Roadmap to sustainable carbon-neutral energy and environment: can we cross the barrier of biomass productivity?

Geo-mechanical and geo-morphology characterisation of the cap rocks in the Niger Delta for potential carbon capture and storage

The world has been battling climate change which is caused by an excessive amount of carbon dioxide in the atmosphere. Carbon sequestration in geological sinks was identified as one of the major methods to curb and reduce the amount of carbon dioxide in the atmosphere. The carbon dioxide stored in the geological formations must not escape back into the atmosphere. Characterisation of potential reservoirs for geological sequestration is pertinent for injectivity, capacity, and most importantly containment of carbon dioxide. The cap rock is one of the most important factors determining carbon sequestration success. This study focuses on the preliminary characterisation of the caprocks for evaluating potential subsurface storage of carbon dioxide based on their petrophysical characteristics. X-ray Diffraction and X-ray Fluorescence provided the mineralogical composition and geochemical data of the cap rocks while Scanning Electron Microscopy-EDS was used to identify the qualitative information on the micromorphological textural structure of the cap rocks in the Niger Delta. Conventional Triaxial experiments were used to determine the elastic and geo-mechanical strength of the caprocks. It was identified that the grain skeleton of caprocks in the region is predominated by Quartz, Albite, and Muscovite. The ratio of the tectosilicate and phyllosilicate minerals indicates that the cap rocks are silicate shale. The peak strength of the caprocks ranged from 48.85 to 80.50 MPa and are classified as strong rocks. The cap rocks showed a quasi-elastic behaviour after being subjected to compressive axial force. The elastic modulus of the caprocks was also observed. The characteristics exhibited by the shale caprock at the rock matrix level are highly favourable for sealing carbon dioxide and hence indicate capability for use in carbon sequestration.

Pine needle gasification-based electricity production: Understanding the effect of supply chain

Pine needles (pine tree leaves), found abundantly across continents such as North America, Asia, Europe, South America, Africa, and parts of the Southern Hemisphere, are a significant global concern due to their high susceptibility to catching fire, especially in dry and hot climates. The same issue persists in the Uttarakhand state of India, which boasts ample pine forests, yielding a substantial 1.67 × 109 kg of pine needles annually. In the present study, the annual potential emissions from forest fires in Uttarakhand were estimated to be 58.37 × 109 kg of CO2 equivalent. Therefore, the present research aims to unlock pine needles' potential via gasification for green electricity and biochar production, offering an alternative to coal-based plants while reducing forest fire frequencies. Nevertheless, obstacles hindering pine needle gasification include an unsteady supply chain, limited collection windows (100 days), and plant expenses, including transportation and operational costs. The primary focus of the research is to design and assess the performance of a gasification-based supply chain for pine needles in the Almora District of Uttarakhand. Ten plant capacity scenarios were considered, ranging from 25 to 250 kW. The study incorporated critical factors, encompassing diverse losses within the supply chain, selecting potential plant sites, minimizing transportation distance, and evaluating the supply chain's economic and environmental performance. The economic analysis revealed that the 250-kW plant scenario exhibited a minimum discounted payback period (DPP) of 3.93 years, alongside an internal rate of return (IRR) of 19% and a net present value (NPV) of 653.32 million INR without government subsidies. With subsidies included, the DPP decreased to 1.30 years, improving the IRR to 69% with an NPV of 916.17 million INR. The emission analysis indicated that gasification plant capacity scenarios could potentially reduce 44.63 × 106 to 46.16 × 106 kg of CO2 equivalent emissions annually compared to grid electricity while meeting nearly 5.5% of the electricity demand of Almora district. The present study aligns with SDG-7 (Affordable and Clean Energy), SDG-13 (Climate Action), SDG-9 (Industry, Innovation, and Infrastructure), SDG-11 (Sustainable Cities and Communities), SDG-3 (Good Health and Well-being), and SDG-15 (Life on Land).

Are we really addressing the roadblocks to adoption of renewable and sustainable energy technologies? Total interpretive structural modeling approach

Urban areas serve as a vital contribution to the global structural change towards renewable and sustainable energy technologies which also influence climate change. The aim of this paper is to identify the adoption roadblocks to renewable and sustainable urban energy technologies. This research has three parts: a mini-systematic literature study was conducted to identify the most prevalent roadblocks. Using total interpretive structural modeling (ISM), the relationships between the roadblocks and the source of causation were then examined. The roadblocks are classified based on their dependence and driving powers using MICMAC analysis in the third part of this research. The principal results and major conclusions demonstrate that all roadblocks are necessary for renewable and sustainable urban energy technologies. The roadblocks at level I are insufficient infrastructure, lack of coordination among authorities, lack of quality and reliable data and information, and competition with non-renewable technologies; roadblocks in level II are lack of skilled and trained personnel, limited public participation, awareness, and consumer interest, and lack of standardized technology; roadblock in level III is high initial investment cost; and lastly, roadblocks in level IV are lack of subsidies and financial support programs and absence of coherent related policies. Furthermore, as a result of the MICMAC analysis, none of the aforementioned roadblocks are classified as autonomous variables, implying that they are all required. The dependent roadblocks to renewable and sustainable energy technologies are defined as lack of coordination among authorities, lack of information, and competition with non-renewable technologies. Moreover, linkage roadblocks have high dependence and driving powers which are insufficient infrastructure, limited awareness and consumer interest, and lack of standardized technology. Lastly, high initial investment costs, lack of subsidies and financial support programs, absence of coherent related policies, and lack of skilled and trained personnel are the driving roadblocks with high driving power however not dependent.

Responding to light signals: a comprehensive update on photomorphogenesis in cyanobacteria

Cyanobacteria are ancestors of chloroplast and perform oxygen-evolving photosynthesis similar to higher plants and algae. However, an obligatory requirement of photons for their growth results in the exposure of cyanobacteria to varying light conditions. Therefore, the light environment could act as a signal to drive the developmental processes, in addition to photosynthesis, in cyanobacteria. These Gram-negative prokaryotes exhibit characteristic light-dependent developmental processes that maximize their fitness and resource utilization. The development occurring in response to radiance (photomorphogenesis) involves fine-tuning cellular physiology, morphology and metabolism. The best-studied example of cyanobacterial photomorphogenesis is chromatic acclimation (CA), which allows a selected number of cyanobacteria to tailor their light-harvesting antenna called phycobilisome (PBS). The tailoring of PBS under existing wavelengths and abundance of light gives an advantage to cyanobacteria over another photoautotroph. In this work, we will provide a comprehensive update on light-sensing, molecular signaling and signal cascades found in cyanobacteria. We also include recent developments made in other aspects of CA, such as mechanistic insights into changes in the size and shape of cells, filaments and carboxysomes.

Activated wood surface and functionalized cellulose co-building strong chemical wood bonding performance

Herein, an activated wood surface rich in CHO groups was constructed by spraying a sodium periodate aqueous solution on a natural wood surface. Besides, microcrystalline cellulose was functionalized to obtain aminated cellulose, which was dissolved in an aqueous solution and used as a specific adhesive. Subsequently, an ultrastrong wood bonding interface was co-constructed with the activated wood surface and aminated cellulose, which was formed by a chemical covalent reaction between aldehyde groups at the activated wood interface and amino groups on aminated cellulose. The dry, hot-water, and boiling-water lap shear strengths of the plywood specimens were 1.47, 1.07, and 1.08 MPa, respectively. The boiling-water strength of the plywood made from the activated wood surface achieved increased to 1.08 MPa from 0 MPa of the plywood constructed on the nonactivated wood surface. The chemical crosslinking reaction and bonding mechanism between the adhesive and activated wood surface were clarified by density functional theory calculations, attenuated total reflectance-Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results showed that chemical bonding (aminal NCN and imine CN) at the bonding interface played an important part in improving the water resistance and bonding strength. This work provides new concepts for designing durable and moisture-resistant wood products.

Hydrolysis of regenerated cellulose from ionic liquids and deep eutectic solvent over sulfonated carbon catalysts

The efficient hydrolysis of cellulose into its monomer unit such as glucose or valuable cello-oligosaccharides is the critical step for the cost-effective production of biofuels and biochemicals. However, the current cellulose hydrolysis process involves high energy-demanding pretreatment (e.g., ball-milling) and long reaction times (>24 h). Herein, we investigated the feasibility of the dissolution/regeneration (DR) of cellulose in ionic liquids (ILs) and deep eutectic solvent (DES) as an alternative to ball-milling pretreatment for the effective hydrolysis of cellulose. Because chlorine-based solvents were reported to be the most active for cellulose pretreatment, [EMIM]Cl and [DMIM]DMP were selected as the IL molecules, and choline chloride-lactic acid and choline chloride-imidazole were selected as the DES molecules. The level of the crystallinity reduction of the regenerated cellulose were analyzed using XRD and SEM measurements. The hydrolysis kinetics of the regenerated cellulose from ILs and DES were examined at 150 °C using sulfonated carbon catalysts and compared with those of the ball-milled cellulose. Overall, the cellulose pretreatment using the ILs and the DES had superior kinetics for cellulose hydrolysis to the conventional ball milling treatment, suggesting a possibility to replace the current high energy-demanding ball-milling process with the energy-saving DR process. In addition, the utilization of supercritical carbon dioxide-induced carbonic acid as an in situ acid catalyst for the enhanced hydrolysis of cellulose was presented for the first time.

Advances in technology and utilization of natural resources for achieving carbon neutrality and a sustainable solution to neutral environment

The greatest environmental issue of the twenty-first century is climate change. Human-caused greenhouse gas emissions are increasing the frequency of extreme weather. Carbon dioxide (CO₂) accounts for 80% of human greenhouse gas emissions. However, CO₂ emissions and global temperature have risen steadily from pre-industrial times. Emissions data are crucial for most carbon emission policymaking and goal-setting. Sustainable and carbon-neutral sources must be used to create green energy and fossil-based alternatives to reduce our reliance on fossil fuels. Near-real-time monitoring of carbon emissions is a critical national concern and cutting-edge science. This review article provides an overview of the many carbon accounting systems that are now in use and are based on an annual time frame. The primary emphasis of the study is on the recently created carbon emission and eliminating sources and technology, as well as the current application trends for carbon neutrality. We also propose a framework for the most advanced naturally available carbon neutral accounting sources capable of being implemented on a large scale. Forming relevant data and procedures will help the "carbon neutrality" plan decision-making process. The formation of pertinent data and methodologies will give robust database support to the decision-making process for the "carbon neutrality" plan for the globe. In conclusion, this article offers some opinions, opportunities, challenges and future perspectives related to carbon neutrality and carbon emission monitoring and eliminating resources and technologies.

Photoautotrophic black-colored cyanobacterial soil crust biosynthesizes photoprotective compounds and is capable of using blue, green, and red wavelengths of light for its growth

Several cyanobacteria can adjust their light-harvesting machinery in response to existing light signals in a process called chromatic acclimation (CA) which permits the utilization of available light resources for photosynthesis. CA involves alteration in the pigment composition of a major light-harvesting complex called phycobilisome (PBS) and allows some cyanobacteria to utilize green light (GL) to drive photosynthesis. However, cyanobacteria, in contrast with eukaryotic algae and higher plants, can not utilize blue light (BL) for photosynthesis due to their dependency on PBS. Here, we studied a black-colored soil crust that was composed of a single cyanobacterium identified and named Oscillatoria sp. Malviya-1 after phenotypic and phylogenetic analyses. The black-colored crust can absorb light from almost all parts of photosynthetically active radiation (400-700 nm) and ultraviolet radiation (280-400 nm) due to the presence of photosynthetic pigments and microbial sunscreens such as chlorophyll ɑ, carotenoids, phycoerythrin, phycocyanin, allophycocyanin, mycosporine-like amino acids, and scytonemin. Unlike other cyanobacteria, Oscillatoria sp. Malviya-1 can grow using GL, BL, and red light (RL) in addition to white light (WL) which was accompanied by the different colors of the mat under different light conditions. The presence of CA and sunscreens compounds can maximize the fitness of soil crust under a dynamic light environment, UVR, and desiccation. Detailed study of Oscillatoria sp. Malviya-1 will provide information on the mechanism of CA in cyanobacterial soil crust and its unique ability to use both GL and BL.

Utilization of agricultural waste biomass and recycling toward circular bioeconomy

The major global concern on energy is focused on conventional fossil resources. The burning of fossil fuels is an origin of greenhouse gas emissions resulting in the utmost threat to the environment and subsequently which leads to global climate changes. As far as sustainability is concerned, fuels and materials derived from organic or plant wastes overcome this downside establishing the solution to the fossil resource crisis. In this context, exploration of agricultural residue appears to be a suitable alternative of non-renewable resources to support the environmental feasibility and meet the high energy crisis. The use of agricultural waste as a feedstock for the biorefinery approach emerges to be an eco-friendly process for the production of biofuel and value-added chemicals, intensifying energy security. Therefore, a prospective choice of this renewable biomass for the synthesis of green fuel and other green biochemicals comes up with a favorable outcome in terms of cost-effectiveness and sustainability. Exploiting different agricultural biomass and exploring various biomass conversion techniques, biorefinery generates bioenergy in a strategic way which eventually fits in a circular bioeconomy. Sources and production of agricultural waste are critically explained in this paper, which provides a path for further value addition by various technologies. Biorefinery solutions, along with a life cycle assessment of agricultural waste biomass toward a wide array of value-added products aiding the bioeconomy, are summarized in this paper.

Wastewater substrate disinfection for cyanobacteria cultivation as tertiary treatment

Cultivation of microalgae or/and cyanobacteria in nutrient-rich wastewaters offers an opportunity for enhancing sustainability of tertiary wastewater treatment processes via resources/energy recovery/production, mitigation of emitted GHGs and provision of added value products. However, maintaining a monoculture in wastewater-media constitutes a significant challenge to be addressed. In this regard, the present work assesses the efficiency of the low-cost wastewater substrate disinfection techniques of filtration, use of NaClO, H₂O₂ or Fe(VI), as a preliminary treatment stage upstream a cyanobacteria cultivation photobioreactor. The growth rate of cyanobacterium Synechococcus elongatus PCC 7942, and nitrate and phosphate removal rates, were experimentally assessed in cultivation setups with biologically treated dairy wastewater that had been subjected to a single or a synergetic couple of disinfection techniques. The results showed that filter thickness has a greater effect on disinfection efficiency than filter pore size. Furthermore, the disinfection efficiency of Fe(VI), which was produced on-site by electrosynthesis via a Fe⁰/Fe⁰ cell, was greater than that of NaClO and H₂O₂. Filtration at ≤ 1.2-μm pore size coupled with chemical disinfection led to unhindered Synechococcus elongatus PCC 7942 growth and efficient nitrate and phosphate removal rates, at dosages, in terms of Concentreation-Time (CT) product, of CT ≥ 270 mg min L^-1 for NaClO and CT ≥ 157 mg min L^-1 for Fe(VI). The coagulation action of Fe(III) species that result from Fe(VI) reduction and the oxidation action of Fe(VI) can assist in turbidity, organic compounds and phosphorous removal from wastewater media. Moreover, the residual iron species can assist in Synechococcus elongatus PCC 7942 harvesting and may enhance photosynthesis rate by increasing light transfer efficiency. Thus, a filtration configuration coupled with chemical disinfection, preferably using ferrates, downstream of sedimentation tank of a secondary biological wastewater treatment stage is proposed as a necessary, efficient and low-cost disinfection technique for full-scale scale implementation of cyanobacteria cultivation as tertiary wastewater processes.

Sustainable electrification planning of rural microgrid using renewable resources and its environmental impact assessment

The global population continually increases, and providing power and ensuring sustainable development is becoming increasingly challenging. As a result of increased industrialization and mobility, population growth produces changes in land usage and greenhouse gas emissions. Air quality is influenced by the amount of energy used. The release of carbon dioxide and other pollutants into the atmosphere harms the ecosystem. Although renewable energy sources can help reduce carbon emissions, their unreliability means that energy output is unpredictable, necessitating the development of battery storage to bridge the demand-supply gap. Much attention has been paid to combining renewable energy sources with batteries into rural electrification. The designing and operation of a rural standalone microgrid with electrical loads modeled for the electrification energy deficient village of Uttarakhand (India). The proposed work optimized the component size, cost of energy, net present cost, and pollutant emission reduction in the environment. The optimization is carried out using the gray wolf optimization algorithm. Four different microgrid systems are investigated for the feasibility evaluation of cost-effective rural power. A comparative evaluation of models is provided based on environmental and economic factors. The optimum design has an energy cost of 0.313 $/kWh and a net present cost of $ 65,241.32. The second arrangement, which has the most significant level of renewable energy penetration (90%), has provided a reliable power supply to the region. On the other hand, the proposed design satisfied all constraints while retaining a competitive energy cost.

Microalgae-based biotechnological sequestration of carbon dioxide for net zero emissions

Excessive carbon dioxide (CO₂) emissions into the atmosphere have become a dire threat to the human race and environmental sustainability. The ultimate goal of net zero emissions requires combined efforts on CO₂ sequestration (natural sinks, biomass fixation, engineered approaches) and reduction in CO₂ emissions while delivering economic growth (CO₂ valorization for a circular carbon bioeconomy, CCE). We discuss microalgae-based CO₂ biosequestration, including flue gas cultivation, biotechnological approaches for enhanced CO₂ biosequestration, technological innovations for microalgal cultivation, and CO₂ valorization/biofuel productions. We highlight challenges to current practices and future perspectives with the goal of contributing to environmental sustainability, net zero emissions, and the CCE.

Sustainable valorization of asphaltenes via flash joule heating

The refining process of petroleum crude oil generates asphaltenes, which poses complicated problems during the production of cleaner fuels. Following refining, asphaltenes are typically combusted for reuse as fuel or discarded into tailing ponds and landfills, leading to economic and environmental disruption. Here, we show that low-value asphaltenes can be converted into a high-value carbon allotrope, asphaltene-derived flash graphene (AFG), via the flash joule heating (FJH) process. After successful conversion, we develop nanocomposites by dispersing AFG into a polymer effectively, which have superior mechanical, thermal, and corrosion-resistant properties compared to the bare polymer. In addition, the life cycle and technoeconomic analysis show that the FJH process leads to reduced environmental impact compared to the traditional processing of asphaltene and lower production cost compared to other FJH precursors. Thus, our work suggests an alternative pathway to the existing asphaltene processing that directs toward a higher value stream while sequestering downstream emissions from the processing.

A scenario analysis of Chinese carbon neutral based on STIRPAT and system dynamics model

With the statement of Chinese government on energy saving in 2020 at the United Nations General Assembly, carbon neutral was widely spread as a new concept. As a big country, China has the responsibility and obligation to make its own contribution to global climate change. This paper aims to explore and find effective ways for China to achieve carbon neutrality by 2060. We identify the main factors affecting carbon emissions by STIRPAT model; combined with the scenario analysis, we divide the year 2020 to 2060 into three stages: year 2020-2030 is carbon peak stage, year 2030-2050 is rapid emission reduction stage, and year 2050-2060 is complete carbon neutralization stage. At each stage, three development models, high, medium, and low level, were established. There are a total of 27 different scenarios in three stages. A system dynamics model was established to simulate the effects of carbon emission factors and changes in carbon sinks in different scenarios. Finally, 8 paths were found which in line with Chinese current goal of achieving carbon neutrality with treating reach carbon peak in 2030 as an additional filter condition. Comparing per capita GDP levels in different scenarios, we eventually find that keeping economic development at a low level in the first stage, a high level in the second stage, and a medium level in the finally stage, the point where net carbon emissions are less than zero for the first time will appear between year 2056 and 2057. By then, the per capita GDP will reach 144,500 yuan (based on year 2000), nearly four times 2000's. In all, these findings are helpful for policymakers to implement reasonable policies to achieve carbon emission peaking and carbon neutral in China.