Qingshi Tu

Hydrogen (H₂) is a promising clean energy carrier for mitigating climate change impacts of energy systems. Hydrogen can be produced from a diverse group of feedstocks through different technology pathways. Reducing the greenhouse gas (GHG) emissions from hydrogen production is critical for the transition to a low-carbon energy system. A systematic literature review was conducted on hydrogen production from steam reforming, water electrolysis, and biomass gasification. This led to a harmonized hydrogen production inventory dataset including both nominal and distributions of values for the critical parameters for modelling these hydrogen production pathways, which addressed the issue of lacking consistent hydrogen production inventory data in the current literature. Furthermore, to address the lack of a generic optimization framework for the entire hydrogen energy system (i.e., from hydrogen production to end use), a hydrogen superstructure framework was developed for identifying an optimal combination of hydrogen production and distribution technologies for a specific hydrogen application scenario, given a specific objective function of interest (e.g., minimizing the climate change impacts). The framework includes a life cycle assessment (LCA) model that calculates the environmental impacts of each process within the supply chain and a supply chain model that implements linear programming for optimization. This framework can also reveal the processes that contribute significantly to the environmental impacts and illustrate the influence of various factors on the optimal choice and associated impacts. A case study was performed to demonstrate the application of the framework on a hydrogen energy system within different end-use scenarios of light-duty fuel cell vehicles in British Columbia, Canada, for 2030. The case study indicates that meeting the GHG emission target of below 4.37 kg CO2 eq/kg H₂ is feasible with accessible resources. Sensitivity analysis was conducted to investigate the influence of (1) hydrogen supply-demand on GHG emissions, and (2) hydrogen transport distances on storage decisions. Results show that doubling hydrogen demand may render the climate target unachievable, indicating the need for strategic planning in hydrogen deployment.

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Forests play a crucial role in addressing climate change by serving as integral components of the carbon cycle. Primary production in forests actively fixes carbon from the atmosphere, whereby the interactions between this carbon sequestration and natural disturbances establishes carbon storage within the forest ecosystem. Numerous studies have been dedicated to evaluating carbon management in forests. Harvested logs undergo various manufacturing processes throughout their lifetime. From these processes, as well as natural decay, there are emissions associated with the production of harvested wood products. Despite these missions, wood products used as renewable materials contribute to climate change mitigation by substituting high-carbon-intensity materials. For example, bioenergy can replace coal in electricity generation, and cross-laminated timber (CLT) can substitute concrete in mid-to-high-rise commercial buildings. Life cycle analysis has been used to monitor emissions and replacement benefits of wood products. While forest carbon management and Harvested Wood Products (HWP) life cycle emissions have been modelled separately, a disconnect exists between these two methodologies, hindering a holistic view. To bridge this disconnection, this work developed an open-source forest system climate impact assessment model that incorporated forest carbon sequestration, dynamics of the forest ecosystem carbon pool, HWP life cycle emissions, and substituted emissions from HWP. The model is available online at Forest System Climate Assessment Model1. Through testing various harvesting and fertilization scenarios, this system-level model ex-plored the climate impact of different scenarios and HWP usage strategies. Key findings include:1. Forest harvesting practices have the potential to transform forest systems from sourcesof carbon emissions into carbon sinks.2. Temporal carbon storage in CLT plays a vital role in system emission reduction, with an impact two times higher than the substitution effect.3. HWP end-use could alter forest management strategies. These experiments underscore the importance of conducting a system-level climate impact assessment, while also demonstrating the potential utility of this information in policy making and carbon credit determination.

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