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Carbon pricing mechanisms have been identified as a key strategy for reducing global greenhouse gas emissions to achieve the net-zero target. The present study aims to fill the gap by investigating the effects of carbon pricing under different specific target emission constraints and their potential implications for the transportation sector in India. A total of five scenarios have been developed, including a reference scenario with current policy assumptions and four climate policy scenarios. In the climate policy scenarios, emission constraints varied between the year 2030 and the year 2060, with implementation occurring in 10 y intervals until the year 2070. The net-zero year remains constant across all scenarios, which is set at the year 2070. These scenarios are developed using the global change assessment model (GCAM). The study reveals that a reduction in the time gap between the year of implementation and the year of achieving net-zero emissions will lead to an increase in carbon prices. The maximum projected cost of carbon will be 981.36 USD/t of CO₂ emission ($/tCO₂) if the carbon pricing is implemented starting in the year 2030 and 1062.79 $/tCO₂ if it is implemented from the year 2060. The implementation of carbon prices resulted in considerable emission reductions, as well as variations in service demand and energy usage patterns in the transport sector. The findings hold promise for positively influencing SDGs 11 and 13 and have significant implications for policymakers and other stakeholders. [ABSTRACT FROM AUTHOR]

Efficient domestic wastewater management is essential for mitigating the impact of wastewater on human health and the environment. Wastewater management with conventional technologies generates sewage sludge. The present study considered a modelling approach to evaluate various processing pathways to produce energy from the sewage sludge. Anaerobic digestion, gasification, pyrolysis, and hydrothermal liquefaction are analysed in terms of their energy generation potentials with the Aspen Plus software. A techno-economic assessment is performed to assess the economic viability of each pathway. It reveals that gasification appears as the most promising method to produce electricity, with 0.76 kWh/kg drysludge , followed by anaerobic digestion (0.53 kWh/kg drysludge), pyrolysis (0.34 kWh/kg drysludge), and hydrothermal liquefaction (0.13 kWh/kg drysludge). In contrast, the techno-economic analysis underscores the viability of anaerobic digestion with levelized cost of electricity as 0.02 $/kWh followed by gasification (0.11 $/kWh), pyrolysis (0.14 $/kWh), and hydrothermal liquefaction (2.21 $/kWh). At the same time, if the products or electricity from the processing unit is sold, equivalent results prevail. The present study is a comprehensive assessment of sludge management for researchers and policymakers. The result of the study can also assist policymakers and industry stakeholders in deciding on alternative options for energy recovery and revenue generation from sewage sludge. [Display omitted] • Comparative analysis of four sewage sludge processing units. • Gasification produces 41% more electricity than anaerobic digestion. • Anaerobic digestion has 81% lower LCOE than gasification. • Pyrolysis has the highest energy content per kg. • Anaerobic digestion has the highest NPV through electricity or other products. [ABSTRACT FROM AUTHOR]

Algal biofuel production requires CO2, electricity, and process heat. Previous studies assumed CO2 sourcing from nearby coal or natural gas power plants. This may not be viable at a large scale or for the long term. The diurnal algal growth cycle imposes additional system design challenges for CO2 delivery. For ethanol produced by cyanobacteria in photobioreactors, we design onsite systems that provide heat, power and CO2 (CHP‐CO2), fueled by natural gas or biomass. Meeting the CO2 requirement produces excess electricity, which can be sold back to the grid. The scale of the CHP‐CO2 can be reduced by night‐time capture and refrigerated storage of CO2. The lifecycle greenhouse gas (GHG) emissions for 1 MJ ethanol are about −19 g CO2e for biomass CHP‐CO2, and +31–35 CO2e g for natural gas CHP‐CO2 options, compared with +19 g CO2e for the direct use of coal flue gas, and 91.3 g CO2e for 1 MJ of conventional gasoline. This work evaluates the energy and GHG implications of onsite CHP‐CO2 for algal ethanol production and other CO2 sourcing options. Combined heat and power (CHP) facilities, fueled by natural gas or biomass, could be co‐located with algal ethanol production, capturing and utilizing carbon dioxide to make biofuel, and thus providing an essentially stand‐alone biofuel operation, free from the constraints of co‐location with anthropogenic sources. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Refined bio-crude production from hydrothermal liquefaction of algae holds the potential to replace fossil-based conventional liquid fuels. The microalgae act as natural carbon sequestrators by consuming CO2. However, this absorbed CO2 is released to the atmosphere during the combustion of the bio-crude. Thus, the life-cycle greenhouse gas (GHG) emissions of refined bio-crude are linked to the production and supply of the materials involved and the process energy demands. One prominent raw material is CO2, which is the main source of carbon for algae and the subsequent products. The emissions associated with the supply of CO2 can have a considerable impact on the sustainability of the algae-based refined bio-crude production process. Furthermore, the diurnal algae growth cycle complicates the CO2 supply scenarios. Traditionally, studies have relied on CO2 supplied from existing power plants. However, there is potential for building natural gas or biomass-based power plants with the primary aim of supplying CO2 to the biorefinery. Alternately, a direct air capture (DAC) process can extract CO2 directly from the air. The life-cycle GHG emissions associated with the production of refined bio-crude through hydrothermal liquefaction of algae are presented in this study. Different CO2 supply scenarios, including existing fossil fuel power plants and purpose-built CO2 sources, are compared. The integration of the CO2 sources with the algal biorefinery is also presented. The CO2 supply from biomass-based power plants has the highest potential for GHG reduction, with a GHG footprint of −57 g CO2 eq./MJ refined bio-crude. The CO2 supply from the DAC process has a GHG footprint of 49 CO2 eq./MJ refined bio-crude, which is very similar to the scenario that considers the supply of CO2 from an existing conventional natural gas-based plant and takes credit for the carbon utilization. [ABSTRACT FROM AUTHOR]