Cost-benefit analysis of ballast water treatment for three major port clusters in China: evaluation of different scenario strategies

IntroductionThe expansion of maritime trade has led to the introduction of invasive species into aquatic ecosystems through ballast water discharge. China, being a major player in global trade and manufacturing, has experienced negative impacts on its coastal ecosystems and marine biodiversity.MethodsThis study examines the cost‒benefit trade-offs of ballast water management policies for major port clusters in China and other global ports. This paper evaluates compliance costs for individual vessels and fleets under different policy scenarios and ballast water treatment system (BWTS) installation strategies.ResultsThe onboard BWTS installation strategy appears to be more cost-effective under the existing International Maritime Organization (IMO) policy. However, with stricter global discharge requirements or a substantial increase in BWTS capital and operating costs, strategies based on port location could prove more beneficial due to potential economies of scale. Notably, ships with high ballast water discharge volumes, like bulk carriers, are potentially better equipped to cope with future policy shifts. In the face of stricter regulations in China, projected annual compliance cost increases range from $456 million (cost data based on China) to$1.205 billion (cost data based on US).DiscussionPolicymakers are advised to adopt a comprehensive view of ballast water management policies, taking into account the trade-offs between compliance costs and environmental risks. Other essential factors, such as advancements in BWTS technology, fuel consumption, emissions, and maintenance costs, also demand careful consideration in policy development

Approaching high thermoelectric performance in p-type Cu3SbS4-based materials by rational electronic and nano/microstructural engineering

Due to the eco-friendly and earth-abundant features, p-type Cu3SbS4-based sulfides have shown great potential as cost-effective thermoelectric materials for practical applications in power generation and refrigeration. However, low electrical conductivities of p-type Cu3SbS4-based sulfides result in insufficient thermoelectric properties. In this work, a high average ZT of 0.45 and a maximum ZT of 0.85 at 623 K were obtained in Cu3SbS4-based sulfides through rational electronic and nano/microstructural engineering, achieved by mechanical alloying combined with fast spark plasma sintering techniques. Guided by theoretical calculations, we first study the physical properties of Cu3SbS4-xSex to explore the best composition (Cu3SbS3Se) that balances high thermoelectric performance, high thermal stability, and high mechanical performance. Based on this composition, we employed 4 % p-type AgSnSe2 with a narrow bandgap of ∼0.15 eV to further boost the electrical conductivity of Cu3SbS3Se, generating a high power factor of 12.65 μW cm−1 K−2 at 623 K. In addition, comprehensive nano/microstructural characterizations indicate that a combination of dense grain boundaries, phase boundaries, and multi-dimensional lattice defects acts as rich sources to intensely scatter multi-frequency phonons, leading to a decreased thermal conductivity of 0.93 W m−1 K−1 at 623 K. This work provides a new route to boost the thermoelectric properties of sulfides for practical applications.</p