A Critical Study on Waste to Low Carbon (CCS-abated) Hydrogen

Overview

This study presents a systematic review of waste-to-hydrogen (WtH) technologies and conducts analysis of the technological, economical, and environmental aspects of the most promising waste-to-low carbon hydrogen technologies for near-term commercial deployment. The findings provide valuable insights into the opportunities, challenges, and potential solutions to foster and expedite the global adoption of waste-to-hydrogen projects.

Further, the report introduces a modular environmental justice (EJ) framework designed to assess the fairness of waste-to-hydrogen projects, enabling a thorough evaluation of their potential environmental and social impacts.

Key Findings

• Following a review of thermochemical, biochemical, electrochemical, and photochemical processes for hydrogen production pathways from municipal solid waste (MSW), gasification, pyrolysis, dark fermentation, and incineration electrolysis were identified for further study with carbon capture and storage (CCS) retrofit due to their high technology readiness levels (TRLs).
• This report develops a modular EJ framework to assess the fairness of waste-to-hydrogen projects by evaluating six EJ dimensions2 across five critical aspects. Applied to the FUREC (FUse REuse ReCycle) project in the Netherlands, the EJ fairness evaluation showed strong performance in environmental & economic opportunities. However, the FUREC waste-to-hydrogen site location choice in Chemelot scores very poorly in terms of fairness, which can be attributed to its proximity to residential areas and the current uncertainty of the FUREC funding status.
• Thermochemical processes stand out as the most balanced and promising waste-to-hydrogen pathways. They offer high hydrogen yields and energy efficiency with relatively lower levelized costs of hydrogen (LCOH) compared to biochemical conversion pathways. Specifically, gasification requires ~23 kg of MSW to produce 1 kg of hydrogen, while pyrolysis uses ~25 kg of MSW to achieve the same hydrogen output.
• Dark fermentation exhibits a markedly lower efficiency, requiring approximately ~143 kg of MSW to generate 1 kg of hydrogen, underscoring its limited effectiveness compared to thermochemical methods. Meanwhile, the incineration-electrolysis process requires ~80 kg of MSW to produce the same amount of hydrogen, reflecting its suboptimal resource utilisation.
• Maintaining an economically viable LCOH in waste-to-hydrogen technologies hinges on both the cost and consistent availability and quality of MSW. While the baseline scenario assumes zero-cost MSW, implementing a waste tipping fee can further reduce LCOH. A steady supply of MSW is essential; fluctuations in availability, reflected in the capacity factor, can lead to increased costs due to lower operational efficiency.
• Variability in the quality of waste feedstock presents a significant obstacle for waste-to-hydrogen projects, when waste quality fluctuates, operational efficiency is compromised, and the LCOH increases to address this, pre-treatment methods such as torrefaction (as used in the RWE Fuse Reuse Recycle (FUREC) project) are increasingly implemented to standardise feedstock and reduce variability, ensuring more reliable hydrogen production.
• Economically, WtH-CCS processes are currently not viable, as indicated by the significantly high LCOH (US$5.15/kg-US$14.91/kg across the pathways examined in this study) compared to the costs of hydrogen from coal (US$1.20-2.21/kg without CCS or US$2.10-2.62/kg with CCS) and natural gas (US$0.91-1.79/kg without CCS or US$1.21-2.11/kg with CCS). The high LCOH for WtH-CCS is primarily driven by high CAPEX and OPEX due to the complexity and/or currently limited efficiency of the process.
• The cost feasibility improvement analysis suggests that a combination of efficiency improvements, byproduct recovery, CAPEX reduction, effective waste management and carbon incentives are required to lower the LCOH for CCS-abated gasification, pyrolysis, incineration-electrolysis, and dark fermentation pathways. In addition, economies of scale are essential to establish a cost-effective waste-to-low-carbon-hydrogen conversion.
• Hydrogen production via pyrolysis and gasification are the most environmentally favourable processes across most impact categories. However, their reliance on natural gas leads to higher ozone depletion potential (ODP) compared to dark fermentation and incineration. Dark fermentation has the highest overall environmental impact due to significant chemical usage, high power demands from fossil-fuel grids, and complex wastewater treatment. Incineration, on the other hand, has the greatest impact on terrestrial ecotoxicity, primarily due to the disposal of char and ash from high MSW consumption.
• Substituting energy inputs with renewable energy generally reduces environmental impacts across most categories. However, it also introduces new challenges, such as heightened water consumption, increased land use, and the depletion of metals. Electrifying the heating system within the process could further mitigate environmental impacts, but doing so would necessitate expanding the lifecycle assessment (LCA) boundary to encompass the generation, manufacturing, and recycling of renewable energy technologies.
• Deploying WtH-CCS to produce clean hydrogen faces notable logistical and economic hurdles, particularly due to the complexities of coordinating transport, storage of feedstock, the CO2 captured, and the hydrogen produced. Small-scale, geographically dispersed projects may struggle with economic feasibility, especially given the potential for fluctuating waste availability and quality.