Point source removal vs. diffuse removal

Hi all,

Want to get the community’s thoughts on point source removal and areas for ambitious innovation. Based on our research, I get the sense that we are already really good at removing pollution at the source (EPA emissions control database seems to show removal effectiveness of >90% is achievable across many pollutants and sources). So in my mind, this isn’t an issue of capability, this is an issue of enforcement, compliance, and political will.

But what if I’m wrong? Experts have universally told us that ambient air pollution removal is incredibly hard and we should instead focus on point source removal/reduction.

What if reducing the price of emissions control tech by 10x could actually get more actors to buy in and reduce emissions? Or what about filtration of smaller, disaggregated sources, such as home heating systems or diesel engines? Or is there some game changing pathway to reduce emissions at the largest sources? Where might the greatest impact lie?

Thoughts? @bartc @carlbozzuto @akb @Ananya_Roy @djaffe @hopkepk @hlee

@jamesburbridge
If we are talking about particulates, technology for capture already exists for both point source and point use. A room air conditioner has a filter in front of the heat exchanger to help prevent dust from depositing on the tubing. The 4 billion people that you referenced, mostly living in Asia, may still be living in rather primitive conditions. I haven’t been to India in a while, but the last time I was there, many villages still consisted of mud huts with thatched roofs. Sure, there was a road going through the village, but that just stirred up fugitive dust. We need to be careful here. We are assuming that particulates have the same impact there as we might expect in OECD countries. However, in these same villages, on market day, raw meat is hung out in the open for sale on an 85 F day. I would imagine that spoilage could be a significant problem. Consumption of tainted meat is more likely to result in death than particulate concentration. Reducing particulate concentration may do little to reduce death rates in these circumstances. A much better understanding of local conditions will be needed to reduce ambient concentrations in these areas. One size will not fit all.

This is a great question @jamesburbridge and it’s got me thinking… :slight_smile:

Here’s an initial thought [though there are many more opportunities too, I suspect].

During the research for the XPRIZE energy design this striking fact arose: about one billion people have no access to electricity, and a significant proportion use indoor fires (e.g. wood) for heating and cooking. The associated air pollution causes health problems. So a successful, low cost, clean electricity source would be helpful; and in the absence of such a breakthrough a clean heating device with no emissions would be useful.

An XPRIZE might facilitate the creation of a clean heating device.

Innovations have to tick lots of boxes before they become successful, and one of those boxes is: will the innovation still be relevant in the future?

A big producer of air pollution is combustion, but we are moving away from combustion towards electricity (particularly as a source of energy, and for transport). So the question I ponder to myself and others is: would accelerated innovation towards a combustion free world be a better solution for preventing air pollution?

I can see both sides of that argument. A rapid removal of all combustion processes and a move to clean electricity would probably solve the air pollution challenge (to a large extent - but other sector issues remain, such as agriculture). Conversely, for some change takes a long time even when a technical solution exists. For example, it might take ten years before old polluting vehicles are phased out.

So perhaps pursuing both options (electricity and pollution reduction) makes sense [?]

Electric Cars are often cited as the wave of the future. As long as the life cycle emissions of the electric car are lower than the emissions from the grid, there will be an improvement. That falls into the category of “both”.

Electrification of trucks needs to happen faster and cheaper:
Heavy duty trucks are by far the most polluting in both conventional air pollutants and GHG. The older they are the worse the performance. This sector of emissions is the projected to grow worldwide and the rate of growth is higher in developing countries.
Electric battery technology for trucks is on it’s way with several automotive companies engaged. But the uptake of this is going to be slow and only targets new trucks bought. The policy targets reflect this.


Older trucks and equipment are used longer and at lower degrees of maintenance in developing countries where air pollution is worse.

One option is cheap conversion kits. This is what facilitated the switch to CNG as a fuel in India. I don’t see much discussion about this in the electrification strategies being discussed.

Even for cars. The current conversion kits/ companies are not cheap (ranging from $5000-20000). This is at par or higher than buying a new Maruti alto car in India.

@bartc thoughts?

Note that transportation emissions are a small contributor to air pollution health burden in the developing world. As it urbanizes it is going to be a bigger source.
https://theicct.org/publications/health-impacts-transport-emissions-2010-2015


One more link on electrification of trucks:

Regarding diesel retrofits, some are in fact being proposed.

In this 10/10/19 press release:

ENGIE and Anglo American to co-develop renewable hydrogen solution to decarbonize the mining industry

Engie says about these 300+ tonne trucks:

“The modifications to the existing truck include replacing the diesel tank with hydrogen tanks, and replacing the engine with hydrogen fuel cells and a battery pack.”

@KeithDPatch that is awesome new! What is the cost of the retrofits?
My concern is that solutions that are viable for large companies are out of range for the kind of consumers in India, Africa etc… places where old trucks/ outdated equipment often get sold because there aren’t stringent local emission norms or lax implementation of rules. Then they get used longer because of the upfront cost of replacement.

@Ananya_Roy it is the first hydrogen fuel cell-powered 300 t mining truck, so even the design of this prototype might not match the final FCV-powered truck design. So no retrofit cost info is available.

Also, nobody has mentioned that old/retired school buses from the USA and other developed countries get sent to less-developed countries. Perhaps a bus buyback or other program could prevent these polluting vehicles from being shipped overseas, where they continue belching emissions for years?

OTOH, if the supply of old/retired school buses dries up, those less-developed countries will get mad that they now have to buy brand-new, expensive buses. So a separate rebate program would be needed to cushion the blow from buying all those new, clean buses.

Here is a UN document on the flow of second hand vehicles. It points out the impact national policies on age and emission standards have on the flow.

Thanks, @Ananya_Roy

Good points @Ananya_Roy about dealing with old polluting lorries.
Here’s one approach that can be used to reduce emissions of existing lorries:
Reducing toxic emissions from diesel powered vehicles (PDF, 358kB)

There are a few companies adopting these new opportunities (electrically powered assistance to reduce emissions on acceleration; and total replacement of the diesel engine with electric power). An acceleration of innovation in this area to produce low cost components and quick, low cost, installations could be beneficial for a decade or so (prior to all vehicles becoming zero emission).

Hi @JimGaston , @josephjjames , @Shaina , @tito , @John_Kay , @nemet ,
What according to you is the most effective; point source removal or diffuse removal of pollution. Please join the discussion thanks.

@jamesburbridge
Point source removal is more effective simply because the concentration of the pollutant in question is less dilute. For example, the concentration of SO2 in flue gas is in the range of 3000 ppm. Ambient air concentration is less than 75 ppb. Thus, one would have to treat 400,000 times as much gas to treat the same number of lbs of SO2 in air as that in flue gas. Furthermore, the driving force to dissolve the SO2 gas into the liquid scrubbing solution is proportional to the concentration difference between the gas phase and the liquid phase. Since an alkaline solution is typically used, the back pressure is small but still positive. That means that much more solution will be needed to get the same amount of removal. Consequently, the cost per ton of sulfur removed is much, much less for point source capture than for air capture. The combination of larger size equipment and greater liquid flow rate would mean roughly 1 million times more expensive for air capture. Thus, if the market price for SO2 allowances is on the order of $100/ton for point source capture, the price for air capture would be around $100 million/ton. Air capture only really works for protecting equipment or when it is a by product of something else. The air filter on a car is there to protect the engine. The little filter on the face of a window air conditioner is there to keep dust off of the heat transfer surface. It also takes dust out of the room. The cost of the filter is negligible. We don’t calculate the cost/ton of dust removed from these devices.

Dear Mr. James Burbridge ( @jamesburbridge ), There MAY be a valid heating device for the poorest people of the world, which everyone overlooked! Way back in the 1960s, the USA’s EPA was looking into using Fresnel Lenses, which are flat, transparent sheets of plastic, with concentric rings in them, which can be used to focus sunlight to a point so hot it melts metals. They used a big Fresnel Lenses to put that focused heat, into a system that incinerated liquid nerve gas safely in the Nevada dessert. The EPA’s big idea here, was that, although conventional incinerators do work to incinerate toxic wastes, the cost of the fuel needed to empower them gets very high, when dealing with the massive amounts of toxic wastes we have. But, the sunlight is FREE! But, this thing never caught on. Anyway, recently, www.formlabs.com , a 3D printed product company, made a 3D printer that makes such large, wide Fresnel lenses CHEAPLY. So, it should be economically possible, to mass produce such Fresnel Lenses, to give to all of the places on earth, where an alternative to costly fuel or coal or fire wood needed to cook food or boil water, is needed. PLUS, no smoke or CO2 emissions to make global warming worse! This could save a LOT of trees too. Finally, these lenses could be used to do on the spot incinerations, of dog or cat or farm animal manure, or to eliminate the homeless population’s #2 deposits in the streets in many large cities, and to clean up the incredible human manure deposits that piled up all over Mount Everest, in Tibet, left by the mountain climbing tourists. And, the ashes from this procedure could be collected to sell as a mineral potash for lawns and farm crops. It could also be used to boil urine into a thick slurry, that could be commercially processed into Miracle-Grow pellets, or as a new source of phosphate for fertilizer or industry. That covers it.

Hi @sagnikdey , @thomasferguson85 , @brgentry , @thester , @skedia2 , @dmatross , @Chandra_Bhushan
Please share your views which is more effective; Point Source Removal Vs. Diffuse Removal?
Thanks.