I believe EPA estimates that ~3 billion gallons of waste cooking oil are currently produced by restaurants per year in the U.S. That's still a rather limited supply for renewable diesel though.

Large wind turbines can promote surface warming by disrupting surface-based nocturnal inversions which typically form over land surfaces (absent significant synoptic feature). Instead the lower levels of the atmosphere remain mixed and surface temperatures don't cool as much at night.

But again, from an air quality perspective, lower NOx emissions at the expense of higher HC, CO, PM/PN, and NH3 emissions is potentially counter-productive. Comparing the CARB certified emissions of the ROUSH "near-zero" propane engine and a competitor diesel engine (Detroit Diesel DD8)... ROUSH - 0.04 g/hp-hr (NMHC); 0.01 g/hp-hr (NOx); 5.0 g/hp-hr (CO); 0.002 g/hp-hr (PM) DD8 - 0.000 g/hp-hr (NMHC); 0.05 g/hp-hr (NOx); 0.4 g/hp-hr (CO); 0.000 g/hp-hr (PM). https://www.arb.ca.gov/msprog/onroad/cert/mdehdehdv/2018/roush_hdoe_a3440086_6d8_0d02_lpg.pdf (ROUSH) https://www.arb.ca.gov/msprog/onroad/cert/mdehdehdv/2018/detroitdiesel_mhdd_a2900163_5d1-7d7_0d20-0d01.pdf (Detroit Diesel) The ROUSH engine also has 18% higher GHG emissions than the DD8 Diesel per cert.

From an air quality perspective, lower NOx emissions at the expense of higher HC, CO, PM/PN, and NH3 emissions is a dubious proposal, and even potentially counter-productive.

Gasoline technology may have generally lower NOx emissions, but that's offset by generally higher VOC, CO, and PM emissions. Not a good trade-off for urban air quality concerns in my opinion. Diesel technology is well on its way of solving the NOx emissions issue anyway. https://www.fleetnews.co.uk/news/environment/2018/06/22/new-diesels-found-to-be-71-cleaner-than-petrol-models

Some FT systems can be configured to co-produce electricity from the waste heat generated from the process. Not sure if this particular system is conducive to the co-production of electricity, but it would be a good way of utilizing the waste heat if it is.

Surface-based monitors are mostly concentrated in urban areas, so satellite measurements may provide much more data in rural/non-urban areas, but determination of attainment with the U.S. NAAQS is based solely on the surface-based monitoring data last I knew.

I don't see how this study sheds any new light on this topic. Based on EPA's monitoring data, which are publicly available, the rate of decline in ambient NO2 and CO levels has been known to be slowing. Even then, ambient NO2 levels have declined by 20% between 2010 and 2016, while ambient CO levels have declined by 14%. Although no monitoring data are available, anthropogenic VOC emissions have declined by 10% between 2010 and 2016 according to EPA.

@bhtooefr - the problem with avoiding idling (stop-start) is that gasoline engines have been shown to produce relatively high PN emissions at each restart in hybrids (Camry specifically), higher than the conventional version of the Camry. https://trid.trb.org/view/1092112 Gasoline engines, especially GDI, really need particle filters to effectively lower their PM/PN emissions.

If you look at the studies, a special more realistic duty cycle was developed especially for these studies. I have two diesel vehicles, neither one of which smoke or have any exhaust smell whatsoever. There are still many legacy diesel vehicles (pre-2007) on the road and it's not always easy to know if they are new-technology diesel engines.

This is interesting because CARB measured particle concentrations of a diesel car during active regeneration of the DPF. The PN during active regeneration was fairly constant at about 5.0E+07 particles/cm3 (State Of California, California Environmental Protection Agency, Air Resources Board, "California’s Informal Participation in the Particle Measurement Programme (Pmp) Light Duty Inter-Laboratory Correlation Exercise (ILCE_LD) Final Research Report." October 2008). According to this Chinese study, even under the most optimal conditions, PN from the GDI car is about the same as a diesel car during active regeneration! The concentration of particles during non-regeneration events (~98% of the time) was indistinguishable from HEPA-filtered background air (~1.3E+03 particles/cm3, or at least four orders of magnitude below what the GDI emits continuously while idling according to this study.)

That's already been addressed, Harvey. The "Advanced Collaborative Emissions Study" (ACES) looked at over 300 unregulated emissions from three 2007-compliant diesel truck engines (Phase 1) and three 2010-compliant diesel truck engines (Phase 2). The results... "...Unregulated emissions that included single ring aromatics, PAH, nitroPAH, alkanes, alcohol and organic acids, hopanes/steranes, carbonyls, metals and elements, organic carbon, elemental carbon, and dioxins/furans were 79 to 99 percent lower than the emissions from a similar 2004 technology engine...." "Advanced Collaborative Emissions Study (ACES) Phase 1 Final Report." June 2009 (Page 83) "...Unregulated emissions that included single ring aromatics, PAH, oxyPAH, nitroPAH, alkanes, alcohol and organic acids, hopanes/steranes, carbonyls, metals and elements, organic carbon, elemental carbon, dioxins and furans were 50% to 99% percent lower than those emitted from 2007 technology engines tested in ACES Phase 1...." "Phase 2 of the Advanced Collaborative Emissions Study - Final Report." November 2013 (Page 69 of 70) Phase 3 of ACES looked at health effects of diesel exhaust by exposing laboratory mice and rats to concentrated diesel exhaust from a 2007-compliant diesel truck engine. The animals showed to ill-effects of the exposure - https://www.energy.gov/sites/prod/files/2014/03/f13/ace044_greenbaum_2013_o.pdf (Slide #19)

@Harvey - not sure what you smelled from the Nova bus, but there's an actual demonstration by Dr. Bruce Hill of Clean Air Task Force of a diesel school bus retrofitted with DPF emitting "1/60th of what's in the outdoor air that we're breathing right now." In other words, it's filtering the ambient air of particles. https://www.youtube.com/watch?v=Wm3i6YQOKKc @3:32-3:58 mark Just to be clear, CATF is an environmental activist group and is NOT a supporter of diesel engine technology.

Cheating on emissions certification of conventional vehicles is now essentially impossible in the U.S./Canada. The regulators are now taking as much as 6 months longer to certify light-duty diesel vehicles due to all of the rigorous extra testing that's being done, including real-world driving using PEMS under a myriad of ambient conditions.

ICCT can't even stay consistent with their own reports. http://www.greencarcongress.com/2017/07/20170711-icctdiesel.html

VW has several Euro6 diesel vehicles that meet the NOx limit in real-world conditions according to Emissions Analytics "Equa Index." Some even meet the petrol NOx limit. Even the 2017 Porsche Panamera 415 hp diesel meets the petrol limit for NOx emissions in that test. There's no fundamental reason diesels can't achieve NOx emission levels as low as petrol.

@EP According to a report by the National Academy of Sciences (“Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two”), a particle filter would not be needed with DME as a fuel. No mention of methanol though.

Even diesel-hating California Air Resources Board has confirmed that diesel cars with DPF have particle number emissions that are indistinguishable from HEPA-filtered dilution air (State Of California, California Environmental Protection Agency, Air Resources Board, "California’s Informal Participation in the Particle Measurement Programme (Pmp) Light Duty Inter-Laboratory Correlation Exercise (ILCE_LD) Final Research Report." October 2008, pages 28-30). The VW cheating had to do with NOx emissions, NOT PM. Even in the ICCT/WVU study that discovered the VW cheating in the first place, PM emissions were barely measurable: "…In general, PM emissions are on the order of 0.01mg/km ±0.005mg/km (±1σ), thereby nearly 100% (99.89%) below the US-EPA Tier2-Bin5 standard…." [Page 83 of report]. So in this case, the cars are polluting a tiny fraction of what the manufacturer claimed (certified PM emissions of 2013 Passat TDI were 0.002 g/mile (2 mg/mile)). Even in the case of NOx emissions, all diesel vehicles certified in the U.S. are subject to months of extensive additional testing and have since the NOV was issued to VW in September 2015. The additional testing is conducted to ensure the vehicles' certified emissions are representative in all "driving cycles and conditions that may reasonably be expected to be encountered in normal operation and use."

@Jeffgreen54 This isn't recent, but take a look at this presentation from ORNL http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2003/session9/2003_deer_storey.pdf , slide #10, to confirm what Peter_XX said. Also see https://www.youtube.com/watch?v=Wm3i6YQOKKc @3:32 - 3:58 of video for a demonstration of the "filtering" capabilities of diesels with DPF.

Based on personal communications with EPA, all diesel vehicles certified in the U.S. undergo months of rigorous extra testing, including real-world testing under a variety of ambient conditions using PEMS. The certification process has become so onerous that some manufacturers have pulled the certification requests. The Equa tests are real-world tests conducted with PEMS. According to ICCT: "...Recent actions by California’s Air Resources Board and US EPA indicate that future LD diesel NOx emissions will be much closer to regulatory emissions limits. These actions include ARB’s newly-developed defeat device screening methods, which notably include the use of “special driving cycles and conditions that may reasonably be expected to be encountered in normal operation and use”. As a result, average NOx emission factors for future vehicles certified to Tier 3 standards are estimated to be within 30% of the certification limit, equivalent to 14 mg/km...." Anenberg et al. "Impacts and mitigation of excess diesel-related NOx emissions in 11 major vehicle markets." Nature 545, 467–471 (25 May 2017), page S7

Four out of four diesel cars tested by Equa in the U.S. have received an air quality rating of "A", which corresponds to meeting California's SULEV limit for NOx (<0.02 g/mile). Europe is implementing RDE testing, which should preclude any diesel vehicle that exceeds the Euro6 NOx limit from being certified.

According to ANL's GREET model (GREET_2017), bioDME has the greatest GHG reductions of any transportation fuel pathway available in GREET. BioDME has net GHG emissions of -206 grams/CO2e/MJ (WTW) when configured to co-generate electricity according to GREET1_2017.

It should be noted that a previous study by CMU showed that increasing the ambient NMOG:NOx ratio increased SOA production non-linearly; increasing NMOG:NOx ratio from 4:1 to 10:1 increased SOA yield by a factor of 8. http://www.greencarcongress.com/2017/06/20170622-robinson.html Thus, decreasing NMOG emissions while leaving NOx emissions as is would decrease the NMOG:NOx ratio and result in much lower SOA production.

The various reports of air quality in Europe is so conflicting that it is impossible to really tell what's going on there. For example, this IMechE report states: "...It has become evident that London has a particularly bad NO2 problem, with levels similar to such cities as Shanghai and Beijing. This puts it among the worst cities globally in terms of overall air quality...." (Page 07) However, the latest official report by the European Environmental Agency - "Air quality in Europe — 2017 report; EEA Report, No 13/2017" - states that <10% of Europe's population lives in an area that exceeds Europe's ambient air quality standard for NO2, and that's mostly because Europe has adopted the extremely restrictive (overly restrictive?) WHO guidelines for ambient NO2 of 40 µg/m3. EU has NOT adopted the WHO guidelines for any of the other criteria pollutants. If it had, PM10, PM2.5, ozone, SO2, and benzo(a)pyrene would all be far more of a concern that NO2. Based on Figure 6.1 (page 42) of the EEA report, there would NOT be any monitor (of the thousands monitoring for NO2) that would exceed the U.S. ambient air quality standards (NAAQS) for NO2. The U.S. NAAQS for NO2 is 53 ppb or about 100 µg/m3, i.e., about 2.5 times higher than the European standard for NO2. USEPA JUST reviewed the adequacy of its NAAQS for NO2 and concluded the 53 ppb (100 µg/m3) was adequate as is (https://www.epa.gov/no2-pollution/primary-national-ambient-air-quality-standards-naaqs-nitrogen-dioxide). Hard to believe there is such a crisis when there would not be any monitors in London or anywhere else in Europe that would violate the U.S. NAAQS for NO2.

"...I wonder about their ability to meet emission standards when VW and many others have failed." It will have to or it won't be certified. Every light-duty diesel vehicle line certified in the U.S. is subject to months of extensive additional testing and has since the NOV was issued to VW in September 2015. The additional testing is conducted to ensure the vehicles' certified emissions are representative in all "driving cycles and conditions that may reasonably be expected to be encountered in normal operation and use."