiency of the inexpensive electrodes is increased and the requirements of using expensive catalysts can be minimized (Yang et al., 2015; Cai et al., 2016). Bio-cathodes have been reported also to be pretreated with nickel and carbon nanotubes with positive results (Guo et al., 2013). Another approach is the addition of conjugated oligo-electrolytes that enhance electron transfer between the electrode and bio medium (Yan et al., 2015) but there are still doubts with its feasibility (Wang et al., 2014).

going on in this field to reduce the cost and make use of the renewable energy resources. The possible approaches for making electricity available for use during the time of demand during the day are: to use direct electrical energy supply, solar energy, wind energy and the hybrid approach (Zhang et al., 2017). 2.5.6. Applied potential Another important factor is the applied potential (Fischer et al., 2015; He et al., 2016). Optimum conditions should be selected for the investment, microbial culture, operational factors and production capacity with respect to applied potential. It has been reported that useful chemicals can also be produced directly with the application of applied voltage from carbon dioxide by microbial transformations (Cheng et al., 2009). Applied potential and electricity are interlinked, but here described separately because current measurement is also important during operation in the MES for some cases. 3. Products from direct microbial transformation of CO2 Direct MT is a recent developing technique. It is used to produce chemicals in the presence of suitable biocatalyst. Different chemicals are reported to be produced using different substrates, here according to the scope of the review, the chemicals produced using carbon dioxide as a substrate are summarized. The products from direct microbial transformation of carbon dioxide are divided into several categories, which are discussed in this section briefly.

2.5.3. Reactor design The reactor design is an important step towards the successful operation of the process. New innovations are first tested at small scale in laboratories and if successful, can be tried at the large-scale implementation. In many cases, reactor design selected is similar to design of the MFCs under the same conditions. Cost is one major factor in selecting reactor design. Chambers should be designed in a way to increase the area of the fluid path so that it behaves like a plug flow reactor and multiple feeds can be considered. The usual design options are: single chamber design and double chamber design. A single chamber design is simple, easy to scaleup and is also reported to have almost the same efficiency as a double chamber for some applications (Sasaki et al., 2012). A standard double chamber cell design is more efficient than single chamber cell design and is often used (Call and Logan, 2008). Membranes can be avoided to reduce the cost. Double chamber without membrane is also reported and with the similar performance and output. This type of application depends on the applied potential and microbial consortia involved in the system. An optimized design scheme cannot be generalized rather it depends on several factors such as the type of application, capacity, feasibility of operation, scale-up, cost, and other operating constraints. Design should be such that minimum fouling is occurring. Other parameters that need consideration are the operating temperature and the distance between the electrodes. The lower the temperature, the lower will be the current (Lu et al., 2012; Heidrich et al., 2013) and the smaller the distance between the electrodes, the higher will be current (Cheng and Logan, 2011). The optimum operational temperature also depends upon the microbial culture.

3.1. Methane Methane is a useful energy carrier, and has not the limitations of storage and transportation as compared with hydrogen. Methane has been reported to be produced through direct MT using bio-anode and biocathode in different applications. Methane along with hydrogen, acetate and format was reported to be produced by mixed microbial culture using carbon dioxide as the only substrate already in 2012 (Marshall et al., 2012). Methane is also reported to be produced during low temperature anaerobic digestion followed by fermentation to acetic acid (Yasin et al., 2015). 3.2. Acetate One of the major of products from direct CO2 MT is acetate. Acetate is derived from acetones (Van Eerten-Jansen et al., 2013a). Generally, the production occurs using hydrogen as electron donor, but some acetogenic bacteria also use electricity for production of acetate (Nevin et al., 2011). It is reasonable to mention acetate separately from fatty because it is the main intermediate of most of the biochemical operations and can be used to produce valuable chemicals other than fatty acids (Bajracharya et al., 2016).

2.5.4. Reactor scale-up For the scale-up of the reactor, the design should be simple and be able to allow the operational changes, if required. Scale-up is feasible, as reported in the literature, but problems of large potential required at the electrode and less energy recovery need to be addressed (Heidrich et al., 2013). For reactors with different capacities, one important factor to consider is the ratio of the volume of the reactor versus electrode surface area. For a given surface area of the electrodes, a reactor with reduced volume may produce good results, but at the same time this volume must be sufficient for the electrolyte to sustain and other connected parameters should also stay within allowable limits (Farhangi et al., 2014). Two companies namely “Cambrian innovation” and “Emefcy” are currently working on manufacturing of industrial scale bio-electro-synthesis (BES) reactors for wastewater treatment based on MFC technology. One comprehensive review about concepts of a rector design is also cited (Krieg et al., 2014).

3.3. Fatty acids Another line of products are fatty acids. Fatty acids can be used to produce biofuels, animal feed and are used in many industries such as paper and pulp, polymer, soap and surfactant and pharmaceutical industries (Van Eerten-Jansen et al., 2015). 3.4. Alcohols Alcohols are another line of commercially useful multi carbon compounds in addition to fatty acids and acetates produced by direct carbon dioxide MT. The literature to produce methane, acetate, fatty acids and alcohols from direct microbial transformation of carbon dioxide is presented in Table 3. 3.5. Other useful products

2.5.5. Electricity source The source of electricity is an important factor and a lot of work is

The process of direct MT/MES can also produce other useful 7

8

CH4 CH4 CH4 CH4 CH4 CH4 CH4 CH4 CH4 CH4 Acetate & oxybutyrate Acetate, oxobutyrate & format Acetate Acetate Formic acid H2 & acetate H2 & acetate Acetate Acetate, propionate, butyrate, butanol ethanol and H2 Butyrate Isopropanol Acetate H2, & ethanol Acetate Acetate Acetate H2, CH4 & acetate H2, CH4 & acetate CH4, Acetate CH4, Acetate

Enriched mixed culture Methanobacterium palustre ATCC BAA-1077 Enriched mixed culture Enriched mixed culture Enriched mixed culture Enriched mixed culture Methanobacterium thermoautotrophicus Mixed culture WWTP sludge Defined mixed cultures dominant microbe methanobacterium sp Enriched mixed culture Sporomusa ovate Clostridium ljungdahlii Moorella thermoacetica Sporomusa ovate Enriched mixed culture Adapted mixed acetogen from brewery WW sludge

Mixed culture domestic WWTP sludge Mixed culture sludge Enriched culture from bog sediment

WW: Wastewater TP: Treatment Plant. a Calculated at standard conditions and unit of projected cathode surface area = (L/m2 d1). b Maximum production.

Enriched mixed culture Engineered Ralstonia eutropha Clostridium ljungdahlii Pond sediments and WWTP sludge Enriched mixed culture Mixed microbial culture dominated by Clostridiales Brewery WW sludge Mixed culture WW Enriched mixed culture Enriched mixed culture

Product

Microbial catalyst

Double chamber-Batch Double chamber-Batch Double chamber batch fed Double chamber batch fed Double chamber-Batch Double chamber-Batch Double chamber-Batch Double chamber batch fed Single chamber-Batch Single chamber-Batch

−0.8 – −1.1 −1.05 −0.9 to −1 +0.21 −0.79 −1.1 0 0

−0.9 to −1.1 −1 to −1.15 −0.6

−0.4 −0.8 −0.9 −0.9 −0.7 −1.25 −1.5 −1 to −1.15 −0.7 0 −0.6 −0.6 −0.6 −0.6 −1.58 −0.79

Double chamber-Batch Double chamber-Batch Double chamber-Batch Single-chamber-Batch Double chamber-Batch Single chamber-Batch Single chamber-Batch Double chamber-Batch Double chamber-Batch Single chamber-Batch Double chamber Batch Double chamber Batch Double chamber Batch Double chamber-Batch Series stacked MFCs Double chamber-Batch Double chamber-Batch Double chamber-Batch Double chamber-Batch

Applied potential (V)

Mode of operation

Table 3 Production of different chemicals (methane, acetate, fatty acids and alcohols) in the literature using carbon dioxide as substrate.

37.89 g m−2 d−1 78.49 µmol/(l·d), 0.15 mol/l 102.3 µmolb, 4.8 µmol/(l.d)

1.82 mM C/d 216 mg/l 19.19 g/m2 d 1.3 mm/cm2 d1 400 mg/ld 19.2 g/m2 d1

(Chaudhuri and Lovley, 2003) (Cheng et al., 2009) (Villano et al., 2010) (Rader and Logan, 2010) (Van Eerten-Jansen et al., 2012) (Kobayashi et al., 2013) (Sato et al., 2013) (Jiang et al., 2013) (Van Eerten-Jansen et al., 2013a,b) (Ma et al., 2018a) (Nevin et al., 2010) (Nevin et al., 2010) (Nevin et al., 2010) (Nevin et al., 2010) (Zhao et al., 2012) (Marshall et al., 2013)

8.7a 0.26a 9.2a 1.8a 1.4a 10a 1.0a 129.32 ml/d 4.1a 147 µmolb – – – 282 mM/d m2 4.27 mg/l1h1 1.04 g/l d 0.2 g/l d 0.38 mM/d 94.73 mg/d –

(Ganigué et al., 2015) (Torella et al., 2015) (Bajracharya et al., 2015) (Jourdin et al., 2016) (Bajracharya et al., 2017) (Gildemyn et al., 2017) (Marshall et al., 2012) (Bajracharya et al., 2015) (Ma et al., 2018b) (Ma et al., 2019)

(Min et al., 2013) (Jiang et al., 2013) (Zaybak et al., 2013)

Reference

Production rate

M. Irfan, et al.

Bioresource Technology 288 (2019) 121401

Bioresource Technology 288 (2019) 121401

M. Irfan, et al.

chemicals in addition to methane, acetate, fatty acids and alcohols. One example is the use of urine for the energy generation (Kuntke et al., 2012). Hydrogen peroxide and caustic soda are other products produced in this respect (Rozendal et al., 2009; Jarvis and Samsatli, 2018). Overall, direct microbial transformation has the potential to reduce the environmental and energy problems largely.

2CO2 + 3H2 O

2C2 H6 O+ 3O2 ( G (J/mole) =

1328)

(3)

It is evident from the reactions that production of the acetic acid, oxalic acid and ethanol is thermodynamically feasible. 4.3. Initial assessment An initial assessment is made based on energy derived from thermodynamics and market price analysis of the products. Energy requirement for acetic acid, oxalic acid and ethanol is 4.06, 1.01 and 8.02 MWh per ton. Considering the standard conditions of temperature and pressure and a standard electrical energy efficiency of 30% and electricity price as 230 RMB per MWh (National Energy Board, 2018), the energy cost for acetic acid, oxalic acid and ethanol is 3112, 774 and 6148 RMB per ton respectively. The market price (Alibaba-2018) for the products is also taken as an estimate and based on this, market value for acetic acid, oxalic acid and ethanol is 4920, 5480 and 3390 RMB per ton respectively. This shows that initial assessment results are positive for acetic and oxalic acid as the market values are higher than the cost of energy required while for ethanol market values are less than cost of energy required, thus making this process non-viable for it. In

4. Applications and scale-up feasibility of the direct microbial transformation of CO2 New technologies are interesting for investors only if they are environmentally friendly and techno-economically feasible. Thus, technologies must be cross-matched technically with existing old technologies (Dimitriou et al., 2015). In this section, technoeconomic feasibility analyses for the scale up of the microbial transformation of carbon dioxide to acetic acid, oxalic acid and ethanol are made and reviewed. The process of carbon dioxide microbial electrosynthesis is considered, because it is the mostly used one for large scale applications. The loop diagram for the economic feasibility analyses of the processes is shown in Fig. 5.

Fig. 5. Loop diagram for economic feasibility analysis.

this calculation, 1 ton is equal to 1000 kgs. RMB (Renminbi) is Chinese currency and 1 RMB = 0.15 US dollar.

4.1. Market survey and possible strategies The market survey is a technique to evaluate whether there is a profitable gap in the market with respect to the demand and supply of the considered chemicals. If supply and demand are balanced or supply is more than the demand, there will be no need to invest in the new process. Only if the new process is cheaper than the existing ones, chances for the establishment exist. The other possible strategy to enter in this kind of market is either to produce same product by introducing some innovation. However, if the demand is high and the supply is low, then there are no problems. The chemicals under consideration are highly valuable and demanded chemicals in the industries making the survey for market entry surely positive.

4.4. Capital investment One electrolysis cell consisting of three compartments is considered for the operational setup. Setup contains one central compartment is closed by the cathode compartments from both sides and separated by gas permeable membranes. Different fixed capital costs related to the equipment are shown in Table 4. The costs used in this study include marginal increase with time. These costs sum up to almost 67 kRMB per unit. Inventory account generally requires electrodes, membranes and assembly repairing and its capital cost usually varies between 20 and 30% of the fixed capital investment (13.4–20.100 kRMB). A standard large-scale setup contains 250 units, So the total investment is about 17 million RMB. As the assembly also requires electrical, civil, material requirements, pretreatment facility at the start and product separation facility at the end (25% of cost) respectively so those costs must also be added. These costs are estimated to be around 83.7 kRMB. Thus, a total capital cost of around 21.5 million RMB is resulting.

4.2. Technical feasibility of the process Market survey and technical feasibility go side by side. Technical feasibility involves different technical aspects of the process including mainly the thermodynamic feasibility. In this case, thermodynamic feasibility means the screening of the different thermodynamic parameters towards the production of acetic acid, oxalic acid and ethanol. The chemical reactions in this case are:

2CO2 + 2H2 O

C2 H 4 O2 + 2O2 ( G (J/mole) =

876)

(1)

4CO2 + 2H2 O

2C2 H2 O4 + O2 ( G (J/mole) =

328)

(2)

4.5. Operational costs The biocatalyst is an essential requirement. Other operational costs include purchasing cost for off gas, pretreatment, product purification, 9

Bioresource Technology 288 (2019) 121401

M. Irfan, et al.

Table 4 Different capital and fixed costs involved in the economic feasibility analysis for scale-up of carbon dioxide microbial electrosynthesis. Item Electrode Membrane Current collector Piping Metal coating on electrode Fixed cost for the skid Assembly Polymer framing Electricity Off gases CO2 as a revenue stream Pretreatment of gases Product separation Storage and Transportation cost Labor cost

Cost

Reference 2

150 RMB/m 75 RMB/m2 75 RMB/Electrode 150 RMB/Electrode 75 RMB/Electrode 1515 RMB 50% of material cost 190 RMB/m2 230 RMB/MWh 110–380 RMB/ton 55 RMB/ton 75 RMB/ton 75 RMB/ton 200 RMB/ton 62,029 RMB per person per year

(Rozendal et al., 2008) (Fumatech, 2018) (Lu et al., 2012; Rozendal et al., 2008) (ElMekawy et al., 2016) (Pires et al., 2012) (Fumatech, 2018) (National Energy Board, 2018) (Pires et al., 2012) (Investing.com, 2018) (Xu et al., 2014) Product is a mixture of 80:20 with 80% water and heat required to evaporate water gives cost. (Pires et al., 2012) (China Labour Costs, 2018)

utilities like air, nitrogen, electricity, transportation, storage and labor. Estimates for different operational costs are given in Table 4. The water cost is taken at an average of 2.5 RMB per cubic meter, since it varies from one location to another. It is to be noted that electricity cost is taken as 230 RMB/MWh as average, fluctuations in price on an hourly basis are not taken in account, because it depends upon the production strategy of the investor. Similarly, off-gases are considered to be purchased at an average cost of 200 RMB per ton. Costs related to China are considered for calculation on a general basis. Consumption of carbon dioxide is taken as revenue stream.

4.8. Overall economic feasibility analysis and limiting factors From the analysis given in Table 5, it can be concluded that the production of oxalic acid is economically more feasible than acetic acid. This process contributes largely towards mitigation of carbon dioxide from atmosphere. This is the reason for taking the carbon dioxide consumption as the base load to calculate an overall production rate, which depicts the focus on the green environment in addition to valueadded chemicals production. The limiting factors in this process are efficiency of energy usage in the equipment, frequency of maintenance, conversion rate of carbon dioxide, operational strategy of the plant and usage of utilities at optimum conditions. The market value of the products, energy requirement and location of the plant are also equally important factors as they affect the transportation and operating costs and revenue respectively.

4.6. Consumption of carbon dioxide and production of organic acids For different conversion rates of carbon dioxide, the consumption of this gas to produce acetic acid and oxalic acid are shown in Table 5. With the increased conversion of carbon dioxide, the overall consumption of carbon dioxide and production of acetic acid and oxalic acids increases. Higher conversion leads to optimized usage of utilities and maximum profit.

4.9. Comparison of overall feasibility analysis with previous studies One report discussing the feasibility analysis for the production of formic, acetic and oxalic acid is cited (ElMekawy et al., 2016). This report takes the chemicals production capacity as the overall basis of the case study instead of the total carbon dioxide consumption in our case. Both these studies are based on different conditions and a different overall basis. So, an exact comparison cannot be made. Depending on the similar aspects in both studies, the results are compared in Table 5. It is indicated that the frequency of change of electrode is influencing the discounted pay-back period. The main cause of differences in the results of discounted pay-back period is the change in operational costs depending on the location of the plant. Reduction in the overall investment lowers the discounted pay-back period. The effects of change in the conversion rate of carbon dioxide on its total consumption and consequently, the production of organic acids is also evident. Overall, both the studies yield positive results for the overall economic feasibility and hence indicate that a scale-up of carbon dioxide biotransformation is feasible and will have fruitful environmental perspectives.

4.7. Discounted payback period and net present value The total investment has been calculated by a summation of all fixed and operating costs, and from the revenue of the production output at market price. The overall feasibility is realized in terms of discounted payback period and net present value (worth). The formula for the discounted payback period is: DPP = ln [1/{1 − (O1 × r)/CF}]/ln (1 + r), here, O1 = Initial investment; r = Rate; CF = Periodic cash flow and DPP = Discounted pay-back period. While the formula for the net present value is: NPV = −C0 + {C1/(1 + r)1} + {C2/ 2 T (1 + r) } + … + {CT/(1 + r) }, here are, NPV = Net present value; C0 = Initial investment; r = Discount rate; C = Cash flow and T = Time. A nominal discount rate of 10% and time of 10 years is considered for the feasibility analysis and consumed carbon dioxide is taken as the revenue stream. The results presented in Table 5 show that production of both oxalic acid and acetic acid is feasible.

10

11

Electrical efficiency (%)

Our result

22.19 30.57 22.19 30.57

For electrode change two times in a year 50 30 14.79 20.5 75 30 20.38 30.8

Our result

20.5 30.8

ElMekawy et al., 2016

20.5 30.8

20.5 30.8

ElMekawy et al., 2016

21.7 29.9

21.7 29.9

Our result

21.7 29.9

30.1 45.2

ElMekawy et al., 2016

30.1 45.2

21.7 29.9

Our result

Oxalic acid

Acetic Acid

Acetic acid

Oxalic acid

CO2 consumption (kton/yea

Production (kton/year)

For electrode change one time in a year 50 30 14.79 75 30 20.38

CO2 conversion (g/m2h)

20.1 30.1

20.1 30.1

ElMekawy et al., 2016

314.3 438.1

340.9 481.1

Our result

Acetic acid

N/A N/A

N/A N/A

ElMekawy et al., 2016

NPV10 (MRMB)

646.1 916.4

666.5 939.4

Our result

Oxalic acid

N/A N/A

N/A N/A

ElMekawy et al., 2016

Table 5 Results of economic feasibility analysis for scale-up of carbon dioxide microbial electrosynthesis (MES) in our case and its comparison with ElMekawy et al. (2016).

2.113 2.05

1.655 1.5

Our result

Acetic acid

– 20

– –

ElMekawy et al., 2016

0.92 0.743

0.731 0.590

Our result

Oxalic acid

Discounted pay-back period (Years)

3.2 1.4

1.8 1

ElMekawy et al., 2016

M. Irfan, et al.

Bioresource Technology 288 (2019) 121401

Bioresource Technology 288 (2019) 121401

M. Irfan, et al.

5. Commercialization Finally, a commercialization follows, because the new techniques must have a potential for industrial application on a large scale and fulfill the increasing demand. Having analyzed and reviewed the technical and economic feasibility for the scale-up of microbial electrosynthesis from carbon dioxide, here in Table 6, some of the companies using carbon dioxide at the commercial scale are summarized along-with their products and applications in the following scenarios: carbon dioxide conversion to value-added chemicals; carbon dioxide capture; direct use of carbon dioxide in different application and carbon dioxide capture and conversion to value-added chemicals.

•

milder conditions than the other available processes, still it remains a costly technique. The infrastructure required is expensive since the infrastructure is available for the classical chemical processes but not for the new ones. The process also needs development in terms of the purity of the product. In addition, there is a need to integrate the different stages of the process and optimize the parameters to minimize the process cost and maximize the production rate and quality. In this respect, mathematical modeling tools need to be developed and/or for optimization of process parameters and integration of the process. They will also provide a better way for understanding the different aspects of the process. Having in mind the techniques of EOR and ECBM and the im-

Table 6 Different carbon dioxide capture and utilization companies in operation on the commercial scale around the globe. Type of Utilization

Company Name

Product

Application

Reference

Conversion to value-added chemicals

Carbon Clean Solutions™

Soda ash

Food/Fire extinguisher industry

Newlight Technologies™

AirCarbon plastics

Plastic industry

Dell Algenol™ Cambrian Innovation Joule Energy™ Novomber™ Bayer Material Science™ Liquid Light™ Carbon Engineering™ Climeworks™ Petra Nova Project Shell Global Thermostat Chevron NRG Energy Fuel Cell Energy ExxonMobbil Strata Worlwide Ayala Land Inc. Dyecoo Textile Systems™ PRAXAIR™ Great Point Energy™ XPRIZE CO2 solutions Inc Technology™

Carbon neutral packaging Ethanol Bioreactor Fuel Polypropylene carbonate Polyols Ethylene glycol N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A High pressure CO2 Cryogenic agent High pressure CO2 Fuel Pure CO2

Packaging industry Green energy Biochemical industry Energy Polymer industry Plastic industry Plastic industry N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A Dyeing operation Food industry (Cooling, chilling etc.) Enhanced oil recovery process Energy Using enzyme enhanced efficiency solvent-based CO2 capture

(Carbon Clean Solutions, 2018) (Newlight Technologies, 2018) (Dell, 2018) (Algenol, 2018) (Cambrian Innovation, 2018) (Joule Energy, 2018) (Novomer, 2018) (Bayer, 2018) (Liquid Light, 2018) (Carbon Engineering, 2018) (Climeworks, 2018) (Petra Nova, 2018) (Shell, 2018) (Global Thermostat, 2018) (Chevron Corporation, 2018) (NRG Energy, 2018) (Fuelcell Energy, 2018) (ExxonMobil, 2018) (Strata Worldwide, 2018) (Ayala Land Inc, 2018) (Dyecoo, 2018) (Praxair, Inc., 2018) (GreatPoint Energy, 2018) (XPRIZE, 2018) (CO2 Solutions Inc., 2018)

Carbon capture

Direct utilization CO2 capture and conversion to valueadded chemicals

6. Challenges and future research directions A sustainable environment and green energy production are global challenges. Sustainability can be achieved by increasing the efficiency of machines emitting carbon dioxide, reducing the carbon dioxide in an eco-friendly manner and increasing the production and usage of the renewable fuels. The process of direct microbial transformation of carbon dioxide is one of the options, which will lead to a sustainable environment by reducing carbon dioxide levels and the production of green energy plus value-added chemicals. Although this emerging technology is promising, it has a lot of challenges and shortcomings until now indicating the immediate focus of future research. These need to be addressed and overcome to make this technique generally usable and more successful. Some of the challenges and future research directions are presented here.

•

•

• One key parameter is the biocatalyst. The biocatalyst must be se-

•

•

lected based on the best performance in the process. It is noted that sometimes a microbial community caused effects that some of the community members inhibit the production. Thus, the selection and development of the right kind of biocatalyst is a challenging factor in this process and needs more research in respect of selectivity and productivity (adaptation, genetic modification, etc.). Although direct microbial carbon dioxide transformation occurs at 12

portance of carbon dioxide biotransformation, the future work should also be focused on the studies for the direct microbial transformation of carbon dioxide into useful chemicals in the petroleum reservoirs, meaning in-situ carbon dioxide microbial transformation. The electron transfer mechanism is one of the key questions in this area and considerable research work is ongoing. Still understanding is limited indicating more efforts are needed in this field. Different electron donors and mediators also need to be explored in detail for the study of their interaction with microorganisms and their effect on the reaction pathway. The development of alternative pathways which might be more energy efficient is thus a possible future direction. Carbon dioxide conversion to carbon monoxide and the further use of this compound for the production of different value-added chemicals in an economical manner is also another promising alternative. The reaction rate of direct microbial carbon dioxide transformation is low. The scale-up of the process is challenging. There is a need to develop industrial scale bioreactors suited to the process requirements to enhance the capacity. In addition, strategies and tools should be developed, which use the iterative approach for a reliable scale-up of the production facility without compromising the

Bioresource Technology 288 (2019) 121401

M. Irfan, et al.

product purity. The technoeconomic feasibility analysis in Section 4 and different commercial applications of such processes as enlisted in Section 5 give brief insight into this aspect of the process and indicate its bright future.

in mediator less microbial fuel cells. Nat. Biotechnol. 21, 1229–1232. Cheah, W.Y., Ling, T.C., Juan, J.C., Lee, D.-J., Chang, J.-S., Show, P.L., 2016. Biorefineries of carbon dioxide: From carbon capture and storage (CCS) to bioenergies production. Bioresour. Technol. 215, 346–356. https://doi.org/10.1016/j.biortech.2016.04.019. Chen, Y., Jiang, W., Liang, D.T., Tay, J.H., 2008. Biodegradation and kinetics of aerobic granules under high organic loading rates in sequencing batch reactor. Appl. Microbiol. Biotechnol. 79, 301–308. https://doi.org/10.1007/s00253-008-1421-6. Cheng, J., Huang, Y., Feng, J., Sun, J., Zhou, J., Cen, K., 2013. Mutate Chlorella sp by nuclear irradiation to fix high concentrations of CO2. Bioresour. Technol. 136, 496–501. Cheng, S., Logan, B.E., 2011. High hydrogen production rate of microbial electrolysis cell (MEC) with reduced electrode spacing. Bioresour. Technol. 102, 3571–3574. Cheng, S., Logan, B.E., 2007. Ammonia treatment of carbon cloth anodes to enhance power generation of microbial fuel cells. Electrochem. Commun. 9, 492–496. Cheng, S., Xing, D., Call, D.F., Logan, B.E., 2009. Direct biological conversion of electrical current into methane by electromethanogenesis. Environ. Sci. Technol. 43, 3953–3958. Chevron Corporation, https://www.chevron.com/ (accessed 26.11.18). China Labour Costs, 2012-2018, https://tradingeconomics.com/china/labour-costs (accessed 26.11.18). Climeworks, http://www.climeworks.com/ (accessed 26.11.18). Clomburg, J.M., Crumbley, A.M., Gonzalez, R., 2017. Industrial biomanufacturing: the future of chemical production. Science (80) 355. https://doi.org/10.1126/science. aag0804. CO2 Solutions Inc., http://www.co2solutions.com/en (accessed 26.11.18). Croese, E., Jeremiasse, A.W., Marshall, I.P.G., Spormann, A.M., Euverink, G.J.W., Geelhoed, J.S., Stams, A.J.M., Plugge, C.M., 2014. Influence of setup and carbon source on the bacterial community of biocathodes in microbial electrolysis cells. Enzyme Microb. Technol. 61–62, 67–75. De Bhowmick, G., Sarmah, A.K., Sen, R., 2018. Lignocellulosic biorefinery as a model for sustainable development of biofuels and value added products. Bioresour. Technol. 247, 1144–1154. https://doi.org/10.1016/J.BIORTECH.2017.09.163. De Silva, G.P.D., Ranjith, P.G., Perera, M.S.A., 2015. Geochemical aspects of CO2 sequestration in deep saline aquifers: a review. Fuel 155, 128–143. Dell, http://www.dell.com/en-us (accessed 26.11.18). Desloover, J., Arends, J.B.A., Hennebel, T., Rabaey, K., 2012. Operational and technical considerations for microbial electrosynthesis. Biochem. Soc. Trans. 40, 1233–1238. Dimitriou, I., García-Gutiérrez, P., Elder, R.H., Cuéllar-Franca, R.M., Azapagic, A., Allen, R.W.K., 2015. Carbon dioxide utilisation for production of transport fuels: process and economic analysis. Energy Environ. Sci. 8, 1775–1789. Dong, D., Aleta, P., Zhao, X., Choi, O.K., Kim, S., Lee, J.W., 2019. Effects of nanoscale zero valent iron (nZVI) concentration on the biochemical conversion of gaseous carbon dioxide (CO2) into methane (CH4). Bioresour. Technol. 275, 314–320. https://doi. org/10.1016/J.Biortech. 2018.12.075. Durmaz, T., 2018. The economics of CCS: Why have CCS technologies not had an international breakthrough? Renew. Sustain. Energy Rev. 95, 328–340. https://doi.org/ 10.1016/j.rser.2018.07.007. Dyecoo, http://www.dyecoo.com/ (accessed 26.11.18). ElMekawy, A., Hegab, H.M., Mohanakrishna, G., Elbaz, A.F., Bulut, M., Pant, D., 2016. Technological advances in CO2 conversion electro-biorefinery: a step toward commercialization. Bioresour. Technol. 215, 357–370. Escapa, A., San-Martín, M.I., Mateos, R., Morán, A., 2015. Scaling-up of membraneless microbial electrolysis cells (MECs) for domestic wastewater treatment: Bottlenecks and limitations. Bioresour. Technol. 180, 72–78. ExxonMobil, http://corporate.exxonmobil.com/ (accessed 26.11.18). Farhangi, S., Ebrahimi, S., Niasar, M.S., 2014. Commercial materials as cathode for hydrogen production in microbial electrolysis cell. Biotechnol. Lett. 36, 1987–1992. Farrelly, D.J., Everard, C.D., Fagan, C.C., McDonnell, K.P., 2013. Carbon sequestration and the role of biological carbon mitigation: a review. Renew. Sustain. Energy Rev. 21, 712–727. Fernandez, Y.B., Green, K., Schuler, K., Soares, A., Vale, P., Alibardi, L., Cartmell, E., 2015. Biological carbon dioxide utilisation in food waste anaerobic digesters. Water Res. 87, 467–475. Fischer, K.M., Batstone, D.J., van Loosdrecht, M.C.M., Picioreanu, C., 2015. A mathematical model for electrochemically active filamentous sulfide-oxidising bacteria. Bioelectrochemistry 102, 10–20. Flexer, V., Marque, M., Donose, B.C., Virdis, B., Keller, J., 2013. Plasma treatment of electrodes significantly enhances the development of anodic electrochemically active biofilms. Electrochim. Acta 108, 566–574. Freguia, S., Tsujimura, S., Kano, K., 2010. Electron transfer pathways in microbial oxygen biocathodes. Electrochim. Acta 55, 813–818. Fuelcell Energy, https://www.fuelcellenergy.com/ (accessed 26.11.18). Fumatech, http://www.fumatech.com/Startseite/index.html (accessed 26.11.18). Ganesh, I., 2014. Conversion of carbon dioxide into methanol – a potential liquid fuel: fundamental challenges and opportunities (a review). Renew. Sustain. Energy Rev. 31, 221–257. Ganigué, R., Puig, S., Batlle-Vilanova, P., Balaguer, M.D., Colprim, J., 2015. Microbial electrosynthesis of butyrate from carbon dioxide. Chem. Commun. 51, 3235–3238. Geelhoed, J.S., Stams, A.J.M., 2011. Electricity-assisted biological hydrogen production from acetate by Geobacter sulfurreducens. Environ. Sci. Technol. 45, 815–820. Gildemyn, S., Verbeeck, K., Jansen, R., Rabaey, K., 2017. The type of ion selective membrane determines stability and production levels of microbial electrosynthesis. Bioresour. Technol. 224, 358–364. Global Thermostat, http://globalthermostat.com/ (accessed 26.11.18). Goli, A., Shamiri, A., Talaiekhozani, A., Eshtiaghi, N., Aghamohammadi, N., Aroua, M.K., 2016. An overview of biological processes and their potential for CO2 capture. J.

7. Conclusions Without hesitation one can say that despite certain challenges, the direct carbon dioxide microbial transformation has good chances to be implemented by the chemical industry in the near future. Utilization of carbon dioxide to produce value-added chemicals will help to mitigate global warming, reduce the reliance on fossil fuels and increase the usage of renewable fuels. It has novel advantages over conventional technologies such as in situ usage of the feedstock, capability to include innovation, mild process conditions, product flexibility and energy efficiency. These prominent features allow us to expect a bright future of this process for a sustainable environment. Acknowledgements This work was supported by the National Science Foundation of China [41530318, 41403066]; the Research Foundation of Shanghai, China [15JC1401400]; the Fundamental Research Funds for the Central Universities of China [222201817017, 22221818014], The Research Program of State Key Laboratory of Bioreactor Engineering and the University of Engineering and Technology KSK Campus, Lahore, Pakistan. References Alaswad, A., Dassisti, M., Prescott, T., Olabi, A.G., 2015. Technologies and developments of third generation biofuel production. Renew. Sustain. Energy Rev. 51, 1446–1460. Algenol, http://algenol.com/ (accessed 26.11.18). Alshehry, A.S., Belloumi, M., 2015. Energy consumption, carbon dioxide emissions and economic growth: the case of Saudi Arabia. Renew. Sustain. Energy Rev. 41, 237–247. Amiri, H., Karimi, K., 2018. Pretreatment and hydrolysis of lignocellulosic wastes for butanol production: challenges and perspectives. Bioresour. Technol. 270, 702–721. https://doi.org/10.1016/J.Biortech. 2018.08.117. Ampelli, C., Perathoner, S., Centi, G., 2015. CO2 utilization: an enabling element to move to a resource- and energy-efficient chemical and fuel production. Philos. Trans. R. Soc. A-Mathematical Phys. Eng. Sci. 373. Ayala Land Inc., https://www.ayalaland.com.ph/ (accessed 26.11.18). Babu, P., Linga, P., Kumar, R., Englezos, P., 2015. A review of the hydrate based gas separation (HBGS) process for carbon dioxide pre-combustion capture. Energy 85, 261–279. Bacik, D.B., Yuan, W., Roberts, C.B., Eden, M.R., 2011. Systems analysis of benign hydrogen peroxide synthesis in supercritical CO2. Comput. Aided Chem. Eng. 29, 392–396. Bajracharya, S., Ter Heijne, A., Dominguez Benetton, X., Vanbroekhoven, K., Buisman, C.J.N., Strik, D.P.B.T.B., Pant, D., 2015. Carbon dioxide reduction by mixed and pure cultures in microbial electrosynthesis using an assembly of graphite felt and stainless steel as a cathode. Bioresour. Technol. 195, 14–24. Bajracharya, S., Vanbroekhoven, K., Buisman, C.J.N., Pant, D., Strik, D.P.B.T.B., 2016. Application of gas diffusion biocathode in microbial electrosynthesis from carbon dioxide. Environ. Sci. Pollut. Res. 23, 22292–22308. https://doi.org/10.1007/ s11356-016-7196-x. Bajracharya, S., Yuliasni, R., Vanbroekhoven, K., Buisman, C.J.N., Strik, D.P.B.T.B., Pant, D., 2017. Long-term operation of microbial electrosynthesis cell reducing CO2 to multi-carbon chemicals with a mixed culture avoiding methanogenesis. Bioelectrochemistry 113, 26–34. Bayer–Global, https://www.bayer.com/ (accessed 26.11.18). Berg, I.A., 2011. Ecological aspects of the distribution of different autotrophic CO2 fixation pathways. Appl. Environ. Microbiol. 77, 1925–1936. Cai, W., Liu, W., Han, J., Wang, A., 2016. Enhanced hydrogen production in microbial electrolysis cell with 3D self-assembly nickel foam-graphene cathode. Biosens. Bioelectron. 80, 118–122. Call, D., Logan, B.E., 2008. Hydrogen production in a single chamber microbial electrolysis cell lacking a membrane. Environ. Sci. Technol. 42, 3401–3406. Cantrell, K.B., Ducey, T., Ro, K.S., Hunt, P.G., 2008. Livestock waste-to-bioenergy generation opportunities. Bioresour. Technol. 99, 7941–7953. https://doi.org/10.1016/ J.Biortech. 2008.02.061. Carbon Clean Solutions, http://www.carboncleansolutions.com/home (accessed 26. 11.18). Carbon Engineering, http://carbonengineering.com/ (accessed 26.11.18). Chaudhuri, S.K., Lovley, D.R., 2003. Electricity generation by direct oxidation of glucose

13

Bioresource Technology 288 (2019) 121401

M. Irfan, et al. Environ. Manage. 183, 41–58. https://doi.org/10.1016/j.jenvman.2016.08.054. GreatPoint Energy, http://www.greatpointenergy.com/ (accessed 26.11.18). Guo, K., Freguia, S., Dennis, P.G., Chen, X., Donose, B.C., Keller, J., Gooding, J.J., Rabaey, K., 2013. Effects of surface charge and hydrophobicity on anodic biofilm formation, community composition, and current generation in bioelectrochemical systems. Environ. Sci. Technol. 47, 7563–7570. Hassan, S.S., Williams, G.A., Jaiswal, A.K., 2018. Emerging technologies for the pretreatment of lignocellulosic biomass. Bioresour. Technol. 262, 310–318. https://doi. org/10.1016/J.Biortech. 2018.04.099. He, A.Y., Yin, C.Y., Xu, H., Kong, X.P., Xue, J.W., Zhu, J., Jiang, M., Wu, H., 2016. Enhanced butanol production in a microbial electrolysis cell by Clostridium beijerinckii IB4. Bioprocess Biosyst. Eng. 39, 245–254. Heidrich, E.S., Dolfing, J., Scott, K., Edwards, S.R., Jones, C., Curtis, T.P., 2013. Production of hydrogen from domestic wastewater in a pilot-scale microbial electrolysis cell. Appl. Microbiol. Biotechnol. 97, 6979–6989. Huang, C.-H., Tan, C.-S., 2014. A review: CO2 utilization. Aerosol Air Qual. Res. 14, 480–499. Huntley, M.E., Redalje, D.G., 2007. CO2 mitigation and renewable oil from photosynthetic microbes: a new appraisal. Mitig. Adapt. Strateg. Glob. Chang. 12, 573–608. Praxair, Inc. http://www.praxair.com/ (accessed 26.11.18). Investing.com, https://www.investing.com/ (accessed 26.11.18). Jarvis, S.M., Samsatli, S., 2018. Technologies and infrastructures underpinning future CO2 value chains: a comprehensive review and comparative analysis. Renew. Sustain. Energy Rev. 85, 46–68. https://doi.org/10.1016/J.RSER.2018.01.007. Jeremiasse, A.W., Hamelers, H.V., Croese, E., Buisman, C.J., 2012. Acetate enhances startup of a H 2-producing microbial biocathode. Biotechnol. Bioeng. 109, 657–664. Jiang, Y., Su, M., Zhang, Y., Zhan, G., Tao, Y., Li, D., 2013. Bioelectrochemical systems for simultaneously production of methane and acetate from carbon dioxide at relatively high rate. Int. J. Hydrogen Energy 38, 3497–3502. Joshi, P.B., 2014. Carbon dioxide utilization: a comprehensive review. Int. J. Chem. Sci. 12, 1208–1220. Joule Energy, https://joule-energy.com/ (accessed 26.11.18). Jourdin, L., Lu, Y., Flexer, V., Keller, J., Freguia, S., 2016. Biologically induced hydrogen production drives high rate/high efficiency microbial electrosynthesis of acetate from carbon dioxide. Chemelectrochem 3, 581–591. Kobayashi, H., Saito, N., Fu, Q., Kawaguchi, H., Vilcaez, J., Wakayama, T., Maeda, H., Sato, K., 2013. Bio-electrochemical property and phylogenetic diversity of microbial communities associated with bioelectrodes of an electromethanogenic reactor. J. Biosci. Bioeng. 116, 114–117. Krieg, T., Sydow, A., Schröder, U., Schrader, J., Holtmann, D., 2014. Reactor concepts for bioelectrochemical syntheses and energy conversion. Trends Biotechnol. 32, 645–655. Kumar, M., Sundaram, S., Gnansounou, E., Larroche, C., Thakur, I.S., 2018. Carbon dioxide capture, storage and production of biofuel and biomaterials by bacteria: a review. Bioresour. Technol. 247, 1059–1068. https://doi.org/10.1016/J.BIORTECH. 2017.09.050. Kundu, A., Sahu, J.N., Redzwan, G., Hashim, M.A., 2013. An overview of cathode material and catalysts suitable for generating hydrogen in microbial electrolysis cell. Int. J. Hydrogen Energy 38, 1745–1757. Kuntke, P., Śmiech, K.M., Bruning, H., Zeeman, G., Saakes, M., Sleutels, T.H.J.A., Hamelers, H.V.M., Buisman, C.J.N., 2012. Ammonium recovery and energy production from urine by a microbial fuel cell. Water Res. 46, 2627–2636. LaBelle, E.V., Marshall, C.W., Gilbert, J.A., May, H.D., 2014. Influence of acidic pH on hydrogen and acetate production by an electrosynthetic microbiome. PLoS One 9. Lane, S., Dong, J., Jin, Y.-S., 2018. Value-added biotransformation of cellulosic sugars by engineered Saccharomyces cerevisiae. Bioresour. Technol. 260, 380–394. https://doi. org/10.1016/J.Biortech. 2018.04.013. Li, M., Zhou, M., Luo, J., Tan, C., Tian, X., Su, P., Gu, T., 2019. Carbon dioxide sequestration accompanied by bioenergy generation using a bubbling-type photosynthetic algae microbial fuel cell. Bioresour. Technol. 280, 95–103. https://doi.org/10.1016/ J.BIORTECH.2019.02.038. Li, Y., Zhao, R., Liu, T., Zhao, J., 2015. Does urbanization lead to more direct and indirect household carbon dioxide emissions? evidence from China during 1996–2012. J. Clean. Prod. 102, 103–114. Liquid Light, http://llchemical.com/ (accessed 26.11.18). Liu, P., Zhang, T., Sun, S., 2019. A tutorial review of reactive transport modeling and risk assessment for geologic CO2 sequestration. Comput. Geosci. 127, 1–11. https://doi. org/10.1016/j.cageo.2019.02.007. Lu, L., Xing, D., Ren, N., Logan, B.E., 2012. Syntrophic interactions drive the hydrogen production from glucose at low temperature in microbial electrolysis cells. Bioresour. Technol. 124, 68–76. https://doi.org/10.1016/j.biortech.2012.08.040. Ma, L., Liang, B., Wang, L.-Y., Zhou, L., Mbadinga, S.M., Gu, J.-D., Mu, B.-Z., 2018a. Microbial reduction of CO2 from injected NaH13CO3 with degradation of n-hexadecane in the enrichment culture derived from a petroleum reservoir. Int. Biodeterior. Biodegrad. 127, 192–200. Ma, L., Zhou, L., Mbadinga, S.M., Gu, J.-D., Mu, B.-Z., 2018b. Accelerated CO2 reduction to methane for energy by zero valent iron in oil reservoir production waters. Energy 147, 663–671. https://doi.org/10.1016/j.energy.2018.01.087. Ma, L., Zhou, L., Ruan, M.-Y., Gu, J.-D., Mu, B.-Z., 2019. Simultaneous methanogenesis and acetogenesis from the greenhouse carbon dioxide by an enrichment culture supplemented with zero-valent iron. Renew. Energy 132, 861–870. https://doi.org/ 10.1016/j.renene.2018.08.059. Marshall, C.W., Ross, D.E., Fichot, E.B., Norman, R.S., May, H.D., 2013. Long-term operation of microbial electrosynthesis systems improves acetate production by autotrophic microbiomes. Environ. Sci. Technol. 47, 6023–6029. Marshall, C.W., Ross, D.E., Fichot, E.B., Norman, R.S., May, H.D., 2012. Electrosynthesis

of commodity chemicals by an autotrophic microbial community. Appl. Environ. Microbiol. 78, 8412–8420. Mehrabadi, A., Craggs, R., Farid, M.M., 2017. Wastewater treatment high rate algal pond biomass for bio-crude oil production. Bioresour. Technol. 224, 255–264. https://doi. org/10.1016/J.Biortech. 2016.10.082. Min, S., Jiang, Y., Li, D., 2013. Production of acetate from carbon dioxide in bioelectrochemical systems based on autotrophic mixed culture. J. Microbiol. Biotechnol. 23, 1140–1146. National Energy Board, http://www.nea.gov.cn./ (accessed 26.11.18). Nevin, K.P., Hensley, S.A., Franks, A.E., Summers, Z.M., Ou, J., Woodard, T.L., Snoeyenbos-West, O.L., Lovley, D.R., 2011. Electrosynthesis of organic compounds from carbon dioxide is catalyzed by a diversity of acetogenic microorganisms. Appl. Environ. Microbiol. 77, 2882–2886. Nevin, K.P., Woodard, T.L., Franks, A.E., Summers, Z.M., Lovley, D.R., 2010. Microbial electrosynthesis: feeding microbes electricity to convert carbon dioxide and water to multicarbon extracellular organic compounds. MBio 1. Newlight Technologies, https://www.newlight.com/ (accessed 26.11.18). Novomer, https://www.novomer.com/ (accessed 26.11.18). Nrg Cosia Carbon Xprize, https://carbon.xprize.org/ (accessed 26.11.18). NRG Energy, https://www.nrg.com/home.html (accessed 26.11.18). Oh, Y.-K., Hwang, K.-R., Kim, C., Kim, J.R., Lee, J.-S., 2018. Recent developments and key barriers to advanced biofuels: a short review. Bioresour. Technol. 257, 320–333. https://doi.org/10.1016/J.Biortech. 2018.02.089. Onumaegbu, C., Mooney, J., Alaswad, A., Olabi, A.G., 2018. Pre-treatment methods for production of biofuel from microalgae biomass. Renew. Sustain. Energy Rev. 93, 16–26. https://doi.org/10.1016/J.RSER.2018.04.015. Pandit, S., Nayak, B.K., Das, D., 2012. Microbial carbon capture cell using cyanobacteria for simultaneous power generation, carbon dioxide sequestration and wastewater treatment. Bioresour. Technol. 107, 97–102. Park, J.-H., Kang, H.-J., Park, K.-H., Park, H.-D., 2018. Direct interspecies electron transfer via conductive materials: a perspective for anaerobic digestion applications. Bioresour. Technol. 254, 300–311. https://doi.org/10.1016/J.Biortech. 2018.01. 095. Pasupuleti, S.B., Srikanth, S., Mohan, S.V., Pant, D., 2015. Development of exoelectrogenic bioanode and study on feasibility of hydrogen production using abiotic VITOCoRETM and VITO-CASE(TM) electrodes in a single chamber microbial electrolysis cell (MEC) at low current densities. Bioresour. Technol. 195, 131–138. Petra Nova, https://www.nrg.com/case-studies/petra-nova.html (accessed 26.11.18). Pires, J.C.M., Alvim-Ferraz, M.C.M., Martins, F.G., Simões, M., 2012. Carbon dioxide capture from flue gases using microalgae: engineering aspects and biorefinery concept. Renew. Sustain. Energy Rev. 16, 3043–3053. https://doi.org/10.1016/j.rser. 2012.02.055. Pires, J.C.M., Martins, F.G., Alvim-Ferraz, M.C.M., Simoes, M., 2011. Recent developments on carbon capture and storage: an overview. Chem. Eng. Res. Des. 89, 1446–1460. Poncin-Epaillard, F., Legeay, G., 2003. Surface engineering of biomaterials with plasma techniques. J. Biomater. Sci. Polym. Ed. 14, 1005–1028. Qiao, Y., Li, C.M., Bao, S.J., Lu, Z., Hong, Y., 2008. Direct electrochemistry and electrocatalytic mechanism of evolved Escherichia coli cells in microbial fuel cells. Chem. Commun. 1290–1292. Rader, G.K., Logan, B.E., 2010. Multi-electrode continuous flow microbial electrolysis cell for biogas production from acetate. Int. J. Hydrogen Energy 35, 8848–8854. Rana, A., Baig, N., Saleh, T.A., 2019. Electrochemically pretreated carbon electrodes and their electroanalytical applications – a review. J. Electroanal. Chem. 833, 313–332. https://doi.org/10.1016/j.jelechem.2018.12.019. Rossi, F., Olguin, E.J., Diels, L., De Philippis, R., 2015. Microbial fixation of CO2 in water bodies and in drylands to combat climate change, soil loss and desertification. N. Biotechnol. 32, 109–120. Rosso, D., Stenstrom, M.K., 2008. The carbon-sequestration potential of municipal wastewater treatment. Chemosphere 70, 1468–1475. Rozendal, R.A., Hamelers, H.V.M., Rabaey, K., Keller, J., Buisman, C.J.N., 2008. Towards practical implementation of bioelectrochemical wastewater treatment. Trends Biotechnol. 26, 450–459. Rozendal, R.A., Leone, E., Keller, J., Rabaey, K., 2009. Efficient hydrogen peroxide generation from organic matter in a bioelectrochemical system. Electrochem. Commun. 11, 1752–1755. Saba, B., Christy, A.D., Yu, Z., Co, A.C., 2017. Sustainable power generation from bacterio-algal microbial fuel cells (MFCs): an overview. Renew. Sustain. Energy Rev. 73, 75–84. https://doi.org/10.1016/J.RSER.2017.01.115. Salmiati, Dahalan, F.A., Mohamed Najib, M.Z., Salim, M.R., Ujang, Z., 2015. Characteristics of developed granules containing phototrophic aerobic bacteria for minimizing carbon dioxide emission. Int. Biodeterior. Biodegrad. 102, 15–23. Sasaki, K., Morita, M., Sasaki, D., Matsumoto, N., Ohmura, N., Igarashi, Y., 2012. Singlechamber bioelectrochemical hydrogen fermentation from garbage slurry. Biochem. Eng. J. 68, 104–108. Sato, K., Kawaguchi, H., Kobayashi, H., 2013. Bio-electrochemical conversion of carbon dioxide to methane in geological storage reservoirs. Energy Convers. Manag. 66, 343–350. Shell Global, https://www.shell.com/ (accessed 26.11.18). Sivaramakrishnan, R., Incharoensakdi, A., 2018. Microalgae as feedstock for biodiesel production under ultrasound treatment – a review. Bioresour. Technol. 250, 877–887. https://doi.org/10.1016/J.Biortech. 2017.11.095. Strata Worldwide, https://www.strataworldwide.com/ (accessed 26.11.18). Szuhaj, M., Acs, N., Tengoelics, R., Bodor, A., Rakhely, G., Kovacs, K.L., Bagi, Z., 2016. Conversion of H2 and CO2 to CH4 and acetate in fed-batch biogas reactors by mixed biogas community: a novel route for the power-to-gas concept. Biotechnol. Biofuels 9.

14

Bioresource Technology 288 (2019) 121401

M. Irfan, et al. Thakur, I.S., Kumar, M., Varjani, S.J., Wu, Y., Gnansounou, E., Ravindran, S., 2018. Sequestration and utilization of carbon dioxide by chemical and biological methods for biofuels and biomaterials by chemoautotrophs: opportunities and challenges. Bioresour. Technol. 256, 478–490. https://doi.org/10.1016/J.BIORTECH.2018.02. 039. Thauer, R.K., 2008. Biologische Methanbildung: Eine erneuerbare Energiequelle von Bedeutung? Die Zukunft der Energie, Munich. Verlag C. H. Beck, pp. 119–137. Torella, J.P., Gagliardi, C.J., Chen, J.S., Bediako, D.K., Colón, B., Way, J.C., Silver, P.A., Nocera, D.G., 2015. Efficient solar-to-fuels production from a hybrid microbial-watersplitting catalyst system. Proc. Natl. Acad. Sci. U.S.A. 112, 2337–2342. Tsai, H.Y., Wu, C.C., Lee, C.Y., Shih, E.P., 2009. Microbial fuel cell performance of multiwall carbon nanotubes on carbon cloth as electrodes. J. Power Sources 194, 199–205. Van Eerten-Jansen, M.C.A.A., Heijne, A.T., Buisman, C.J.N., Hamelers, H.V.M., 2012. Microbial electrolysis cells for production of methane from CO2: long-term performance and perspectives. Int. J. Energy Res. 36, 809–819. Van Eerten-Jansen, M.C.A.A., Jansen, N.C., Plugge, C.M., de Wilde, V., Buisman, C.J.N., ter Heijne, A., 2015. Analysis of the mechanisms of bioelectrochemical methane production by mixed cultures. J. Chem. Technol. Biotechnol. 90, 963–970. Van Eerten-Jansen, M.C.A.A., Ter Heijne, A., Grootscholten, T.I.M., Steinbusch, K.J.J., Sleutels, T.H.J.A., Hamelers, H.V.M., Buisman, C.J.N., 2013a. Erratum: Bioelectrochemical production of caproate and caprylate from acetate by mixed cultures. ACS Sustainable Chem. Eng. 1 (5), 513–518 DOI: 10.0121/sc300168z). ACS Sustain. Chem. Eng. 1, 1069. Van Eerten-Jansen, M.C.A.A., Ter Heijne, A., Grootscholten, T.I.M., Steinbusch, K.J.J., Sleutels, T.H.J.A., Hamelers, H.V.M., Buisman, C.J.N., 2013b. Bioelectrochemical production of caproate and caprylate from acetate by mixed cultures. ACS Sustain. Chem. Eng. 1, 513–518. https://doi.org/10.1021/sc300168z. Varjani, S.J., 2017. Microbial degradation of petroleum hydrocarbons. Bioresour. Technol. 223, 277–286. https://doi.org/10.1016/J.Biortech. 2016.10.037. Venkata Subhash, G., Rajvanshi, M., Navish Kumar, B., Govindachary, S., Prasad, V., Dasgupta, S., 2017. Carbon streaming in microalgae: extraction and analysis methods for high value compounds. Bioresour. Technol. 244, 1304–1316. https://doi.org/10. 1016/J.BIORTECH.2017.07.024. Villano, M., Aulenta, F., Ciucci, C., Ferri, T., Giuliano, A., Majone, M., 2010. Bioelectrochemical reduction of CO2 to CH4 via direct and indirect extracellular electron transfer by a hydrogenophilic methanogenic culture. Bioresour. Technol. 101, 3085–3090. Wang, V.B., Chua, S.-L., Cao, B., Seviour, T., Nesatyy, V.J., Marsili, E., Kjelleberg, S., Givskov, M., Tolker-Nielsen, T., Song, H., Say, J., Loo, C., Yang, L., 2013. Engineering PQS biosynthesis pathway for enhancement of bioelectricity production in Pseudomonas aeruginosa microbial fuel cells. PLoS One 8. Wang, V.B., Kirchhofer, N.D., Chen, X., Tan, M.Y.L., Sivakumar, K., Cao, B., Zhang, Q., Kjelleberg, S., Bazan, G.C., Loo, S.C.J., Marsili, E., 2014. Comparison of flavins and a conjugated oligoelectrolyte in stimulating extracellular electron transport from

Shewanella oneidensis MR-1. Electrochem. Commun. 41, 55–58. Wang, X., Ruan, Z., Sheridan, P., Boileau, D., Liu, Y., Liao, W., 2015. Two-stage photoautotrophic cultivation to improve carbohydrate production in Chlamydomonas reinhardtii. Biomass Bioenergy 74, 280–287. Cambrian Innovation http://cambrianinnovation.com/ (accessed 26.11.18). Xu, G., Liang, F., Yang, Y., Hu, Y., Zhang, K., Liu, W., 2014. An improved CO2 separation and purification system based on cryogenic separation and distillation theory. Energies 7, 3484–3502. Yadav, G., Sen, R., 2017. Microalgal green refinery concept for biosequestration of carbon-dioxide vis-à-vis wastewater remediation and bioenergy production: recent technological advances in climate research. J. CO2 Util. 17, 188–206. https://doi. org/10.1016/j.jcou.2016.12.006. Yan, H., Catania, C., Bazan, G.C., 2015. Membrane-intercalating conjugated oligoelectrolytes: impact on bioelectrochemical systems. Adv. Mater. 27, 2958–2973. Yang, Q., Jiang, Y., Xu, Y., Qiu, Y., Chen, Y., Zhu, S., Shen, S., 2015. Hydrogen production with polyaniline/multi-walled carbon nanotube cathode catalysts in microbial electrolysis cells. J. Chem. Technol. Biotechnol. 90, 1263–1269. Yasin, N.H.M., Maeda, T., Hu, A., Yu, C.-P., Wood, T.K., 2015. CO2 sequestration by methanogens in activated sludge for methane production. Appl. Energy 142, 426–434. Zaybak, Z., Pisciotta, J.M., Tokash, J.C., Logan, B.E., 2013. Enhanced start-up of anaerobic facultatively autotrophic biocathodes in bioelectrochemical systems. J. Biotechnol. 168, 478–485. Zhan, G., Li, D., Tao, Y., Zhu, X., Zhang, L., Wang, Y., He, X., 2014. Ammonia as carbonfree substrate for hydrogen production in bioelectrochemical systems. Int. J. Hydrogen Energy 39, 11854–11859. Zhang, L., Mabee, W.E., 2016. Comparative study on the life-cycle greenhouse gas emissions of the utilization of potential low carbon fuels for the cement industry. J. Clean. Prod. 122, 102–112. Zhang, Q., Wang, Y., Zhang, Z., Lee, D.-J., Zhou, X., Jing, Y., Ge, X., Jiang, D., Hu, J., He, C., 2017. Photo-fermentative hydrogen production from crop residue: a mini review. Bioresour. Technol. 229, 222–230. https://doi.org/10.1016/J.Biortech. 2017.01. 008. Zhang, Y., Sun, J., Hu, Y., Li, S., Xu, Q., 2012. Bio-cathode materials evaluation in microbial fuel cells: a comparison of graphite felt, carbon paper and stainless steel mesh materials. Int. J. Hydrogen Energy 37, 16935–16942. Zhao, H.Z., Zhang, Y., Chang, Y.Y., Li, Z.S., 2012. Conversion of a substrate carbon source to formic acid for carbon dioxide emission reduction utilizing series-stacked microbial fuel cells. J. Power Sources 217, 59–64. Zhu, L., Nugroho, Y.K., Shakeel, S.R., Li, Z., Martinkauppi, B., Hiltunen, E., 2017. Using microalgae to produce liquid transportation biodiesel: what is next? Renew. Sustain. Energy Rev. 78, 391–400. https://doi.org/10.1016/J.RSER.2017.04.089. Ziobrowski, Z., Krupiczka, R., Rotkegel, A., 2016. Carbon dioxide absorption in a packed column using imidazolium based ionic liquids and MEA solution. Int. J. Greenhouse Gas Control 47, 8–16.

15