Repositioning ICE Vehicles with engine decarbonization

Engine decarbonization refers to a range of technologies and processes that reduce or eliminate carbon dioxide emissions from ICE vehicles. In practice, engine decarbonization covers combustion optimization, hybrid integration, and the adoption of low-carbon or renewable fuels, supported by advances in materials and lifecycle efficiency. 

Engine decarbonization reframes ICE vehicles from legacy to transitional assets and tools that can complement electric mobility rather than compete with it — and positions them as a credible part of the global strategy for decarbonization of cars on the road to net-zero.

Cleaner ICE technologies, hybridization, and low-carbon fuels offer viable pathways to reduce emissions while maintaining affordability and scalability. Recognizing the continued relevance of ICE within the broader decarbonization framework is essential for crafting realistic, regionally tailored mobility strategies.

The global mobility narrative is often framed as a binary: EVs represent the future, while ICE vehicles are relics of the past. 

In reality, ICE vehicles are far from being obsolete. They are evolving and remain a critical component of the net-zero strategy, especially in markets where full electrification faces economic or infrastructural barriers.

Hybridization: Bridging the gap

Hybrid powertrains balance ICE efficiency with electrified propulsion, cutting fuel use and emissions while avoiding full EV infrastructure needs. The chart below shows 2030 life-cycle carbon intensity for new light vehicles by fuel type, split into upstream emissions (from materials and components) and downstream emissions (Well-to-Wheel during use).¹

Transitioning from pure ICE to PHEV increases upstream emissions by around 18% due to battery production but cuts downstream emissions by nearly half through better energy efficiency. Overall, switching to PHEVs can lower total CO₂ intensity by almost 40%.

This pathway is particularly relevant in regions where charging infrastructure is limited or where consumers still face range anxiety. Hybridization also allows OEMs to leverage existing ICE platforms while incrementally improving environmental performance.

The transition to net-zero does not necessitate the extinction of ICEs.  Low-carbon fuels—particularly e-fuels and waste-based biofuels—offers a viable pathway to decarbonize ICE vehicles while leveraging existing infrastructure. These fuels are compatible with current ICE platforms with minimal modification, making them a scalable solution for reducing lifecycle greenhouse gas (GHG) emissions.

Recent life cycle assessments (LCA) from Concawe indicate that e-fuels—including e-hydrogen, e-methane, e-methanol, e-diesel, and e-kerosene—can achieve cradle-to-grave GHG emissions below 6 gCO₂e/MJ in Northern Europe by 2050. This represents a 92% reduction compared to conventional fossil fuels (94 gCO₂e/MJ), and comfortably meets the EU RED II threshold of 28.2 gCO₂e/MJ (equivalent to a 70% reduction).

While e-fuels produced in Central and Southern Europe are expected to have slightly higher emissions due to regional variations in grid carbon intensity, they still demonstrate significant reductions. For example, projected emissions for these regions remain below 13 gCO₂e/MJ, representing an 86% reduction compared to fossil fuel baselines.

These findings underscore the importance of regional energy mix and infrastructure in determining the carbon intensity of synthetic fuels. Nonetheless, e-fuels remain a promising solution for sectors where electrification is challenging, and for extending the utility of existing ICE fleets.

Biofuels—particularly those derived from waste oils and agricultural residues—offer another compelling route to decarbonize ICE vehicles. Depending on feedstock and production geography, lifecycle GHG emissions from biodiesel can be reduced by 50–80% compared to fossil diesel.

A 2025 study published in (Energy Journal Volume 320 – Elsevier) assessed the carbon footprint of biodiesel produced from waste cooking oil (WCO). The results showed lifecycle emissions of 359.33 kg CO₂ per ton of biodiesel, translating to an 88.4% reduction relative to petroleum diesel. Similarly, a 2022 U.S. study found that biodiesel and renewable diesel (RD) derived from soybean, canola, and carinata oils achieved 40–69% reductions, even after accounting for land-use change impacts.

These findings highlight the potential of waste-based biofuels to contribute meaningfully to transport sector decarbonization, especially in urban contexts where feedstock availability and circular economy principles align.

As OEMs adjust their electrification strategies, advanced combustion technologies have become essential tools for improving fuel economy and reducing emissions across internal combustion platforms. These innovations not only extend the relevance of ICE vehicles but also enhance their compatibility with hybrid systems and low-carbon fuels—making them a vital part of the broader decarbonization landscape.

To illustrate the impact of these technologies, the following matrix presents a structured overview of selected solutions categorized by functional domain, fuel applicability, and fuel consumption benefit. These examples reflect some of the most effective approaches currently deployed across the industry. 
 

These technologies are deployed in varying combinations depending on regional fuel types, regulatory requirements, and vehicle platforms. Their cumulative impact can yield double-digit improvements in fuel efficiency and significant reductions in lifecycle CO₂ emissions—especially when integrated with hybrid architectures or alternative fuels.

The examples shown here represent high-impact solutions that are shaping the next generation of ICE innovation. They reflect a broader engineering effort across the industry to optimize combustion systems for a net-zero future.

Achieving substantial reductions in overall emissions from internal combustion engine (ICE) vehicles requires consideration of supply chain impacts, not just operational usage. Original equipment manufacturers (OEMs) are actively pursuing strategies to reduce Scope 3 Category 1 emissions by optimizing materials and manufacturing processes. 

The accompanying chart demonstrates that aluminum accounts for approximately 30% of the embedded carbon in a typical ICE vehicle constructed primarily from virgin materials and powered by average electricity sources. The carbon footprint of aluminum production spans a broad range—from 0.37kg to 17.53kg CO₂ per kg—depending on specific methods and energy inputs. Selecting lower-emission aluminum offers significant potential for reducing supply chain-related CO₂ emissions.

Many global OEMs have recalibrated their electrification ambitions either by extending their 100% electrification timelines or lowering their target ratios. This shift reflects the realities of market demand, regulatory uncertainty, supply chain constraints, and evolving consumer sentiment. 

Rather than signaling a retreat from decarbonization, these adjustments have prompted OEMs to diversify their strategies, leveraging hybridization, alternative fuels, advanced ICE technologies, and life-cycle emission management to keep their transition on track.

Despite these adjustments, OEMs are actively pursuing a range of decarbonization measures. The table below maps selected OEMs to the strategies they are adopting, highlighting both common approaches and leaders in aggressive fleet decarbonization.

To illustrate the impact of these strategic shifts, S&P Global Mobility has modelled the projected emission landscape for major OEMs under both “original” and “revised” electrification scenarios. This simulation demonstrates how diversified decarbonization measures—beyond pure electrification—can still drive significant fleet emission reductions.