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Study uncovers role of longer-chain unburned hydrocarbon emissions from diesels in London air pollution; calls for regulatory shift

Researchers at the University of York (UK) have found that longer-chain unburned hydrocarbons released from diesel—which are not currently explicitly considered as part of air quality control strategies—represent only 20–30% of the total atmospheric hydrocarbon mixing ratio but contribute more than 50% of the total atmospheric hydrocarbon mass and are a dominant local source of secondary organic aerosols (SOA) in London—and by extension to other developed megacities.

The study found that 60% of the winter primary hydrocarbon hydroxyl radical reactivity in London is from those diesel-related hydrocarbons; the authors predicted that the longer-chain HCs contribute up to 50 % of the ozone production potential in London. The results, they said in an open access paper published in the journal Atmospheric Chemistry and Physics, suggest the need for a shift in policy focus onto gas-phase hydrocarbons released from diesels as this vehicle type continues to displace gasoline world-wide.

The primary regulated air pollutants (criteria pollutants) are particulate matter (PM), nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds (VOCs). However, these can react in the atmosphere to create secondary pollutants, such as ozone (O3), oxygenated VOCs (OVOCs), peroxy acyl nitrates (PANs) and SOAs, adding to the overall pollution load.

Hydrocarbons are key precursors to two priority air pollutants, ozone and particulate matter. Those with two to seven carbons have historically been straightforward to observe and have been successfully reduced in many developed cities through air quality policy interventions. Longer chain hydrocarbons released from diesel vehicles are not considered explicitly as part of air quality strategies and there are few direct measurements of their gaseous abundance in the atmosphere.

… Comparing real-world urban composition with regulatory emissions inventories in the UK and US highlights a previously unaccounted for, but very significant, under-reporting of diesel-related hydrocarbons; an underestimation of a factor ∼ 4 for C9 species rising to a factor of over 70 for C12 during winter. These observations show that hydrocarbons from diesel vehicles can dominate gas phase reactive carbon in cities with high diesel fleet fractions.

—Dunmore et al.

The York team used two gas chromatography (GC) instruments to investigate the abundance and trends of diesel-related hydrocarbons in the atmosphere at a typical urban background site in London.

Acp1
Total mass by carbon number and functionality from UK 2012 (left) and US 2011 (right) emission inventories suggest little presence of the long-chain diesel hydrocarbons. Dunmore et al.


Acp1
The York study’s findings on the seasonal median values for hydrocarbon mixing ratio, mass concentration and primary hydrocarbon OH reactivity in London air grouped by carbon number and potential emission source. Dunmore et al.


Acp1
Underestimations in the winter emissions inventory (left axis and blue columns) and the number of isomers included in each grouped set of compounds (right axis and black squares). The faint grey line near the bottom of the chart indicates a factor of 1—i.e., the inventory emission estimation is consistent with the study’s observations. Dunmore et al.

Based on their findings, the researchers concluded that current inventories and emissions estimates do not adequately represent emissions of gas phase long-chain hydrocarbons from the diesel fleet under real-world conditions and in a developed urban environment. The calculated impact of these species is significant, they found, particularly in terms of OH reactivity, ozone formation potential and SOA production.

The shift to an increasingly diesel-powered fleet in many developed cities in response to energy efficiency drivers has shifted the balance of hydrocarbons in urban air from short to long chain compounds, they concluded, pointing to their results as providing direct atmospheric evidence of this effect in London.

Previous air quality assessments of diesel-related hydrocarbons in the atmosphere are few in number, and as discussed previously, have been made only in the US where geographic characteristics and vehicle fleet composition are very different to London, and Europe more widely. In many cities the impact of diesel hydrocarbons remains to be determined, but this work demonstrates that it will likely be significant in locations with substantial diesel fleets. An improvement in measurement infrastructure appears to be essential if this source is to be quantified more widely or the impacts of policy evaluated.

—Dunmore et al.

Resources

  • Dunmore, R. E., Hopkins, J. R., Lidster, R. T., Lee, J. D., Evans, M. J., Rickard, A. R., Lewis, A. C., and Hamilton, J. F. (2015) “Diesel-related hydrocarbons can dominate gas phase reactive carbon in megacities,” Atmos. Chem. Phys., 15, 9983-9996, doi: 10.5194/acp-15-9983-2015

Comments

Lad

So we now know that diesel fuel, with its increased carbon produces more smog than gasoline that has less carbon atoms. If we move up the refinery chain and burn propane, that should perhaps produce even less pollution. How about we just not burn hydrocarbons at all and go directly to electromagnetics. You know back to electric trains, trolleys, buses and electric cars, like a hundred years ago.

CheeseEater88

EU will probably follow the US and adopt the DPF style of equipment the US makers have taken up.(and some foreign makes) It takes the long chained carbons and re-burns them in hope to make CO2 or vastly smaller chains.

Modern diesels are about as clean as they can get. Might not be clean enough for the individuals here.

Diesels have multiple catalysts and technologies acting on the exhaust stream that Oxidizes HC/Soot and turns them to CO2 in the DPF, takes NOx and combines it with ammonia/urea in the SCR negating the NOx from the exhaust... Sulphur is eliminated from the fuel (to protect all of the emissions equipment)... Modern stuff is a heck of a lot cleaner than in the past. You're basically left with CO2, which is an inherent by product of most power generation today. Even big hydro has negative effects on the world. We don't have to wherewithal to make a 0 emission society today... but we can take what we have and make the best of it.


Lad, when I get my time machine working, you're going to be first in line ;) (but you'll have to leave me a time capsule of gold bricks, and you're not allowed to take a sports almanac. Those are my terms)


electric-car-insider.com

Electric or plug in hybrids with electricity provided by residential and commercial solar panels.

A few extra panels added to a solar installation would only cost $2,000-3,000. Nearly free EV fuel for 30 years. That's only $5.55 - $8.33 *per month* to fuel your EV. Less than one cent per mile. The rough equivalent of twenty five cent per gallon gasoline. And zero emissions.

CheeseEater88

Yeah, but you'd need a battery if you didn't have net metering available to charge your EV.

I'd love about 5Kw of installed capacity on home. Cover the HVAC and appliances during the day.

I am also looking into co-generation. wider studs for the walls to accommodate more insulation etc.

Homes are the largest expense of energy that we have... its just sad that we can't do more to further efficiencies there without going through expensive and "non-conventional" means to achieve it.

I was looking around for information on rooftop solar, and cogeneration, but there is sooo much legwork involved. Solar is fairly common, but to get a small 4-5Kw cogen setup for a home its very hard to find something in my region. Cogen I can easily get my investment back quickly as early as 2-3 years(also its a good back up generator if need be), solar would take a bit longer but could see returns during my time as an owner.

mahonj

Presumable all the VWs will have to do is to be reprogrammed.
If they can pass emissions tests, they can do more or less the same on the open road following a reprogramming.

This might reduce the power and mpg, but so what,they'll still work and they won't produce so much smog etc.

Next, in Europe, we need to get real about emissions testing.
This will be a bit of a shock as the mpg goes down 20-40% and the CO2 goes up by a similar amount, but so what.

Then, the countries will have to modify their emissions limits for tax purposes to avoid taxing new cars off the roads, they could, for instance, increase the limits by 30% and just suck it up.

They could reduce them by say 3-5% per year to bring them back into alignment.

The EU will have to put back their 95 gms/km limit by a few years to give the car companies time to catch up. They might as well do that as they will crucify their own car companies if they don't.

The EU regulators are as guilty as the car companies as they watched this happen, like a slow motion car crash and they did nothing about it. The VW thing is worse, as it was so deliberate, but the abuse of the NEDC test was known to all and allowed to happen.

That is it really, the cars on the roads are no worse than they were the day before the scandal was unearthed, we just need to get real and use the technology we have.

The kernel of the problem was focusing too much on CO2 which is a global pollutant to the detriment of NOx and HCs and particulates, which are local problems. You only have to smell the air in European cities to detect this. (Like outside my front door at 8.30 in the morning).

So you can blame the greens for most of this mess.

Lad

CE88:
How about advance knowledge of the lotto numbers?

mahonj:
So What?: Then what's the advantage of a diesel over gas for more money? Hurry up with that battery Tesla, so we can bury all this nonsense over ICEs.

DaveD

Yet another nail in the coffin of diesel.

I say again: VW has unwittingly fired the starting pistol for the race to EVs.

HarveyD

ICEs/ICEVs manufacturers (and their OIL friends) will find other ways to convince potential buyers NOT to buy partially or fully electrified vehicles.

The new (2016) 55+ mpg Prius (and similar units) all PHEVs and BEVs do much better than diesel and regular gassers. Buyers should be encouraged (via larger subsidies and tax and/or registration fees breaks) to buy those units instead of noisy dirty diesels and gas guzzlers.

DaveD

It really depends on politics at this point. If the US goes Republican during the 2016 election, then the EPA will end up peeling back standards and we'll have another 8 years of further dependence on foreign oil, and funding terrorist organizations through Saudi Arabia, etc. If it goes Democrat, then we'll keep pushing through the higher standards and electrification is inevitable.

Europe will react harshly to all of this VW mess and they'll go against diesel now and they'll start to finally push more EVs.

It will eventually happen, the move to EVs, but the timing here in the US is dependent on the next election.

Lad

DaveD:
Agree; BTW, does anyone really think OPEC forced the price of crude down without approval of the five U.S. international oil companies(IOCs)? You can bet it's a move well-planned. The IOCs know the boom and bust game and how to sweat out the competition, renewable energy and electromagnetism drive companies in this case, by manipulating prices. That was what Rockefeller did a hundred years ago. Unfortunately it the poor oil workers that suffer the most during these ups and downs because oil company management see them as nothing more than a pool of peons.

Remember RE and EVs are local and their pricing is local not international.

SJC

OPEC was told by Saudi Arabia to reduce the price of oil, they did not so Saudi did.

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