Australia’s new emissions rules will put yet another bump in the road for diesels

Varun Rao, Monash University and Damon Honnery, Monash University

Diesel cars have been rather controversial lately, as anyone who has been following Volkswagen’s recent tribulations will know.

In the past few years diesels have surged in popularity in Australia. They now account for 19.7% of all registered vehicles (up from 13.8% in 2010). The number of registered diesels increased by more than 60% from 2007 to 2012.

Consumers have embraced diesels mainly because of the savings delivered by their favourable fuel economy. But the Volkswagen scandal suggests that some manufacturers can design engines that meet either the requisite emissions standards or the market’s expectations of fuel economy and driveability, but might struggle to achieve both.

Australian emissions standards have generally lagged behind those of Europe and the United States, but the gap will reduce in November 2016, when Australia will adopt the full Euro 5 standard for all light vehicles.

Motorists will see the advent of hitherto unfamiliar emissions control devices, and it could potentially signal the end of the road for booming diesel sales.

Exhausting issue

Diesel exhaust contains many compounds, although the regulations are mainly concerned with just three: carbon dioxide (CO₂), nitrogen oxides (NOx), and particulate matter. CO₂ is a greenhouse gas and one of the principal combustion products of the fuel itself (the other being water). Virtually all of the carbon in the fuel is converted to CO₂, so a reduction in these emissions must necessarily come from an improvement in fuel economy.

NOx is formed in diesel engines under the twin conditions of high temperature and high oxygen concentrations. Particulate matter, meanwhile, consists mainly of carbon nanoparticles from partially burnt fuel and is formed when temperature and oxygen concentrations are low.

This means that any attempt to reduce NOx emissions by altering temperatures and/or air-fuel mixing would tend to increase particulate matter emissions, and vice versa.

Australia’s impending move from the Euro 4 to Euro 5 standards will require a 28% reduction in NOx emissions and an 80% cut in particulate matter emissions, as this graph shows.

Successive sets of Euro standards call for ever-lower pollution emissions.

There are several methods to achieve these cuts, each with its own technical problems. Exhaust gas recirculation (EGR) returns a portion of the exhaust gas to the engine’s air intake, thus reducing the amount of air (hence oxygen) entering the cylinders. This also reduces cylinder temperatures, all of which helps cut NOx emissions.

The downsides of EGR are a reduction in fuel economy (and therefore an increase in CO₂ emissions), as well as reduced power and an increase in particulate matter. The system is also prone to fouling by particulate matter and can increase maintenance costs.

Diesel particulate filters (DPFs) are widely recognised as the most practical way to meet the 80% reduction in particulate matter emissions required by the Euro 5 standard, but these are also problematic for car owners.

To avoid the DPF becoming clogged, removal of the particulate matter collected by the filter is done periodically by oxidation. This typically requires at least 10 minutes’ continuous fast driving, such as on a highway, roughly once every 300-800 km. So if the car is predominantly driven on short urban trips between home, work and the shops, the DPF could prematurely stop working.

Even for diligent owners who follow this procedure, DPFs are not without their problems. By acting as an obstacle to the free flow of exhaust gases, they reduce engine efficiency and fuel economy, resulting in higher CO₂ emissions. And while the carbon in the collected particulate matter can be oxidised, metallic ash from lubricating oils and engine wear remains in the filter, which necessitates periodic cleaning.

Buyers of used cars in particular should factor in the cost of replacing a DPF, which can be several thousand dollars.

The future of diesel

Where does this leave diesel cars versus petrol ones? Diesel engines have historically offered fuel economy savings of 5-20% relative to petrol (see here and here), and these savings increase with the size and weight of the vehicle.

Against these savings must be weighed the generally higher price of diesel fuel over petrol in Australia, greater vehicle purchase and maintenance costs, and now the fuel economy penalty caused by new emissions control systems.

EGR and DPFs can reduce fuel economy by up to 6% and 3%, respectively. The need to regenerate DPFs through periodic long-distance driving might be a burden for some drivers not used to driving these distances.

As increasingly stringent emissions standards begin to weaken the financial rationale for owning a diesel, we may start to see diesel car sales drop – particularly for small and mid-sized passenger cars, where the fuel economy advantages were weakest to begin with.

The Conversation

Varun Rao, Research Engineer, Maintenance Technology Institute, Department of Mechanical and Aerospace Engineering, Monash University and Damon Honnery, Professor, Department of Mechanical Engineering, Monash University

This article was originally published on The Conversation. Read the original article.


Delving deep into caves can teach us about climate past and present

Gabriel C Rau, UNSW Australia; Andy Baker, UNSW Australia; Mark O Cuthbert, University of Birmingham, and Martin Sogaard Andersen, UNSW Australia

Have you ever enjoyed the cool refuge that an underground cave offers from a hot summer’s day? Or perhaps you have experienced the soothing warmth when entering a cave during winter?

When descending into a cave, you may not only enjoy the calm climate, you may also admire the beauty of cave deposits such as stalagmites, stalactites and flowstones, known by cave researchers as speleothems.

Perhaps you already know that they grow very slowly from minerals in the water that drips off or over them. This water originates from rain at the surface that has travelled through soil and limestone above, and seeped into the ground and ended up in the cave.

As speleothems grow, they lock into their minerals the chemical signatures of the environmental and climatic conditions of the time the rainwater fell at the surface. So, as a stalagmite grows, the surface climate signature is continuously trapped in the newly created layers.

Some very old stalagmites hold climatic signatures of the very distant past, in some cases up to millions of years. They contain an archive of the past climate as long as their age, often predating global weather station records.

Above and below

But if a cave remains cool during summer and warm during winter, how is its climate related to that of the surface? And how does this affect the chemical signature recorded by speleothems?

To understand the relationship between surface and cave climate, our research group, Connected Waters Initiative Research Centre at UNSW Australia, conducted multiple field experiments at the Wellington Caves Reserve in New South Wales.

During the experiments, the surface and the cave climates were measured in detail. For example, highly accurate temperature sensors were used to measure the water temperature at the surface, and at the point where water droplets hit the cave floor forming stalagmites.

Installation of high-resolution temperature sensors inside the cave
Martin S Andersen

The research team initiated controlled dripping in the cave by irrigating the surface above the cave with water that was cooled to freezing point to simulate rainfall.

The cold water allowed us to determine whether the drip water in the cave is affected by the conditions at the surface or those along its pathways through the ground.

We also added a natural chemical to the irrigation water, which allowed us to distinguish whether the water in the cave originated from the irrigation or whether it was water already present in the subsurface.

Our results revealed a complex but systematic relationship between the surface and the cave climate. For example, surface temperature changes are significantly reduced and delayed with depth.

Our research illustrates how to decipher the surface temperature from that in the cave. Understanding this is necessary to correctly decoding past surface temperature records from their signatures preserved in stalagmites.

Keeping it cool

We also discovered that air moving in and out of the cave can cool cave deposits by evaporating water flowing on the cave deposits. This cooling can significantly influence the chemical signature trapped in the cave deposit and create “false” signals that are not representative of the surface climate.

In other words, it will make the surface climate “look” cooler than it actually was, if not accounted for. While this is more likely to occur in caves that are located in dry environments, it may also have to be considered for stalagmites in caves that were exposed to drier climates in the distant past.

Temperature loggers installed on stalactites to measure the drip water temperature
Martin S Andersen

Our new knowledge can also help scientists select the best location and type of stalagmite for the reconstruction of past climatic or environmental conditions.

This new discovery is significant because it can improve the accuracy of past climate signals from cave deposits. It may also help us understand previously unexplained artefacts in existing past climate records. By improving our understanding of the past climate we can better understand future climate variations.

The Conversation

Gabriel C Rau, Associate Lecturer in Groundwater Hydrology, UNSW Australia; Andy Baker, Director of the Connected Waters Initiative Research Centre, UNSW Australia; Mark O Cuthbert, Research Fellow in Hydrogeology, University of Birmingham, and Martin Sogaard Andersen, Senior lecturer, UNSW Australia

This article was originally published on The Conversation. Read the original article.

Will the Paris agreement be legally binding?

Katherine Lake, University of Melbourne

The inability of previous climate summits, notably Copenhagen in 2009, to deliver a legally binding agreement led some people to declare those negotiations a failure. But in practice, this should not be the central criterion for gauging success.

In Paris, the outcome should be judged on how far it goes towards supporting countries to scale up existing emissions reductions and stay within the agreed 2℃ global warming limit. It is not necessary that the agreement be legally binding, as long as the outcome establishes a process for achieving the necessary scale of action.

At the Durban meeting in 2011, negotiators agreed to create “a protocol, another legal instrument or an agreed outcome with legal force” by the end of the Paris summit. This wording was deliberately chosen so as not to limit the options for how much legal force the agreement should carry.

There is now a growing recognition that the outcome will be either entirely political, or a hybrid approach consisting of a legally binding agreement relating to process and conduct (such as provisions on scaling up the mitigation pledges), but in which countries’ emissions targets themselves are non-binding.

While a comprehensive treaty may seem ideal, in practice there is no necessary connection between the legally binding nature of an international agreement and its effectiveness in producing outcomes.

Legally binding treaties tend to encourage countries to make modest commitments in order to minimise their risk of non-compliance, or else to opt out entirely. The Kyoto Protocol was internationally binding but this came at a cost of reduced participation (the United States did not ratify it) and ambition (Australia’s Kyoto target, for example, actually allowed it to increase emissions, while developing nations were not given any emissions restrictions at all).

Ultimately, political will and state action are what makes an international deal effective, so the outcome in Paris should provide a basic framework that will support countries to scale up the emission reductions that they are already making, so that we can achieve the 2℃ goal as efficiently as possible.

Domestic action leads the way

Unlike the highly prescriptive Kyoto Protocol, the approach adopted in the run-up to Paris gives countries more freedom to choose their own climate targets (or in UN-speak, their Intended Nationally Determined Contributions, or INDCs) and to outline how they plan to meet them.

While not legally binding, INDCs are publicly available, so countries are accountable not only to other states but to a wide range of domestic and international stakeholders.

This is likely to lead to a more ambitious outcome in Paris, not least because the pledges are not “locked in” as they were under the Kyoto Protocol but are intended to be reviewed at regular intervals (the United States has suggested every five years), with the aim of ratcheting them up until the 2℃ goal can be met.

For this approach to succeed, however, the INDCs need to be underpinned by a core set of rules, preferably embodied in a legally binding agreement, or at least in decisions made by consensus by the Parties. These should cover processes for scaling up pledges, as well as procedures for monitoring, reporting and verifying countries’ progress towards their targets.

At a minimum, the rules should also make it clear what industry sectors and greenhouse gases are included in a country’s climate pledge; the policies and laws it has passed (or intends to pass) to deliver it; and whether it proposes to use mechanisms such as international carbon trading.

Emissions trading

The new approach puts a much greater focus on mitigation within countries. As a result, the Paris outcome is unlikely to establish any new market mechanisms, as the Kyoto Protocol did. Yet many developing countries’ INDCs state that their emissions pledges are dependent on buyers of international offsets from projects in their country.

Carbon markets will need to play a central role in transitioning the global economy, and the expansion of these key carbon markets will increasingly be led by alliances and “clubs” of willing countries and organisations, rather than being enshrined in UN protocols. One such alliance that has already emerged is the Carbon Pricing Leadership Coalition, which includes the World Bank, the International Monetary Fund, and global leaders such as German chancellor Angela Merkel.

We are entering a new era of international climate cooperation. It may be less legally standardised than the Kyoto era, but it is also likely to be more effective.

The Conversation

Katherine Lake, Research Associate at the Centre for Resources, Energy and Environmental Law, University of Melbourne

This article was originally published on The Conversation. Read the original article.