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The fossil fuel replacement situation is changing rapidly.


Whether you believe in climate cage or not isn’t the issue: the fact is that all engine makers are heading down the alternatives-to-fossil-fuel path and a tiny market like Australia’s isn’t going to influence global developments.


The whole alternative-power scene is in a continual state of change, as new technology shifts the goal posts almost every day. We’re keeping abreast of developments and here’s the state of play, as at June 2023.

Combustion engines that power the transport sector, dominated by cars, trucks, buses and bikes, produce 16 percent of Australia’s greenhouse gas emissions. That proportion alone makes transport a target for reductions, plus there are the additional factors of reliance on imported powertrains and fuel stocks, in an uncertain trading world.

Any change to our fossil-fuelled world is going to be evolutionary, rather than revolutionary, because the supermarket shelves have to be filled and people have to move around. In a way, it’s almost beneficial that Australia lags way behind the developed world in adopting global emissions targets, because at least we get to see overseas mistakes and may avoid making them ourselves.



Diesel alternatives


Currently there are only three viable alternatives to fossil fuels: battery electric vehicles (BEVs), fuel cell electric vehicles (FCEVs) and renewable-fuel internal combustion engines (ICEs). ICEs can also be used in conjunction with BEV drivelines, in the form of Hybrids.

All major engine makers have developed BEVs to varying stages of production readiness, but at this stage all of them are suitable only for short-haul work, probably within 150km of a place where batteries can be recharged overnight.

Proton-exchange membrane (PEM) FCEVs use hydrogen gas as a ‘fuel’ to produce combustion-free electricity. Only Toyota and Hyundai now have FCEV production passenger cars and neither has been a market success in the USA or the EU; Hyundai is spot-selling FCEV trucks and buses into selected applications and Daimler, Volvo, Cummins and GM have truck-suitable fuel cells under development.

Neither BEVs nor FCEVs are suitable for long distance driving at this stage, because of the limited range of BEV batteries and the volume of hydrogen tankage needed on an FCEV.

That’s why most engine makers are developing ICEs that can run on a variety of renewable fuels. If a fuel is derived from natural growth or decay processes and burnt, its CO2 emissions are considered neutral, because they can be absorbed by plants once more. Some alternative fuels have no carbon content at all and produce no CO2 when burnt.

OK, what’s happened so far in the real world?





BEVs are already a given and all major makers have at least one variant in development or limited production. Sure, you can’t yet wander into an Australian dealership and take delivery of your new BEV real-4WD, but you can get a BEV SUV for short-haul vocations.

As battery energy density improves, so will the operational range of BEVs. However, without en route fast-charge infrastructure, or induction charging on sections of all major highways – charging BEVs as they drive over charging coils – BEVs will not be suitable for long distances, or use in remote areas.

At present, BEVs have batteries and electric components wedged into chassis designed for fossil fuel powertrains, but the next generation will be specifically designed for BEV powertrains. The result will be more battery capacity for a given tare weight and drivelines with lighter eAxles, not conventional drive axles.

Volume production BEVs are a certainty.





Referred to as ‘fool cell vehicles’ by Elon Musk, fuel cell electric vehicles don’t have the clear, if application-limited, acceptance that BEVs do. However, like BEVs, FCEVs have the attraction of emissions-free operation, plus the potential of increased operating range.

However, as this chart clearly shows, an FCEV is far less efficient than a BEV and it’s significantly more expensive as well.



Unlike the almost universal development of BEVs by major makers, FCEVs have been developed by only a few. If the experience with FCEV cars is any indication of market success, FCEV 4WDs don’t seem to have much of a future at all.

Now that GM and Mercedes-Benz have abandoned FCEV car initiatives and Honda has ceased production of the Honda Clarity FCEV,  Hyundai’s NEXO and Toyota’s Mirai are the only series production FCEV cars in the market. Both makes scored volume increases in 2021, but slumped badly in 2022.

Toyota, Hyundai and the governments supporting the rollout of FCEVs jumped through financial hoops to achieve any sales at all. In California, the Mirai was given a 65-percent discount from its US$50k list price, while US federal and state-level tax incentives discounted it a further US$12.5k. Toyota also offered a US$15k fuel credit for the first three years of operation. 

Nearly all the Hyundai NEXOs sold in 2021 were in South Korea, where there was  a subsidy provision of around US$30k that halved the sticker price.

Nevertheless, Hyundai is persevering with its hydrogen-powered FCEV XCIENT trucks and five evaluation units arrived at the Port of Auckland in New Zealand in late 2021. New Zealand is only the third country to have access to these trucks, following Switzerland and Korea.



Construction of a state-of-the-art ‘green hydrogen’ production and fast-refuelling facility is located near the entrance of Port of Auckland. New Zealand’s green hydrogen will be produced from geothermal power, in contrast to nearly all industrial hydrogen that’s produced from natural gas (CH4), in a high-emissions process.

By way of contrast, there are only four retail hydrogen outlets in all of Australia:  in Melbourne, Brisbane and Canberra.

Interestingly, the US military establishment has invested in FCEV development for one very significant reason: a fuel cell has no ‘heat signature’ and unlike an ICE, can’t be detected by heat sensitive equipment.



‘Agnostic’ ICEs

Parallel with its investment in electric vehicles, Cummins is actively pursuing internal combustion engine (ICE) developments that use low-carbon and renewable fuels, in variants of its spark-ignition and compression-ignition engines.

Low-carbon fuels emit less CO2 than diesel fuel; carbon-neutral fuels also emit CO2 when burned, but the carbon emissions are fully offset by another activity;  zero-carbon fuels, such as ‘green’ hydrogen, do not emit CO2 at all when burned; and carbon-negative fuels are those where fuel generation and consumption results in a net reduction in greenhouse gas emissions.

At this stage the fuel field looks like this: hydrogen, natural gas, biodiesel and synthetic ‘e-fuels’. However, it’s important to remember that all these fuels – even hydrogen – produce oxides of nitrogen (NOx) when burnt and these emissions have to be eliminated using existing selective catalytic reduction (SCR) technology.

Hydrogen is being touted as the ‘new diesel’, but it’s far from that. Even with the best available technology, production of ‘green’ hydrogen is expensive and inefficient, so that by the time it’s burnt in an engine the net result is only around 18-46 percent thermal efficiency, according to MIT.

Hydrogen is notoriously difficult to store and transport, so tankage is an issue.

Natural gas or methane (CH4) produces less CO2 than diesel and renewable natural gas (RNG) can be carbon negative. For example, RNG produced from degradation of organic matter that would otherwise be left to emit methane emissions, has negative carbon intensity. 

Biodiesel is a renewable fuel produced primarily from fats and vegetable oils. The plants used as feedstock to produce biodiesel withdraw carbon from the atmosphere and when biodiesel is burned, it returns the same carbon atoms back to the atmosphere – theoretically, making biodiesel carbon neutral. 

Blends of biodiesel are already in diesel pumps around Australian and the next step towards lowering emissions are engines that can run on B40 and then on B100.

Synthetic fuels – e-diesel and e-gasoline can be produced using CO2 and green hydrogen, so they’re carbon-neutral, because they release the carbon that was originally used to create them back to the atmosphere. Obstacles are high cost and limited availability.

Cummins’ so-called ‘fuel-agnostic’ engine and powertrain platforms are designed to expand the use of low to zero carbon fuels. They consist of a series of engine versions that are derived from a common base engine. The bottom end of the engine looks the same, but unique cylinder heads are designed to accommodate different low- or zero-carbon fuels. 

Toyota/Lexus 2.4-litre petrol hybrid engine


In what direction Australia heads is anyone’s guess at present, given our widely-spaced population concentrations. At OTA we think that for most 4WD applications, petrol-hybrid powertrains will start to replace diesels for many buyers, from 2024.




























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