Great Western Coffee Shop

No, not at all. No poo whatsoever. There'll be no poo-pooing these buses. A year or so after the demise of Bristol's "poo buses", we're to get 100 buses running on... "bio-methane". 
::)

According to my Googlings, these buses should emit 70% less GHG and 'virtually no' PM10s. Not to be sniffed at, I'd say. Wonder how the total cost of ownership compares?

Is this like palm reading, except consulting a different part of the body?

Yes.

I'm sure we all look forward to the orificial official release concerning the first buses to run.

This bus gets the runs for those who wait, it does not wait for those who get the runs.

Remains to be seen whether it runs a sh1t service.....

...I'm here all week...

Is this the same story from The BBC (http://www.bbc.co.uk/news/uk-england-bristol-41072878)

The part of the grant aimed at the buses rather than the refuelling plant equates to a little over £27,000 per vehicle. I suppose this is how much more than a standard diesel bus that these cost. An article on the Bristol 24/7 website (https://www.bristol247.com/lifestyle/environment/bristol-launches-bio-gas-bus/) gives a manufacturing cost of £295,000, compared to £675,000 for the electric buses used on the UWE to Temple Meads route.

Before I pour scorn on some of the hyperbole, I will say that I fully support anything within reasonable cost that could help to clear up the air in Bristol, and the world beyond it. As Red Squirrel has pointed out, greenhouse gases are greatly reduced (with a caveat), and small particles of soot are absent. So far as I can tell, much less nitrogen dioxide (NO₂) is produced by a gas powered engine than by a diesel, because it operates at a lower pressure, so does not initiate the reaction between atmospheric nitrogen and oxygen that has suddenly made diesel engines so unpopular. These buses will certainly emit less unwanted rubbish than even the cleanest diesel. 110 cleaner vehicles in Bristol won't clear the air overnight, but it's a start. The refuelling station will also be open to third parties, which might encourage local delivery firms to invest in the technology.

The caveat is that the engine produces carbon dioxide and water vapour, both greenhouse gases. They are, however, much weaker in effect than the methane the were produced from, were it to be introduced into the atmosphere, as is the case whenever organic waste is buried in landfill.

Now for the hyperbole. Another more cynical headline could be "Government gives First Bus a bung of nearly £5 million to run MetroBust". South Gloucestershire may have signed the letter asking for the cash, but they won't any of the assets. I assume this misleading spin is to avoid the potential embarrassment caused by government giving public money to private companies. I'm not bothered by that when it is for the greater good, but there are some who would be.

To read the various news articles at face value, you would be forgiven for thinking that First will be taking hourly deliveries of food waste, and shovelling it into a giant machine, producing a special gas that is quite different from normal natural gas. Not so - biomethane is chemically identical to the fossil fuel version. First's refuelling plant will be connected to the gas national grid in much the same way as mu=y gas boiler is. The biomethane will be produced elsewhere, possibly in Avonmouth by someone such as New Earth Solutions (http://www.newearthsolutions.co.uk/wp-content/uploads/2012/01/New-Earth-Corporate-brochure-2012-web.pdf), although I am not sure if they are still going. Viridor are currently building a much bigger plant (http://www.bioenergy-news.com/display_news/12158/viridor_contracts_clugnston_to_build_avonmouth_wastetoenergy_plant/) in Avonmouth. The gas from such plants is "bought" by First, then pumped into the national gas supply. First then turn on the tap and draw an equal amount from the same national supply, making this an accounting device, because the plant would be producing gas anyway. Again, I have no issue with the process, which solves more than one problem. Waste is used rather than buried, energy is produced, and greenhouse gases fall. It's the somewhat dishonest gloss put on the story that I object to. On the plus side, if we get too many gas buses to be able to fuel them all from biogas, we will be able to use the methane producedd by hydraulic fracturing of deep rocks.

An analogy. Some years ago, a French bottler of naturally sparkling water was found to have been removing the carbon dioxide from the spring water before transporting it to its distant bottling plant. Its explanation was that it expelled the gas into the atmosphere to make the water easier to transport to much closer to its customers. It then removed the same gas from the air and injected it back into the water - voila! It didn't go down well.

So I welcome the introduction of gas-powered buses, but would like to see more honesty. GHG and PM10 are now listed in the Abbeviations and Acronyms page.

Except that:

AIUI, Both CO2 and H2O are greenhouse gases but only in the upper atmosphere.  CO2 released at ground level will find its way to the upper atmosphere and be a greenhouse gas.  But water vapour released at ground level will not result in more water vapour in the upper atmosphere because water vapour as we know condenses onto surfaces and in clouds and often falls out the atmosphere as rain.

Methane - CH4 is itself a greenhouse gas and a potent one at that so care must be taken to avoid leaks of the fuel in production and distribution. 

But the combustion products are CH4, per unit energy produced are much better for the environment than the combustion products of say petrol or diesel and better still than coal.

CH4 + 2O2 -> CO2 + 2H2O, ie two molecules of (harmless) water are produced for every molecule of CO2 when methane is burnt.  For diesel the proportion of CO2 in the exhaust is much higher.  I appreciate that this is a simplification because the energy produced when making a molecule of CO2 will depend on where the Carbon is bonded in the fuel and will be different from the energy produced when making a molecule of H2O, but simply it is enough to know that oxidising the C atoms in a fuel produces energy as does oxidising the H atoms, the former is harmful to the climate and the later is not so a fuel with a greater proportion of oxidisable  H atoms to C atoms will be better for the climate. 

Hold on - there's two things going on here, and getting mixed up: "bio" and "methane".

Being bio means this is not fossil carbon at all, it's already out in the atmosphere and the biosphere (and the sea) that communicates with it. Hence grabbing it at a point in its cycle where it's got energy that can be release by burning has no long-term effect on the climate.

Being methane does alter the amount of CO₂ produced per energy released, compared with longer hydrocarbons or coal. That affects its rating as a fossil fuel, if you have the choice of what you dig up and what you leave in the ground. Hence gas-fired electricity generation is still being built while coal-fired is being shut down, though that is also because gas plant is easier to fire up quickly when the sun goes in (or is eclipsed).

But being methane has nothing to with the status of  biomethane as "zero emission". It's not what you emit that counts, it where you got it from (if you're a bus, that is). If there was a shortage of truly bio methane, and mineral methane is used instead, it still has low to lowish emissions.

I was simply thinking "A poo by any other name would smell as rosy." Surely this is a poo bus, but with funding (and different accounting)?

Thank you, FTN, for the clear but extensive explanation of the process in both chemical and financial terms. One little thing I'd quibble with though: "110 cleaner vehicles in Bristol won't clear the air overnight, but it's a start." Yes, but they will only do their little bit to clear the air to the extent that they replace rather than supplement dirtier vehicles. Though even if they are supplementary they still set an example and make available the refuelling station, as you point out.

Who's getting these mixed up? I think Tim made a typo: his


should read 'But the combustion products of CH4...'; other than that I can't see any obvious source of confusion.

FTN makes an interesting observation:


There's nothing dishonest about this - it's a mechanism we all use when we choose our energy supplier. They buy it wholesale and sell it retail. If you subscribe to a 'green energy' tariff, you won't be able to tell whether the electricity you use was generated using coal or wind, but you know that you are supporting sustainable sources.

I did make the typo.   

Making methane from poo is good of course, but just how good depends on what would have otherwise happened to the poo.   If the poo was going to be sent to an aerobic  sewage works where it was put in a tank and aerated until the bugs in the water respired all the poo to water and CO2 and heat then the only gain by making the poo into bio methane is that the heat is not wasted by used to do work and drive the bus forward.  The climate gain is equivalent to the cancelation of the damage which would have been done by the emissions produced by having the bus run on a fossil energy.

But if the poo was going to be sent to an anaerobic sewage works where it would mostly settle out into sludge which would then be land-filled and ferment over years in the landfill site releasing huge amounts of methane which escapes into the atmosphere where it is 200 times more potent a greenhouse gas than CO2 then then the poo bus scheme alternative delivers a huge climate gain (however note that the vast majority of this climate gain would have been provided by capturing the bio methane and burning it off in a big flare)

If the poo bus scheme ends up diverting poo from an aerobic treatment works to an anaerobic treatment work where it produces methane rather than CO2 and just 1% of that methane escapes accidentally into the atmosphere during production and transport than the poo bus scheme has a negative effect on climate.   

 

Excellent point, thank you Red Squirrel. I am now even more in favour. (Not MetroBust, obviously)


As there aren't enough drivers in the Bristol area to move the existing fleet of buses slowly around the city, I would imagine that the non-MetroBust vehicles will be deployed in the usual way, displacing older vehicles that can be redeployed in smaller towns in place of even older vehicles. After several levels of similar cascade, the oldest in the fleet are sold abroad. When MetroBust finally gets going, the 30-odd new vehicles will displace those working on ordinary services which are no longer viable.

Ah, the trickle-down effect in action in bus fleets and the great carbon economy!

And at the same time these new cleaner burning buses will actually be scrubbing the air,so some more advantage to be had from the introduction  ;D.

I'm am a bit wary of any scheme which increases the production, transport or handling of methane.  Methane is a massively powerful greenhouse gas in its own right and just a tiny fraction of it needs to be lost to the atmosphere for any climate benefits to be cancelled out.   It might be best just to take the poo and incinerate it to CO2 optionally using the heat for heating homes or generating electricity. 

I have the same concerns about the "dash for gas" in electricity generation.  Sure methane is a cleaner fuel than coal in power stations, but extracting it is a messy business with quite a lot lost to the atmosphere especially when you get it from fracking.

Not like in the old days... https://www.youtube.com/watch?v=drE3lgaTgTA

I believe the First manager responsible used to run Reading Buses, so no shit there.