Sustainability In The Air

In this episode, Dirk Singer speaks with James Hygate, Founder and CEO of Firefly Green Fuels, about one of the more unconventional and potentially scalable sustainable aviation fuel pathways: converting sewage biosolids into jet fuel.
Hygate discusses: 
Why Firefly is “feedstock-led”, and why that matters more than the technology
How sewage biosolids emerged as the preferred feedstock for Firefly due to their abundance, consistency, and increasing difficulty of disposal.
How hydrothermal liquefaction (HTL) works like “a pressure cooker” to turn sewage into biocrude and biochar 
Why Firefly believes its fuel could achieve over 90% lifecycle CO2 savings, potentially even becoming carbon-negative
How sewage-to-SAF could scale in the UK  and why it could “come from left field” in mandate maths
What is required for SAF projects to be bankable including long-term feedstock supply and offtake agreements
How sewage-based SAF can reach cost parity with Jet A
If you LOVED this episode, you’ll also love the conversation we had with Dr Mar Fernández-Méndez, Co-founder of MacroCarbon, who shares how the startup plans to turn seaweed into SAF. Check it out here. 
Learn more about the innovators who are navigating the industry’s challenges to make sustainable aviation a reality, in our new book ‘Sustainability in the Air: Volume 2’. Click here to learn more.
Feel free to reach out via email to [email protected]. For more content on sustainable aviation, visit our website green.simpliflying.com and join the movement. It’s about time.
Links & More:
Firefly Green Fuels
What & How - Firefly
Poop-powered planes: Could jet fuel made from sewage take off? - CNN
Wizz Air and Firefly collaborate on turning human waste into SAF - Biofuels International Magazine

In this episode, we speak with Adam Klauber, Chief Sustainability Officer at World Energy, who has been at the forefront of developing book and claim mechanisms for sustainable aviation fuel since its earliest days.
He discusses:
The co-claims approach: Why aviation needed to diverge from renewable electricity market models by enabling both airlines (scope 1) and their corporate customers (scope 3) to claim emissions reductions from the same SAF molecules, unlocking new sources of funding.
What it took to get early deals done: How some of the earliest SAF buyers like Microsoft moved before the supporting infrastructure was fully in place, including clear registries and standardised accounting rules, and why that early willingness mattered.
Insetting vs offsetting: The moral hazard of buying cheap offsets outside aviation, and how insetting addresses this while maintaining economic efficiency.
Making SAF contracts “bankable”: How long-term commitments from credible corporate buyers can help producers secure debt capital at lower interest rates, thereby lowering financing costs and easing the SAF price premium over time.
Building market infrastructure that benefits the whole sector: Why World Energy deliberately builds frameworks that benefit competitors, recognising that growing the overall SAF market serves everyone’s interests and that no single company wins with only a trickle of supply.
If you LOVED this episode, you’ll also love the conversation we had with Gene Gebolys, founder and CEO of World Energy, who delves into the intricacies and future of SAF. Check it out here. 
Learn more about the innovators who are navigating the industry’s challenges to make sustainable aviation a reality, in our new book ‘Sustainability in the Air: Volume 2’. Click here to learn more.
Feel free to reach out via email to [email protected]. For more content on sustainable aviation, visit our website green.simpliflying.com and join the movement. It’s about time.
Links & More:
World Energy
Blueprints for Bankability - RMI 
Re-thinking the blueprint for financing SAF - SimpliFlying
Efficient, effective decarbonization with carbon insets - World Energy

In this episode, we speak with Rachel Gardner-Poole, GAIN steering group chair and sustainable aviation consultant at NATS, the UK’s leading air traffic control provider. 
Gardner-Poole shares how GAIN (Green Aviation Insights Network) is bringing together air navigation service providers from around the world to optimise flight paths and reduce emissions using tools and insights that can deliver results today. She discusses:
GAIN’s dual purpose: A global collaboration of air navigation service providers (ANSPs) and a dashboard tool that measures airspace efficiency, enabling ANSPs to identify inefficiencies, benchmark performance by airline and route, and track CO2 emissions in real time.
Why airspace efficiency matters now: Whilst SAF faces supply constraints and hydrogen aircraft remain years away, airspace optimisation can deliver immediate carbon savings. 
Breaking down communication barriers: How misaligned assumptions between airlines and air traffic controllers often lead to suboptimal flight paths, and how GAIN’s data visualisation enables targeted conversations to unlock tactical savings.
The founding members’ impact: With five founding members helping shape the tool, GAIN could save over 450,000 tonnes of CO2 annually.
Addressing greenwashing concerns: Unlike complex carbon credit schemes or predictive modelling, GAIN uses real, verifiable flight path data.
Future expansion plans: The goal is to reach 40% of the world’s 160 ANSPs by 2030, with potential features including non-CO2 effects like contrails, and partnerships with organisations across the aviation sector.
If you LOVED this episode, you’ll also love the conversation we had with Sian Andrews, SESAR Environmental Lead at NATS, who shares how air traffic management can reduce aviation’s environmental impact. Check it out here. 
Learn more about the innovators who are navigating the industry’s challenges to make sustainable aviation a reality, in our new book ‘Sustainability in the Air: Volume 2’. Click here to learn more.
Feel free to reach out via email to [email protected]. For more content on sustainable aviation, visit our website green.simpliflying.com and join the movement. It’s about time.
Links & More:
NATS 
Green Aviation Insights (GAIN) - NATS 
NATS and leading ANSPs unite to drive sustainable aviation through a novel data-driven insights tool - CANSO
NATS environmental initiative GAIN-ing momentum - Aviation Week Network

In this special year-end episode, we explore conversations with industry leaders revealing where sustainable aviation truly stands in 2025.
Matt Gorman, Director of Carbon Strategy at Heathrow Airport, reveals airports control just 0.1% of their carbon footprint directly but use landing charges to incentivise SAF adoption.
Tamara Vrooman, CEO of Vancouver Airport, explains moving their net-zero target forward to 2030 by leveraging control of central infrastructure.
Lena Wennberg, Chief Sustainable Development Officer, and Therese Forsström, Head of Environmental Department at Swedavia, explain achieving fossil-free operations in 2020 and how they are looking to support fossil-free domestic flights in Sweden by 2030.
Aaron Robinson, Vice President of SAF at International Airlines Group, identifies airlines’ reluctance to adopt SAF as a cultural problem rooted in safety-first mindsets that resist innovation.
Matthew Ridley, Director of Sustainability at The oneworld Alliance, discusses their $150 million fund with Breakthrough Energy Ventures for next-generation SAF.
Trevor Best, CEO of Syzygy Plasmonics, details their photocatalytic technology converting biogas into SAF at smaller scales, targeting jet fuel parity.
Tim Boeltken of INERATEC explains their modular e-fuel technology deployable wherever green hydrogen is produced.
Marc Allen, CEO of Electra, describes how electric aircraft will succeed by enabling new capabilities like 150-foot takeoffs rather than competing with jet fuel.
Billy Thalheimer of Regent introduces Seagliders – wing-in-ground effect vehicles offering new transportation for coastal routes.
Jolanda Stevens, Program Manager for Zero Emission Aviation at KLM, emphasises airlines’ responsibility in enabling hydrogen and electric aircraft.
Luke Farajallah, CEO of Loganair, discusses how their mandatory £1 carbon levy receives almost no passenger complaints.
If you LOVED this episode, you’ll also love all the conversations we had through the year with dozens of industry executives, technology leaders and scientists. Check out the archive here. 
Learn more about the innovators who are navigating the industry’s challenges to make sustainable aviation a reality, in our new book ‘Sustainability in the Air: Volume 2’. Click here to learn more.
Feel free to reach out via email to [email protected]. For more content on sustainable aviation, visit our website green.simpliflying.com and join the movement. It’s about time.
Links & More:
Book: Sustainability in the Air, Vol Two - SimpliFlying
Sustainable Aviation Outlook Report 2025 - SimpliFlying

In this episode, we speak with Nanna Baldvinsdottir, co-founder of IðunnH2, about how Iceland’s unique energy system could turn the country into a green fuel bridge between Europe and North America. 
A veteran of Iceland’s power sector, Nanna has spent two decades working in renewables before turning to hydrogen and e-fuels development.
Nanna shares how IðunnH2 is developing a 300 MW, ~70,000 tonne-per-year e-SAF project near Keflavík International Airport, designed first to decarbonise Icelandic aviation and only then supply the wider world via book-and-claim. She explains why social licence for new wind power, local energy security, and predictable permitting make Iceland a testbed for scaling e-fuels where other regions are still stuck on the drawing board.
Nanna discusses:
Why SAF, not hydrogen export, came out on top in IðunnH2’s feasibility work – and how switching mid-study unlocked a path to true commercial scale rather than niche pilot projects.
The Helguvík project: locating a commercial-scale e-kerosene facility a stone’s throw from Iceland’s main international airport, using 100% renewable power contracted via long-term PPAs.
Book-and-claim as a strategic tool: using it to serve committed early partners like Luxaviation and other motivated buyers outside Iceland, while keeping the bulk of production for Icelandic decarbonisation.
Moving beyond “Jet A price parity”: why chasing price parity with fossil jet fuel misses the point since jet fuel is heavily subsidised and untaxed, and how 15-year price stability can be more valuable to airlines than simply being the cheapest.
Her role as a “system builder”: why e-fuel plants are far more complex than traditional power projects, and what it takes to keep partners aligned on timelines, risk, margins, and ambition.
The wider Icelandic hydrogen roadmap: how aviation, maritime, and road transport could all draw on the same hydrogen and e-fuels backbone as the market matures.

Learn more about the innovators who are navigating the industry’s challenges to make sustainable aviation a reality, in our new book “Sustainability in the Air: Volume 2.” Click here to learn more.
Feel free to reach out via email to [email protected]. For more content on sustainable aviation, visit our website green.simpliflying.com and join the movement. It’s about time.
Links & more:
IðunnH2
Why Iceland? - IðunnH2
SAF – IðunnH2
Hydrogen and E-fuels Roadmap for Iceland
Nanna Baldvinsdottir - LinkedIn
EU ReFuelEU Aviation Mandate