This study investigated the technical feasibility of using electrogermination to activate dormant cysts as an inoculum for subsequent 14-d photosynthetic astaxanthin production in Haematococcus lacustris. Electrotreatment affected the cell viability, surface charge, and morphology of H. lacustris cysts. At an optimal voltage of 2 V for 60 min, the cyst germination rate peaked at 44.6 % after 1 d, representing a 2.2-fold increase compared with that of the untreated control. Notably, electrogermination significantly enhanced both the astaxanthin content (44.9 mg/g cell) and productivity (13.2 mg/L/d) after 14 d of photobioreactor cultivation, corresponding to 1.7- and 1.5-fold increases compared with those in control, respectively. However, excessive electrotreatment, particularly at voltages exceeding 2 V or for durations beyond 60 min, did not enhance the astaxanthin production capability of H. lacustris. Proper optimization of renewable electrogermination can enable sustainable algal biorefinery to produce multiple bioactive products without compromising cell viability and astaxanthin productivity.

Companies are increasingly relying on emission reductions attributable to their adoption of renewable electricity to achieve net-zero emission targets. However, there is a risk of double counting of emission reductions threatening the credibility of corporate climate actions due to defective accounting rules of GHG emissions related to electricity consumption and the overlap between different market-based instruments, including carbon credit markets, renewable power purchase agreements, and renewable energy certificates. Using data of 63 major Chinese companies in seven sectors, we quantitatively assess the risks of double counting related to corporate sourcing of renewables and their consequent influences on the alignment of corporate emission trajectories with the 1.5 °C goal of the Paris Agreement. Results show that 7.1% of the electricity consumed by sample companies in 2021 was from renewable energy procurement and deployment, with which they reported 8.27 Mt of CO2e emission reductions compared to the scenario with no renewable electricity consumption. However, emission reductions that could be double counted are predicted to be 0.9-1.3 times as many as emission reductions that companies will report during 2021-2030. After adjustment of the reported emissions that might be underestimated due to double counting, the overall emission trajectories of sample companies are no longer aligned with the 1.5 °C goal. Our findings suggest that it is urgently needed to improve the corporate carbon accounting rules and increase the transparency of corporate carbon disclosures.

Recent investments in \"clean\" hydrogen as an alternative to fossil fuels are driven by anticipated climate benefits. However, most climate benefit calculations do not adequately account for all climate warming emissions and impacts over time. This study reanalyzes a previously published life cycle assessment as an illustrative example to show how the climate impacts of hydrogen deployment can be far greater than expected when including the warming effects of hydrogen emissions, observed methane emission intensities, and near-term time scales; this reduces the perceived climate benefits upon replacement of fossil fuel technologies. For example, for blue (natural gas with carbon capture) hydrogen pathways, the inclusion of upper-end hydrogen and methane emissions can yield an increase in warming in the near term by up to 50%, whereas lower-end emissions decrease warming impacts by at least 70%. For green (renewable-based electrolysis) hydrogen pathways, upper-end hydrogen emissions can reduce climate benefits in the near term by up to 25%. We also consider renewable electricity availability for green hydrogen and show that if it is not additional to what is needed to decarbonize the electric grid, there may be more warming than that seen with fossil fuel alternatives over all time scales. Assessments of hydrogen\'s climate impacts should include the aforementioned factors if hydrogen is to be an effective decarbonization tool.

This study examines the validity of the environmental Kuznets curve (EKC) hypothesis and the role of environmental regulation, renewable electricity, industrialization, economic complexity, and technological innovation in sustainable environment for the G-10 economies, namely, Belgium, Canada, Germany, Italy, Japan, Netherlands, Sweden, Switzerland, the United Kingdom, and the USA, from 1994 to 2020. We employed CS-ARDL (cross-sectional augmented distributed lag (CS-ARDL), FMOLS (fully modified ordinary least squares), and DOLS (dynamic ordinary least squares) for the analysis of the data. The estimates confirm the N-shaped EKC hypothesis between the GDP and CO2 emission. Moreover, the long-run estimates exhibit that environmental tax, renewable electricity, economic complexity, and technological innovation have negative effect on CO2 emission, while GDP, industrialization and arable land have positive effect on CO2 emission. Based on these findings, we propose that governments must implement large-scale government plans and initiatives to encourage the development of environmentally friendly technologies and ideas based on renewable energy. Moreover, further growing renewable energy, environmental policies like a carbon tax, investments in green technologies, subsidies, and rewards for renewable energy infrastructure investment should be taken into account.

Future energy systems necessitate dispatchable renewable energy to balance electrical grids with high shares of intermittent renewables. Biogas from anaerobic digestion (AD) can generate electricity on-demand. High-rate methanogenic reactors, such as the Upflow Anaerobic Sludge Blanket (UASB), can react quicker to variations in feeding as compared to traditional AD systems. In this study, experimental trials validated the feasibility of operating the UASB in a demand-driven manner. The UASB was operated with leachate produced from a hydrolysis reactor treating grass silage. The UASB demonstrated a high degree of flexibility in responding to variable feeding regimes. The intra-day biogas production rate could be increased by up to 123% under 4 hours in demand-driven operation, without significant deterioration in performance. A model based on kinetic analysis was developed to help align demand-driven operation with the grid. The findings suggest significant opportunities for UASBs to provide positive and negative balance to the power grid.

This study investigates the impact of environmental technological innovation, economic complexity, energy productivity, the use of renewable electricity generation, and environmental taxes on carbon dioxide (CO2) emissions in the G-10 countries for the timeframe from 1995 to 2020. The purpose of the study is to examine the need for a clear plan or strategy to achieve environmental objectives in G-10 countries. In both short-term and long-term projections, the increased use of environment-based technology, economic complexity, and renewable electricity generation has a major positive impact on carbon emission reduction. Moreover, the results demonstrate both unidirectional and bidirectional causality from carbon emissions to renewable energy, electrical generation, and environment-based technologies, respectively. Based on the results, the study proposes a number of concrete policies, such as updating modernized tax systems, increasing tax collection, providing individuals with the means to finance the Sustainable Development Goals through incentive regulations, and making grants from international organizations and the private sector available to finance investments toward the Sustainable Development Goals (SDGs) and carbon neutrality environment targets. This is the study\'s most significant contribution in order to attain a sustainable and low-carbon future in the G-10 countries, which has policy implications for governments and policymakers.

Plastics are essential materials for modern societies, but their production contributes to significant environmental issues. Power-to-X processes could produce plastics from captured CO2 and hydrogen with renewable electricity, but these technologies may also face challenges from environmental perspective. This paper focuses on environmental sustainability assessment of CO2-based low-density polyethylene (LDPE) compared to bio-based LDPE. Life cycle assessment has been applied to study climate impacts and land use related biodiversity impacts of different plastic production scenarios. According to the climate impact results, the carbon footprint of the produced plastic can be negative if the energy used is from wind, solar, or bioenergy and the carbon captured within the plastic is considered. In terms of biodiversity, land-use related biodiversity impacts seem to be lower from CO2-based polyethylene compared to sugarcane-based polyethylene. Forest biomass use for heat production in CO2-based polyethylene poses a risk to significantly increase biodiversity impacts. Taken together, these results suggest that CO2-based LDPE produced with renewable electricity could reduce biodiversity impacts over 96 % while carbon footprint seems to be 6.5 % higher when compared to sugarcane-based polyethylene.

Addressing extensive global goals including growing energy-sourced electricity and advancing sustainable development plans strongly depends on natural gas as a transition fuel to renewable forms of energy. Therefore, by using pooled, random, and fixed-effects models, the current study investigates the effects of electricity sourced from natural gas (ENG), renewable energy (RE), and trade in information and communication technologies (ICTs) on economic growth and carbon dioxide (CO2) emissions in Africa\'s top three natural gas producers, Algeria, Egypt, and Nigeria, from 1990 to 2020. The findings indicate that CO2, ENG, ICT trade, and urbanization (UP) are all strongly and positively correlated to economic progress, with the exception of RE, which has an insignificant influence. For the environment, data indicate that RE and GDP degrade the environment while ENG and ICT trade boost it. The causality results that ENG and RE cause both economic growth and CO2 emissions. Based on these empirical results, it is recommended that policymakers should step up their efforts to usage natural gas as a transition fuel to renewable energy sources and acknowledge the advantages of the significant contribution that green ICT trade can make to economic advancement and a clean environment.

Reducing greenhouse gas (GHG) emissions from the steel industry is one of the top priorities for mitigating climate change. Although hydrogen has been considered as a key element to accomplish this task, the effects of various hydrogen-using technologies in steel mills have not been analysed and compared to each other. This paper quantitatively analysed the greenhouse gas reduction in steel mills by the use of hydrogen produced from electrolysis with renewable electricity. The four following methods of using green hydrogen were proposed and analysed: 1) use of hydrogen directly in the hydrogen steelmaking process, 2) use of hydrogen to convert byproduct gases produced from steel mills into methanol, 3) use hydrogen to convert the byproduct gases into methane, and 4) sell hydrogen to the hydrogen station and use of oxygen, another product of electrolysis, to reduce the use of air separating unit in steel mills. Not only the greenhouse gas reduction benefits but also the economic cost of these four methods were evaluated. As those results can vary according to country, the economic cost and GHG reduction benefits were determined for the representative steel-producing countries of China, India, Japan, the United States, Russia, South Korea, and Germany. The economic cost was evaluated not only for the present (2020) but also for the future (∼2040) because these methods are more likely to be implemented in the future. Currently, in the representative steel-producing countries, Method 1 was analysed to have the largest GHG reduction among the four methods; but it also showed the largest cost because of its large capital expenditures and electricity cost. Method 2, which converts the byproduct gases into methanol, was shown to offer larger GHG reduction and smaller economic cost than Method 3, which converts the byproduct gases into methane. Comparing Methods 1 and 2, Method 2 offered smaller GHG reduction but a much smaller economic cost than Method 1. Although the cost of Method 4 is currently the smallest, the economic cost of Method 2 is predicted to become lower than that of Method 4 in the future, near 2030, because the future prices of hydrogen and the CO2 allowance are expected to decrease and increase, respectively. These results can be utilized when steelmaking country or steelmaking company make their decision on how to decrease the GHG emissions by using green hydrogen.

Thermal power industry is one of China\'s leading sources of carbon emissions. China has launched a national carbon emissions trading scheme (ETS) and renewable energy incentive programs to achieve its peak emission target by 2030. However, since 2021, China no longer provides a central feed-in tariff (FIT) for new centrally located solar photovoltaic (PV) power plants, commercial and industrially distributed PV projects, and newly approved onshore wind power projects. This change in policy may threaten China\'s carbon reduction targets and economic development. Using a dynamic computable general equilibrium (CGE) model, we assess the combined effects of carbon ETS and FIT on China\'s electricity sector, carbon emission peak target, renewable energy and economic development. In terms of policy overlap and integration, we analyze the impact of these policies and estimate how to coordinate FIT and carbon ETS policies to ensure their effectiveness. Results show that the overall effects of FIT subsidies are superior to phasing-out FIT scenarios. The fiscal pressure caused by FIT is lower than its actual expenditure because it stimulates economic activity and boosts government revenue. However, considering the multiplier effect of the FIT on promoting government revenue growth and GDP growth, the most effective FIT should be terminated in 2025, followed by subsidies ending in 2030 and 2035.