ROAD TRANSPORTation

The automotive industry is currently experiencing a major transformation in the powertrain design due to the urgent need for reduced carbon footprint. There are significant opportunities and challenges for the road transportation sector to reduce its global warming impact, which accounts for approximately 10% of global anthropogenic greenhouse gas emissions.
Almost all of the world's transportation energy comes from petroleum-based fuels, largely gasoline and diesel. The primary reason for the dominant use of liquid hydrocarbon fuels in the transportation sector is that they have superior energy density, resulting in minimal weight and size of onboard energy storage. CO2 is the major greenhouse gas currently emitted from the road transportation industry, which correlates with the fuel consumption of the conventional powertrain unit.
Fuel consumption and criteria pollutant standards for both light- duty and heavy-duty vehicles have been decreasing globally to reduce the emissions in road transportation. The European Union has set the most stringent emissions standards requiring a 37.5% in CO2 emissions for passenger vehicles by 2030 compared to 2021 and a 30% reduction for heavy-duty vehicles, respectively. There are several pathways that have been explored to reduce the carbon footprint of the automotive industry such as improving the efficiency of conventional internal combustion engines, using low- and zero-carbon fuels, and electrification. The use of alternative fuels on the powertrain system can affect the net CO2 emitted depending on changes in the C/H ratio of the fuel and how renewable the fuel is.
Electrification has gained a lot of traction recently due to multiple factors, the most important being the drastic decrease in the battery cost the past decade (85% decrease in battery cost/ kWh), primarily due to economies of scale. However, the sales of new battery electric vehicles (BEV) and plug-in hybrid electric vehicles (PHEV) still represent less than 3% of the global sales in new passenger vehicles.
Electrification can offer a lot of benefits in the path towards sustainable road transportation, but there are also many challenges and misconceptions about purely electrified vehicles. The peak efficiency of the best gasoline engines is approximately 40%, however the average efficiency of the conventional engine is lower due lower efficiency regions during idle and low load engine operation. The use of an electrified powertrain with large battery capacity can eliminate the operation of the internal combustion engine at the inefficient operating regions, and allow for energy recuperation in the battery during braking. Additionally, the use of electrified powertrain eliminates local pollution, which is important in densely populated, metropolitan cities. However, there is a widespread argument that electric vehicles are zero emissions vehicles, which can be misleading.
While battery electric vehicle do not produce CO2 emissions during operation, there are considerable upstream CO2 emissions produced primarily from the electricity generation and battery production. Unlike fossil fuels, the sun or the wind, which are primary energy sources, electricity is a secondary energy source or otherwise an energy carrier. As a result, comparisons between the efficiency of electric motors with internal combustion engines are pointless, since electric motors are not converting a primary energy source to mechanical energy. Tank-to-wheel CO2 benefits of plug-ins (PHEV) and batteries electric vehicles (BEV) are huge but it is a meaningless way to look at this topic, since the life cycle emissions of the vehicles must be taken into account.
The International Energy Agency recently published a cradle-to-grave life cycle analysis on carbon reduction technology pathways for a 110kW midsize passenger car (see graph). Using the global average grid carbon intensity of 518g- CO2 /kWh, hybrid- electric vehicles (HEV) can achieve on average approximately 20% lower CO2 emissions than conventional internal combustion engine (ICE) vehicles. Plug-in hybrid electric vehicles (PHEV) offer an additional 10% in CO2 reduction compared to hybrid electric vehicles, which is similar to the CO2 reduction from battery electric vehicles (BEV).
Short range driving using a small battery electric vehicle (e.g. 200 km) was shown to be a very good application for BEV, but increasing the battery capacity to achieve a 400 km range could lead to higher CO2 emissions compared to the best hybrid powertrain vehicles. Geographical regions (e.g. China, India, Germany, Greece) where the electricity grid has high carbon intensity (>450g- CO2 /kWh), the short-to-medium term use of hydrid vehicles has immediate impact on the carbon footprint with minimal additional cost and, therefore, should be promoted. Other regions (e.g. Canada, California, Norway, UK) which have a low carbon intensity electricity grid (<200g- CO2 / kWh), battery electric vehicles provide a substantial benefit in CO2 reduction and they are the best way to reduce the carbon footprint from transportation. However, even for cleaner grids, the higher initial cost, the limited charging infrastructure and low charging rate can become barriers for wider adoption of battery electric vehicles.
Global transport energy demand is large and increasing, but there is no silver bullet solution for sustainable transportation due to a combination of barriers related to technology, economics, energy affordability and security. All technology solutions have an environmental impact, therefore it is essential to use a cradle-to-grave lifecycle analysis to effectively reduce the carbon footprint from road transportation. The internal combustion engine has been recently demonized but, in reality, the main problem is the great reliance on fossil fuels, which by definition result in a net increase in carbon in the atmosphere. In the short- to-medium term, there are many regions in the world that would achieve an immediate CO2 reduction from the use of hybrid powertrains, without the challenges associated with the use of purely battery electric vehicles.
In the long term, as the electricity grid becomes greener, battery vehicle costs are in parity with hybrids, the technology for cost-effective integration of renewable power is available, and the charging infrastructure is mature, widespread use of battery electric vehicles in road transportation will be imperative in most passenger vehicles. The long-term goal for sustainable transportation would be to replace fossil fuels with renewable electricity in light-duty passenger transportation and urban transport, and rely on renewable fuels in transportation where high energy density is necessary, such as heavy-duty vehicles and machinery.

By Vassilis Triantopoulos, PhD Research Fellow, Lay Automotive Lab,
University of Michigan, This email address is being protected from spambots. You need JavaScript enabled to view it.

Marine transportation

The maritime industry is undergoing a technological transformation motivated by the recent International Maritime Organization (IMO) regulations to reduce the carbon intensity of international shipping. Initial targets are to reduce the average CO2 emissions per "transport work" by at least 40% by 2030 compared to 2008 levels, aiming at 70% by 2050 along with a 50% reduction in total GHGs by 2050. In addition, the IMO has adopted a global sulphur cap of 0.5% vol. for the fuels used since January 1, 2020, as well as NOx Tier III emissions regulations. In order to meet these goals, the maritime industry will have to adopt an array of solutions including alternative fuels, technological improvements, and operational measures.

Alternative Fuels

The available fuel options can be categorized into three pathways: (i) light gas, (ii) heavy gas and alcohol, and (iii) the bio/synthetic fuel pathway. The selection of the fuel pathway and the associated technologies should be based on two foundational criteria: the type of vessel and its operating profile. Light gas includes fuels such LNG offers up to 21% lower CO2 emissions compared to heavy fuel oil, but this does not include carbon release from methane slip. Minimizing methane slip is critical to realizing the benefits of LNG as a bridge fuel to meet the 2030 emissions-reduction goals. In the long term, hydrogen can be a solution for zero-carbon vessels. It offers the highest energy content per mass among all candidate fuels, but it requires cryogenic storage and dedicated fuel supply systems. Significant technical advances are needed before hydrogen can be considered a large-scale commercial fuel option. The heavy gas/alcohol fuel category includes fuels such as LPG, methanol, ethanol, and ammonia. When used as the primary fuel, methanol can reduce CO2 emissions by around 10% compared to heavy fuel oil. However, methanol has the potential to be a carbon-neutral fuel in the future, if it is produced renewably as bio-methanol or electro-methanol. LPG has higher energy content than the alcohols and may be more conducive to use in modern engines, but it has not been as widely adopted as LNG. However, methanol and LPG are currently thought of as mature fuels by engine manufacturers, which have marketed engine platforms able to use them. At the end of the heavy gas or alcohol spectrum lies ammonia, which can be a zero-carbon fuel if produced renewably. Despite its toxicity and more stringent handling requirements, ammonia is considered as a viable long-term fuel option. However, comprehensive supply-side infrastructure would need to be built along with safety regulations. Bio/synthetic fuels are produced from biomass and have similar properties to diesel oil, thus they can be used as drop-in biofuels with minimal or no changes to marine engines and their fuel delivery systems. Currently, the most widely used component is fatty acid methyl esters (FAME) or biodiesel, which is offered by major oil companies. However, hydro- treated vegetable oil (HVO) is an advanced first-generation biofuel with similar properties to marine gas oil (MGO), making it fully compatible with existing equipment. Renewable diesel also can be produced from biomass gasification, often referred to as a gas-to-liquid or biomass-to-liquid fuel, which can offer reductions in carbon output with minimal capital expenditures.

Technological Improvements

Modern vessels are designed based on optimization of the hull and can be equipped with efficient propeller design using energy saving devices, such as pre-swirl ducts, stators and fins, rudder bulb, and a twister rudder. Designers are also exploring the use of anti-fouling systems and low friction coatings for the hull. The machinery of modern vessels is continuously improved, with further advancements in the main and auxiliary engines, focused on increasing their efficiency and reducing emissions formation. Other auxiliary equipment, such as pumps and climate control systems, are also improved to reduce the base electrical load of a vessel. Core new technologies considered for future vessels are hybrid electric power systems, as well as wind-assisted and solar powered systems. Hybrid- electric propulsion is currently used in offshore support vessels and harbor tugs, where the systems readily provide additional energy on demand. The architecture of a hybrid system can be designed specifically for the requirements of each vessel and thus optimize the use of each component for maximum efficiency.

Operational Measures

Technological improvements can be combined with operational measures, which aim to increase the efficiency of a voyage, and can be equally effective. Two of the most effective operational measures are just-in-time (JIT) arrival and optimum ship routing. Ships spend roughly 50% of their time in berth, anchoring or maneuvering, which account for more than 15% of their annual fuel consumption. Adoption of JIT operations would reduce the time spent waiting for berths or trade, maximize the utilization of ports and reduce the fuel costs and others associated with port stays. This would substantially reduce the emissions of greenhouse gases and other pollutants. JIT can be achieved by optimizing the vessel speed during the voyage to ensure that it arrives and departs without unnecessary delays. Implementing the JIT arrival concept requires a holistic view of the voyage, including the port operations. Optimum ship routing is another technique that is directly related to JIT. Weather conditions, geography and other factors may necessitate following a route other than the shortest distance in order to minimize fuel consumption. Identifying this route involves an optimization task using numerical algorithms.

By Sotirios Mamalis, PhD - Global Sustainability Manager,
American Bureau of Shipping (ABS), This email address is being protected from spambots. You need JavaScript enabled to view it.